Geosciences | Physical Research Laboratory

2026

Strontium Isotopic evidence for Heterogeneous sediment-water interactions in inland groundwater of the western Bengal Basin

Date: 2026-03-03
Speaker: Dr. Pousali Pathak
Venue: Ground Floor Lecture Hall

Abstract

The diverse geochemical composition of Ganga-Brahmaputra floodplain sediments found in the inland aquifers of the Bengal Basin, and their impact on groundwater chemistry over a seasonal timescale, has been poorly investigated yet. This study combines seasonal groundwater geochemistry with isotope-based mass-balance modelling to constrain the controls on dissolved Sr and 87Sr/86Sr in depth-bound inland groundwater from the western Bengal Basin (West Bengal, India) located within the Ganga (Hooghly) floodplain. To further understand the spatial variations in the inland groundwater composition across the Bengal floodplain, the present groundwater database has been compared with available inland groundwater data from the eastern Bengal Basin (Bangladesh) located in both the Ganga and Brahmaputra drainage basins. The shallow groundwater in western Bengal Basin exhibits variable hydrogeochemistry and radiogenic 87Sr/86Sr with limited seasonal variability; however, showing higher solute loads during pre-monsoon period. Comparing with available geochemical data on the Ganga River bedload sediments-water, we suggest detrital radiogenic calcite dissolution (74 - 93%) from the Ganga floodplain sediments and a subordinate localized contribution from silicate mineral weathering may drive heterogeneous Sr release with radiogenic 87Sr/86Sr in the seasonal shallow groundwater, which may further undergo secondary interactions with exchangeable clay-sediment fractions.

Advancing Palaeoclimate Reconstructions using Triple Oxygen Isotopes in Carbonates

Date: 2026-02-24
Speaker: Ms. Aishwarya Singh
Venue: Ground Floor Lecture Hall

Abstract

The challenge in predicting monsoon is difficult to overcome by relying on instrumental data from only the past few decades. Palaeomonsoon reconstructions help us understand and predict the sensitivity and response of monsoon to forcings on multi-decadal-centennial timescale. Numerous palaeomonsoon reconstructions based on oxygen-18 in speleothems have been done in India to investigate the drivers of Indian Summer Monsoon Rainfall (ISMR). However, it can be difficult to deconvolve the δ18O signal into individual components, including possible kinetic isotope effects, temperature, precipitation amount, moisture source and transport, which can lead to an overstated climatic signal. In such a case, the extent to which the variability in ISMR in the instrumental period reflects natural variability, still remains debatable. In this seminar, I will discuss how triple oxygen isotope systematics can provide a way to identify kinetic effects and delineate the influencing processes. I will present results from in-house setup that have resolved the existing theoretical-experimental gap and interlaboratory inconsistencies, crucial in standardising triple oxygen measurements in carbonates. I will also present preliminary investigations of paired speleothem-dripwater samples from Indian caves.

Reconstructing Climate and Environmental Shifts in the Levantine Corridor across the Pliocene-Early Pleistocene

Date: 2026-02-09
Speaker: Prof. Nicolas Waldmann
Venue: Ground Floor Lecture Hall

Abstract

The Pliocene was the last significant sustained warm period on Earth. Atmospheric carbon dioxide and global temperatures during this interval can be comparable to those modeled and proposed for the near future. Considering a similar continental and oceanic positioning to the present, it is possible to assume that the oceanic and atmospheric circulation patterns were also comparable to those of today. Current data on the Pliocene, and the transition to the cooling conditions of the Pleistocene, mostly arrive from marine archives, thus leaving the continental regions mostly barren of reliable and continuous information. Therefore, continental climate archives from this interval are highly valuable for comprehending the impact of climate change on terrestrial areas and serve as good analogues for understanding present conditions without the influence of humans.
In the present study, a multi-proxy approach was applied to both sediment cores and outcrop samples retrieved from three different lacustrine formations exposed in the Near East, which are chronologically constrained to the Pliocene and Early Pleistocene. The multi-proxy analyses indicate major fluctuations in the lakes hypsometry, transitions from anoxic to oxic conditions in the sediment-water interface, and major changes in the limnic states, indicating a response of the lake systems to changing conditions in the precipitation patterns through time. It appears that the different lakes responded to orbital-scale forcing, which may have played a key role in governing the dry-wet climate cycles in the Near East. Results from this study provide an important understanding of the hydrological conditions that may have dominated the region during a warmer climate phase, challenging previous estimations, while concurrently providing clues to the role of the climate system in greening the path of early hominin migrations out of Africa through the region.

Short-lived isotope systematics to understand Hadean-Archean crust-mantle evolution in Indian cratons

Date: 2026-01-27
Speaker: Dr. Arathy Ravindran
Venue: Online, Link: https://meet.google.com/jgf-svgu-tsq

Abstract

The evolution of crustal and mantle reservoirs in Archean cratons has been extensively investigated through conventional geochemical techniques for decades. However, these approaches are often limited by poor geochemical preservation and analytical challenges. Non-conventional, short-lived isotopes such as 182W and 142Nd provide robust temporal constraints on Hadean mantle extraction and hidden crustal reservoirs. This talk highlights the application of novel geochemical techniques to unravel the crust-mantle evolution of Indian cratons. Dr. Arathy Ravindran is doing her postdoctoral research work at the University of Cologne, Germany with a focus on isotope geochemistry. She carried out her previous postdoctoral positions at ETH Zurich, Switzerland and her doctoral research at University of Bern, Switzerland.

Detection of Microplastics in a Complex Matrix: A Case Study on Urban Road Dust

Date: 2026-01-20
Speaker: Dr. Abisheg Dhandapani
Venue: Ground Floor Lecture Hall

Abstract

Microplastics (MPs) are an emerging environmental pollutant, with urban road dust serving among major reservoir due to tyre and brake wear abrasion and atmospheric deposition. The heterogeneous composition of road dust poses significant challenges for isolating and identifying polymers. This presentation will discuss the application of Fourier Transform Infrared (FTIR) microscopy for the qualitative and quantitative analysis of MPs in urban dust samples.

Biogeochemical controls on dissolved micronutrient (Ni, Cu, Zn, Cd) distributions in the Equatorial Pacific Ocean

Date: 2026-01-06
Speaker: Dr. Naman Deep Singh
Venue: Ground Floor Lecture Hall

Abstract

The Equatorial Pacific Ocean (EPO) is among the most productive oceanic regions and is characterized by strong CO2 outgassing, playing a pivotal role in the global carbon cycle. Here, we present the distributions of micronutrients along the German GEOTRACES GP11 transect in the EPO during a developing El Niño. This study aims to assess the biogeochemical controls governing micronutrient distributions along the transect, which are critical for elucidating potential linkages between surface productivity and nutrient supply. Model estimates combined with observational constraints indicate that equatorial upwelling and strong zonal currents exert primary controls on micronutrient fluxes and biological uptake ratios. These findings have important implications for the bioavailability of micronutrients in the surface EPO under an increasing frequency of extreme El Niño and La Niña events, which modulate upwelling strength and Equatorial Undercurrent (EUC) intensity across the EPO. Overall, this study highlights the differential impacts of water mass mixing and vertical processes including, organic matter remineralization, particle scavenging, and benthic fluxes, on micronutrient distributions in the EPO and provides new insights into their inter-basin variability and biogeochemical cycling in the Pacific Ocean. About the speaker: Dr. Naman Deep Singh is a geochemist and completed his integrated BS-MS degree at the Indian Institute of Science Education and Research (IISER) between 2010 and 2015, followed by a Ph.D. at the Physical Research Laboratory from 2015 to 2020. He is currently working as a postdoctoral researcher at GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany. His research interests focus on understanding the biogeochemical cycling of trace metals in the ocean and their influence on biological ocean productivity and chemical weathering processes in terrestrial systems.

2025

Investigating the Chautang-Drishadvati-Harappan connection

Date: 2025-12-30
Speaker: Aditya Vikram Mishra
Venue: Ground Floor Lecture Hall

Abstract

Numerous Harappan urban centers have been discovered along the floodplains of Ghaggar and Chautang in northwestern India. These minor seasonal streams could not have supported large settlements in the past. Many believe that these streams occupy the channels of two mighty, perennial rivers of yesteryears - the Sarasvati and the Drishadvati, respectively. Although the timelines of the river Sarasvati's evolution/demise and the nature of its water/sediment sources have been established, very little is known about the river Drishadvati and its connection to the Harappan civilization. My PhD study aims to investigate this question using modern geochronological, geochemical, and isotopic tools. In the seminar, I shall provide a brief overview of my thesis problem.

Geochemical Investigation of Neoproterozoic Bhander Shales: Implications towards Provenance

Date: 2025-12-30
Speaker: Deependra Singh
Venue: Ground Floor Lecture Hall

Abstract

The Neoproterozoic Eon, which spanned 1000-538 Ma, marks an important time in crustal history between the break-up of Rodinia and the assembly of Gondwana. To understand the evolutionary history of the Earth’s crust in this time frame, Sedimentary basins act as an excellent natural laboratory by preserving the signature of evolution in the sedimentary rocks. The Vindhyan basin of India is such an archive which provides an opportunity to investigate sediment provenance and basin evolution by the analysis of its sedimentary rocks. So, to understand the provenance of the sediments of this vast basin becomes important to characterize the source of these sediments and to infer the tectonic setting and climatic conditions of the source region at that time. In this talk, I will discuss the basic idea of the sedimentary provenance of Neoproterozoic shales of the Bhander group from the Rajasthan section of the Vindhyan Basin. I will also present some preliminary results of my work and my future plans in this direction.

Role of ocean anoxia in the Permian–Triassic crisis: Evidence from geochemical and isotopic data

Date: 2025-12-26
Speaker: Nilima Mishra
Venue: Ground Floor Lecture Hall

Abstract

The Permian–Triassic boundary (“Great Dying”), the most severe mass extinction in Earth's history, was accompanied by extreme perturbations in ocean oxygenation. Reconstructing ocean redox conditions during this event is critical for evaluating the vulnerability of modern oceans and for distinguishing reversible environmental stress from tipping-point behavior in Earth’s life-support system. In this talk, I will discuss how molybdenum isotopic geochemistry provide a powerful framework for reconstructing changes in global ocean redox conditions across the Permian–Triassic boundary.

Assessing environmental microplastics using FTIR

Date: 2025-12-26
Speaker: Maitri Maheshwari
Venue: Ground Floor Lecture Hall

Abstract

Microplastics are the fragmented particles of plastic debris that are generated from degradation or waste release, contaminating our environment. Found in mountains, polar caps, and deep-ocean trenches, MPs are proving their ubiquitous nature with every new study. To accurately assess their presence and effects on our ecosystems, various analytical techniques have been developed, of which Fourier Transform–Infrared Spectroscopy (FTIR) is widely employed. In the talk, I will discuss this non-destructive and convenient method and how it has made MP analysis easier. Furthermore, certain limitations need to be addressed, and complementary solutions are necessary to achieve reliable results.

Novel Tools to assess the Health Risks from Outdoor and Indoor Air Pollution

Date: 2025-12-23
Speaker: Dr. Vishal Verma
Venue: Ground Floor Lecture Hall

Abstract

The capability of ambient particulate matter (PM) to generate reactive oxygen species (ROS), conveniently called the oxidative potential is proposed as a better metric for relating the PM pollution with health effects. In this talk, I would present our work on the measurement of oxidative potential of ambient and indoor PM. Through these measurements and comparisons, we demonstrate the need for a comprehensive toxicity and health impact assessment of PM emanating from indoor and outdoor sources.

N₂ Fixation in Inland Water Ecosystem

Date: 2025-12-16
Speaker: Md. Fahad Alam
Venue: Ground Floor Lecture Hall

Abstract

We know that the atmosphere is composed of approximately 78% nitrogen, but it is inaccessible to most organisms due to the inert nature of N₂ gas. In that case, N₂ fixation plays a role in transforming this N₂ gas into a bioavailable form. There are a lot of Studies are happening on N₂ fixation in the world and in PRL, also, but Most are in marine ecosystems. Here, I will discuss the inland water ecosystem, as inland and coastal waters cover less than 10% of Earth's surface area, yet they can contribute 15-20% to the global nitrogen budget, which was previously underestimated. I will talk about the water column and benthic N₂ fixation in the inland water ecosystem.

Size-resolved Sources, Composition and Optical Characteristics of Brown Carbon Aerosols

Date: 2025-12-16
Speaker: Garima Verma
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric aerosols are critical component of the Earth's climate system and a dominant factor in urban air quality. However, their precise impact on climate and human health is one of the largest uncertainties in modern atmospheric science (IPCC, 2021). Organics are the least studied components in ambient aerosols because of their multiple natural and anthropogenic origins, multifarious chemical composition, and complex formation mechanisms (Andreae and Gelencsér,2006). Brown carbon (BrC), the light absorbing fraction of organic carbon (OC), exerts vital effects on climate change as well as human health. BrC optical properties and radiative forcing effects as a function of aerosol size, which would provide direct evidence as to how important is BrC in driving aerosol climate forcing over Indian megacities. Size-segregated studies offer critical insights into distinct sources and formation pathways that are often obscured in bulk measurements. Understanding of sized aerosols is therefore necessary to comprehend their chemical reactivity, atmospheric lifetime, and impacts on human health and climate.

Marine Microbes at the Air–Sea Interface: From SML Ice-Nucleating Bacteria to Microbial Aerosols in the Indian Ocean

Date: 2025-12-08
Speaker: Prof. Koji Hamasaki
Venue: Room no. 469, THEPH Division Seminar Room

Abstract

Sea-spray aerosols (SSA) are a major natural source of cloud condensation nuclei (CCN) and ice-nucleating particles (INPs), yet the microbial drivers behind their production and variability remain poorly constrained. The sea-surface microlayer (SML), enriched in organic matter and microorganisms, acts as a selective interface that promotes the transfer of microbe-associated particles to the atmosphere. In this talk, I present two complementary studies that reveal a consistent role of specific marine bacterial lineages—particularly Flavobacteriia and Gammaproteobacteria—in shaping the composition and cloud activity of SSA. First, cultivation-based experiments in a coastal inlet of Japan identified SML bacteria from these groups exhibiting heat-labile, protein-associated ice-nucleating activity above –15 °C, demonstrating their potential as INP sources. Second, ocean-basin-scale microbial profiling during the research cruise across the Bay of Bengal and southeastern Indian Ocean showed that these same taxa are selectively aerosolized from particle-associated fractions, whereas coarse aerosol particles over the Bay of Bengal were more influenced by terrestrial intrusions. This highlights strong ecological and atmospheric controls on which marine microbes enter the air. Together, our findings indicate that microbe-rich SML communities—especially Flavobacteriia and Gammaproteobacteria—represent dynamic contributors to cloud-active aerosols, underscoring the need to integrate microbial ecology into predictions of ocean–atmosphere climate feedbacks. About the speaker: Professor Koji Hamasaki's research is focussed on understanding the microbial diversity and functions within surface ocean ecosystems and their critical roles in biogeochemical cycles. His group is notably recognized for pioneering studies on "actively growing bacteria" in natural seawater, employing advanced bromodeoxyuridine (BrdU) incorporation methods to investigate various metabolic processes, including bacterial photosynthesis, nitrogen fixation, and organic sulfur degradation. More recently, his research has concentrated on the specific role of microbial activity at the air-sea interface and its direct influences on climate processes.

The Evolution of Granite-Greenstone Belts of the Western part of Dharwar Craton, Dharwar Craton, South India

Date: 2025-12-02
Speaker: S V Balaji Manasa Rao
Venue: Online

Abstract

The evolution of granite-greenstone belts within the Western Dharwar Craton (WDC), a Paleoarchean-Neoarchean crustal accretion, represents the major Archean records of Early Earth. In this contribution, an integrating field relationships-whole-rock geochemistry (major/trace elements, REE patterns), and isotope systematics (Sm-Nd, Lu-Hf) depict an initial TTG-komatiite formation at 3400-3300 Ma linked to juvenile mantle inputs and elevated geothermal gradients, and a mixed tectonic setup. Subsequently, the dome-and-keel architectures emerge through subduction and plume tectonics represented by Sargur Group volcanics (~3.3 Ga), indicating high mantle potential temperatures and distinct tectonic manifestation of Archean Earth. While the younger Bababudan (~2.9 Ga) and Chitradurga (~2.7 Ga) greenstones hosting volcano-sedimentary assemblages reflect back-arc volcanism atop stabilised TTG basement, with two phases of 3.0Ga and 2.6 Ga. The Isotopic U-Pb zircon and radiogenic isotope data reveal episodic crustal growth, contrasting WDC's stable, thick (~42-51 km) core with major growth events at 3.35-3.25Ga, including TTG and Komatiitic Volcanism. Vertical tectonics dominate over nascent subduction, underscoring plume-driven nucleation of proto-cratons globally. Therefore, the eventual formation of granite greenstone belts of Western Dharwar Craton from a wide early Earth time window and proxies to investigate the sequential evolution of Archean cratonic units.

What controls the oxygen isotope–salinity relation in the northern Indian Ocean?

Date: 2025-11-25
Speaker: Dr. Arvind Singh
Venue: Ground Floor Lecture Hall

Abstract

Seawater oxygen isotopic composition (δ18O) and salinity show a near-linear covariance, forming the basis of widely used δ18O–S relationships. These relationships are often applied to reconstruct past salinity in the ocean from foraminiferal δ18O, yet the associated uncertainties can be large, with errors in inferred salinity reaching >50%. Much of this uncertainty stems from the limited availability of high-quality modern seawater δ18O measurements and an incomplete understanding of the processes that shape this relationship. In this talk, I will present a comprehensive modern seawater δ18O dataset generated at PRL, and discuss how it advances our understanding of the controls governing the δ18O–salinity relationship in the northern Indian Ocean.

Seasonal Variability of Water Vapor Dynamics in the Semi-Arid Region of Western India - revelations from isotopic investigation at Mt. Abu, Rajasthan.

Date: 2025-11-11
Speaker: Mr. Virendra R Padhya
Venue: Ground Floor Lecture Hall

Abstract

This study presents the first continuous year-long measurement of stable isotopes (d18O, dD, and d-excess) in atmospheric water vapor over semi-arid western India. Continuous in-situ observations captured isotopic variations from daily to seasonal scales to identify key controlling processes. Temporal changes in vapor isotopes are governed by shifts in moisture sources and the influence of recycled moisture, producing a distinct seasonal isotopic baseline. A pronounced isotopic depletion precedes rainfall events by several days, suggesting its potential as a precursor to precipitation. A sharp isotopic transition observed in late April indicates a major shift in vapor source. The dominant moisture sources—northern and southern Arabian Sea, arid terrestrial regions of Iraq–Iran–Afghanistan–Pakistan, and the wetter eastern landmass of India and the Bay of Bengal—each impart distinct isotopic characteristics, enabling the identification of seasonal vapor origins and their hydrometeorological implications.

Nitrogen fluxes and primary productivity in Archaean Ocean

Date: 2025-11-04
Speaker: Mr. Janaarthanan P A
Venue: Ground Floor Lecture Hall

Abstract

The most oxidised form of nitrogen - Nitrate (NO3⁻) - serves as an essential and often limiting nutrient for life in the modern well-oxygenated ocean. However, ~3 billion years ago (Archean eon) the Earth’s surface environment and oceans were largely deprived of oxygen. Nitrogen isotopic composition (δ¹⁵N) of sedimentary rocks of that time suggests ammonium (NH4+) dependent anaerobic nitrogen cycling. In an attempt to quantify nitrogen fluxes and productivity in such ammonium-based ecosystem, we have developed a numerical two-box model that simulates Archean nitrogen cycling under ammonium-dependent conditions. In this seminar I will be discussing the results of the model and evaluate the Archean nitrogen isotopic record.

Coastal Groundwater: Effects of Climate Change and Abuse on a Critical Resource

Date: 2025-10-17
Speaker: Prof. Willard S. Moore
Venue: Ground Floor Lecture Hall

Abstract

Groundwater is an essential resource for most coastal communities. Abuse of this resource and global sea level rise due to climate warming endanger its sustainability. In this talk, I will discuss less obvious aspects of changing coastal groundwaters. Along some coastlines, excess groundwater mining leads to land subsidence. Combined with global sea level rise, this causes enhanced coastal flooding and saltwater intrusion (SWI) into coastal aquifers. The intrusion of seawater into these aquifers poisons an essential resource. The movement is not one-way. Coastal aquifers are an underground link between the land and sea. Terrestrial freshwater and seawater are constantly mixed and exchanged within these permeable sediments, called subterranean estuaries. The flow of fresh or salty groundwater into the ocean is called submarine groundwater discharge (SGD). SWI radically alters the groundwater chemistry by introducing sulfate, a major ion in seawater and a powerful oxidizing agent. Fresh groundwater has low oxidation capacity due to the low solubility of oxygen. The sulfate in seawater brings 200 times greater oxidation capacity, allowing considerably more carbon to be oxidized. The byproducts of marine carbon oxidation include CO2, nutrients (N, P), sulfide (H2S), dissolved organic carbon and nitrogen, and reduced metals (Fe2+, Mn2+). SGD transports these byproducts of carbon oxidation into estuarine and coastal waters, where they may stimulate biological productivity – sometimes to excess, and deplete dissolved oxygen concentrations through reactions with sulfide and other reduced substances. My focus in this talk will be on the interplay between SWI and SGD and the effects on estuarine and coastal waters. About the speaker: Prof. Willard S. Moore is Distinguished Faculty Emeritus in the School of the Earth, Ocean and Environment at the University of South Carolina, USA. He is an internationally renowned marine geochemist whose pioneering research has transformed our understanding of coastal and oceanic processes through the application of naturally occurring radioisotopes, particularly radium isotopes. Prof. Moore’s work has been instrumental in quantifying submarine groundwater discharge and assessing its role in the transport of nutrients, trace metals, and carbon to the coastal oceans. Prof. Moore has been elected Fellow of both the American Geophysical Union (AGU) and the American Association for the Advancement of Science (AAAS), and is a recipient of the prestigious “Buck” Ketchum Award from the Woods Hole Oceanographic Institution.

Role of picophytoplankton in the carbon cycle of the northern Indian Ocean

Date: 2025-10-07
Speaker: Dr. Sipai Nazirahmed
Venue: Ground Floor Lecture Hall

Abstract

Picophytoplankton are vital drivers of marine biogeochemical cycles and serve as indicators of ocean productivity, ecosystem health, and climate change. As the smallest single-celled phytoplankton, they play a crucial role in ocean ecosystems, being globally recognized as major primary producers and significant contributors to the oceanic carbon stock. Despite their ecological importance, their role is often underestimated, particularly in the northern Indian Ocean—an oceanic region characterized by high environmental variability and dynamic biogeochemical processes. In this seminar, I will present the results that aimed to quantify the abundance and carbon biomass of picophytoplankton and to assess the influence of regional physicochemical parameters on their spatial distribution and ecological role in the northern Indian Ocean. Our findings demonstrate that the contribution of picophytoplankton carbon biomass to the total particulate organic carbon (POC) pool was substantial in both the Arabian Sea and the Bay of Bengal. This underscores their significant, yet often overlooked, role in supporting the regional biological pump and influencing carbon fluxes.

Geochemical Insights into the formation of Andaman Ophiolite during Subduction Initiation

Date: 2025-09-30
Speaker: Mr. G N S Sree Bhuvan
Venue: Ground Floor Lecture Hall

Abstract

Ophiolites are fragments of the oceanic lithosphere exposed on land. It is essential to understand the magmatic history of an ophiolite, which holds geochemical clues to its tectonic setting. Recent research on the Neo-Tethyan ophiolites suggests that the ophiolite formation is related to subduction, likely during subduction initiation. Andaman ophiolite, exposed on the forearc of the Andaman subduction zone in the Andaman Islands, India, is a dismembered ophiolite containing mantle peridotites, cumulate gabbros, intrusive plagiogranites, massive and pillow basalts, with later dyke intrusions. Although the age of the Andaman ophiolite is well constrained to be 98±8Ma, its formation remains debated, with views suggesting a diverse range of tectonic settings. Hence, it presents an opportunity to test the hypothesis of ophiolite formation during subduction initiation. Using bulk rock major and trace element abundances and Sr-Nd isotopic compositions, I will present new inferences on the origin of the Andaman ophiolite.

Accelerator Mass Spectrometry - Current Understanding, Recent advancements and the way forward

Date: 2025-09-09
Speaker: Mr. A Shivam
Venue: Ground Floor Lecture hall

Abstract

Accelerator Mass Spectrometry (AMS) has revolutionized ultra-sensitive radio isotopic analysis across scientific disciplines. PRL Houses state-of-the-art 1MV Accelerator Mass Spectrometer for analysis of radioisotopes like 14C, 10Be and 26Al. This seminar explores the current understanding of AMS principles, highlights current status and recent developments in PRL-AURiS (PRL-Accelerator Unit of Radioisotope Studies) and the session will conclude with perspectives on future directions, exploring the possibilities of new isotopic targets, and broader interdisciplinary impact. Attendees will gain a comprehensive overview of AMS, its functioning principles, its evolving capabilities, and critical developments shaping the field. The seminar shall be in most general language - and shall be able to cater to a wide audience working in any field.

From Suppression to Reprogramming: Precision Nanomedicine for Rheumatoid Arthritis and Beyond

Date: 2025-09-02
Speaker: Dr. Ashutosh Kuma
Venue: Ground Floor Lecture Hall

Abstract

Chronic inflammatory diseases, including rheumatoid arthritis and certain cancers, remain among the most challenging conditions to treat. Conventional therapies often work broadly across the body, suppressing the immune system in ways that can cause serious side effects and fail to provide lasting benefit. My lab is pursuing an altered path: nanomedicine designed to bring treatment directly to the source of inflammation. My lab engineer long-circulating lipid nanoparticles, including immunoliposomes, that selectively accumulate in inflamed tissues. These carriers allow us to deliver RNA-therapeutics like siRNA and miRNA, along with anti-inflammatory drugs, precisely where they are needed, reducing systemic toxicity and expanding the therapeutic window. This targeted approach not only calms harmful immune activity but also reprograms immune cells toward reparative states, offering the possibility of rebuilding tissue function rather than merely suppressing disease. Our work addresses multiple levels of immune regulation, including silencing key cytokines, modulating the NF-κB and JAK–STAT pathways, and investigating PAD inhibition to prevent early autoimmune triggers. Beyond treatment, the lab is developing early detection strategies to identify disease before irreversible damage occurs. By tracking biomarkers such as protein modifications driven by PAD enzymes, we aim to capture the earliest molecular signals of autoimmunity. At the same time, we are making efforts to integrate laboratory findings with retrospective patient data to understand how inflammation, comorbidities, and lifestyle factors shape treatment responses. Together, these efforts outline a translational roadmap that links mechanistic insight with clinical application.

Uranium in the ocean: Inferences on bottom water anoxia during the Last Glacial Period

Date: 2025-08-19
Speaker: Prof. Manmohan Sarin
Venue: Ground Floor Lecture Hall

Abstract

The paleo-oceanographic studies suggest that deep ocean was depleted in dissolved oxygen (O2) during the last glacial period (LGP, ~18 kyr BP). Therefore, paleoceanographers have sought a direct tracer for studying the changes in dissolved O2 in the deep ocean during the LGP. Geochemical proxies like redox-sensitive trace elements (Vanadium, Molybdenum, Uranium, Manganese) in bulk sediments have been used to reconstruct the past bottom water environment. Example, in oxic seawater, uranium is present in relatively high concentration as uranyl-carbonate complexes which are highly soluble. Under O2 deficient (anoxic) conditions, uranium can be reduced from U(VI) to a less soluble tetravalent state U(IV), which is particle reactive and gets fixed into the sediments. A geochemical study validating this concept was published in 1993 (‘Geochemical evidence for anoxic deep water in the Arabian Sea during the last glaciation’; Sarkar, Bhattacharya & Sarin; Geochimica et Cosmochimica Acta). The purpose of this seminar is to discuss two recent articles (Geochemical Perspectives Letters 2024 and Marine Geology 2025) using the very same concept/approach published more than three decades ago (PRL study).

Evolution of the Laxmi Basin, Arabian Sea, during the Deccan volcanism

Date: 2025-08-12
Speaker: Dr. Sibin Sebastian
Venue: Ground Floor Lecture Hall

Abstract

The Laxmi Basin is a prominent geomorphic feature and a marginal depression in the Northwest Indian Ocean (Arabian Sea). This ~300 km wide basin separates the western Indian continental margin from the Laxmi Ridge (LR), which is believed to be continental. The precise nature of the basin's basement remains controversial, with differing views suggesting it could be either a stretched continental crust with magmatic intrusions related to continental rifting (contemporaneous with Deccan volcanism) or a pre-Paleogene oceanic crust. Additionally, a geochemical study of the basin's igneous basement indicates that these rocks formed in a subduction zone setting. Understanding the crust's nature has implications for the geodynamic events of continental breakup and the formation of the Indian Ocean during the Late Cretaceous. To address this controversy, we conducted geochemical and isotopic studies on basaltic lava samples from this basement, recovered during IODP 355. In this talk, I will present the results of our study and our inferences regarding the crustal nature of the Laxmi Basin.

Nitrogen loss processes in aquatic ecosystems

Date: 2025-08-05
Speaker: Dr. KM Ajayeta Rathi
Venue: Ground Floor Lecture Hall

Abstract

Nitrogen, though abundant in the atmosphere, often limits primary productivity in aquatic ecosystems. These ecosystems play a crucial role in regulating the global nitrogen cycle both by converting inert atmospheric nitrogen into bioavailable forms through dinitrogen fixation and by removing excess reactive nitrogen via microbially mediated loss processes, including denitrification, anaerobic ammonium oxidation (anammox), and, to some extent, dissimilatory nitrate reduction to ammonium (DNRA). However, with increasing anthropogenic nitrogen inputs and climate-driven environmental changes, the efficiency and dominance of these pathways are shifting, with significant implications for ecosystem health, biogeochemical feedbacks, and nitrogen budgets. In this seminar, I will discuss the mechanisms, environmental controls, and experimental approaches used to study nitrogen loss processes in aquatic ecosystems.

Genesis of uranium mineralization in the Singhbhum Shear Zone: constraints from geochemistry and geochronology of hydrothermal minerals

Date: 2025-07-29
Speaker: Dr. Sarita Patel
Venue: Ground Floor Lecture Hall

Abstract

The genesis of uranium mineralization in the Singhbhum Shear Zone (SSZ), including the sources of the hydrothermal fluids has consistently remained a subject of debate. The present research deals with the Mohuldih and Bagjata uranium mine along the SSZ, India. The chemical and isotopic studies on the accessory minerals such as tourmaline, magnetite, fluorapatite, and monazite from the aforementioned mines were conducted to understand the mineralizing history in the Singhbhum Shear Zone. This discussion will focus on the distinct hydrothermal events and associated mineralization processes, as inferred from chemical compositions, isotopic signatures, and age data.

Chemical compositions of the Ganga, Yamuna, Narmada and Tapi Rivers: An assessment of spatial and temporal variability

Date: 2025-07-22
Speaker: Dr. Rakesh Kumar Tiwari
Venue: Ground Floor Lecture Hall

Abstract

Rivers are the major pathways which supplies metals from the continents to the oceans. The chemistry of these pathways plays a crucial role in riverine systems as they influence water quality and terrestrial biogeochemistry. Further, their riverine supply to ocean is crucial in regulating ocean productivity, influencing the oceanic biological pump, which modulates the atmospheric CO2 levels and global climatic variability. In this talk I will present a detailed investigation of the elemental chemistry in seasonally and spatially resolved samples from the Ganga, Yamuna, Narmada and Tapi rivers.

Sediment Connectivity in India’s Large River Basins under Climate and Human-Induced Stress

Date: 2025-07-08
Speaker: Dr. Abhishek Dixit
Venue: Ground Floor lecture hall

Abstract

Currently, large river systems are under increasing stress due to climate-driven extreme events, floods, human interventions, and concerns over delta sustainability. These systems span diverse geomorphological, climatic, and lithological domains, each contributing uniquely to the basin’s sediment dispersal processes. These domains are activated or suppressed in response to external forcings such as climate extremes and human activities. In this talk, I will discuss these factors in the context of three major Indian river basins: the Brahmaputra, the Ganga, and the Godavari. I will show how the alluvial plains, particularly in the Ganga and Brahmaputra basins, may be highly sensitive to seasonal-scale fluctuations, which in turn influence sediment budgets and provenance signals. At the same time, climate-driven extreme events are leaving far-reaching and persistent imprints, with sediment signals traceable as far downstream as the Bengal delta. I will also explore how human interventions, particularly dams, have disrupted sediment connectivity within these river systems. Almost all of the observed reduction in sediment load can be attributed to reservoir storage, placing parts of the delta at risk of sinking. In conclusion, while climate-driven forces are significant, human-induced interventions are leaving equally, if not more, profound imprints on the sediment dynamics of India’s large river systems. A carefully integrated methodological approach is essential to effectively address these complex interactions.

Palaeoceanographic implications of single planktonic foraminiferal isotopic analysis

Date: 2025-07-01
Speaker: Dr. Sanchita Banerjee
Venue: GFL

Abstract

Planktonic foraminifera have the ability to archive geochemical signatures of seasonal scale due to their short life spans. We utilized stable isotopes in individual foraminiferal tests to reconstruct sur-face ocean conditions and climate fluctuations over the past few thousand years in the Northern In-dian Ocean. We developed a state-of-the-art methodology for measuring the clumped isotope com-position (Δ47) of individual foraminiferal tests, marking the first such attempt. This approach holds the potential to reconstruct past ocean temperatures, offering unprecedented insights into short-term climate dynamics. We also analyzed δ13C and δ18O isotopic ratios in single foraminifera to resolve vertical habitat signals and understand the variation in mixed layer depths. These multi-isotope da-tasets allow us to better understand the physical and chemical structure of the upper ocean and its response to past climate change. In this talk, I will present preliminary results from this novel single-foram clumped and conventional isotope analysis, and discuss their implications..

Factors affecting gas-particle partitioning of the NHx system

Date: 2025-06-24
Speaker: Ms. Chandrima Shaw
Venue: Ground Floor Lecture Hall

Abstract

Ammonia (NH3) and its particulate form ammonium (NH4⁺) together form the reactive nitrogen system NHx, which plays a key role in air quality, particulate matter formation, and nitrogen deposition. The gas-particle partitioning of NHx is influenced by several factors like meteorology (temperature and relative humidity) and atmospheric chemistry (pH and aerosol liquid water content (ALWC)) with a complex interplay between them. While low temperature and high RH promote the partitioning towards the particulate phase, higher temperature shift it back to the gas phase. Aerosol pH and ALWC further control this balance, by governing the effect of this partitioning on PM load. While pH and ALWC influence the partitioning of gases into their particulate counterparts, this partitioning in turn affects the aerosol pH, creating a two-way interaction between chemical composition and aerosol thermodynamics. Given the multifaceted importance of the NHx system, it is essential to understand how meteorology and aerosol chemistry together, shape the gas-particle partitioning. This seminar aims to provide a deeper insight into the gas-particle partitioning dynamics of NH3 and NH4+, focusing on the role of temperature, RH, pH, and ALWC under different conditions.

Dynamics of Dissolved Organic Matter in Regulated River Systems

Date: 2025-05-20
Speaker: Ms. Ganika Kushwah
Venue: Ground Floor Lecture hall

Abstract

The dynamics of dissolved organic matter has always been complex because of their largely unexplored nature. Freshwater systems such as rivers are vital components of the global biogeochemical system as they act as conduits for transporting large quantities of dissolved organic matter (DOM) from terrestrial landscapes to the ocean. However, their role in DOM dynamics still remains underexplored, specifically from a biogeochemical perspective. Moreover, the anthropogenic alteration to it’s flow regime has put a limit to its transport mechanism-reducing its export. In ths seminar, a basic review of a DOM in riverine system along with results obtained from regulated river systems in western India will be presented

Can CO2 outgassing explain the Lomagundi carbon isotope excursion?

Date: 2025-05-15
Speaker: Mr. Janaarthanan P A
Venue: Ground Floor Lecture hall

Abstract

The Lomagundi-Jatuli excursion event (2.3-2.0 Ga) is one of grandest carbonate isotopic excursion events in the geological history, that is said to mark a global perturbation in carbon cycle. The canonical explanation given for this excursion attributes it to be the resultant of enhanced organic carbon burial. But, the lack of geological evidence for an enhanced organic matter accumulation prior to or synchronous with the excursion, leaves this event an unanswered puzzle. Furthermore, recent insights from sedimentological facies-based studies challenges the presumed global extent of this excursion. In this discussion we will evaluate the canonical organic burial mechanism and explore the possibility of CO2 outgassing as a potential driver responsible for this excursion.

Fate of Environmental Microplastics

Date: 2025-05-13
Speaker: Prof. Neeraj Rastogi
Venue: Ground Floor Lecture hall

Abstract

Microplastics (MPs) are omnipresent on the Earth, found everywhere from Mount Everest to the Mariana Trench, and from fishes to human body. MPs are known to affect human and environmental health directly/indirectly. However, research on MPs is in initial stage only with major focus on 'MPs in water bodies'. This talk will provide a brief overview on the MP research done in different environmental systems and future perspectives.

Corals as geochemical proxy for N:P ratio: Insight from modern corals

Date: 2025-05-06
Speaker: Dr. Abul Quasim
Venue: Ground Floor Lecture hall

Abstract

Globally, phytoplankton typically maintain the Carbon:Nitrogen:Phosphorus (C:N:P) ratios close to the Redfield ratio (~106:16:1), which reflects the balance of nutrients required for their growth. Therefore, these ratios serve as a baseline for assessing nutrient availability or limitation and carbon export efficiency. Understanding the future shifts in oceanic C:N:P ratios is essentially required for predicting the future trends of the biological pumps under the global climate change scenario. Recent studies reveal that the C:N:P ratios in the global ocean vary regionally, and their future projections are highly uncertain. Understanding the past variability in the C:N:P ratios could improve predictions. However, no geochemical proxy for C:N:P ratios at present. In this context, we analyzed C:N:P stoichiometry as well as d13C and d15N in different layers of modern corals (including coral-mounted algal biofilms) and surrounding seawaters and particulate organic matter collected from the Gulf of Kutch. In this talk, I will share insights into C:N:P ratios in the global ocean, and key findings highlight the efficiency of corals in capturing marine nutrient signatures and the biogeochemical processes shaping elemental and isotopic patterns.

Magnitude and regulation of methane emission from tropical streams and rivers

Date: 2025-04-24
Speaker: Dr. Latika Patel
Venue: Online

Abstract

Inland waters, particularly fluvial systems, are significant sources of atmospheric methane (CH4), a greenhouse gas with 34 times the global warming potential of carbon dioxide. However, large uncertainties persist regarding the extent and controls of CH4 emissions, especially in tropical river basins like those in Southeast Asia. Research work during my PhD addressed three critical knowledge gaps in understanding CH4 dynamics in tropical fluvial systems: (1) the effect of land use changes on CH4 concentration and emissions, (2) the occurrence and regulation of oxic CH4 production (OMP), and (3) the extent and environmental controls of aerobic CH4 oxidation (MOX), which will be discussed during the seminar.

Biogeochemical implications of Ocean Alkalinity Enhancement

Date: 2025-04-22
Speaker: Ms. Shreya Mehta
Venue: Ground Floor Lecture hall

Abstract

Over the past few centuries, anthropogenic activities have significantly altered the global carbon cycle, leading to a ~ 50% increase in atmospheric CO2 concentration relative to the pre-industrial levels. This rise has contributed to a global surface temperature increase of approximately 1.1°C (IPCC, 2023). To limit the future warming, it is being widely acknowledged that in addition to immediate reduction in greenhouse gas emissions, excess CO₂ needs to be actively removed from the atmosphere through carbon dioxide removal (CDR) methods. One promising CDR approach is Ocean Alkalinity Enhancement (OAE), which involves the addition of alkaline mineral to the ocean to enhance the oceanic uptake of atmospheric CO2 and is subsequently stored as dissolved inorganic carbon (DIC) over long periods. In addition to CO2 removal, OAE may also help mitigate ocean acidification by increasing the pH of water. Despite its potential, significant uncertainties remain regarding the feasibility, effectiveness, and environmental implications of implementing OAE at a global scale. To address these knowledge gaps, we conducted mesocosm experiments in the coastal waters of the Arabian Sea. These experiments aimed to investigate the effects of OAE on the carbon (C) and nitrogen (N) biogeochemical cycles within the marine ecosystem. In this seminar I will present some preliminary findings on how OAE influences carbon and nitrogen uptake rates in the coastal regions of the Arabian Sea.

Anatomy of Monsoon Break Spells: A Probabilistic Approach

Date: 2025-04-08
Speaker: Mr. Akash Ganguly
Venue: Ground Floor Lecture hall

Abstract

The Indian Summer Monsoon (ISM) is vital to India’s economy, and is intrinsically linked to the dreams and aspirations of over a billion people residing in the Indian subcontinent. Several causal mechanisms operating at differing spatio-temporal scales dictate the ISM performance, driving large inter-annual variability. Since the turn of the century, there has also been a conspicuous rise in both the frequency as well as intensity of extreme events, marking a discernible shift from the climatological trends. Such events have significant consequences necessitting the need for improved understanding of the causal mechanisms, as well as improved forecast skill for efficient water resources management. One such type of climatic extremes: the ‘monsoonal breaks’ are marked by a pause in the ISM synoptic system, resulting in reduced overall rainfall, and are accompanied by suppressed convection over the Monsoon Core Zone (MCZ), extended dry periods, heatwaves, and severe droughts as a direct consequence. However, the spatio-temporal pattern of rainfall distribution over the MCZ exhibit significant variability. Due to this inherent unpredictability and randomness, analyses often focus on aggregated rainfall data to discern broader trends and patterns. In this study, we dmonstrate that the seemingly random pattern of rainfall, when analysed at small (1̊X1̊) spatial scales is indeed information rich, which can be efficiently churned out with the help of simple statistical tools. We find that the divergence of the rainfall distribution from the climatological trend exhibits symmetries. This information, which is otherwise averaged out can be leveraged to gain novel insights into the underlying causal mechanisms, thereby contributing to improved skill of forecasting extended monsoonal breaks. We extend the analysis to map the rainfall anomalies to the corresponding anomalies in the mean wind field, thereby identifying the dominant pathways of anomaly propagation and further extending the possible scope of forecasting such precipitation extremes.

Habitat Selection by Early Humans in the Indian Subcontinent

Date: 2025-04-01
Speaker: Ms. Nandini Sharma
Venue: Ground Floor Lecture Hall

Abstract

The dispersal of our species out of Africa is believed to have occurred in multiple phases from the middle to late Pleistocene. Earliest fossil evidences for this migration of Homo sapiens is documented around 200-100 kya. These dispersals are influenced by the climate shifts, which shaped their habitats during migration. According to the Southern Dispersal Hypothesis, the dispersal of Homo sapiens from Africa into South Asia (130–75 kya) coincided with periods of favorable monsoon-driven green corridors, which influenced migration pathways and habitat selection. In this seminar, we will explore hominin habitat selection patterns by reconstructing woody cover along these dispersal routes using pedogenic carbonates as a vegetation proxy, providing insights into the environments they might have encountered and adapted.

Banded Iron Formations: Archives of Precambrian ocean-atmospheric redox conditions

Date: 2025-03-25
Speaker: Dr. Ajay Dev Asokan
Venue: Ground Floor Lecture Hall

Abstract

Banded Iron Formations (BIFs) are chemical sedimentary rocks with alternating silica and iron-rich bands. The composition of well-preserved BIFs records the seawater composition from which they precipitated and hence, can be used to infer the evolution of Precambrian ocean, ocean-atmospheric redox conditions as well as the emergence of continental crust. Based on associated litho units, BIFs are classified mainly into two variants, i.e., Algoma-type BIFs, that are associated with volcano-sedimentary sequences and Superior-type BIFs, that are associated with clastic sediments. In this presentation, I’ll discuss about different views on BIFs, including the origin of their banding, primary mineralogy and post-depositional alteration, with a focus on trace element compositions of Superior-type BIF from the Bastar Craton and Algoma-type BIF from the Dharwar Craton. The BIFs from the Bastar Craton records Archean seawater compositions, while those from the Dharwar have been significantly modified by post-depositional alteration.

Echoes of the Ancient Earth: A Quarter Century of Exploring the Vindhyan Basin’s Secrets

Date: 2025-03-04
Speaker: Dr. Jyotiranjan S. Ray
Venue: Ground Floor Lecture Hall

Abstract

The first known animal life on Earth dates back to 630 million years. However, in 1998, a couple of fossil discoveries shook the geoscience world with their spectacular claims of the presence of advanced animal life in rocks of the Vindhya mountains that were generally considered to be older than 1100 million years. These findings sparked intense controversies about their legitimacy and the host rocks' ages. We took up the challenge of dating these rocks deposited in India's largest Proterozoic sedimentary basin. In the last 25 years, we have not only been able to resolve the chronology of the Vindhyan Supergroup, but also made many significant contributions to the study of regional stratigraphy and environment, ocean chemistry and tectonics during the Proterozoic. In the talk, I shall share some of our important findings.

Health risks of air pollution in a warming climate: Current evidence and New directions

Date: 2025-02-26
Speaker: Dr. Sagnik Dey
Venue: Ground Fllor Lecture Hall

Abstract

Air pollution has been identified as the leading environmental health risk globally. In India, air pollution has been identified as the second largest health risk after maternal and child malnutrition. Health risks attributable to air pollution require robust exposure estimates, sociodemographic conditions and background disease rates. The Global Burden of Disease (GBD) Study has provided a robust framework to estimate the health burden of air pollution. However, the current estimates, available at state levels, have two critical assumptions. First, the risk is considered to be uniform across the composition, neglecting the issue of particle toxicity. Second, the exposure-response functions are derived from cohorts primarily conducted in developed countries. Lack of robust exposure data hindered the generation of India-specific exposure-response functions for non-communicable diseases. In this talk, I will demonstrate the recent advancements in exposure modelling and how such data is being used for health studies, addressing these two aspects. I will also highlight the complex pathways between air pollution and climate and how the air pollution attributable burden is expected to change in future. My talk will demonstrate the urgent need for a collaborative and systematic approach to understand and minimise environmental health risks in India.

Biogeochemistry of the Arabian Sea since JGOFS

Date: 2025-01-28
Speaker: Prof. Sanjeev Kumar
Venue: Ground Floor Lecture Hall

Abstract

The Arabian Sea is one of the most productive oceanic basins of the world. Most of our understanding related to physical, chemical and biological aspects of the Arabian Sea was developed during the Joint Global Ocean Flux Studies (JGOFS) program in the early 90s. This talk will delve upon some of the landmark findings of that era and progress made, if at all, since then.

Exploring the Dynamics of Oxygen Minimum Zones in the Bay of Bengal over the last 25 ka

Date: 2025-01-21
Speaker: Dr. Deepak Kumar Rai
Venue: Ground Floor Lecture Hall

Abstract

Anthropogenic warming has significantly reduced oceanic oxygen levels, raising concerns about the expansion of Oxygen Minimum Zones (OMZs) and their impact on marine habitats. The northern Indian Ocean hosts one of the world's three major OMZs, with pronounced oxygen-deficient conditions in the northeastern Arabian Sea. In this region, dissolved oxygen levels drop below 10 nM at intermediate depths, intensifying anaerobic processes such as denitrification and ammonium oxidation (anammox). These processes contribute to the loss of bioavailable nitrogen and nitrous oxide production—a potent greenhouse gas. In contrast, while dissolved oxygen concentrations in the Bay of Bengal fall below 20 μM, evidence for nitrogen loss processes remains inconclusive. However, the Bay of Bengal OMZ is considered to be at a geochemical tipping point, where further oxygen depletion—driven by anthropogenic nutrient input or climate change—could amplify its role in the marine nitrogen cycle by triggering nitrogen loss processes. Natural mechanisms influencing OMZ variability, aside from global warming, remain poorly understood, likely due to limited observations that are already influenced by anthropogenic signals. Therefore, it is essential to explore long-term OMZ variations under diverse climatic conditions through paleo reconstructions, which can provide crucial insights into the natural variability of OMZs, aiding in more accurate future predictions. In this talk, I will discuss the current understanding of OMZ dynamics in the northern Indian Ocean and highlight key research gaps in the field.

Organic Matter Sulfurization Dynamics in Natural Systems

Date: 2025-01-15
Speaker: Dr. Tushar Adsul
Venue: Online

Abstract

The sulfurization of organic matter is a globally significant biogeochemical process with far-reaching implications for the Earth's carbon, sulfur, and oxygen cycles. This process has been a subject of intense investigation due to its role in several critical areas: (1) petroleum formation and quality, (2) the coupled global biogeochemical cycles of carbon, sulfur, and oxygen, (3) sedimentary microbial activity, and (4) the preservation of organic matter and its application in molecularly based paleoenvironmental reconstructions. Despite its significance, our understanding of organic matter sulfurization remains incomplete. One major challenge in unraveling the sulfurization process is the immense diversity of organic sulfur compounds in nature, which form via various pathways. Sulfur can be incorporated intramolecularly into organic molecules, forming cyclo-sulfur compounds such as thiophenes or thianes. Alternatively, sulfur can be added intermolecularly, leading to macromolecular moieties linked by C-Sx-C bonds. This diversity complicates efforts to establish universal mechanisms for organic sulfur formation. Another critical challenge lies in the complexity of sedimentary sulfur cycling, which involves both biological and abiological processes. The precise source of sulfur incorporated into organic matter is not well understood. Whether pore-water sulfide, polysulfides, elemental sulfur, or a combination of these sources contributes to the sulfurization process remains unclear. The interactions among these sulfur pools and organic substrates further add to the complexity of the system. The sulfurization process is particularly significant in anoxic environments, such as marine sediments, where sulfate-reducing bacteria generate hydrogen sulfide. This reactive sulfide interacts with organic matter, stabilizing it by forming sulfur-rich compounds. These compounds, such as thiophenes, are resistant to degradation and play a vital role in the long-term preservation of organic matter in sediments. Furthermore, sulfurization contributes to the formation of sulfur-rich petroleum and coal, such as the Paleogene Superhigh-Organic-Sulfur Coals of Meghalaya, India. Recent advancements in analytical techniques are opening new avenues for understanding the mechanisms of organic matter sulfurization. The use of sophisticated tools such as GC-MS/FID/FPD for organic sulfur compound identification, coupled with compound-specific sulfur isotope analysis (CSIA), enables researchers to trace sulfur fractionation at the molecular level. These techniques help establish precursor-product relationships and provide insights into the pathways of sulfur incorporation into organic matter.

Are humans now the dominant geological agent?

Date: 2025-01-08
Speaker: Prof. Stephen Tooth Dept. Geography & Earth Sciences Aberystwyth University, Wales
Venue: Ground Floor Lecture Hall

Abstract

The Anthropocene is a term that has been proposed to account for the arguably ‘dominant’, ‘overriding’ or ‘overwhelming’ role of human activities in shaping the Earth’s geological record. Some academics have argued that we have now exited from the Holocene (the present interglacial time division) and entered a new geological age, one now defined by humanity’s profound influence on Earth’s atmospheric, biological, and earth surface processes. Although a subcommittee of the International Commission on Stratigraphy (ICS) has recently decided that the Anthropocene will not become an official epoch in Earth’s geological timeline, the term itself will endure because for many people it encapsulates the sense that humans are now a fundamental part of the Earth system and integral to its processes. The Anthropocene proposal has many philosophical, ethical, moral and practical implications, and will continue to generate lively academic debate across the natural sciences, social sciences, humanities and arts, while also providing scope for greater public engagement with environmental decision making. Adopting a geoscience perspective, this talk will outline the case for and against an Anthropocene, and outline ways in which we might compare landscape shaping by human activities and natural processes.

Loss Pathway of organic Carbon in the Himalayan Permafrost Region

Date: 2025-01-07
Speaker: Rahul Kumar Agarwal
Venue: Ground Floor Lecture Hall

Abstract

Soil organic carbon (SOC) stored in permafrost regions represents a critical component of the global carbon cycle. Climate change significantly influences the distribution and dynamics of carbon across Earth's systems. It is widely believed that climate change is driving substantial carbon loss from high-latitude and high-altitude soils, including permafrost areas. However, the pathways through which soil organic matter is lost remain poorly understood, and the extent of older organic matter degradation, particularly in the high-altitude Himalayan permafrost regions, is not well quantified. To address this gap, we measured radiocarbon content in soil organic carbon, soil CO2, and soil CH4 across various depths of a peat profile located at approximately 4500 meters above mean sea level in the Sikkim Himalayas. In this talk I will discuss about the basics of mountain permafrost, radiocarbon dating of soil methane, and loss pathway of organic carbon in the permafrost region.

2024

Speleothem Paleoclimatology: Insights from Clumped and Triple Oxygen Isotopes

Date: 2024-12-24
Speaker: Ms. Aishwarya Singh
Venue: Ground Floor Lecture Hall

Abstract

A multitude of creditable terrestrial paleoclimate reconstructions have been done using oxygen isotope ratios in speleothems based on the temperature dependency of the carbonate-water isotope exchange equilibrium. However, these interpretations remain inadequate due to improper constraints on drip-water isotopic compositions and possible kinetic isotopic effects. Moreover, the variations in the oxygen isotopes of speleothems are affected by both temperature and precipitation, making it challenging to estimate their individual contributions. Clumped isotope thermometry, based on the abundance of 13C-18O bonds, is capable of constraining the growth temperature of carbonates independent of the isotopic composition of drip water. The clumped-derived temperature can be combined with oxygen isotopes to constrain the paleo-temperature and paleo-precipitation values, subject to the maintenance of thermodynamic equilibrium. To validate the latter, triple oxygen isotopes will be analysed alongside clumped isotopes in modern speleothems. Triple oxygen isotopes also present a potential strategy to decipher the various fractionation processes from the moisture source, en route to its final sink. In this seminar, I will discuss how these emerging techniques can be used to significantly improve our understanding of the paleoclimate beyond what was possible with the conventional methods.

Terrestrial Recycling and its linkages to Meteorology: Insights from stable water isotopes in vapor in conjunction with Machine Learning, at a high-altitude site in western India

Date: 2024-12-17
Speaker: Akash Ganguly
Venue: Ground Floor Lecture Hall

Abstract

The implications of a warming climate have raised awareness towards potential hydrological challenges, with a conspicuous rise in both frequencies, as well as intensity of extreme events. Moisture recycling, accounting for ~67 (40) % of the net terrestrially sourced precipitation globally (India), is a vital component of the water cycle. The recycled moisture is primarily contributed via two major sources- i) direct evaporation from surface reservoirs ii) transpiration from dense forests. However, delineating their relative contributions has proved challenging using conventional tools. In this study, we leverage stable water isotopes in vapor from the highest point in western India to track moisture transport, and constrain the role played by the regional meteorology in governing terrestrial recycling during pre-monsoon. The study location (Gurushikhar, Mt. Abu) perfectly aligns with our objective, with it being a natural bio-diversity hotspot, with ~288 sq. km. of densely forested terrain, and very low levels of air pollution. A novel statistical-machine learning framework is developed to quantitatively infer the non-linear relationships, governing the high-dimensional coupled land-atmospheric system. Here, we find 1) A strong inverse relationship between wind-speed, and deuterium excess, suggesting increased role of kinetic processes. 2) Dominant role of valley recycling, with ~30-40 % contribution from transpiration alone. 3) Elevated levels of tropospheric ozone (> 65 ppbv.) suppressing transpiration rates, resulting in up to 2 ‰ depletion in δ18O. 4) Possible signs of upper atmospheric coupling via waves, extending to ~ 10 km (above msl) 5) Development of a robust, accurate ML model with mae ~ 3.50 ‰ in δ18O, using only meteorological inputs. This study highlights the benefit in using stable water isotopes in vapor, since they can be leveraged to better understand linkages between terrestrial recycling, and regional hydro-meteorology. This brings to light the important role played by the dense vegetation cover around Mt. Abu, acting as nature’s pump and enhancing terrestrial recycling. This is of even more significance in the tropics, given the rapid loss of wetlands, and forest cover in the developing countries located in the region.

Estimation of fine particulate matter and aerosol acidity at Ranchi, India

Date: 2024-12-10
Speaker: Dr. Abisheg Dhandapani
Venue: Ground Floor Lecture Hall

Abstract

The annual PM2.5 concentration was 67 ± 46 μg m-3 at Mesra, Ranchi, varying seasonally. There was a significant underestimation in MERRA-2-derived PM2.5, and machine learning techniques were used to overcome the challenge. Further, water-soluble inorganic ions accounted for 50.5% of PM2.5, and the annual mean pH estimated using ISORROPIA was 1.97 ± 0.8 units. Secondary aerosols formation (45%) and a combination of coal combustion and dust sources (10%) were the primary sources of PM2.5 identified using PCA.

Major ion and trace element geochemistry of the Mahi River

Date: 2024-12-03
Speaker: Dr. Shailja Singh
Venue: Ground Floor Lecture hall

Abstract

River Mahi drains through semi-arid regions of Western India and is the third-major river draining into the Arabian Sea. This work presents an extensive dataset on the major ion and trace element (TE) geochemistry of the Mahi River which forms a part of our continued geochemical investigation on the role of the medium-sized river system in transporting dissolved loads to the Arabian Sea. The major ion data was used to get detailed insights into sources of major ions and their relative contributions by a forward model; seasonal, spatial, and inter-annual variability of these ions, weathering rates, and associated CO2 drawdown of the basin. Likewise, the trace element data was analyzed to identify the role of natural and anthropogenic sources in contributing to TE distribution and understand their spatial and temporal variability. With TEs' obvious link to water quality issues and human health, this work also attempted predictive modeling of pollution indices by Machine Learning models. In this talk, the important results borne out of the work will be discussed.

Understanding the Ocean Conditions during the Neoproterozoic: Depositional Environment, Primary Productivity and Hydrographic Setting of Vindhyan Basin

Date: 2024-11-26
Speaker: Mr. Deependra Singh
Venue: Ground Floor Lecture hall

Abstract

Neoproterozoic Ocean is considered as a profound interval of global environment changes in the geological history. To asses the redox history and primary productivity in the Neoproterozoic ocean is crucial for better understanding of past climate and the changes happened that time. In this talk, I will discuss about utilization of various trace elements and Mo isotopic composition as proxy to understand the paleo environmental conditions of Neoproterozoic upper Vindhyan basin.

Holocene climate reconstruction from the southern Arabia: A tale of monsoons, humans, and lakes

Date: 2024-11-19
Speaker: Mr. Shah Parth
Venue: Ground Floor Lecture hall

Abstract

The Arabian Desert is considered climatic sensitive zone which is susceptible to changes subtle global atmospheric circulation. The unique geographical location of this region can provide an excellent opportunity to understand the interactions between the monsoons, zonal migrations of the Inter-Tropical Convergence Zone (ITCZ) and regional environmental change. Thus, this project aims to provide the lacking high-resolution information on climate variability in the southern margins of the Arabian Desert through multiproxy approach carried out on a sediment core retrieved from Lake Karif Shawran and paleolake Gayal el Bazal, southern Arabian Desert. The multi-proxy approach includes granulometry analysis, elemental geochemistry, TOC/TIC, ostracod, biomarkers (n-alkanes, Pr/Ph, PAHs, Coprostanol, Stigmastanol and compound specific isotopes). Changes in the lithology and related measured proxies clearly indicate alternating wet and dry periods throughout the last ~4400 years. The wet climatic episodes coincide with globally recognized climate events including the Medieval Climate Anomaly (MCA), and the Roman Warming Period (RWP), whereas the dry intervals occurred during the Little Ice Age (LIA), Late Antique Little Ice Age (LALIA), and the ‘4.2k event’. Overall, we have reconstructed the late Holocene in the southern Arabian desert and discussed the impact of climate on the regional environment and lake system. Moreover, estimating the impact of climate on humans in the region by differentiating climatic signals from anthropogenic signals. The study provides key insights into the main driving forcing behind hydroclimatic changes in the region and sheds light on the role of the ITCZ vis-à-vis monsoonal dynamics. Additionally, it lays the foundation for better understanding long-term seasonal predictions for Southern Arabia.

The Mesoarchean Gabbro anorthosite suite: a window to understand the Mesoarchean crustal formation.

Date: 2024-11-12
Speaker: Ms. Mudita Tater
Venue: Ground Floor Lecture hall

Abstract

Gabbro anorthosite rocks preserved in Archean terranes give an important view of early earth geodynamic processes. One such Gabbro anorthositic complex is also reported from the Singhbhum craton. These Mesoarchean rocks preserves the crustal record from Hadean to Archean. In this talk, I will summarize the work done till date on these Mayurbanj Gabbro anorthosite rocks and upbring the current controversies or current research gaps within this area. I will also talk about the potential lunar analogue site. Whether the present gabbro anorthosite complex can be established as potential lunar analogue site.

Graphitization for Radiocarbon Dating with AGE3: Development & challenges

Date: 2024-10-22
Speaker: Mr. Ankur Dabhi
Venue: Ground Floor Lecture Hall

Abstract

Radiocarbon dating is a widely used dating technique in earth sciences and archaeology. 1MV Accelerator Mass Spectrometer at PRL has been successfully measuring radiocarbon in variety of natural samples. Graphitization is a crucial step in radiocarbon dating, enabling the transformation of carbonaceous samples into a form suitable for AMS. Graphitization with Automated Graphitisation Equipment(AGE-3) is an innovative approach designed to enhance the efficiency and accuracy of graphitization. In this talk, I will discuss the procedural advancements and optimization of graphitization with AGE3,the challenges and some results showing the quality of graphite produced with AGE-3.

Molecular Characterization of Brown Carbon Using Fluorescence Spectroscopy

Date: 2024-10-08
Speaker: Dr. Devprasad M.
Venue: Ground Floor Lecture Hall

Abstract

On a global scale, aerosols cool the atmosphere by scattering incoming solar radiation. However, absorbing aerosols such as black carbon (BC), brown carbon (BrC), and dust can significantly alter this effect on a regional scale. Radiative forcing (RF) estimates for BC and dust are relatively straightforward due to their simpler structures and primary emissions. In contrast, brown carbon is more complex, with a wide variety of forms and both primary and secondary sources. A detailed treatment of BrC is often lacking in climate models. Observations suggest that the RF due to BrC can be 20–40% of the RF due to BC, with even higher values reported for biomass-burning-dominated regions. A significant spatial and temporal variations have been observed in the RF of BrC, necessitating their characterization on molecular level. Various methods are used for this purpose. Among these, fluorescence spectroscopy stands out for its high sensitivity, repeatability, minimal sample preparation, non-destructive nature, and ease of operation. In this talk, I will discuss the basics of brown carbon and how fluorescence spectroscopy can be used to identify its dominant species.

Riverine carbon and nitrogen biogeochemistry in critical zone sites in the western India

Date: 2024-09-24
Speaker: Mrs. Sangeeta Verma
Venue: Ground Floor Lecture Hall

Abstract

पश्चिमी भारत में महत्वपूर्ण क्षेत्र स्थलों में नदी कार्बन और नाइट्रोजन जैव-भू-रसायन

Unraveling the mysteries of Harappan Ernestite: A Geochemical prospective

Date: 2024-09-10
Speaker: Dr. Milan Mahala
Venue: Ground Floor Lecture Hall

Abstract

The Harappan (Indus Valley) civilization, one of the most sophisticated Bronze Age civilizations, survived for over two millennia (5300-2600 yrs BP) in the alluvial plains of the northwestern Indian subcontinent. The Harappan Gujarat was the center of bead manufacturing activities and inter-regional trade networks. The Harappans, known as master crafters and traders of their period, manufactured beads of agate, carnelian, jasper, terracotta, etc., for ornaments and trading purposes. Besides thousands of beads discovered, numerous stone drill bits have also been found from many Harappan sites. These drill bits are believed to have been ground out from certain hard stones, which have been named Ernestites. The origin of Ernestite remains an enigma because it does not resemble any natural rock. If produced artificially, what raw materials were used, and what process was followed in their making? Since deciphering the origin of Ernestite is essential for understanding the manufacturing abilities of these Bronze Age people, we undertook a detailed petrographic, geochemical, and isotopic study of the Ernestites from multiple sites in Gujarat. In this seminar, I shall discuss our findings.

Advances in integrating petrochronological and geodynamic models of high-grade metamorphic systems

Date: 2024-09-03
Speaker: Prof. Chris Clark
Venue: Ground Floor Lecture Hall

Abstract

The field of metamorphic petrology has undergone several evolutions beginning with the recognition that certain groupings of minerals reflect thermobaric conditions (index minerals and the facies concept of Eskola). This was followed by the realisation that these same minerals partition elements in a systematic way allowing temperatures and pressures to be quantified (classical thermobarometry) and that whole systems can be mapped in thermodynamic space to generate phase diagrams that capture the evolution of a rock (the pseudosection approach of Holland and Powell in the late 80’s early 90’s). These evolutions have progressed in lock step with the evolution of analytical capabilities that facilitate the collection of chemical (electron microprobes) and isotopic (SIMS and laser ablation mass spectrometry) information from mineral grains that enable the pressure-temperature-time (P–T–t) histories of rocks to be constrained (the field of “Petrochronology” pioneered by researchers such as Daniela Rubatto and Brad Hacker in the early 2000’s). Despite these advances we are still faced by the challenge that the rocks we collect and analyse provide only a snapshot of the journey a single sample takes through an orogenic (mountain building) cycle. A potential path to address this issue is the application of diffusion geospeedometry where the zoning profiles of different mineral can be used to construct a detailed temperature–time history for rocks – as always, a key mineral in this endeavour is garnet. Diffusion chronometry coupled with thermochronometers and 4+ cation thermometers allow more detail on P–T-t paths to be constrained. However, there now exists a dichotomy in the results produced by each approach wherein diffusion based geospeedometry studies generally yield timescales that are orders of magnitude faster that the classical U–Pb geochronological investigations. Begging the question how much of an orogenic evolution are we capturing and are orogenic events long and slow or constructed through a series of pulses? In this talk I will present progress towards the integration of phase diagram tools, diffusion processes, geochronological and petrological datasets with geodynamic models to constrain the evolution of lower crustal rocks during orogenic cycles. This approach, in our opinion, is the obvious next evolution in metamorphic petrology and is being enabled by the concomitant advances in both open-source geodynamic codes, in this case Underworld, and increasing computational power (both at the desktop and supercomputer level). These developments enable individual researchers to develop and test multiple scenarios to see what is plausible based on real geological data and the physics of rock systems at their desk rather than waiting for access to scarce resources such as access to national supercomputer facilities

THE MARINE BIOGEOCHEMICAL CYCLE OF SILICON: INSIGHTS FROM SILICON STABLE ISOTOPES

Date: 2024-08-20
Speaker: Mr. Mahesh Gaddam
Venue: Ground Floor Lecture hall

Abstract

Silicon (Si) is the second most abundant element in the Earth’s crust and is an important nutrient in the ocean. The global Si cycle plays a critical role in regulating primary productivity and carbon cycling on the continents and in the oceans. Silicon has a complex biogeochemical cycle, interacting with other globally important elemental cycles (e.g Carbon and Nitrogen). Dissolved silicon (DSi) and its isotopes (δ30SiDSi) are powerful tool for understanding biogeochemical and ocean processes. In this talk, an outline of Si cycle, along with the measurement methods and application of Si isotope composition in seawater will be discussed.

Paleo-pCO2 Reconstructions in the Equatorial Indian Ocean using Boron Isotopic Records of Planktonic Foraminifers

Date: 2024-08-13
Speaker: Dr. Sanjit Kumar Jena
Venue: Ground Floor Lecture hall

Abstract

Carbon dioxide (CO2) constitutes around 80% of the global greenhouse gases in the present atmosphere significantly contributing to global warming and its major climatic consequences such as the melting of ice sheets, sea level rise, ocean acidification and extreme weather events. The global ocean with its substantial storage and exchangeability plays a crucial role in regulating the widespread distribution of atmospheric pCO2, thereby influencing regional and global climatic changes. Reconstruction of past oceanic CO2 is essential to understand the temporal evolution of the climate, helping predict its future trends. Boron isotopic records in planktonic foraminifers offer a key method to reconstruct past oceanic CO2 records. However, precise measurement of boron isotopes has remained a major challenge, especially from mass limited foraminifera samples subject to contamination and isotopic mass fractionation issues. This talk will highlight the potential implications of paleo-pCO2 reconstructions in the Equatorial Indian Ocean to the global paleoclimatic research, and glimpses of the methodological advancements in extraction and precise measurement of boron isotopes in planktonic foraminifera samples.

Insights into High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS): Principles, Components, and Applications

Date: 2024-08-06
Speaker: Mr. Rohit Meena
Venue: Ground Floor Lecture hall

Abstract

High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS) represents a significant advancement in atmospheric chemistry and aerosol science. This technology combines high-resolution mass spectrometry with time-of-flight to measure real-time, non-refractory, size-resolved particulate chemical composition and mass. It facilitates a deeper understanding of aerosol dynamics, source apportionment, and their impacts on air quality and climate. In this talk, I will cover the fundamentals of HR-ToF-AMS, its key components, and their functions and its application.

Ocean Alkalinity Enhancement: A redemption?

Date: 2024-07-30
Speaker: Ms. Shreya Mehta
Venue: Ground Floor Lecture Hall

Abstract

The increased global emissions of greenhouse gases due to anthropogenic activities have led to an increase in climate warming, with present-day mean atmospheric temperature reaching 1.1°C above the preindustrial level. The alarming increase in greenhouse gas emissions has motivated the discussion of climate change and the need to limit the emissions so as to limit the warming below 1.5°C or 2.0°C by the year 2100. To combat this and limit the warming below 1.5°C or 2.0°C by the year 2100, along with reducing CO2 emissions, Negative Emission Techniques (NETs) or Carbon Dioxide Removal (CDR) methods are required. Ocean Alkalinity Enhancement (OAE) is one of the NETs, but uncertainties surround the feasibility and consequences of implementing OAE on a global scale. To address this, we conducted mesocosm experiments in the coastal waters of the Arabian Sea. In this talk, I shall be discussing some of the preliminary findings from these experiments.

Graphitisation for Radiocarbon Dating : Advancement with AGE-3 & challenges

Date: 2024-07-23
Speaker: Mr. Ankur Dabhi
Venue: Ground Floor Lecture Hall

Abstract

Radiocarbon dating is a widely used dating technique in earth sciences and archaeology. 1MV Accelerator Mass Spectrometer at PRL has been successfully measuring radiocarbon in variety of natural samples. Graphitisation is a crucial step in radiocarbon dating, enabling the transformation of carbonaceous samples into a form suitable for AMS. Graphitisation with Automated Graphitisation Equipment(AGE-3) is an innovative approach designed to enhance the efficiency and accuracy of graphitisation. In this talk, I will discuss the procedural advancements and optimization of AGE3, pre-treatments for different organic and inorganic samples which streamlines carbon extraction and reduces contamination ,the challenges with AGE3 and some results showing the quality & reliablity of graphite produced with AGE-3.

Late Quaternary Turbidite deposits in the eastern Bay of Bengal

Date: 2024-07-16
Speaker: Dr. Prajith
Venue: online

Abstract

The Bay of Bengal is an enormous repository of continent-derived sediments stored in the world’s largest submarine fan, the ‘Bengal Fan’. Huge loads of sediments from the Himalayas, Indo-Burman ranges, and Peninsular India were transferred to the deep sea through the submarine channels developed on the Bay of Bengal seafloor. Currently, only one channel is active in supplying sediment to the Bengal Fan, whereas other channels are disconnected (inactive) from the land. Much about the evolution of the fan and its controlling factors, particularly the timings of major fluctuations in turbidite activity, is unknown. This work is based on sedimentological, geochemical, and Sr-Nd isotopic records from a gravity core collected from the now-defunct submarine channel E7 in the Bengal Fan to examine the roles of various environmental factors on the growth of the fan. Our results suggest that turbidite deposition through channel E7 was active during 27 to 12 kyrs and hemipelagic sedimentation started from 12 kyr BP to present. This work highlights the complex interplay between the climate and coastal geomorphology in the growth of the fan.

The cursed Eukaryotes!

Date: 2024-07-02
Speaker: Mr.Janaarthanan P A
Venue: Ground Floor Lecture Hall

Abstract

In spite of early rise of eukaryotic organisms about ~1800 million years ago, their diversification happened only after a billion year later. This retardation in evolution of eukaryotic organisms has been attributed to low atmospheric oxygen abundance and nutrient limited conditions in the oceans of that time. In this talk, I will be discussing the nitrogen isotope dynamics during this period and evaluate its impact on eukaryotic evolution.

Radiocarbon in soil organic carbon and soil CO2 in a semi-arid tropical region of western India: implications to tropical soil carbon dynamics

Date: 2024-06-25
Speaker: Mr. Ranjan Mohanty
Venue: Ground Floor Lecture hall

Abstract

The exchange flux between the soil and the atmosphere is the largest carbon flux (~110×1015 g/yr) making it one of the most important components of global climate change on decadal to century scales. Therefore, it is very important to understand the dynamics of carbon in soil as a slight imbalance in the flux can drastically change the climate. We measured radiocarbon in soil organic matter and soil CO2 to estimate SOC turnover time and sources of CO2 in soils in forests and agricultural lands of Gujarat to assess the role of climatic conditions on SOC turnover time and identify major contributors responsible for CO2 emission from the soil. Results indicate that SOC contents and turnover times in tropical semi-arid soils are significantly influenced by precipitation, vegetation density and land use changes which I will discuss in this talk.

Origin of granitoids from the Chitradurga greenstone belt: Constraints from geochemical modelling

Date: 2024-06-13
Speaker: Dr. Sibin Sebastian
Venue: Online

Abstract

The Chitradurga greenstone belt was intruded by potassic granite and low-K trondhjemite during the Neoarchean. Understanding their origin has implications on reworking of crust and stabilization of the western Dharwar craton. Geochemical and Nd isotopic data suggest partial reworking of different pre-existing crustal lithology. Tonalite-Trondhjemite-Granodiorite (TTG) gneisses represent the most abundant lithology and basement rocks of the craton. Partial melting of TTG gneisses and differentiation of melt resulted in compositionally different potassic granite. Simultaneously, partial melting of metabasites resulted in the formation of trondhjemite. The extent of melting and differentiation are quantified through numerical modelling. Quantitative modelling attests low temperature melting of crustal rocks at different depths and the modification of melt by fractional crystallization during ascent for the formation of the studied rock types. Such reworking event was likely triggered by mafic underplating and H2O dominated fluid flux.

Insights into the major sources and formation pathways of p-NO3- using dual isotope proxy

Date: 2024-05-30
Speaker: Ms. Chandrima Shaw
Venue: Ground Floor Lecture Hall

Abstract

NOx plays a significant role in atmospheric chemistry, influencing air quality, human health, climate change. It contributes to the formation of particulate matter (p-NO3-), tropospheric ozone, acid rain, and smog, while also serving as a nutrient for both oceanic and terrestrial ecosystems. Despite its significant role, the sources of NOx and its conversion pathways to p-NO3- remain poorly understood both globally and regionally (South-East Asia). Dual isotopes (δ18O and δ15N) of p-NO3- can serve as a powerful tool to understand the formation pathways of p-NO3- and sources of NOx. In this talk I will discuss the application of dual isotopes (δ18O and δ15N) of p-NO3- in understanding the atmospheric chemistry and sources related to p-NO3- and NOx

Scientific computing with open source: An in-house developed Software for PRL-AURiS Data Exploration

Date: 2024-05-21
Speaker: Ms. Pratheeksha Nayak
Venue: Ground Floor Lecture Hall

Abstract

Use of open source tools can play a pivotal role in scientific computing by providing robust, flexible solutions for various data analysis tasks. Python, with its extensive libraries and frameworks, is particularly well-suited for scientific computing. SPADE (Software for PRL-AURiS Data Exploration) is a web application developed using Python to enable computation of radiocarbon age estimates using the raw data from the 1 MV Accelerator Mass Spectrometer(AMS) at PRL. It is the first step in the development of a software suite for various data treatment and analysis protocols that can be implemented on data obtained from AMS. SPADE has an interactive interface and can be deployed anywhere without the need to install Python or any of its packages. In this talk, I shall discuss the nature of the raw data, workflow of the data processing pipeline, the details of implementation and the future objectives of SPADE.

Physical and Chemical Properties of Stratospheric Aerosols using Balloon Borne Instruments

Date: 2024-05-14
Speaker: Dr. Gwenael Berthet
Venue: Online

Abstract

Aerosol particles of the stratosphere are key components of the Earth’s radiative balance and of the processes controlling the ozone layer. They have various sources, both of anthropogenic and natural origin, more or less sporadic like volcanic eruptions and intense wildfires. We will present an overview of the knowledge of stratospheric aerosols regarding their chemical and physical properties with a specific focus on in situ observations from balloon-borne instruments (optical particle counters, backscatter sondes, aerosol collectors) launched from various locations on the globe. These measurements, together with space-borne observations and chemistry-transport model simulations, show particles of different sizes and types like sulphuric acid droplets, organics, nitrates, meteoric material with proportions dependent on seasons and regions. Specifically, we will show results from balloon campaigns (called BATAL) conducted by TiFR in India from Hyderabad.

Atmospheric Water Vapor Dynamics at Guru Shikhar, Mt. Abu, the highest point of the Aravalli Range, Rajasthan

Date: 2024-04-30
Speaker: Mr. Virendra R. Padhya
Venue: Ground Floor Lecture Hall

Abstract

The stable isotope ratios (δ18O and δD) of water vapor are used to characterize continuous variations in large-scale and boundary-layer atmospheric processes. We carried out continuous measurements of δ18O and δD in Ground level water vapor at Gurushikhar, Mount Abu, Rajasthan, from Feb 2023 to Feb 2024 to understand how large-scale and local atmospheric processes influence variations in water vapor δ18O and δD on daily to seasonal time scales. Most of the variabilities are associated with the transition between the Indian summer monsoon and the westerlies, which transport distinct moisture to the study area. The local temperature, specific humidity and boundary layer height impact the diurnal variations in water vapor δ18O. The data reveal interesting seasonal and diurnal atmospheric phenomena which will be discussed in the talk.

Enhancing Geological Insights: Information-Theoretic Analysis of REE Concentrations for Rock Discrimination and Source Provenance Studies

Date: 2024-04-23
Speaker: Mr. Shivansh Verma
Venue: NanoSims Hall

Abstract

In the past decade, the application of information-theoretic methods has substantially enhanced our understanding of intricate complex processes. In this talk, I will discuss one such method based on Kullback-Leibler (KL) divergence, which utilizes Rare Earth Elements (REEs) concentrations to identify the similarities and differences among co-existing rocks of any given complex. In case of igneous rocks, the order of KL-divergence effectively distinguishes between rocks that have undergone different degrees of physical differentiation during their genesis. Moreover, when employed in conjunction with isotopic data, the method can yield robust constraints for source provenance studies in the context of sedimentary rocks. I will also discuss the differences between the KL-divergence method and Principal Component Analysis (PCA), highlighting the unique information provided by the former

Solar Wind Ion Spectrometer (SWIS), A miniature mass spectrometer onboard the Aditya-L1 mission: Objectives, Configuration, and Development

Date: 2024-04-09
Speaker: Mr. Pranav Adhyaru
Venue: NanoSims Hall

Abstract

The Solar Wind Ion Spectrometer (SWIS) is a subsystem of the ASPEX (Aditya Solar Wind Particle Experiment) payload, developed by PRL and one of seven payloads onboard the Aditya-L1 mission. The Aditya-L1 was launched in September 2023 and reached the Sun-Earth system's first Lagrangian point, L1, in January 2024. The primary focus of the ASPEX payload is to understand the Sun and solar wind processes as well as the acceleration and energization of the solar wind particles. ASPEX consists of two subsystems, SWIS and STEPS. The SWIS measures the particles in the energy range from 100 eV to 20 KeV, whereas STEPS works in 20 KeV to 5 MeV. SWIS is a miniature mass spectrometer customized for the space application to understand the origin of solar wind (slow and fast wind) and supra-thermal ions, thermal anisotropy, turbulence, and arrival of ICME (Interplanetary Coronal Mass Ejection) and SIR (Stream Interface Region) at L1 for space weather science and applications. In this seminar, I will highlight the science and technical objectives and configuration of the SWIS experiment. The design and development aspects of the High Voltage Power Supplies and Front-End-Electronics will also be discussed. The SWIS subsystem was switched on in December 2023 during the cruise phase of the Aditya-L1 for the performance verification of all its units. The data acquired during this phase and the preliminary results will also be presented.

A geochemical study on the Kali River with emphasis on chemical weathering and anthropogenic impacts, south-western India

Date: 2024-04-02
Speaker: Dr. Arun Kumar
Venue: Online

Abstract

Small mountainous rivers (SMRs) in tropical regions are some of the most active sites for chemical weathering and associated CO2 consumption. Studies have revealed the incredibly high rates of chemical weathering in these areas. Geochemical sampling on the Kali River Basin (KRB) revealed that silicate weathering is the major contributor to cation yields, while carbonate weathering has a minor impact. These rates are among the highest reported for granitic-gneiss terrains in SMRs, emphasizing the importance of studying geochemical processes. The pollution effects on the riverine ecosystem are assessed by examining chemical and biological components. The findings of this study have important implications for environmental management and for the development of effective strategies to mitigate human activities' adverse impacts on riverine chemistry and the ecological health of the river and coastal areas.

Geochemical behaviour and cycling of Uranium and Molybdenum in the Ganga (Hooghly) river estuary, India

Date: 2024-03-19
Speaker: Dr. Rakesh
Venue: Online

Abstract

The study forms a detailed investigation of sources and processes involved in the geochemical cycling of selected redox-sensitive elements (U and Mo) in the estuary of the Ganga (Hooghly) River. Being dominated by monsoonal climate and characterized by large suspended sediment load, the Hooghly River estuary (HRE) provides an opportunity to study the impact of variable water discharge and suspended sediment concentration on the nature and magnitude of elemental cycling via solute-particle interaction in the estuarine mixing zone. We have investigated the chemical compositions of the (i) river/estuary water samples, (ii) coexisting suspended particulate matter (SPM), (iii) bed sediments, (iv) exchangeable phases of the sediments, (v) estuarine core sediments, and (vi) urban and industrial effluent waters. Specifically, we seek to determine if the estuary acts as a source or sink for these elements or if they behave perfectly conservatively. Investigation of the coexisting dissolved and solid phases allows us to evaluate the nature and intensity of solid-solution interaction processes in modifying the dissolved distributions of U and Mo. Using data of the dissolved, bulk SPM and its exchangeable phases in the mass balance calculations, it is evaluated whether the excesses (or deficit) of dissolved U and Mo are sustained by their complementary loss from (or gain onto) the suspended particulate matter. Furthermore, the role of tidally-induced resuspended sediments and suboxic diagenesis in the sediment column is brought out through the compositions of the bottom and core sediments. The data of industrial and urban effluents are utilized to assess the role of anthropogenic source(s) in supplying U and Mo. Finally, we evaluate the magnitude of modification of riverine dissolved fluxes of these elements due to the estuarine processes.

Large Submarine Groundwater Discharge from Karnataka Coast, Southwestern India: Quantification, Influencing Factors, and Ecological Implications

Date: 2024-03-12
Speaker: Dr. Lino Yovan
Venue: NanoSims Hall

Abstract

Submarine groundwater discharge (SGD) contributes a notable portion, ranging from 6-12%, of the total freshwater inputs to the global ocean and has immense implications in coastal zone management. In my presentation. I will discuss our study focused on delineating the SGD dynamics along the Karnataka coast, specifically its flow into the Arabian Sea. Employing subsurface seepage meters, the first of their kind, we quantified the fluxes of carbon, nutrients, and trace metals associated with SGD. Our findings reveal that the estimated SGD rates in this locale surpass those reported elsewhere globally, with the productivity of the coastal aquifer and monsoonal precipitation identified as primary influencers of SGD discharge mechanisms. By employing subsurface seepage meters, we achieved precise estimations of seepage rates, without the influence of tides and waves that traditional seepage meters face. Additionally, we observed that SGD flow dynamics are linked to inland hydraulic gradients and tidal fluctuations, along with the extensive coastal deposits. These findings emphasize the need for proactive coastal ecosystem conservation, especially amid escalating climate change and human activities.

Deglacial evolution in ventilation of the western equatorial Atlantic Ocean and its link to atmospheric CO2 changes

Date: 2024-02-27
Speaker: Dr. Partha Jena
Venue: NanoSims Hall

Abstract

The marine and atmospheric carbon pools are strongly linked to one another and the air-sea gas exchange processes considerably control the atmospheric CO2 budget. In this regard, Radiocarbon provides unique insights into the air-sea exchange and the Ocean’s ability to sequester atmospheric CO2. We combine results from Radiocarbon measurements of foraminifera specimens and intermediate complexity numerical model simulations to understand the role of the Atlantic Ocean and Atlantic Meridional Overturning Circulation (AMOC) in driving atmospheric CO2 changes. We reconstruct a ‘Radiocarbon ventilation age’ record from the intermediate depth western equatorial Atlantic (WEA) Ocean, which acts as a gateway for CO2 trapped in North Atlantic Deep Water (NADW) before getting released to the atmosphere in the Southern Ocean. The model simulation highlights a near-complete shutdown of AMOC during Heinrich Stadial (HS)-1, resulting in a poorly ventilated Atlantic Ocean that aligns well with the high B-P ventilation ages at our study site. On the contrary, the Atlantic Ocean was properly ventilated during North Atlantic interstadials i.e., the Holocene and the Bølling–Allerød (BA) resulting in low B-P ventilation ages. The high resolution (resolved at every 150 years) Radiocarbon ventilation age record focuses on the deglaciation period (~18 to 12 ka BP) during which multiple short-term (~200 years) CO2 overshoot events have been observed amid a steady CO2 rise. Concurrent with the CO2 overshoot events, we observe prominent ventilation age drops in WEA intermediate depths. A strong coupling between AMOC strength, atmospheric CO2 and North Atlantic temperature is observed during the 14.8 ka and the 11.7 ka events. On the contrary, in the case of the 16.3 ka event, the rise in atmospheric CO2 was not directly associated with AMOC strength. Nevertheless, it is plausible that the Southern Ocean remained a significant source of atmospheric CO2 during that period. In this presentation, our findings underlining the important role played by the Atlantic Ocean and AMOC in deglacial carbon cycle changes will be discussed.

Timekeepers in Earth Sciences: Application of U-Pb geochronology to earth and planetary processes

Date: 2024-02-13
Speaker: Dr. Amal Dev J
Venue: NanoSims Hall

Abstract

The application of insitu analytical techniques has garnered substantial attention in the past decades owing to its increasing potential in resolving many fundamental problems in earth and planetary processes. Recent advancements in the application of texturally controlled laser ablation (LA) ICPMS analysis of accessory mineral phases in rocks have added significantly to the petrochronological studies owing to their high spatial resolution, fast data acquisition, improved precision-accuracy, and cost-effectiveness. The insitu LA-ICPMS studies have been highly explored to unravel the geodynamic evolution of sedimentary basins; timing, nature, and duration of crust forming and crust recycling events; tectonothermal evolution of polydeformed terranes and isotopic characteristics of planetesimal bodies etc. This is in conjunction with the fact that individual accessory phases in the samples can fingerprint discrete events due to their variable response to physio-chemical conditions. Among the different isotopic systematics, the application of insitu U-Pb geochronology combined with relevant isotopic information has been widely recognized as the most robust tool to gain insights into these processes. Some relevant applications of U-Pb geochronometry along with specific case studies will be addressed in the talk with future prospects.

Extreme Indian Monsoon states lead to oceanic productivity collapses

Date: 2024-02-07
Speaker: Dr. Kaustubh Thirumalai

Abstract

Indian summer monsoon (ISM) hydrology fuels biogeochemical cycling across South Asia and the Indian Ocean, exerting a first-order control on food security in Earth's most densely-populated areas. Despite projected ISM intensification under greenhouse forcing, large uncertainty surrounds future Indian Ocean stratification and primary production -- processes key to the health of already vulnerable fisheries in the region. Here, we present centennially-resolved records of ISM runoff and marine biogeochemical fluctuations in the Bay of Bengal (BoB) since the Last Glacial Maximum (LGM; ~21 ka). We find that ISM runoff was at its weakest during Heinrich Stadial 1 (HS1; 17.5-15.5 ka) and that peak freshwater discharge occurred during the early Holocene (EH; 10-9 ka). Counterintuitively, our records indicate that BoB productivity collapsed during both extreme states of peak monsoon intensity (EH) and failure (HS1). Using individual foraminiferal analyses (IFA) we demonstrate that both extremes were associated with upper-ocean stratification; whereas thermally-mediated stratification suppressed mixing and nutrient-delivery during HS1, outflow-induced stratification driven by strengthened ISM runoff curtailed productivity during the EH. In contrast to the latest Earth-system model projections, our paleoceanographic results raise the possibility of future deterioration in BoB productivity under strengthening monsoon seasonality.

Insights into the abrupt climatic events (ACE) of Holocene: A paleoclimate conundrum

Date: 2024-01-30
Speaker: Dr. Upasana Swaroop Banerjee
Venue: NanoSims Hall

Abstract

The Indian Summer Monsoon (ISM) plays a pivotal role in the socio-economics of the Indian subcontinent and global climate system. The recent anomalous behaviour of ISM invigorates the need to address spatio-temporal changes of ISM during the ongoing interglacial period, the Holocene Epoch (~11.8 ka- Present). The Holocene has been characterised by various Abrupt Climatic Events (ACE) such as 8.2 ka, 4.2 ka, Bond events, Little Ice Age, etc., based on colossal studies from high latitude regions. Most of these ACEs have been recognised in global natural proxies, however, ISM being a major part of the global climate system, remains poorly understood in terms of its response towards the ACE of the Holocene. Further, the association of the Indian monsoon system with natural forcing and climate variables have remained elusive. In the present talk, a synoptic assessment of Indian monsoon variability and its response towards globally established ACEs will be discussed.

Rheology of the lower crust and its implications for geodynamic studies

Date: 2024-01-16
Speaker: Dr. Sagar Masuti
Venue: NanoSims Hall

Abstract

Postseismic relaxation from large earthquakes and postglacial rebound from the melting of ice sheets induce transient deformation of the solid Earth, particularly in the deep crust and upper mantle. The melting of large ice sheets due to climate change further results in sea-level rise, which is of great societal concern. The deformation of the lower crust is mainly controlled by feldspar. The mechanical properties of feldspar at steady-state are well constrained. However, the physical mechanism underlying transient creep, an evolutionary, hardening phase converging to a steady state asymptotically, is still poorly understood. In order to constrain flow law parameters for the transient creep of feldspar, we performed constant strain rate deformation experiments on synthetic fine-grained anorthite (Ca end member of feldspar) aggregates under wet conditions using a Paterson-type gas deformation apparatus. We analysed the starting and deformed samples in optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). We constrain the mechanical data using a Burgers assembly with a thermally activated nonlinear stress versus strain-rate relationship for the dashpots. I will discuss the inferred flow law parameters of the transient creep and demonstrate their importance by using these parameters to study the postseismic deformation following the 2016 Mw 7.0 Kumamoto earthquake.

Making and collapse of mountain belts: Insights from petrography, thermodynamic modelling and diffusion kinetics

Date: 2024-01-09
Speaker: Dr. Nilanjana Sorcar
Venue: NanoSims Hall

Abstract

Metamorphism, partial melting in conjunction with uplift of the deep crustal rocks are integral part of mountain building process or orogenesis. Recognizing such crustal processes has an important bearing on geodynamics as it provides the information on the tectono-thermal history of the crust. Petrography, thermodynamic modelling and diffusion kinetics are key approaches in decoding metamorphic, cooling and exhumation (upliftment) history of a mountain / orogenic belt by simulating different temperature and pressure conditions of metamorphism over time as well as cooling/exhumation rate of the deep crustal rocks. New analytical capabilities, in particular, the development of the electron micro-probe, played an enabling role by providing the means of analyzing small volumes of materials in different textural settings in intact rock samples which is crucial to develop thermodynamic and diffusion modelling in such study. In this talk, I will address the nature of tectonometamorphic evolution of young and active as well as ancient mountain belt from India and East Antarctica to show how crustal rocks evolve through geological time in different P-T regime. The development of improved methods of diffusion kinetics using compositional zoning of mineral (e.g. garnet) in combination with petrologically constrained paths of thermal evolution will be highlighted to gain insights into the nature of cooling of high- grade metamorphic rocks, as well as into the tectonic evolution of an orogenic belt (e.g. Himalayas, Eastern Ghats Belt etc.). Finally, I will talk about my future research direction using the integrated studies of mineralogy, thermodynamic modelling and diffusion kinetics to the field of Planetary Sciences, for example, to the domain of shock metamorphism and mineralogical studies of other planetary rocks.

Isotopic composition of atmospheric water vapour: recent observations and future potentials

Date: 2024-01-02
Speaker: Prof. M. G. Yadava
Venue: NanoSims Hall

Abstract

Water vapour is a good tracer of atmospheric circulation. The isotopic composition of atmospheric moisture (δ18O and δD) can provide unique constraints on how water is transported, mixed, and changes phase and is thus a valuable tool in the study of the Earth’s hydrologic cycle and for improved understanding of paleoclimate proxies. We have recently started looking into the dynamics of ambient water vapour using stable isotopes as a primary tool. With the adaptation of the laser spectroscopy method for measuring ambient air-water isotopic composition, studies on atmospheric vapour at a temporal resolution of ~100 seconds are possible and are becoming significant topics in understanding hydrological perturbations on daily to seasonal scales. Current measurements, complexities in the method, and future applicability will be discussed.

2022

Comparative study of Climatic Changes and Volcanism on Earth and Extraterrestrial Bodies

Date: 2022-03-25
Speaker: Dr. K.S. Misra
Venue: Online Platform (Bluejeans)

Abstract

2021

Deciphering the water source utilization and transport by plants using stable isotopes

Date: 2021-07-13
Speaker: Ms. Ajayeta Rathi
Venue: Online Platform (Bluejeans)

Abstract

Plants play a major role in global hydrological cycle controlling ecosystem, climate, and natural resources. Water present in plants is mainly transported by a vascular tissue called xylem, which also transports nutrients from the root to the rest of the plants and provide structural support to them. Xylem water also play a major role in plant physiology and plants have the tendency to use different sources of water with respect to its availability. So tracing the isotopic signature of xylem water will provide better insights about utilization of water by plants in a given area. Further, temporal and spatial change in plant species composition and physiology is mainly driven by the climatological settings and hence there is likelihood of differences in water use efficiency and transport mechanism. Considering the above background, in this talk, I will discuss about the importance of stable isotopes in xylem water as a tool to understand water transport in plants.

Reconstruction of ocean deoxygenation using Iodine/Calcium (I/Ca) ratios in marine carbonates

Date: 2021-07-06
Speaker: Mr. Deepak Kumar Rai
Venue: Online Platform (Bluejeans)

Abstract

Oxygen is an essential element for all the heterotrophic organisms in the oceans. Decrease in the ocean oxygen levels has been observed since the middle of the 20th century. This ocean deoxygenation ranks among the most important changes occurring in marine ecosystems. The oxygen content of the ocean constrains productivity, biodiversity, and biogeochemical cycles. Major extinction events in the Earthâ€™s history have been associated with warm climates and oxygen-deficient oceans, and under current trajectories, anthropogenic activities could drive the ocean toward widespread oxygen deficiency. The current climate models and observations generally agree on the loss of oxygen from the oceans. But these models tend to underestimate oxygen spatial variability and temporal trends, especially in the tropical thermoclines. This disagreement between models and observations is problematic for future predictions, as these regions host large open ocean oxygen minimum zones (OMZs), where a further decrease in oxygen levels could have large impacts on ecosystem and biogeochemistry. In such a case, reconstruction of the ocean deoxygenation from the geological past may provide insight into future deoxygenation. For such long-term predictions, a geochemical proxy is required to reconstruct past oxygen levels. One such proxy is Iodine/Calcium (I/Ca) ratios in foraminifera. In this talk, I shall discuss how past ocean levels are reconstructed using I/Ca ratios in foraminifera.

Surface & subsurface oceanography of the Equatorial Indian Ocean: New insights from Thermocline variation study

Date: 2021-06-29
Speaker: Mr. Sanjit Kumar Jena
Venue: Online Patform (Bluejeans)

Abstract

The equatorial Indian ocean (EIO) region is unique in nature in terms of its geography and oceanographic settings compared to other global oceans. Unlike the Pacific and Atlantic, being land locked in the north restricts its northward spread. This characteristic distribution of ocean and subcontinent near to the equatorial regime has helped develop a distinct and dynamic climatic pattern attributed to this region, where mutual interaction of ocean and atmosphere govern the regional climate. Numerous studies carried out so far in the region mostly addressed the understanding of the evolution of EIO climate over time and its implications to the global climatology. While most of the studies are limited to the surface oceans, very little is known about the intermediate levels. The Indian Monsoon plays a major role in governing the surface ocean hydrology with smaller contributions from the terrestrial influxes and upwelling. In principle, the thermocline water of the EIO has three sources: (i) the intimately linked Subantarctic Mode and Antarctic Intermediate Waters (SAMWâ€“AAIW), (ii) the Indonesian Intermediate Water (IIW) from the Indonesian Throughflow, and (iii) combined Persian Gulf and Red Seawaters (PGWâ€“RSW). While, the highly saline and O2-poor PGW and RSW contribute to local intermediate water formation, their combined volume is one order of magnitude lower than the southern source. Evidence of Antarctic Intermediate waters on the EIO temperature have been reported recently, adding a new dimension to the existing understanding. The variations in AMOC strength appear to be an important driver of the thermocline structure in the tropical Atlantic from annual to multi-millennial time scales. Thus, understanding the role of oceanic thermocline and its response to subsurface variations over time would provide better clue. Our study attempts to address this issue based on isotopic data of the planktonic foraminifera shells from the EIO thermocline region.

2020

Understanding and Quantifying the Biological Carbon Pump in the Indian Ocean using naturally occurring radionuclides in seawater as tracers

Date: 2020-10-13
Speaker: Dr. Subha Anand S.
Venue: Online Platform (Google Meet )

Abstract

Ocean acts as a significant reservoir of carbon on the earth’s surface. Tiny photosynthetic organisms, the phytoplankton, present in the sun-lit layers of the ocean accounts for about 50% of the global net primary production. The process by which phytoplankton photosynthetically fixes atmospheric CO2 and produces particulate organic carbon that sinks from sea surface to bottom and remains stored for longer time scales is termed as the biological carbon pump. The efficiency of the biological carbon pump is determined by the ratio of the amount of organic carbon sinking below the euphotic depth to that produced. This efficiency can be determined by using particle reactive radionuclides present in seawater. Particle reactive radionuclide approach is considered to be more advantageous because of the natural occurrence, specific half-life, continuous decay and secular equilibrium. My research work in the Bay of Bengal, Arabian Sea and the Indian Ocean, focuses on (1) estimating the POC export flux from monthly to seasonal time scales using the particle reactive radionuclide pairs, 234Th/238U and 210Po/210Pb. (2) The role of vertical eddy diffusive mixing in enhancing nutrient concentrations in the surface waters from sub-surface depths using Radium isotopes (228Ra and 226Ra) (3) Quantifying lithogenic inputs to the ocean and palaeo particle flux using 232Th, 230Th and 231Pa isotopes (4) Comparison of measured primary production and estimated POC export flux with that of the globally existing empirical models with an approach to develop a model for the Indian Ocean.

Applications of radiogenic and non-traditional stable isotopes to investigate silicate weathering, crustal recycling and mantle geodynamics

Date: 2020-09-22
Speaker: Dr. Anupam Banerjee
Venue: Online Platform (Google Meet )

Abstract

Weathering of silicate rocks releases cations which are transported to the oceans by rivers where calcium carbonate precipitates from the seawater; resulting in the net consumption of atmospheric CO2. These marine carbonates are eventually subducted resulting in mantle heterogeneity, sampled by mantle-derived magmas. Long-lived radiogenic and non-traditional stable isotopes provide insights into both the surface and deep mantle processes. Significant variations in the long-lived radiogenic Nd, Sr and stable Ca isotopic compositions of a 2.5 billion years old weathered basalt suggest that selective weathering of rock forming minerals (plagioclase versus pyroxene) could change the isotopic compositions of silicate rocks in a hand-specimen scale. Such mechanism is likely to be more pronounced in temperate climatic conditions where incongruent weathering is more dominant. This process has important implications for the isotopic variability in global rivers draining through the temperate climate region (e.g., Icelandic rivers). Stable calcium isotope (expressed as 44/40Ca w.r.t NIST SRM 915a) is also a potential tracer of crustal recycling since surface carbonates have much lower 44/40Ca (0.1-0.6‰) than Earth’s mantle (0.94 ± 0.10 ‰). Calcium isotopic compositions of carbonatites, magmatic rocks with more than 50% carbonate minerals, provide insights into the crustal recycling due to its high calcium and carbonate contents. The correlated variation of 44/40Ca with 87Sr/86Sr of global carbonatite samples, of age 2.61 Ga until recent, suggests the presence of recycled carbonates in their mantle source regions. However, a closer inspection reveals that crustal recycling is more prominent in the last 300 million years. The prevalent Ca and Sr isotope signatures observed in carbonatites younger than 300 Ma could reflect the following: (1) an increased amount of subduction flux and high convergence rates due to amalgamation and subsequent break-up of the Pangea supercontinent; (2) enhanced weathering of aragonitic shelf carbonates linked with the Siberian Trap magmatism at ~251.9 Ma.

Cratons to supracrustal belts: growth and unification of the Indian landmass

Date: 2020-09-15
Speaker: Dr. Sabyasachi Chattopadhyay
Venue: Ground Floor Lecture Hall

Abstract

Archean crustal terranes (4–2.5 Ga) consist of gray-gneisses referred to as the tonalite– trondhjemite–granodiorite (TTG) suite of rocks. These TTGs constitute > 50 % of the existing Archean crust and represent the oldest archetypical juvenile felsic components of cratons and marks the transition from a dominantly mafic to a more felsic crust. There is also considerable debate on the nature of the petrogenetic and geodynamic processes that generated the early continental crust. Whether conventional plate tectonics operated in the Archean, the way it switched over in Proterozoic, and when these came into existence remains unclear. The Singhbhum craton in eastern India is underlain by Paleo - to Mesoarchean TTGs and granites that formed in two pulses at 3.45–3.44 Ga and 3.35–3.32 Ga, followed by potassic granite activity at 3.1 Ga. Low heavy-REE concentrations, Sr/Y and Eu/Gd, and high Nb, Ta, and Y concentrations indicate they belong to the low HREE, medium- to low-pressure TTG type. Their compositions are similar to TTGs derived from chondritic source with amphibolitic residue, consistent with rutile-free and garnet-bearing metabasic source. The younger granites represent intracrustal melts of more potassic members of the Paleoarchean TTGs. The trace element characteristics of the granitoids reflect melt generation at different depths in a tectonic setting producing both TTGs as well as granites contemporaneously. Plausible geodynamic settings could be very hot subduction or “dripduction” regime involving shallow melting of delaminated mafic crust producing the 3.45 Ga juvenile TTGs and minor granites. Large-scale delamination and melting of mafic lower crust and felsic protocrust in a thickened crustal pile in a subduction-like regime could have produced granitoids with juvenile as well as recycled isotopic signatures. The Nd-Hf isotope data indicate that the Paleoarchean upper mantle was moderately depleted in response to a spurt in Paleoarchean continental growth.

Hydroxyl Radical Generation from Atmospheric Aerosols over a High Altitude Site in the Indo-Gangetic Plain

Date: 2020-08-31
Speaker: Dr. Anil Patel
Venue: Online Platform (Google Meet )

Abstract

Atmospheric aerosols have been profoundly associated with several cardiovascular and pulmonary diseases. However, the precise mechanism in terms of which species exacerbate toxicity remains unclear. Recent studies have investigated that redox-active organic species and metals present in atmospheric aerosols can initiate the endogenous formation of reactive oxygen species (ROS). Hydroxyl radical (•OH) is the most reactive form of ROS and its high levels may cause lipid peroxidation in the human body. The picture is further complicated by the fact that the atmospheric air is a pool of variety of chemical species emitted from very diverse sources. Further, the atmospheric aging of particular species may enhance/reduce the potential of endogenous ROS generation. In view of this, a study was carried out over Shillong, a high altitude site in the downwind Indo-Gangetic Plain (IGP). We found that organic aerosols over this site composed up to 78% of the mass in total, the highest among the IGP regions. In this discussion, I shall share my preliminary results of how the composition of the aerosols relates to endogenous •OH generation over the Shillong.

Groundwater storage quantification and biogeochemical model development for water quality applications

Date: 2020-08-25
Speaker: Dr. Soumendra Nath Bhanja
Venue: Online Platform (Google Meet )

Abstract

The Indian Sub-Continent (ISC), which hosts the largest and densest global population, faces acute shortage of mostly drinking water and other usable waters as it is witnessing rapid rise in population, urbanization, and change in societal water use and lifestyle. Therefore to ensure groundwater sustainability across the parts of the ISC, the groundwater resources should be studied in detail. My research has been aimed to delineate the details of long-term patterns of groundwater recharge, storage change and quantification, spatio-temporal variability of groundwater storage, groundwater-surface water interaction, and also the effect of water management strategies on groundwater storage in ISC using in situ, satellite-based and numerical model simulations. Depletion of usable groundwater storage is linked with the increase of irrigated area linked with water intensive crops. The large-scale depletion of groundwater resources in Ganges basin has been found to be linked to the summertime drying of the Ganges river in recent years. A ray of hope still exists as it is found that the application of proper water resource management practices in parts of the ISC leads to groundwater storage replenishment. Oxidation-reduction reactions associated with oxygen diffusion and soil organic matter decomposition influence a number of soil biogeochemical cycles. The processes are responsible for controlling oxidation reduction potential (ORP), pH and chemical balance in the soil-water medium. My research also focuses on developing a process based model including microbial kinetics and thermodynamics for simulating the regional scale biogeochemical processes. The model is capable of simulating multiple water quality parameters at one run, for the first time in regional-scale. Water quality being an important component of water security, the approach can be widely used in Indian sub-continent and other parts of the globe for different water quality applications.

Hydrogeological Processes in Kerala: Insights from Oxygen and Hydrogen Isotopes in groundwater Abstract:

Date: 2020-07-21
Speaker: Mr. Amit Pandey
Venue: Online Platform (Google Meet )

Abstract

The state of Kerala, located in the southwestern tip of India is bounded by the Arabian Sea in the west and the Western Ghats in the east. Though it occupies only 1.2% of the total area of the country, it accommodates 3% of the country's population. In spite of copious annual average rainfall of ~3100 mm, the state of Kerala has a high level of dependency on groundwater for agriculture and drinking purposes, due to geohydrological reasons compounded by the high population density and agrarian economy. The groundwater in Kerala is stored in four types of aquifers in the region, and recharged by rain and surface water. In recent decades, Kerala is facing severe groundwater problems due to variety of reasons such as seawater intrusion during summer, drying of wells, and geogenic as well as anthropogenic pollution. Therefore, it is important to understand hydrogeological processes and factors which affects availability and quality of groundwater. This knowledge is important to manage and ensure groundwater sustainably in the region. A large body of current knowledge about groundwater in Kerala is derived from the seasonal fluctuations in water table/ piezometric level and basic chemistry of water. However, there are some knowledge gaps which needs to be bridged through application of oxygen and hydrogen stable isotopic tracers. This study is aimed to address following scientific questions: (1) Is there any hydraulic connectivity between four types of aquifers in Kerala? (2) What are the different sources of groundwater recharge? (3) Can we identify aquifers/regions recharged by NE Monsoon? (4) Are there any linkages between wetlands and groundwaters? (5) Can we estimate average travel time of groundwater from highlands to coast? (6) Does evaporation affect the groundwater of this humid region? Tentative answers to the above questions will be attempted in the seminar.

Deep sea foraminifera Abundance in Central Equatorial Indian Ocean since last glacial maxima: Effect of Productivity and Bottom Water Oxygenation

Date: 2020-07-17
Speaker: Ms. Nisha Bharti
Venue: Online Platform (Google Meet )

Abstract

Benthic foraminifera are widespread and diversified organism in the marine environment and they have a significant role in the deep-sea food web and ocean carbon cycle. They play a pivotal role in the study of paleoclimate, because of the potential capacity of fossilization of their shells. To understand the dependency of benthic foraminifers on overhead productivity, a regional process and deep-water oxygenation, a global process, during the past ~19 ka, a sediment core from the central equatorial Indian Ocean was investigated. Towards this, foraminifera from six-time intervals were separated for benthic foraminiferal abundances and dominant assemblages. The study revealed changing bottom water conditions, especially in terms of change in input of organic carbon to the deep sea and bottom water dissolved oxygen concentration during time period of the analysed samples. Variations in geochemical parameters showed good correlation with the dominant foraminiferal assemblage. This also supports the findings that the dominant assemblages are not only responding to regional processes like organic productivity but also to the global climatic changes controlling the deep-sea oxygenation. This study concludes well oxygenated bottom water throughout Holocene (2.1-12.9 ka BP) and poorly oxygenated bottom water during deglaciation(12.0-17.0 ka BP) and Last glacial maxiam.(17.0-19.3 ka BP).

Chronology of Quaternary Glaciation in the Central and Northwestern Himalaya: Findings in the Recent Decade

Date: 2020-07-14
Speaker: Mr. Partha Sarathi Jena
Venue: Online Platform (Google Meet )

Abstract

The glaciation in Himalaya is a combined influence of climate and orography. To understand the local response of global climate change, a proper chronology of glaciation events is necessary. The Higher Himalayan Range in the south and Karakoram Range in the north play an important role and affect the moisture transport in the region. The dominance of moisture sources varies between monsoon-influenced Central Himalaya and westerlies influenced Northwestern Himalaya. With limited dates on glaciation events earlier, it was observed that the Himalayan glaciers only responded to the Indian Summer Monsoon irrespective of the geographical position. The most interesting/intriguing observation was that no glaciation event was found during the last glacial maximum event in the Nubra valley and the Ladakh Range, which lie in the north of higher Himalaya and are presently influenced by westerlies. Recently, several studies have reported many glacial events dated using both terrestrial Cosmogenic Nuclide and Luminescence dating methods. In this presentation, the timing of glaciation events from recent studies in the valleys from Karakoram, Ladakh, Zanskar, and Higher Himalayan ranges along with the factors responsible for driving quaternary glaciation will be discussed.

Hydrometeorological processes and evaporation from falling rain in Indian sub-continent: Insights from stable isotopes and satellite data

Date: 2020-06-09
Speaker: Mr. Harsh Oza
Venue: Online Platform (Google Meet )

Abstract

Rigorous analysis of measured isotopic composition (δ18O and δD) of 556 daily rainwater samples collected at four Indian stations viz., Jammu, Jorhat, Hyderabad and Ahmedabad, is done in conjunction with satellite and model-derived meteorological and isotopic parameters to discern prominent hydrometeorological processes and factors in four different climatic zones in the Indian subcontinent. A new Indian Meteoric Water Line (IMWL), better representing the different climatic zones, including the semi-arid western India, has been defined: [δD = (7.6±0.1) δ18O + (8±1); R2 = 0.96; P < 0.05; N = 556]. The lower slope of IMWL compared to the Global Meteoric Water Line signifies the role of evaporation from falling rain throughout the Indian subcontinent, though it is surrounded by large marine water body, and bordered by lofty Himalayan mountains in the north obstructing the monsoonal winds. We have tried to quantitatively estimate the evaporative loss from the falling raindrops. In this talk, I will be discussing some of the important results and inferences obtained from this study.

Carbon fixation in the oxygen minimum zones of the ocean

Date: 2020-02-25
Speaker: Mr. Himanshu Saxena
Venue: Ground Floor Lecture Hall

Abstract

Primary production is one of the most important metabolic process and about half of the global primary production (~50 Peta gram of carbon per year) is generated in the euphotic layer of the ocean. But about 75% of the global ocean is dark ocean i.e., below ~ 200 m depth, with more than 98% of the global dissolved inorganic carbon pool. Recent researches showed that carbon fixation also occurs in the dark ocean. This dark carbon fixation (chemoautotrophic) has been suggested to contribute significantly to the global ocean carbon budget, with ~2% of the total estimated yearly marine primary production. In this seminar, carbon fixation in the oxygen minimum zones of the ocean will be discussed.

Study of Paleo Marine Nitrogen cycle using Nitrogen isotopes

Date: 2020-02-04
Speaker: Mr. Deepak Kumar Rai
Venue: Ground Floor Lecture Hall

Abstract

Dinitrogen (N-2) gas is the most abundant form of Nitrogen in the Oceans. Still, most of the organisms cannot utilize it in this form. It first has to be converted to a reactive form by N-fixing bacteria. The fixed N inventory is primarily controlled by principal source (N-2 fixation) and sink (denitrification), both of these processes are mediated by marine organisms. So, the oceanic nitrogen budget provides a critical test case in the broader effort to understand the stabilizing environmental feedbacks on the Earth’s surface. However, it is difficult to quantify, based on temporally and spatially limited modern observations. Fortunately, geological archives have recorded past events those approximate large-scale experiments in which the oceanic N budget responds to naturally imposed forcing. In this talk, I will discuss how nitrogen isotopes are used for studying the palaeo marine nitrogen cycle.

Effect of Monsoon Intra-seasonal Oscillation on the rain isotope variability in northern Bay of Bengal

Date: 2020-01-28
Speaker: Prof. S.K. Bhattacharya
Venue: Ground Floor Lecture Hall

Abstract

Monsoon Intra Seasonal Oscillation (MISO) represents semi-periodic occurrence of rainfall spells over India during summer associated with large-scale movement of wind and clouds connecting convection and circulation, identified by northward propagation of Outgoing Long wave Radiation flux anomaly. The connection of MISO with the hydrological cycle has been explored here through stable oxygen and hydrogen isotope ratios in rainwater samples collected from two stations located near North Bay of Bengal during 2004-2014. The delta-18-O and delta-D values of the samples (total 202) have wide ranges: -18.2 to 2.8‰ and -132 to 28‰ (rel. to VSMOW) respectively. Out of 66 samples associated with 15 MISO events during this period, 46 have significantly low isotope ratios. These ratios are well correlated with the MISO propagation speed and cumulative rainfall over the Bay of Bengal. In addition, the isotope values also show a significant anti correlation (r2=0.88) with satellite derived stratiform rain fraction. The isotopic results were compared with the results obtained using an Isotope Enabled Global Spectral Model (IsoGSM). The model simulation reproduces the amplitude of variation in the observed values, but on average, the model values are higher in delta-18-O and delta-D by about 2‰ and 11‰ respectively and lower in d-excess by about 4.5‰ on average. It is proposed that the discrepancies in delta-18-O, delta-D and d-excess arise due to an overestimation (on average by 13%) of raindrop evaporation effect in the model.

2019

Chalks, Cherts and Fish Clay, and their links to the fall of Dinosaurs

Date: 2019-11-26
Speaker: Dr. Vineet Goswami
Venue: Ground Floor Lecture Hall

Abstract

Oxygen and Carbon Isotopic Composition of the Living Symbiont bearing Benthic Foraminifera from different regions of the Andaman Reefs

Date: 2019-10-15
Speaker: Dr. M. Muruganantham
Venue: Ground Floor Lecture Hall

Abstract

Benthic foraminifera which hosts algal endosymbionts, grow to larger sizes than most other benthic protozoans and are often informally referred to as Larger Benthic Foraminifera (LBF). The LBF are important calcifiers, contributing substantially to reef sediments and carbon sequestration. The LBF grow slowly over periods of months to an year or more to reach diameters usually in excess of 1 mm and commonly >1 cm. They are long lived compared to most other shallow-dwelling foraminifera. Because they host symbiotic algae, they generally require very clear water conditions, especially those living at depths >20 m. With suitable light intensities and limited availability of dissolved inorganic nutrients (e.g., ammonia, nitrite, nitrate and phosphate), the photosynthetic algal symbionts can produce far more photosynthate (i.e., simple sugars and lipids) than inorganic nutrients available to allow algal growth. Instead, the algae excrete their excess photosynthate to the host, providing the host with energy for calcification and feeding, and the latter provides essential nutrients for growth of host and the algae. All these physiological process are generally not observed in the smaller benthic and planktonic foraminifers. The stable oxygen and carbon isotopic composition (δ18O and δ13C ) of different species of live symbiont bearing larger benthic foraminifera from different reef areas of Andaman Islands have been analysed. Processes regulating the isotopic composition of these LBF would be discussed in my presentation.

Mysteries in Error Propagation

Date: 2019-09-03
Speaker: Dr. Arvind Singh
Venue: Ground Floor Lecture Hall

Abstract

We often use “method of error propagation” to determine uncertainty (error) in a dependent variable from the measured uncertainty in the independent variables. Intuitional notion of error propagation in statistics suggests that random relative error in the dependent variable cannot be less than the sum of those in the dependent variable(s). In this talk, I shall explain that some functions, however, do not follow this notion of error propagation. I shall further explain and discuss the behaviour of such functions and their implication to earth science observations.

Hydro-meteorological processes in southern India: Insights from stable isotopes in precipitation at Hyderabad

Date: 2019-07-09
Speaker: Mr. Harsh Oza
Venue: Ground Floor Lecture Hall

Abstract

Understanding hydro-meteorological processes in southern India is important because it governs the availability and distribution of water in this region. Most of the southern Indian states depends predominantly on precipitation for its water requirement. Hyderabad, located almost at the centre of the Indian peninsula, equidistant from both Arabian Sea and Bay of Bengal, makes it an interesting location to study hydro-meteorological processes such as northward extent of North East monsoon (which is known to bring significant rainfall in the state of Tamil Nadu), effect of locally derived moisture in the rain and seasonal variation in the contribution of various moisture sources. Also, Hyderabad experiences frequent extreme weather conditions such as heat waves, droughts, heavy rainfalls and floods superposed over climatological normal. Understanding of these processes is also important because it has significant political and socio-economic implications especially in the wake of recent water crises in southern India. Stable isotopes of oxygen and hydrogen can be used to trace various hydro-meteorological processes such as vapour source variations, rainout history, vapour recycling, post-precipitation modifications, cloud microphysical processes, etc. Considering this, 182 daily rainfall samples were collected from Hyderabad during 2008-11 as a part of IWIN national programme. The isotopic analysis of these samples in conjunction with ground-based and remotely sensed meteorological parameters will be discussed in this presentation. Also, the importance of isotopes in understanding extreme weather events will be discussed.

Nitrogen Fixation during Summer Monsoon in the Bay of Bengal

Date: 2019-06-04
Speaker: Mr. Himanshu Saxena
Venue: Ground Floor Lecture Hall

Abstract

Primary producers are the first link in the food chain. Their production (i.e., primary production) in oceans is limited by the availability of light and nutrients. Dominantly, it is the nutrient (primarily bioavailable nitrogen) that regulates the primary production. Various mechanisms are responsible for providing nutrients to the primary producers. N2 fixation is one such process for supplying bioavailable nitrogen required for the sustenance of primary producers. It has been found that the N2 fixation rates in the Arabian Sea are highest among other oceans. But the Bay of Bengal, north-eastern part of the Indian Ocean, is known for ‘no study’ of N2 fixation rates. Therefore, to contribute to the present knowledge of N2 fixation rates in the Indian Ocean and to know the contribution of fixed nitrogen by N2 fixers to the primary productivity, N2 fixation rates in the Bay of Bengal during summer monsoon were measured. In this seminar, I will be discussing the N2 fixation phenomenon and the potential role of summer monsoon on the N2 fixation in the Bay of Bengal.

Use of Brown Carbon Spectra as a Tool to Understand Their Broader Composition and Characteristics: A Novel Approach

Date: 2019-04-09
Speaker: Dr. Neeraj Rasotgi
Venue: Ground Floor Lecture Hall

Abstract

The eruptive tempo of Deccan volcanism and Dinosaur extinction

Date: 2019-03-05
Speaker: Prof. J.S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Application of Stable Isotopes in delineating recharge areas and identifying the sources of recharge

Date: 2019-02-21
Speaker: Prof. Gh. Jeelani
Venue: Ground Floor Lecture Hall

Abstract

Geological and archaeological implications of drainage morpho–dynamics in NW Indo–Gangetic plains

Date: 2019-02-12
Speaker: Dr. Ajit Singh
Venue: Ground Floor Lecture Hall

Abstract

Indo–Gangetic plains is one of the largest alluvial plains adjacent to orogenic mountains. It comprises of alluvial sediment transported and deposited mainly by the Himalayan sourced antecedent rivers. This resulted in diverse geomorphic settings across the east–west strike of the Indo–Gangetic plains. The inter–basinal area between the Yamuna in east and the Sutlej in west is presently devoid of any major drainage except for the small ephemeral Ghaggar river. However earlier field based studies by geographers and later based on remote sensing approach have suggested presence of Ghaggar–Hakra paleochannel, in the Ghaggar plains, as a manifestation of a large river in the region. Pal et al. identified, few major paleochannels of Sutlej and Yamuna river and proposed that both these rivers were flowing into Ghaggar–Hakra paleochannel to form the large river. Also the largest concentration of Harappa civilisation is located near the Ghaggar–Hakra paleochannel. This led to a hypothesis that perennial Himalayan river flow sustained Harappan settlements in this region. However, such hypotheses have never been tested due to absence of data on subsurface stratigraphy, and provenance of buried sediment beneath the paleochannel. This seminar will deal with new results on shallow stratigraphy, sediment provenance, and chronology that respectively show fluvial architecture, Himalayan sources, and timing of fluvial activity of Ghaggar–Hakra paleochannel. Results will be presented from a new project focused to test the proposed connectivity of Yamuna catchment with the Ghaggar–Hakra paleochannel. This project is designed to understand the hydrology of Ghaggar-Hakra river system that possibly sustained the Harappan civilization.

Understanding the Geochemical Evolution of the Earth’s Mantle: Story from Carbonatites

Date: 2019-01-29
Speaker: Mr. Milan Kumar Mahala
Venue: Ground Floor Lecture Hall

Abstract

The Earth’s surface processes are expressions of its dynamic mantle. It has been established that despite billions of years of mantle convection, Earth’s mantle remains chemically heterogeneous. Therefore, understanding of the chemical evolution of the mantle and its implications for various processes in Earth through time requires study of various mantle derived products at different times in the Earth’s geologic past. Basalts are the obvious choice of such studies; however, to known the nature of fluids that are responsible for mobility of elements within the mantle one needs to study carbonatites. Carbonatites are magmatic rocks, rich in fluids and a whole host of trace elements, that carry and preserve the chemical information of the source regions more efficiently. In this seminar I will introduce the audience to these peculiar magmatic rocks and discuss their usefulness in tracing the mantle evolution through time.

Isotopic characterization of Groundwaters of India: insights into hydrogeological processes

Date: 2019-01-01
Speaker: Mr. Amit Pandey
Venue: Ground Floor Lecture Hall

Abstract

Only 3% of the global water is fresh water, of which only 30% is groundwater (0.009% of total water on earth). In an agrarian country like India, where rainfall is erratic and unevenly distributed, groundwater becomes the important source of irrigation as well as domestic usage. Availability and quality of groundwater is adversely affected due to overexploitation, geogenic and anthropogenic contamination and climate change. While the adverse effects on groundwater, and the dependent economy and ecology, are obviously realised, the mechanism of underlying geohydrological processes is not so well understood. Hence, the knowledge about spatially variable geohydrological processes has become crucial not just from the academic perspective but in order to provide societally relevant information which can be useful in efficient water resource management in the field. In the above backdrop, I will pursue my Ph.D. research in the field of groundwater hydrology whereby I propose to use isotope characteristics of groundwater of first unconfined aquifer to answer some of the emergent scientific questions pertaining to geohydrological processes. In this talk, I would provide a broad outline and objectives of my future doctoral research work, major scientific questions to be addressed, challenges and limitations.

2018

Quarternary glaciation studies using terrestrial cosmogenic nuclides

Date: 2018-12-18
Speaker: Mr. Partha Sarathi Jena
Venue: Ground Floor Lecture Hall

Abstract

Advances in Himalayan glaciers have been found to be linked with regional factors, unlike glaciers from extratropical regions which are controlled by orbital forcing. Previous studies have demonstrated contrasting glaciation pattern in Himalayan region possibly as a result of the orography and climate of the region. Several researchers observed that advancement and retreat of the Himalayan glaciers is affected by the monsoonal or westerlies precipitation. In order to study the paleoclimate, it is a prominent approach to analyze Time, Duration and Extent of glaciation in the geological past. 10Be is a cosmogenic radionuclide produced by interaction of cosmic ray particles with materials in the earth’s atmosphere and surface. By using the production rate and concentration of 10Be in surface rocks samples, estimates of chronology of past glaciation cycles can be made. In this presentation, exposure age dating of glacially eroded rock surfaces and moraine boulders will be discussed along with a brief insight into the past glaciation studies in the Himalayan region using Terrestrial Cosmogenic Nuclide (TCN) Method

Marine Heterotrophic Nitrogen Fixation

Date: 2018-12-11
Speaker: Mr. Himanshu Saxena
Venue: Ground Floor Lecture Hall

Abstract

The fixed nitrogen is the most important nutrient fuelling phytoplankton growth in the ocean. Thanks to the N2-fixers, a special group of marine plankton that are able to convert dissolved nitrogen gas into bioavailable nitrogen such as ammonium. Marine nitrogen-fixing cyanobacteria play a central role in the open-ocean microbial community. Once thought ocean to be dominated by cyanobacteria in the warm oceans, it is now clear that marine N2-fixing organisms in the ocean are more diverse, and are geographically more widespread than expected. In this talk, I will be discussing the types of N2 fixers and how they contribute to the nitrogen budget of the ocean. In addition, lack of knowledge about nitrogen fixation in the Indian Ocean will also be discussed.

Sources and sinks of nitrous oxide in the ecosystem

Date: 2018-12-04
Speaker: Mr. Mohammad Atif Khan
Venue: Ground Floor Lecture Hall

Abstract

Nitrous oxide is an undervalued but an important long-lived greenhouse gas and ozone-depleting entity, which has increased by almost 20 percent compared to the pre-industrial era, thus becoming a global concern. In this talk, the concepts of global warming, the greenhouse effect, and global emission rates of N2O from various reservoirs will be discussed. N2O production by different microbial pathways and factors influencing its emission in the terrestrial ecosystem will also be discussed. At last, the importance of the stable isotopic composition of N2O in identifying the processes responsible for its production and major sources will be introduced.

Mineral phase transformation: Earlier classical ideas to modern concepts

Date: 2018-11-13
Speaker: Dr. Alik Sundar Majumdar
Venue: Ground Floor Lecture Hall

Abstract

Most of our mineralogical concepts bear the legacy of material sciences where minerals are considered as materials and a "dry solid-state" mindset is applied in explaining mineralogical features. However, natural systems are not "dry" and "closed" rather it is commonly "wet" and "open". Following this, I will start the talk with little bit idea about the development of ideas on mineralogy, specially on mineral phase transformation to explain why are all the interpretations of processes in minerals and rocks dominated by “solid-state” mechanisms? Next, I will discuss the fundamentals of mineral stability diagram calculation using "equilibrium thermodynamics" in "dry" system, its pros and cons. Finally, I will focus on - (1) modern observations on mineral phase transformation from nano-scale perspective, (2) concept of "wet" system, non-equilibrium thermodynamics, and (3) the role of fluid on mineral phase transformation and deformation.

Report on the current radiocarbon measurements by PRL-AMS

Date: 2018-10-30
Speaker: Dr. M. G. Yadava
Venue: Ground Floor Lecture Hall

Abstract

AMS (Accelerator Mass Spectrometry) is nowadays a commonly adopted method for the measurement of natural radioisotopes having very low abundance such as radiocarbon. The greatest advantage that AMS radiocarbon dating has over conventional methods is small sample size. AMS needs 1milligram carbon or less for an analysis whereas conventional methods require at least a few grams of carbon. PRL-AMS presently tuned for radiocarbon, is successfully being used for dating variety of small size carbon samples. Basic features of the machine, efforts towards target preparations and some results on sub-milligram level carbon samples will be presented.

Evolution and characteristics of fine organic aerosol in the urban atmosphere through highly time resolved measurements

Date: 2018-09-18
Speaker: Dr. Atinderpal Singh
Venue: Ground Floor Lecture Hall

Abstract

Sub-micron particles are an integral part of Earth's atmosphere with significant impacts (direct and indirect) on air quality and climate. An unprecedented increase in sub-micron particles concentrations over urban regions is a serious threat to both air quality and climate. Organic aerosol (OA), although reported to be a dominant fraction of submicron aerosol, are least understood the component of fine aerosol due to their numerous sources, complex composition, tedious formation mechanism, and complicated atmospheric evolution. The OA can either be primary or of secondary origin. The primary OA (POA) are emitted directly in particulate form from various sources, whereas, secondary OA (SOA) is produced from the oxidation of volatile organic compounds (VOCs) coming from different sources. Furthermore, the composition and properties of both POA and SOA may change dynamically throughout the aerosol lifetime, because of intertwined processes including emission, oxidation, fragmentation, and gas-to-particle partitioning. Until recent years, most of the studies have reported the properties of OA using filters based measurements (offline) which has limitations in capturing OA evolution in the atmosphere due to a low time resolution of measurements. Toward this, the present study investigates the evolution of OA in real-time using high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) during the post-monsoon season over Ahmedabad.

C:N:P Ratio: A Driver of Ocean Biogeochemistry

Date: 2018-08-24
Speaker: Ms. Deepika Sahoo
Venue: Nano Sims Hall

Abstract

Until recently, carbon, nitrogen, phosphorous have been known to remain in a specific proportion (C:N:P = 106:16:1) in the ocean. This ratio is known as the Redfield ratio. Recent studies have reported that the C:N:P ratio in the dissolved inorganic nutrients and phytoplankton communities deviate from the canonical Redfield ratio. Growth rate and nutrient limitation hypotheses have been proposed to understand this variation in the world ocean. However, no stoichiometric studies have been undertaken in the northern Indian ocean, despite that this region is believed to provide a natural in situ laboratory to understand biogeochemical processes. In this talk, I will discuss the basic understanding of variation in stoichiometry in general, and the role of environmental factors affecting the variation in the Bay of Bengal using a conceptual model in particular.

Paleoenvironmental study using Himalayan lake sediments.

Date: 2018-08-21
Speaker: Mr. Abdur Rehman
Venue: Ground Floor Lecture Hall

Abstract

environmental conditions at the regional scale and its linkages with past global climatic events. Stable isotopic compositions of different constituents of lake sediments, like organic matter and diatom, can be used as a powerful proxy to decipher palaeoenvironmental and biological conditions. During this talk, preliminary results obtained from high altitude Himalayan Lake sediments along with methodological endeavour towards measurements of oxygen isotopic composition in silicates will be discussed.

Oxidative potential of ambient aerosol over the Arabia Sea

Date: 2018-08-14
Speaker: Mr. Anil Patel
Venue: Ground Floor Lecture Hall

Abstract

In addition to in-situ production of reactive oxygen species (ROS) as a part of their metabolism during photosynthesis and respiration by phytoplankton in the marine system, atmospheric deposition of aerosol may also enhance ROS concentration in surface water. When the level of ROS exceeds the defense mechanisms, oxidative stress is generated which can pose a threat to cells by causing damage to bio-molecules such as DNA, lipids and nucleic acids. ROS have been hypothesized to reduce marine ammonia oxidation (nitrification) which may affect ocean biogeochemical cycle. To identify aerosol species responsible for ROS generation in the atmosphere and their major sources over the marine atmospheric boundary layer, aerosol samples were collected onboard SS-359 cruise over the Arabian Sea during April 2017 as a case study. Preliminary results of this study will be discussed.

Sea water δ18O and δD dynamics over the Northern Indian Ocean

Date: 2018-08-07
Speaker: Mr. Kiran Kumar P.
Venue: Ground Floor Lecture Hall

Abstract

Sea water oxygen isotopic composition (δ18O) is a widely used proxy to study modern and past dynamics of the ocean. δ18O-Salinity relation in the surface ocean is a useful tracer to study imprints of physical processes, such as runoff, sea ice melting, large-scale ocean mixing and also paleo-salinity. Effect of precipitation (P), runoff (R) and evaporation (E) in the surface ocean as a ‘P+R-E’ budget on δ18O, δD and S is relatively well understood, however in the subsurface waters it still remains elusive. In this seminar I will discuss a new data set of δ18O, δD and Salinity for the surface and subsurface sea water samples collected from the northern Indian Ocean during pre and post-monsoon months in 2016 and 2017 and highlight various controlling processes

Lakshadweep corals and their paleoclimate proxy records

Date: 2018-07-31
Speaker: Mr.Harsh Raj
Venue: Ground Floor Lecture Hall

Abstract

Corals are important natural archives of paleoclimate proxy records. They provide high resolution proxy records of past climate and ocean. These high-resolution proxy records can be used to study past changes in monsoon and sea surface conditions. In Indian context, earlier studies were carried out on Lakshadweep corals establishing them as faithful recorder of sea surface temperature changes. In recent years Lakshadweep corals show reduced growth rate, which could be related to warming of surface waters in the region. Lakshadweep also receives good amount of rainfall during summer monsoon season, however in previous studies no correlation has been observed between monsoon precipitation in coral proxy records. In this talk, I will discuss coral proxy data and possibility of coral recording monsoon signatures.

Oldest to infant rocks: Hadean mantle story

Date: 2018-06-12
Speaker: Dr. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

The Hadean Eon, representing the first five hundred million years of Earthâ€™s history, was one of the most eventful periods when the planet got differentiated to various chemical layers based on density. One of these major events was the segregation of core and mantle from bulk Earth. Direct evidence for subsequent differentiation of the earliest differentiation of mantle is difficult to find, as the preserved Hadean rock record is scanty. However, information about these events can be obtained with the help of extinct radioactivity, in particular from 146Sm-142Nd systematics (Half-life of 103 Ma). Surprisingly, such evidence is not only restricted to the oldest rocks but also found in some infant rocks. In this talk I will discuss recent findings which provide a new perspective on the preservation of such evidence through geologic time. Some similar efforts by us in this direction will also be discussed.

Karst Geomorphology, Cave Development, and Hydrological Characterisation of Karst Aquifers in the Kashmir Valley, Western Himalaya, India.

Date: 2018-06-05
Speaker: Dr. Rouf Ahmad Shah
Venue: Ground Floor Lecture Hall

Abstract

Karst aquifers contribute substantially to freshwater and thermal water supplies in many region of the world. Kashmir Valley, one of the largest karst region on the Indian Subcontinent and the Himalaya, provides significant karst geomorphic imprint due to wide distribution of carbonate rocks. Karstified carbonate rocks has a high hydraulic conductivity ~1000m d-1, thereby, represents a major hydrogeological unit and a regionally important groundwater reservoir. Dissolution of carbonate rocks, (development of exokarstic and endokarstic features), abundant water resources in the form of large cold and warm springs, and subsequent development of floating gardens designed at spring outlets, has led to label the karst areas in the region as State Geoparks, which features the region a popular holiday destination, a backbone to regional economy. Past phreatic morphology and present relict nature suggest that the landscape evolution has changed the hydrologic conditions from phreatic to vadose, and thereby, modified the processes of speleogenesis and the characteristics of the caves. The uplift and erosion in Pilo-Plestocene is dynamic cause which governed the processes of karst development, likewise, climatic oscillations in the same period changed the solutional rates, and dominance of either chemical or mechanical. Although the spring ﬂow is dominantly controlled by the melting of snow and/or glaciers, rain events produce sharp spikes in spring hydrographs, primarily responsible for the undulating/seasonal trend in the δ2H and δ18O of the karst springs. Furthermore, the study provides new insights in understanding the dominant factors affecting the isotopic composition of the precipitation, snowpack, glacier melt, streams and springs. δ18O/ or δ2H of precipitation, snowpacks, glacier melt and karst springs show wide variation both in space and time, and are strongly inﬂuenced by the basin relief and meteorology. Similar temporal trends of isotopic signals in streams and karst springs reflect the rapid flow transfer due to karstification of the carbonate aquifers. Tracer breakthrough curves (TBC), retrieved for different springs suggest short travel time (2 to 7 d) and rapid conduit flow, which has practical consequences like, deterioration of water quality and variation in magnitude of groundwater flux in the region.

Monitoring of Himalayan and Polar Cryosphere using Earth observation data from orbiting satellites

Date: 2018-05-29
Speaker: Dr. Ishmohan Bahuguna
Venue: Ground Floor Lecture Hall

Abstract

Nitrogen dynamics in ecosystems with contrasting climate

Date: 2018-04-24
Speaker: Ms. Niharika Sharma
Venue: Ground Floor Lecture Hall

Abstract

Study of biogeochemical cycling of elements is very important in understanding the changes and responses of ecosystems towards the changing climate. Elemental circulation, its amount and availability within an ecosystem defines the health of ecosystem and species present in it. Nitrogen (N) is one such element which is required by all the species, as it serves as a growth limiting nutrient. Plants also require N for photosynthesis: a process to fix atmospheric CO2 into biomass, thus acts as carbon sink. N, if present in excess, can cause severe damage to ecosystems by emitting greenhouse gases (N2O) in the atmosphere, polluting water bodies (eutrophication) and result in biodiversity loss. In my talk, I will discuss about biogeochemical cycling of N in two different terrestrial ecosystems. These ecosystems differ from each other in terms of vegetation, land-use and climate. I will also compare the N dynamics within these ecosystems to address the differences and controls of N cycle.

Where did all the sand of the Thar Desert come from?

Date: 2018-03-20
Speaker: Dr. Anirban Chatterjee
Venue: Ground Floor Lecture Hall

Abstract

Deserts with their massive dune fields and vast wilderness have always inspired human imaginations. Understanding origin, evolution, ecology and anthropology of deserts has been a fascinating scientific pursuit. The Thar desert of Indian sub-continent is the 9th largest sub-tropical desert of the world that covers an area over 4000 sq. km. It is located along the eastern most stretch of the great Sahara-Arabian desert system of horse latitudes and hosts a variety of sand dunes. Yet it is one of the most populated deserts of the World. Even the first Indian civilisation developed along its margins. In spite of its apparent geographic and geologic importance, the sources of its sand remain largely speculative. In this context, I will discuss findings of previous studies and our effort using geochemical principles.

Model-based analyses of an Ocean acidification mesocosm experiment

Date: 2018-03-13
Speaker: Dr. Shubham Krishna
Venue: Ground Floor Lecture Hall

Abstract

Studies suggest that Ocean acidification (OA) has severe effects on marine phytoplankton. Mesocosm experiments allow investigations on impacts of OA on plankton communities in the vicinity of their natural habitats. Marine ecosystem models serve as an efficient tool to analyze and interpret mesocosm data, as they use mathematical equations to describe processes controlling dynamics of planktonic ecosystems. I will discuss results from a study that investigated effects of OA on phytoplankton growth dynamics by analyzing data from an ocean acidification mesocosm experiment using different model approaches. Applied methods yield the optimized model solutions (with optimised parameter values) that maximize the likelihood probability of models explaining mesocosm data. The model-based data analysis of the experiment suggests that the large variability that was observed in calcification could have been generated due to small differences in initial abundance of coccolithophores during initialization (filling) of mesocosms. The model seems to suggest that OA may enhance carbon fixation rates in phytoplankton, but at the cost of elevated metabolic stress

Paleogene sequences of Jaisalmer basin, Rajasthan - a paleoclimate archive

Date: 2018-03-06
Speaker: Dr. Amitava Patra
Venue: Ground Floor Lecture Hall

Abstract

The Jaisalmer basin is the eastern extension of the shelf part of the Indus basin and represents a more or less central part of the "West Rajasthan Shelf" tectonic province that is located to the west of the Aravalli ranges in western India, occupies an area of 42000 sq km and much of it is covered by the modern sand-dunes. Shallow-water sedimentary successions from the Jaisalmer carbonate platform offer a rare opportunity to learn about the Paleocene–Eocene Thermal Maximum (PETM; 55 Ma) and its impact on the shallow-water ecosystems. The PETM representing the extreme warming event in the Cenozoic Era is of particular interest to the Geoscientists since it is considered as an analog to the present climate change. In the studied carbonate samples, the Mn and Sr concentrations and low Mn/Sr ratio (<1) together with the stable and radiogenic isotope data suggest that they are pristine with little diagenetic alterations and have retained their primary isotopic signatures. A prominent negative excursion in δ13C curves of bulk-rock (- 3‰) is interpreted as the carbon isotope excursion during the PETM. Also, the δ18O (-6.4 to -9.3‰), values are very similar to PETM carbonate values in the studied samples.

Chemical and Isotopic Studies of Atmospheric Aerosol: Sources, Deposition Fluxes and Surface Ocean Biogeochemistry

Date: 2018-02-21
Speaker: Mr. A. K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Characterisation of organic matter source and sediment distribution in Ashtamudi Estuary, southern India

Date: 2018-01-30
Speaker: Dr. Praveen Mishra
Venue: Ground Floor Lecture Hall

Abstract

Modern climate study is essential to develop an understanding of past climate change. The present study is focused on the surface sediments of Ashtamudi Estuary (Kerala, southern India) to understand (i) the fate and sources of organic matter by investigating lipid biomarker (n-alkanes) distribution in modern sediments and vegetation samples; and (ii) the factors controlling the sediment distribution into the lake basin using geochemical approach. A number of n-alkane indices have been calculated to illustrate the variability in space by considering separately the river dominated northern reaches and marine-influenced southern part of Ashtamudi Estuary. The P-aqueous (Paq) and terrigenous/aquatic ratio (TAR) indices demonstrate maximum aquatic productivity (plankton growth and submerged macrophytes) in the tidal dominated region of the Ashtamudi Estuary. The carbon preference index (CPI) and average chain length (ACL) provide evidence for high terrestrial input in the river dominant region, whereas the lower end of the estuary is dominated in high aquatic productivity. The geochemical approach enabled us to delineate natural (fluvial and marine) versus anthropogenic factors in controlling the sediment distribution into the basin.

Characterisation of organic matter source and sediment distribution in Ashtamudi Estuary, southern India

Date: 2018-01-30
Speaker: Dr. Praveen Mishra
Venue: Ground Floor Lecture Hall

Abstract

Modern climate study is essential to develop an understanding of past climate change. The present study is focused on the surface sediments of Ashtamudi Estuary (Kerala, southern India) to understand (i) the fate and sources of organic matter by investigating lipid biomarker (n-alkanes) distribution in modern sediments and vegetation samples; and (ii) the factors controlling the sediment distribution into the lake basin using geochemical approach. A number of n-alkane indices have been calculated to illustrate the variability in space by considering separately the river dominated northern reaches and marine-influenced southern part of Ashtamudi Estuary. The P-aqueous (Paq) and terrigenous/aquatic ratio (TAR) indices demonstrate maximum aquatic productivity (plankton growth and submerged macrophytes) in the tidal dominated region of the Ashtamudi Estuary. The carbon preference index (CPI) and average chain length (ACL) provide evidence for high terrestrial input in the river dominant region, whereas the lower end of the estuary is dominated in high aquatic productivity. The geochemical approach enabled us to delineate natural (fluvial and marine) versus anthropogenic factors in controlling the sediment distribution into the basin.

Mukundpura Carbonaceous Chondrite

Date: 2018-01-23
Speaker: Dr. A. D. Shukla
Venue: Ground Floor Lecture Hall

Abstract

The little chunks of rock and debris in space are called meteoroids. They become meteors or shooting stars when they fall through a planet's atmosphere and leave a bright trail as they are heated to incandescence by the friction of the atmosphere. Pieces that survive the journey and hit the ground are called meteorites. The meteorites, holding immense information of the outer space strike on our planet Earth. However, they are noticed in areas of high human population on the basis of the fireball and the impact on the ground. Mukundpura meteorite is the most recently reported meteorite fall in India. It took place on June 6, 2017 at 5:15 IST, at Mukundpura village in the district of Jaipur, Rajasthan. This is found to be the 6th carbonaceous chondrite type meteorite fall documented in India. Preliminary results will be discussed in the seminar.

Foraminifera, A key to Quaternary Ocean

Date: 2018-01-16
Speaker: Ms. Nisha Bharti
Venue: Ground Floor Lecture Hall

Abstract

Foraminifera forms major part of ocean microfossils and has served as a good archive for paleo-oceanographic processes for decades. There are ~40,000 species found all over the global ocean. These organisms are sensitive to the changes in the environment where they reside. Foraminifers record variations in oceanic conditions in their calcareous shell. Geochemical and isotopic signature of foraminiferal shells extracted from marine sediments have been extensively used to study paleo-circulation, paleoclimate, paleobathimetry, stratigraphy, coastal pollution and sea level changes. This talk would attempt to explain possibility of deciphering past global ocean circulation and ventilation of water masses in Indian ocean using various planktonic and benthic foram species.

Elemental stoichiometry in the Ocean

Date: 2018-01-09
Speaker: Ms. Deepika Sahoo
Venue: Ground Floor Lecture Hall

Abstract

Around eight decades ago, Alfred C. Redfield established that the plankton elemental composition is similar to the composition of inorganic nutrients in the ocean (C:N:P =106:16:1). This elemental stoichiometric similarity, called as Redfield Ratio, has been the cornerstone in ocean biogeochemistry as it is used to infer ocean biogeochemical processes including the patterns of phytoplankton nutrient limitation and the linkages between different nutrient cycles. Studies based on numerical models, field observations and laboratories have shown variable C:N:P among ocean plankton communities. During the talk, I will discuss the latitudinal variation in stoichiometry in global ocean and the possible mechanisms behind such variation. Multiple nutrient limitation concept will be discussed to understand the optimal stoichiometry of plankton and their different growth phases.

2017

Holocene floods in the middle Satluj valley and their climatic implications

Date: 2017-12-27
Speaker: Ms. Shubhra Sharma
Venue: Ground Floor Lecture Hall

Abstract

Projections based on the climate change scenario predict increased frequency and/or increased magnitude of floods in the Himalayan region due to more intense and frequent coupling between the Indian Summer Monsoon (ISM) and the mid-latitude westerlies. In view of this, studies pertaining to the geological evidence of extreme hydrological events (paleo-floods) become important as these extend beyond the instrumental records and ensure better understanding of the river response to the climate variability. The Satluj River in the north-western Himalaya is frequented by devastating floods in the recent past thus suggesting its sensitivity towards extreme hydrological events. We studied the sedimentary records of palaeofloods in the middle Satluj which has preserved around 27 flood events of increasing magnitude. The geochemical fingerprinting (based on CIA) indicates that the floods were generated in the Higher Himalayan Crystalline with contribution from the trans-Himalaya. Optical chronology allowed us to constrain the floods into four major clusters (viz. 13-11 ka, 8-5 ka, ~4 ka and <2 ka). Climatically, these clusters represent the transitional climatic conditions during the Holocene and are contrary to the earlier studies where intensified Indian Summer Monsoon (ISM) was implicated for the floods in the Himalaya. In this presentation, I would be giving a broad overview of the existing studies on paleo floods in the Indian Himalaya, with an emphasis on the causes of Holocene floods in the middle Satluj valley and their implications towards understanding the synoptic scale coupling (Arctic and North Atlantic Oscillation).

Did life originate in ocean-ridge settings?

Date: 2017-12-19
Speaker: Dr. Alik Sundar Majumdar
Venue: Ground Floor Lecture Hall

Abstract

Recent investigations demonstrate that life most likely have originated in the deep ocean when H2 reacted with CO2 to form CH4 via Fischer-Tropsch reaction mechanism. Although it is established that concentration of CO2 was high in the Archean (4-2.5 Ga) ocean water, uncertainty remained on the process of H2 generation in the early Earth. Following this, I will show an example of geosphere (rock) - hydrosphere (water) interaction predominantly at ocean-ridge settings, which has the potential to release H2 as reaction product. Using a combination of natural observations, experimental studies and numerical modeling, I will present how the chemistry of the interacting fluid can influence the reaction products and also how temperature plays an important role on controlling the amount of H2 generation during such process. This study may therefore provide an insight on the origin of life in the early Earth.

Paleoclimate reconstruction using high altitude lake sediments

Date: 2017-12-12
Speaker: Mr. Abdur Rahman
Venue: Ground Floor Lecture Hall

Abstract

Lake sediments form an important archive to study paleoclimate and paleobiological condition in the continental interior. Stable isotopic composition of carbon and nitrogen in organic matter of the lake sediment provide an important insight into the paleovegetation and nutrient conditions. However, reconstruction of paleotemperature and paleoprecipitation in high altitude environment lacking in situ calcite formation remains challenging. Oxygen isotopes measurement of diatoms using laser fluorination technique in lake sediments has the potential to provide a robust proxy for the same. During this talk, I will explain the methodology, its importance and analytical challenges regarding this technique along with preliminary results of carbon isotopic composition in organic matter from a sediment core in a Himalayan lake.

A discussion on controls on the Quaternary glaciation in the NW Himalaya

Date: 2017-11-28
Speaker: Dr. Shubhra Sharma
Venue: Ground Floor Lecture Hall

Abstract

Himalayan glaciation show inter-regional variability on centennial to multi-millennial timescales where the glaciers are fed by two major weather systems ‒ the Indian summer monsoon (ISM) and the mid-latitude westerlies. It is suggested that the terrain that lies in the influence of mid-latitude westerlies (NW Himalaya) should respond in accordance with the northern latitude glaciation, where as those that are located in ISM dominated region (central/eastern Himalaya) should be modulated by the winnowing and waxing of the ISM. In addition to this, there is also suggestion that glaciers located in the orographically shielded region (Trans Himalaya) are sensitive to the precipitation changes whereas those in the trajectory of the ISM are temperature sensitive. In order to understand the pattern of glaciation in the Himalayan region, one need to take into consideration, the above variability that is further modulated and controlled by the Himalayan topography and local factors. In the presentation, I would be giving an over view of the current understanding of late Quaternary glaciation in Himalaya along with presenting our studies from the Nubra (Siachin), Zanskar and Sarchu plain in the westerlies dominated NW Himalaya

Rajmahal and Sylhet Traps Revisited

Date: 2017-11-14
Speaker: Prof. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Reactive Oxygen Species (ROS) generation capacity of ambient aerosol over a semi-urban and a high altitude site

Date: 2017-09-12
Speaker: Mr Anil Patel
Venue: Ground Floor Lecture Hall

Abstract

Aerosol are known to exhibit large temporal and spatial variability, which causes large uncertainty in assessing aerosol effects on air quality and climate. Further, aerosol are increasingly recognized for the production of Reactive Oxygen Species (ROS) in their ambience and thus affect oxidative capacity of the atmosphere, and also human health on inhalation. This presentation will discuss the characteristics and ROS generation capacity of ambient aerosol collected over a semi-urban site (Patiala) and a high-altitude site (Mount Abu).

Monitoring atmospheric Greenhouse gases and secondary organic aerosols over India and Southeast Asia

Date: 2017-09-05
Speaker: Dr. Tania Guha
Venue: Ground Floor Lecture Hall

Abstract

According to WRI, 2013 India contributes 6.43% to the total GHGs emission and 2/3 of national burden comes from urban area. Thus monitoring GHGs over urban area is essential. During 2008-2011, mixing ratio and delta-13-C of atmospheric CO2 was monitored at an urban station in India and revealed possible anthropogenic sources. Similar temporal variability has also been observed in atmospheric CH4 concentration over India. The impact of seasonal wind patterns on CH4 variability are analyzed using 3-dimentional model-simulated CH4. The atmospheric budgeting of N2O is more complicated due to little variability in its observation. During 2013-2015, delta-15-N, delta-18-O and site-preference (SP) values of atmospheric N2O was monitored over a semi-urban station at west Pacific island. The station captured anthropogenic signal and stratospheric intrusion. The atmospheric NOx has increased drastically in last few decades and has implications on air quality. The conversion of NOx to aerosol nitrate makes it suitable for studies the NOx precursors as well as its formation pathways. We carried out nitrates aerosol sampling from high-mountain station in west Pacific island during 2010. The objective of our study is to identify sources of NOx for the nitrate-phase in aerosol and understand the nitrate formation pathways from its precursor-NOx.

Role of ENSO on spatio-temporal variation of rainfall and its delta-18-O over Indian subcontinent using GPCP and isoGSM model

Date: 2017-08-08
Speaker: Mr. P. Kiran Kumar
Venue: Ground Floor Lecture Hall

Abstract

The Indian Summer Monsoon (ISM) plays an important role in the climate of the southeast Asia. Central Indian plains receive ~80% of the annual rainfall during the summer monsoon. The rainfall over India is affected by many ocean-atmospheric coupled processes which lead to phenomenon like El-Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and Madden Julian Oscillation (MJO) which occur at inter-annual to intra-seasonal time scales. These coupled processes control the strength of the monsoon and the climate of the Indian subcontinent. In this seminar, I will discuss the spatial patterns of ISM in response to ENSO at monthly to seasonal time scales. A comparison of rainfall with paleoclimate data and its implications will be presented.

Corals from Indian Ocean - proxy for Indian Monsoon

Date: 2017-07-25
Speaker: Mr.Harsh Raj
Venue: Ground Floor Lecture Hall

Abstract

Indian monsoon is an integral part of climate over Indian subcontinent and has influence on large part of Indian population. Therefore, understanding past changes in strength of Indian monsoon is important. Winds associated with monsoon causes changes in sea surface condition which is recorded by corals. d18O, d13C and delta14C values of coral carbonate skeleton can be used as proxy for past sea surface conditions and can be studied to understand past change in strength of Indian monsoon. Corals from the northern Indian Ocean record sea surface temerature (SST) variations induced by upwelling due to monsoon winds. These SST changes also affects the growth rate of the corals. Some preliminary observations on coral growth rate from Lakshadweep will be discussed

Microbial life: At interface and in the aqueous marine environment

Date: 2017-07-18
Speaker: Dr. Anand Jain
Venue: Ground Floor Lecture Hall

Abstract

Microbes in any bulk phase (liquid or gas) tend to accumulate or attach at interfaces, such as solid-liquid, liquid-gas and solid-gas. The microbial life at interfaces is often termed as biofilms. Biofilm formation is usually detrimental to human health and man-made structures including ships, underwater pipelines, submersibles etc. On the other side, they are beneficial for the degradation of waste, organic carbon and production of value added products. During this presentation we will discuss the mechanisms underlying bacterial adhesion and biofilm formation onto to solid surfaces, as well as electron transfer mechanism in microbial biofilms capable of generating electricity via organic matter oxidation. Microbes in the ocean play an important role in biogeochemical cycling of carbon, nitrogen, phosphorus, iron and sulfur. They form the base of marine food chain, recycling nutrients and organic matter, and producing vitamins and cofactors needed by higher organisms to grow and survive. Understanding of microbial community structure and function is very crucial for elucidating their role in various biogeochemical cycles and impact on or of climate change. The factors influencing bacterial community structure in marine environment and role of marine bacteria in carbon cycling will be discussed.

Long-term isotope record of daily precipitation at Ahmedabad in semi-arid western India: insights into regional hydrometeorological processes.

Date: 2017-07-11
Speaker: Mr. Harsh Oza
Venue: Ground Floor Lecture Hall

Abstract

There are numerous published studies, which confirm that the weather systems across the globe are undergoing changes, as manifested in trends in temperature, rainfall, heat waves, cyclones, floods and droughts on decadal or sub-decadal scales. In spite of the recognition of various broad patterns in weather indices, there is lack of clarity about the changes in the subtle hydro-meteorological processes in different climatic regions. Many of the meteorological phenomena are so localised that concept of a few homogenous meteorological regions across the India is no more convincing. It this scenario, it is important to understand the contemporary hydro-meteorological processes from several locations, which determine the spatio-temporal distribution of water in atmosphere, surface and sub-surface domains. It is the only option, until major climate change is recognized after a few decades of systematic changes in weather and its severe consequences on socio-economy. >From this perspective, Ahmedabad city (23.03°N; 72.55°E) in the hot semi-arid western India is an important geographic location to investigate the hydrometer logical processes because it has been experiencing erratic weather extremes such as heat waves, cloud bursts, floods and droughts, superposed on the climate normal. Stable isotopes of oxygen and hydrogen in precipitation can provide information about the source of vapour, rainout history, vapour recycling, post-precipitation modifications, cloud micro-physical processes etc. Considering this, stable isotopes of oxygen and hydrogen have been monitored in daily precipitation at Ahmedabad since last 12 years(2005-2016). A rigorous analyses of this important isotope dataset in conjunction with other ground based and remotely sensed meteorological parameters will be presented in this seminar.

Modelling the physical and biogeochemical interactions of the north Indian Ocean

Date: 2017-07-04
Speaker: Dr. Abhisek Chatterjee
Venue: Ground Floor Lecture Hall

Abstract

The Indian subcontinent divides the north Indian Ocean (IO) into two smaller basins, Arabian Sea (AS) in the west and Bay of Bengal (BoB) in the east. Owing to the close proximity of the equatorial IO, the circulation in the BoB and AS is not only driven by the local winds, but also largely influenced by forcing from the equatorial Indian Ocean. In this talk, I will discuss various equatorial processes that primarily drive the circulation in the bay and East India Coastal current (EICC) in particular. I will also show results from a biogeochemical model based on Modular Ocean Model (MOM) to explain some of the key bio-physical interactions in the north Indian Ocean.

Understanding Aluminium Biogeochemical Cycle in the Indian Ocean

Date: 2017-06-27
Speaker: Mr. Naman Deep Singh
Venue: Ground Floor Lecture Hall

Abstract

Deposition of mineral dust over oceans and their subsequent partial dissolution in seawater is an important mechanism for supply of bio-essential trace metals to the open oceans. Due to dearth of direct estimates of dust deposition fluxes over oceans (especially in most remote regions such as Southern Oceans), development of proxy to dust supply over global oceans is imperative. Dissolved aluminium (dAl) in the surface waters of remote oceans: 1) is majorly brought through eolian input, 2) has short residence time (few weeks to ~4 years) and 3) is not bio-limiting and redox insensitive. Therefore, dAl distribution in the surface waters of open oceans has been historically and recently used to model the dust deposition fluxes over oceans. However, dAl data in the world oceans is sparse with Indian Ocean among the most under sampled region. Also, dAl concentrations have shown large inter-basin fractionation due to the varying sources (eolian, sedimentary, etc.) and oceanic processes, such as water mass advection, differential scavenging, etc. Evidences of incorporation of Al from the water column to biogenic opal are also present and hence Al coupling with the Si-cycle in seawater is suspected. Together, all the above mentioned processes, suggest for the comprehensive evaluation of biogeochemical cycling of Al in seawater for more refine assessment of dAl derived dust deposition fluxes. In this talk, I shall discuss different processes, source and sinks of dAl to the oceans which govern its distribution. Also, recently established fluorimetric method for the detection of nanomolar levels of dAl in seawater and preliminary results achieved from northern Indian Ocean will be presented.

Impact of the Oxygen minimum zone (OMZ) on marine Zinc cycle: Results from the GEOTRACES GI-10 cruise

Date: 2017-06-13
Speaker: Mr. Venkatesh Chinni
Venue: Ground Floor Lecture Hall

Abstract

Zinc (Zn) is considered as a key trace element for primary production in seawater along with the Iron. Zinc showed a nutrient type behaviour with lower concentration in the surface waters than underlying waters. A strong and significant correlation is observed between Silicate (Si) and Zn in the GI-10 section. However, a lower slope is observed between Zn vs. Si in the Northern Indian Ocean compared with the global data. In addition to this, decoupling of Zinc and Silicate has been observed in the OMZ waters of the Northern Indian Ocean. Results are suggesting that water column oxygen depletion has a substantial impact on Zn biogeochemical cycling, impacting the global relationship between Zn and major nutrients. In this talk, I will discuss about the Zn distributions and its internal cycling in the Northern Indian Ocean.

Nitrogen- Inside and out of the soils

Date: 2017-06-06
Speaker: Ms. Niharika Sharma
Venue: Ground Floor Lecture Hall

Abstract

Nitrogen is a fundamental element required to sustain all life forms. Although there is plenty of nitrogen available in the atmosphere, basic of the hierarchy- the primary productivity which also behaves as the largest natural sink of atmospheric carbon dioxide, is limited by the availability of active forms of nitrogen. Where nitrogen in form of ammonium and nitrate behaves as a nutrient required by primary producers, in another form (nitrous oxide) can act as a potent greenhouse gas. Recent studies shows that the behavior of nitrogen transformations can largely be affected by the anthropogenic activities and climate change. During my talk, I would discuss about the importance of various forms of nitrogen and their dynamics in the terrestrial ecosystems and its status in India.

Organic Aerosol: Composition and Chemistry

Date: 2017-05-30
Speaker: Dr. Neeraj Rastogi
Venue: Ground Floor Lecture Hall

Abstract

Evidence of solar forcing on late Quaternary paleo-monsoonal records from the equatorial Indian Ocean

Date: 2017-05-23
Speaker: Ms. Chandana K.R.
Venue: Ground Floor Lecture Hall

Abstract

The late quaternary period witnessed drastic climate perturbations in the form of glacial-interglacial cycles as results of solar forcing. Migration of the Intertropical Convergence Zone (ITCZ) is significantly influenced by solar variability thereby causing seasonal reversal of monsoonal winds over India and adjacent regions. Based on geochemical and isotopic proxies, changing monsoonal intensity and its influence on overhead productivity during late quaternary period from the intermixing zone of the Bay of Bengal and the Arabian Sea would be discussed. The study demonstrates the solar forcing of various processes as deciphered from solar periodicities in the sediment records of the equatorial Indian ocean.

Evolution of the Mesoproterozoic Chattisgarh basin: A geochemical perspective

Date: 2017-05-16
Speaker: Mr. Bivin Geo George
Venue: Ground Floor Lecture Hall

Abstract

The Mesoproterozoic Era (1.6 - 1.0 Ga) in the Earth’s history is characterized by environmental, evolutionary, and lithospheric stability that contrasts the dramatic changes happened in the preceding and succeeding eras. In the talk, I shall discuss our on-going efforts in understanding the Mesoproterozoic records of India through geochemical studies of the sediments deposited in the Chattisgarh basin. Results of our study aimed at constraining the age, understanding the provenance, paleogeography and tectonic setting of the basin shall be presented in the talk.

Biogeochemical investigation on eastern Indian estuaries

Date: 2017-05-09
Speaker: Dr. Manab Kumar Dutta
Venue: Ground Floor Lecture Hall

Abstract

A comprehensive investigation was conducted at Hooghly estuary and major estuaries of Indian Sundarbans (Saptamukhi, Thakuran and Matla) during summer-time, 2016. The estuaries of Sundarbans were mainly marine dominated (polyhaline) while a sharp salinity gradient was noticed for the Hooghly estuary. At this study, stable isotopes have been widely used for the first-time to understand hydrological as well as biogeochemical processes (mainly carbon) operating within these two contrasting estuarine systems (anthropogenic vs. mangrove dominated estuaries). Variability of δ18O and δD within the given sampling stretch clearly indicates proper mixing of fresh and marine water at Hooghly estuary while the case was not so effective for the estuaries of Sundarbans. Moreover, during summertime impact of these estuarine systems on regional climate will be also discussed based on computed emission of radiatively active trace gases (CO2 and CH4) from water - atmosphere interface.

Status of 1MeV PRL- Accelerator Mass Spectrometer (AMS) for the Measurement of 14C, 26Al and 10Be.

Date: 2017-04-25
Speaker: Dr. Ravi Bhushan
Venue: Ground Floor Lecture Hall

Abstract

A New Accelerator Mass Spectrometry (AMS) Laboratory has been successfully installed at PRL-Thaltej Campus dedicated for the measurement of 14C, 10Be and 26Al. This facility has been acronymed as PRL AURiS (Physical Research Laboratory Accelerator Unit for RadioIsotope Studies). The 1 MeV AMS system manufactured by High Voltage Engineering Europa B.V., The Netherlands comprises: (1) Ion source for production of negative ions (2) Low Energy Mass Spectrometer for the selection and injection of isotopes of interest, (3) 1 MeV Tandetron Accelerator for acceleration and Argon gas for molecular stripping, (4) High Energy Mass Spectrometer for focussing the isotopes leaving the accelerator into the Faraday Cups and towards the Ionisation detector, (5) 120o Electrostatic Analyser (ESA) for focussing and further filtering followed by (6) a Low Background Magnet, and the Ionisation Detector for the measurement of the rare isotopes. Additionally, Automated Graphitisation Equipment (AGE3) for preparation of carbon samples as graphite for AMS measurement has been installed. The AMS facility can measure 14C, 10Be and 26Al and would contribute towards the various research programmes in Oceanography, Geology, Climate Studies, Archeology, Hydrology and Planetary Sciences. Preliminary results obtained on performance of PRL AURiS would be presented.

Brown Carbon Characteristics during Paddy-Residue Burning over the Indo-Gangetic Plain

Date: 2017-04-18
Speaker: Mr. Satish R V.
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric carbonaceous aerosols consisting of black carbon (BC) and organic carbon (OC) influence Earth’s radiative balance by interacting with the solar radiation. The role of BC in the atmosphere is reasonably well understood and incorporated into climate model studies. On the other hand, OC considered as “white” for many years because they efficiently scatter visible radiation. Recent findings suggest that a significant part of organic aerosols absorbs light at near UV and visible region and termed as Brown Carbon (BrC). To assess the role of BrC on regional/global level, it is inevitable to understand their sources and characteristics on temporal and spatial scale. However, such studies are very limited in literature. This study presents the BrC spectral characteristics and chemical composition of PM2.5 samples collected before, during and after a large scale paddy-residue burning over Patiala (30.2oN, 76.3oE), located in the northwestern IGP during October-November, 2014. Results from this study will be discussed.

Latest updates on proxy records of Sunspot activity in the Holocene and the early Permian.

Date: 2017-04-04
Speaker: Dr. M. G. Yadava
Venue: Ground Floor Lecture Hall

Abstract

Cyclicity in time series of climate proxies, belived to be of solar origin, is documented in the high resolution archives such as ice cores or tree rings in the present and the geological past. The smallest cycle with 11 yrs periodicity is attributed to the sunspot activity and has a measurable effect on the Earth’s climate as shown by the Maunder minimum. Indian rainfall also shows 11yr periodicity, in the modern rainfall and the proxy data from climate archives. It seems that 11 yr solar cycle has been affecting the Earth’s climate over hundreds of million years by holding its stable periodicity over time. Some of the proxy based evidences will be presented to discuss a debatable topic, which needs continued investigation for better understanding.

Stream power: A unified concept in fluvial geomorphology

Date: 2017-03-28
Speaker: Dr. Vikrant Jain
Venue: Ground Floor Lecture Hall

Abstract

Last two decades have witnessed major advancements in the quantitative understanding of geomorphological processes at different spatio-temporal scales. Modelling of geomorphic processes needs well defined geomorphic transport law(s) for different geomorphic systems. Studies in fluvial geomorphology has benefitted by a concept of stream power, which is a fundamental parameter to define driving force at any scale. It was incorporated in geomorphic studies from sixties through a study of sediment transport (Bagnold, 1966*). Subsequently, the stream power concept has been successfully applied to model various processes at different scales ranging from sand particle movement to landscape evolution processes. My talk will highlight the significance of unified concept in a geomorphic system, which led to integrate processes at different scales. The work will highlight new advancements and challenges in this research area. *Bagnold, R.A., 1966. An approach to the sediment transport problem from general physics. Geological Survey Professional Paper 422-I, I1– I37.

BIOGEOCHEMISTRY OF ASIA’S LARGEST LAGOON

Date: 2017-03-21
Speaker: Ms. Rupa Mukherjee
Venue: Ground Floor Lecture Hall

Abstract

Wetlands, lakes and lagoons play a central role in regional hydrologic and biogeochemical cycles, in maintaining biodiversity, and in a wide range of human activities. Chilika lagoon, the Asia's largest brackish water lagoon with estuarine character is a very important ecosystem in terms of ecology as well as economy. The talk will focus on the various ecological as well as environmental parameters of the lagoon which has been studied in 2004-2006 along with present understanding of the delta-13-C and delta-15-N isotopic signatures and N uptake rates.

Constraining the exhumation history of the Nagaland ophiolite complex

Date: 2017-03-07
Speaker: Dr. B. Maibam
Venue: Ground Floor Lecture Hall

Abstract

The current understanding of the tectonic significance of blueschist-facies rocks associated with the Indo-Myanmar ophiolite belt is unclear due to a lack of systematic petrological study and the paucity of reliable age data. During the talk, I would present new integrated petrological and geochronological data for samples from the Nagaland complex of the Indo-Myanmar ophiolite belt, northeastern India, which constrains the pressure–temperature conditions and ages of peak and retrograde metamorphism

Depositional Environment of the Paleogene sequences of Jaisalmer basin, Rajasthan, Western India.

Date: 2017-02-21
Speaker: Dr. Amitava Patra
Venue: Ground Floor Lecture Hall

Abstract

The Jaisalmer basin is the eastern extension of the shelf part of the Indus Basin and represents a more or less central part of the "West Rajasthan Shelf"tectonic province that is located to the west of the Aravalli ranges. The Paleogene succession of the Jaisalmer basin has hydrocarbon potential. This succession is dominantly represented by calcareous and argillaceous rocks with a subordinate proportion of arenites in the basal part. The facies associations suggest a complete 2nd order cycle of transgression-regression of the sea from shoreface to tidal flat in the Jaisalmer pericratonic basin. Provenance of the late Paleocene sandstone of the Jaisalmer basin has been determined by petrographic and heavy minerals analysis supported by paleocurrent study.Q-F-L and Qm-F-Lt diagrams suggest for a provenance at the margin of the craton interior and transitional continental. All these suggest that the provenance was dominated by low to medium grade metamorphic and volcanic rocks of the Aravalli Supergroup, Jurassic succession and the Deccan basalts which were denuded during late Paleocene.

A review of PRL’s journey towards measurement of nitrogen transformation rates.

Date: 2017-02-14
Speaker: Dr. Sanjeev Kumar
Venue: Ground Floor Lecture Hall

Abstract

Reconstruction of Mid-Late Holocene Land-Sea interaction using Sulfur Isotopes as a new tracer

Date: 2017-02-07
Speaker: Dr.Upasana Banerji
Venue: Ground Floor Lecture Hall

Abstract

Sea level varied throughout the geological past where eustatic and/or tectonic change played significant role in controlling the sea level. Unlike glacial and interglacial periods, no major sea level fluctuations have been observed during mid-late Holocene period. Thus, reconstruction of local sea level history rather than accepting global sea level change remains a challenge. Various studies have addressed mid-late Holocene sea level changes but only few could delineate the tectonic component involved in it. Saurashtra coast provides an ideal platform to study Holocene land-sea interactions. The southern Saurashtra coast consists of extensive mudflats which can provide a continuous record of sea level change. Sulphur isotope (delta 948;34S) has played a crucial role in constraining the biogeochemical cycle in modern environment and proven to be a valuable tool in unravelling the early history of earth surface oxidation. The talk will address local tectonic event deciphered from sulfur isotopes supported by productivity and redox proxies that resulted in local sea level change during mid-late Holocene period.

The tale of Phosphorus-the devil's element

Date: 2017-01-17
Speaker: Dr. Bhavya P. S.
Venue: Ground Floor Lecture Hall

Abstract

The discovery of phosphorus was an accident while all the alchemists in 17th century were behind the mythological substance, the philosopher's stone. This light bearing substance later on became part of many revolutionary changes in the modern human history. The eventual entry of Haber-Bosch process led to green revolution which enhanced the crop production as well as population density. However, excess nutrient usage led to aquatic eutrophication. The talk will address the revolutionary developments in the history of biogeochemistry after the finding of phosphorus, the devil's element. The talk will also give glimpses of mitigation strategies which have been developed in the past few decades to control the aquatic pollution.

Karoo CFB, Southern Africa-Evolved From MORB By Mixing With A-Type Rhyolite In Bimodal Association

Date: 2017-01-10
Speaker: Dr. Saumitra Misra
Venue: Ground Floor Lecture Hall

Abstract

The ~183 Ma Karoo CFB of southern Africa is a part of the Karoo-Ferrar-SE Australia Large Igneous Province, which is believed to erupt behind the convergent Pacific margin during the break up of Pangea between ~200-175 Ma. Integrated petrographic and geochemical study suggests that magma mixing had an important role in the geochemical evolution of Karoo CFB, and imprinted a lithospheric signature on the Karoo basalts. The Karoo CFB evolved from the MORB-like parent magma through mixing with bimodal rhyolitic magma and hence does not require a mantle plume hypothesis.

2016

Corals - unfolding the history of tropical oceans

Date: 2016-12-20
Speaker: Mr. Harsh Raj
Venue: Ground Floor Lecture Hall

Abstract

Paleoclimatic reconstruction is important for understanding climate and its variations. Geochemical and isotopic proxies have been effectively used to study past climatic variations as they record changes in different properties of ocean. Corals provide unaltered high-resolution records of such proxies. Events like ENSO (El Nino Southern Oscillation) and IOD (Indian Ocean Dipole) observed in tropical Pacific Ocean and Indian Ocean respectively are result of amplified climatic variation. Such events have enormous socio-economic impacts globally and require better understanding. delta-18-O, delta-13-C and delta-14-C in coral skeleton are some of the potential tracers which acts as a proxy indicator of variations in SST, salinity, upwelling, rainfall etc. This presentation highlights use of geochemical proxies in corals for paleoclimatic reconstruction. Possibility of using these proxies to identify ENSO and IOD signatures in context of my proposed research plan would also be discussed.

Classical Isotope Effects in Precipitation and Recent Advancement

Date: 2016-11-29
Speaker: Mr. Harsh Oza
Venue: Ground Floor Lecture Hall

Abstract

The relationship between the oxygen and hydrogen isotopic composition (d18O and dD) of precipitation and certain climatic and geographical factors such as, surface air-temperature, amount of rain, altitude and latitude was well recognised and explained by the early 1960s. These have come to be known as classical isotope effects, namely, amount effect, altitude effect, continental effect, temperature effect etc. Over the years, with the advent of new scientific techniques, larger data sets from in-situ and remotely sensed observations and better understanding of climate systems some new concepts such as dependency of isotopes on types of cloud, atmospheric moisture residences time, late monsoonal depletion, local recycling, and western disturbances, etc. have also been recognized and explained. In this seminar some of the classical isotope effects will be revisited and recently reported newer observations will also be presented. Departure from the classical isotope effects observed in the Indian isotope dataset will also be pointed out along with possible explanation.

Biogeochemistry of trace elements in the seawater

Date: 2016-11-22
Speaker: Mr. Namandeep Singh
Venue: Ground Floor Lecture Hall

Abstract

Oceanic processes (physical, chemical and biological) set major controls on transport and transformation of mass and energy through different spheres of the Earth. Various trace elements present in the ocean waters are the integral part of these processes and are very sensitive to the processes involving their exchange and transport in the ocean. Many trace elements (e.g. Fe, Zn, Mn, Cu, Cd, Ni, Co) are nutrients to the marine primary producers. Consequently, these trace nutrients limit, in large parts of global ocean, the process of carbon and nitrogen fixation into organic matter, which directly regulates the atmospheric CO2 budget and hence the global climate. Trace elements (e.g. Mo, Cr, Pb, Ag) are also excellent tracers of Eh-pH conditions of the ocean waters and anthropogenic inputs to the oceans. A comprehensive study of biogeochemical cycling of these trace constituents is also therefore needed to understand marine ecosystem dynamics and the impact of human activities on it. In this presentation, I will discuss about biogeochemistry of some of the important trace elements involved in the oceanic processes with focus on bio-essential trace metal. Also, recent progress towards the understanding of biogeochemical cycling of some of these trace elements in the Indian Ocean and my near future research plans will be discussed.

What we have learned from 17^O-excess: a new tracer in hydrological cycle

Date: 2016-11-17
Speaker: Dr. Shyam Ranjan
Venue: Ground Floor Lecture Hall

Abstract

The stable isotope ratios of water in different phases acting as a powerful tracer of the global hydrological system. The ratio of 17^O/16^O and 18^O/16^O in air O2 and water is very useful for assessment for photosynthetic production on large scales as well as in the hydrologic cycle. For all these applications, the ratio of 17^O /16^O and 18^O/16^O in water should be known with very high precision. A new hydrological tracer: 17^O-excess can be used to estimate the past humidity changes from ice cores and trace the stratospheric water vapor intrusion (especially at a remote site in East Antarctica). Interestingly trace of stratospheric influence also has been recorded at the mid-latitude during large volcanic eruption i.e. Pinatubo eruption in 1991. Recent work on Western Himalaya (Indian Side) clearly indicates the influence of 17^O -excess during westerly and Indian Summer monsoon. The more in-depth study is needed to understand the role of 17^O-excess in Himalayan Glacier and its ecosystem.

Sources and Characteristics of Brown Carbon Aerosols over North India through Real-time Measurements

Date: 2016-09-12
Speaker: Mr. Satish R V.
Venue: Ground Floor Lecture Hall

Abstract

Recent studies have documented that a certain type of organic carbon (predominantly water soluble) significantly absorb light at near-UV (300-400) and visible regions, which is termed as “Brown Carbon (BrC)”. Recent global models estimate that light absorption by BrC in different regions of the world may be 30–70% of that due to black carbon (BC). To assess the role of BrC on regional and global level, it is important to understand their sources and characteristics on temporal and spatial scale, which is scarce in literature. Semi-continuous measurements of water soluble organic carbon (WSOC), BrC, BC and chemical composition of organic and inorganic aerosols were performed over Kanpur during winter season (December, 2015-Dec to February, 2016) using state-of-the-art instruments. Diurnal variability in the absorption coefficient of BrC at 365 nm (babs_365) showed higher values during late evening through early morning and attributed to primary emissions from biomass burning (BB) and fossil fuel burning (FFB). Primary BrC, assessed based on H:C ratios from HR-ToF-AMS, dominates the total BrC abundance with higher babs_365. Secondary BrC, assessed based on O:C ratios, was abundant in the morning and afternoon with lower babs_365. Further, diurnal variability in ratios of babs_365 with babs_405 and babs_420 suggests that BrC composition is not uniform throughout the day. Fog processing of BrC was also found to be affecting babs_365 positively.

Paleomonsoon reconstruction of Andaman Sea for the last ~66ka inferences based on the planktonic foraminifera

Date: 2016-08-23
Speaker: Mr. Kiran Kumar
Venue: Ground Floor Lecture Hall

Abstract

The Andaman Sea located in the northeastern region of the Indian Ocean, is very less studied and suitable region for studying the past monsoon variability based on the variation in the huge fresh water influx to Andaman Sea. This region is influenced by fresh water influx from the Irrawaddy and Salween river system, direct precipitation and the fresh water mixing from the Bay of Bengal through the surface current transport. The monsoon reconstruction based on the oxygen isotopic variation in the foraminiferal shells can be interpreted in terms of the variation in the paleo-fresh water influx from the river system. The relative difference of δ18O of different depth habitable species can be used as the freshwater induced upper ocean stratification. In this seminar I will discuss paleomonsoon reconstruction and the paleoceanography of Andaman Sea based on oxygen isotopic variation in the planktic foraminifera from the published data.

Nitrogen cycling in terrestrial ecosystems

Date: 2016-08-09
Speaker: Ms.Â Niharika Sharma
Venue: Ground Floor Lecture Hall

Abstract

Nitrogen cycling in terrestrial ecosystems can play an important role in primary productivity and climate change. Study of gross N transformation rates can enable us to determine the capacity of plants to fix atmospheric carbon dioxide and hence the productivity in given set of climatic conditions. Also, emission of nitrous oxide (N2O) as an intermediate product of N-cycling is not fully understood and there remains lack of information regarding the balance in N2O budgets. In my talk, I would discuss these issues in detail and mention the application of stable isotopes in determination of each process. I would also discuss about different ecozones within India and rationale behind selecting such systems as my study areas.

Reactive Oxygen Species (ROS) generation capacity of ambient aerosols over the Indo Gangetic Plain (IGP) during winter

Date: 2016-08-02
Speaker: Mr. Anil Patel
Venue: Ground Floor Lecture Hall

Abstract

Transition metals and other redox active species present in ambient aerosols have potential to produce Reactive Oxygen Species (ROS), which can severely impact the ambient air quality. ROS affect atmospheric chemistry, human health and agricultural productivity. However, studies on ROS generation capacity (i.e., oxidative potential (OP) or toxicity) of ambient aerosols are still lacking over India. The OP of aerosols, collected during winter from a site located in the Indo-Gangetic Plain, has been measured using Dithiothreitol (DTT) assay. Preliminary results suggest that the toxicity depends more on aerosol composition rather than its mass concentration. Relationship of OP with various chemical species has also been investigated. These results will be discussed in the present talk.

Fluorometric detection of dissolved Zinc in seawater

Date: 2016-07-26
Speaker: Mr. Venkatesh Chinni
Venue: Ground Floor Lecture Hall

Abstract

Low Zinc (Zn) concentrations in surface seawater could limit growth of phytoplankton which in turn may limit primary production” – Zinc Hypothesis. Although like Iron (Fe), this hypothesis has not been verified in open oceans through field studies, but cultural experiments show growth of microorganism’s (more than 300) is limited by the low concentrations of Zinc. Also, in the oceans, dissolved Zinc (DZn) has a nutrient like vertical profile with a particularly strong correlation with silicate. Checking the Zinc hypothesis (Whether it can limit primary production or not) and understanding its relation with silicon is the contemporary area of interest for many chemical and biological oceanographers. To understand these things one should have a better knowledge on the biogeochemical cycle of Zn which is poorly understood due to the sparse observations in the world Oceans especially in the Indian Ocean. Measuring Zn concentrations in the ocean is highly challenging due to its presence of sub nanomolar levels, high matrix and its ubiquitous nature of contaminating the samples. In this talk, I will discuss about the sensitive flow injection method which has been established in the lab for the determination of sub nanomolar levels of DZn in seawater using fluorometric detection. Further, the new results on DZn obtained in the North-Eastern Indian Ocean and associated Zinc biogeochemistry will be presented.

A geochemical approach to the history of sedimentation in the Neoproterozoic Marwar Basin, Rajasthan

Date: 2016-07-19
Speaker: Mr. Bivin Geo George
Venue: Ground Floor Lecture Hall

Abstract

The Late Neoproterozoic to Early Cambrian (750Ma- 500Ma) witnessed remarkable events in the Earth’s history such as the break-up of the supercontinent Rodinia and amalgamation of Gondwanaland, evolution of multi-cellular life, a major oxygenation event and the evolution of a climate system that is similar to the present day. These global events often leave their imprints in the contemporaneous sedimentary rocks. In the talk, I shall discuss our ongoing efforts in unravelling some of these mysteries through geochemical studies of the sediments deposited in the Neoproterozoic Marwar basin of Rajasthan. Results of our study aimed at constraining the age, understanding the provenance, paleogeography and tectonic setting of the basin shall be presented in the talk.

Life at high salt concentrations: Sulfate reduction and survival mechanisms

Date: 2016-07-12
Speaker: Prof. Alakendra N. Roychoudhury
Venue: Ground Florr Lecture Hall

Abstract

Holocene Monsoon variability using stalagmite records from Dandak and Kotumsar caves, India.

Date: 2016-06-14
Speaker: Ms. Shraddha Band
Venue: Ground Floor Lecture Hall

Abstract

Variability and trends in the Indian Summer Monsoon (ISM) during mid-Holocene time period has remained a debatable issue. While some proxy based records show changes to be a gradual process in response to decreasing solar insolation, there are postulates of abrupt decline at 6 ka as well. We have attempted to address this long standing controversy using a highly resolved ISM reconstruction, based on delta-18-O measurements (n = 5040) on stalagmite samples, from Dandak and Kotumsar caves from the Core Monsoon Zone of India. Results will be discussed in the seminar.

Vanishing act of 142Nd anomaly: story of the Khariar alkaline rocks

Date: 2016-05-10
Speaker: Ms. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

Understanding of the early differentiation of the silicate earth requires knowledge of 142Nd isotope composition in various terrestrial reservoirs. Produced by decay of short lived 146Sm (t1/2 = 68 Ma) the radiogenic 142Nd is expected in primordial materials or subsequent products that may still carry its memory. Because of extremely low abundance of 146Sm, measurement of radiogenic 142Nd is very cumbersome and the anomalies (if any) in its isotopic ratios are expected in the six decimal place. Every anomalous value reported for 142Nd w.r.t. terrestrial standard is therefore very important and affects the understanding of these early differentiation processes. In this context, the negative anomalous values reported for 1.48Ga alkaline rocks from Khariar are particularly important. These anomalous values have been questioned and reported to be analytical artefacts. We have carried out an independent study of these rocks and studied in detail the data acquisition and reduction methods to understand its effect on data quality control. I will discuss the parameters that can bias the data and the results of our experiment.

Surface active substances in atmospheric aerosol.

Date: 2016-05-03
Speaker: Mr. A. K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Surface active substances (surfactants) are significant part of soluble organic content of atmospheric aerosol. They reduce the surface tension of water droplet and influence the cloud droplet formation and have potential role precipitation process, but, their abundances and extent of surface tension reduction is not well understood. In this talk, indirect methods for measurement surface active substances in atmospheric aerosol and implication will be discussed.

Surface active substances in atmospheric aerosol.

Date: 2016-05-03
Speaker: Mr. A. K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Surface active substances (surfactants) are significant part of soluble organic content of atmospheric aerosol. They reduce the surface tension of water droplet and influence the cloud droplet formation and have potential role precipitation process, but, their abundances and extent of surface tension reduction is not well understood. In this talk, indirect methods for measurement surface active substances in atmospheric aerosol and implication will be discussed.

Post LGM sedimentation record in marine marginal basin of the Great Rann of Kachchh, Western India

Date: 2016-04-12
Speaker: Dr.Niteshkumar N Khonde
Venue: Ground Floor Lecture Hall

Abstract

The enigmatic terrain of the Great Rann of Kachchh (GRK) basin is bounded by Thar Desert; Aravalli ranges in the north and northeast, whereas its southern and western boundary is shared with Kachchh mainland hills and Arabian Sea respectively. Situated on continental margin of Indian subcontinent, the GRK basin has preserved continuous record of post glacial sedimentation that continued till recent past. Structurally a half graben, the GRK has witnessed complex interplay of climate-tectonic forcing throughout the Quaternary times. Several scientific issues regarding GRK basin yet to understand completely such as- the provenance of the sediments, geomorphic evolution, land-sea interaction changes, marine inundation pattern and its role in flourishing the earlier civilization invites earth scientists to reconstruct its past. To address some of these issues, the preliminary results from GRK studies provide evidences of tectonic upliftment, land-sea interaction and paleoclimatic/paleo-environmental changes throughout post LGM would be discussed.

Zircons are forever

Date: 2016-04-05
Speaker: Prof. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Zircon (ZrSiO4) is an omnipresent trace mineral in most silicate rocks present on the surface of the earth. Because of its refractory nature and ability to concentrate uranium and exclude lead it has been widely used as a U-Pb geochronometer for igneous rocks from the very beginning of the Solar System (in meteorites) to the Present. The only physical evidence from the earliest phases of Earth’s evolution comes from zircons. Oxygen isotope ratios from such zircons have been used to infer about the nature of the earliest hydrosphere and its habitability for life. There are countless usefulness of zircons in studies in Earth and Planetary Sciences. In my talk I would highlight some of these and make a case for zircon research for Indian Geology.

Paleoredox and paleo-pH conditions in Earthly Environments: Implications and Application of Calcium Isotopes

Date: 2016-03-29
Speaker: Mr. Wriju Chowdhary
Venue: Ground Floor Lecture Hall

Abstract

To reconstruct oxygenation and pH history of the Earth's surface environment through time and its affect on the evolution of life on our planet, it is essential to know about paleoredox and paleo-pH conditions. Modern analogs and lab simulations have mostly provided a good understanding about the processes responsible for the isotopic and chemical trends. Paleoredox and paleo-pH conditions characteristic of the water column from which precipitates have formed are recorded in REE and trace elemental concentrations and calcium isotopic variations of the lithified records respectively. In this seminar, I plan to discuss how the REE and trace elemental concentrations have been used to decipher paleoredox proxies and concentrate on a proposal to use calcium isotopes as an indirect proxy of paleo-pH. This study has implications for the improvement of predictive power to the understand the processes driving isotope fractionation during changing paleo-environmental conditions through multiproxy approach.

Title: Evolution of Zanskar Valley (Ladakh Himalaya) since Permian

Date: 2016-02-02
Speaker: Dr. Anil Dutt Shukla
Venue: Ground Floor Lecture Hall

Abstract

Zanskar valley in Ladakh Himalaya provides a rich repository of the pre and post collision history which is preserved in the sedimentary sequences spanning a time period ranging from Proterozoic to Eocene. The sedimentary formations belonging to the Tethyan Sedimentary Sequence (TSS) are present in the Zanskar valley which represents the frontal part of large-scale southwest-verging imbricated structures. It has been suggested that the TSS were deposited in the passive continental margin and the lithology provides an entire spectrum of geological history of the Tethyan Ocean ranging from Late Carboniferous to Permian rifting of Gondwana (NeoTethys) till the collision of the India with Asian continent around Eocene. The outpouring of Panjal traps occurred during the opening up of the Neo-Tethyes and is ascribed to the rifting during the Permian. This was followed by near continuous sedimentation which is represented by Triassic to late cretaceous sedimentary facies (arenaceous, argillaceous and bioclastic sediments) in gradually subsiding Tethyan basin till the Eocene when Indian plate sutured with the Asian plate. In this presentation, I would discuss about the current understand of the Zanskar basin with emphasis on the geochemistry of the Panjal volcanic, it implications (if any) in the P-T extinction and subsequent sedimentation till the Indian-Eurasian collision.

2015

Biogeochemical studies of Asia's second largest lagoon during onset of monsoon

Date: 2015-12-29
Speaker: Ms. Rupa Mukherjee
Venue: Ground Floor Lecture Hall

Abstract

The mechanism of nitrogen (N) transport and transformation is very important for freshwater biogeochemistry as the source and sink of dissolved inorganic nitrogen (DIN) can act as an indicator for the autotrophic and heterotrophic nature of the water body. Studies have shown that coastal lagoons are the important source of inorganic carbon to the atmosphere, though its size is small compared to ocean. Chilika lagoon, 64.3 km long and 20.1 km wide, is pear shaped shallow water body(average depth ~ 1.5 m) located on the east coast of India. Chilika is India?s largest lagoon. We measured the natural abundance isotopic composition ( delta-13C and delta-15N) and concentration of particulate organic carbon (POC) and particulate organic nitrogen (PON) covering 16 stations including all sectors of the lake during onset of monsoon (22nd-29th June, 2015). Experiments to measure assimilation rates of inorganic nitrogen were also carried out and lake-wide DIN budget of the lake was estimated. The overall biogeochemistry of the lake will be discussed during the talk.

Indian monsoon intensification and its variabilities on millennial and geological time scales

Date: 2015-12-22
Speaker: Dr. Sajid Ali
Venue: Ground Floor Lecture Hall

Abstract

The Asian Monsoon is a substantial component of the global climate system which affects over 3 billion people living in the area and this is estimated to be over 4 billion by 2050. This large population depends on monsoon rainfall for agriculture, hydroelectric generation and industrial development as well as basic human needs and requires strategies to cope with variations in the timing, intensity and duration of the monsoon. The Asian Monsoon is composed of two sub-systems; the Indian monsoon (also called South Asian monsoon) and the East Asian monsoon. The Indian Monsoon (IM) has displayed a changing relationship with ENSO over recent decades that may be related to global warming and has become less predictable in the last 25 years. Since we have only one century of instrumental data for the IM we must look to paleoclimate proxy records to better understand past IM variability and improve future predictions. New results of mineralogy and radiogenic isotope compositions suggest Indian monsoon well developed around 25 Ma ago and controlled by variable factors at different time scales. The millennial scale variabilities were predominantly controlled by Northern Hemisphere Glaciation (NHG) whereas Himalayan tectonics played vital role in larger scale variabilities. Results from Andaman Sea and Indian Ocean along with Arabian Sea will be considered to discuss Indian monsoon at different time scales.

A study of nitrogen dynamics in soils of India

Date: 2015-12-08
Speaker: Ms. Niharika Sharma
Venue: Ground Floor Lecture Hall

Abstract

Study of terrestrial nitrogen cycling is necessary as it plays an important role in growth and development of plants growing in that ecosystem. Rates of various processes within nitrogen cycle like mineralization and nitrification determine the presence or absence of nutrients and hence the growth of plants and microbes in that particular ecosystem. In India, net rates of mineralization and nitrification have been frequently studied but no literature is available for gross rates of these processes in soils of India. Gross rates are important in order to understand actual production and consumption of individual nutrient, establish and redefine land management and fertilizer application practices and thus to achieve sustainable development. This talk will discuss the attempts being made towards measuring these important rates in different ecosystems of India.

Laser absorption based isotope analysers for stable isotopes of oxygen (16O, 17O and 18O) and hydrogen (1H, 2H) in water, and carbon (12C and 13C) in CO2 and CH4.

Date: 2015-11-30
Speaker: Mr. Thomas Gottschalk
Venue: Ground Floor Lecture Hall

Abstract

Cavity Ring Down Spectroscopy (CRDS) based laser isotope analysers for oxygen and carbon isotopes are slowly replacing conventional IRMS, particularly for water, vapor, CO2 and CH4 samples. Achievable precision is reported to be comparable to IRMS or even better. Simultaneous measurement of dD, d18O and d17O in water or vapor and field deployability are features exclusive to this new generation equipment. Technical aspects of this new isotope analytical technique will be discussed in the special semiar.

Isotopic Characterization of Indian Precipitation: Insights about hydro-meteorological Processes

Date: 2015-10-13
Speaker: Mr. Harsh Oza
Venue: Ground Floor Lecture Hall

Abstract

The SW summer monsoon (June-Sept), NE winter monsoon (Oct-Dec), Western Disturbances (Jan-Apr) and local recycling are the four major contributors to precipitation, governing water availability not only in India but also five other countries (Bangladesh, Bhutan, Nepal, Pakistan and Sri Lanka) of the Indian Sub-continent. This region covers only ~3.2% of the global land area but accommodates ~23.2% of the global population. While seasonal pattern of rainfall and underlying processes are broadly understood, the finer details such as eastern limit of the western disturbances, regions prominently affected by local recycling, effect of large wetlands in Northeast India, etc. is still poorly understood. Oxygen and hydrogen isotopes in precipitation can provide some insights on some of these aspects. Under aegis of the IWIN National Programme efforts were made to isotopically characterize the precipitation monitored at more than 40 stations across India for up to four years. Insights about Hydro-meteorological processes obtained from spatio-temporal variation in isotopic composition of precipitation will be discussed in this presentation.

REEs concentrations, Nd & Hf isotopic composition in the Arabian Sea: Water Mass mixing vs. particle ? water interaction.

Date: 2015-09-29
Speaker: Mr. K Damodara Rao
Venue: Ground Floor Lecture Hall

Abstract

Spatial variation of amount effect over peninsular India and Sri Lanka: role of seasonality

Date: 2015-09-01
Speaker: Ms. Lekshmy P R
Venue: Ground Floor Lecture Hall

Abstract

The negative relationship between rain amount and its delta-18-O (amount effect) helps to reconstruct past rainfall variability from proxies (e.g., tree-rings and speleothems). Analysis of new (and published) data of the delta-18-O of monsoon rains and vapor at 9 stations shows that in regions of distinct seasonality in precipitation (e.g., peninsular India), the noise in such reconstructions can be minimized by a careful selection of sites. Peninsular India receives rain from both the Indian summer monsoon (ISM) and the north-east monsoon (NEM). Significant amount effect is observed only where the NEM rainfall is larger than or comparable to ISM rainfall. This is due to the higher quantity of NEM rain with more depleted 18-O relative to ISM rain. NEM rain is more depleted in 18-O because of cyclonic activity over Bay of Bengal, and the 18-O depletion of Bay of Bengal surface waters due to post-ISM river runoff.

Validation of delta-18-O as a proxy for past monsoon rain by multi-GCM simulations

Date: 2015-08-27
Speaker: Mr. Midhun M.
Venue: Ground Floor Lecture Hall

Abstract

Stable oxygen isotope ratios (delta-18-O) of tree cellulose and speleothem carbonate are useful proxies for past monsoon rain in many tropical regions, as a decrease in rain delta-18-O is observed with increase in rainfall on a monthly time scale. This amount effect varies spatially; therefore a local calibration, with actual measurements of rain amount and its delta-18-Ois required. Such observations, however, are quite limited in space and time. To circumvent this difficulty, many isotope enabled general circulation models (GCMs) are used to aid the interpretation of 18-O proxies; nevertheless, all such simulations taken together are yet to be evaluated against observations over the Indian summer monsoon (ISM) region. Here we examine ten such GCM simulations archived by the stable water isotope intercomparison Group, phase 2. The spatial patterns of simulated ISM rainfall and its delta-18-O are in good agreement with the limited observations available. Simulations nudged with observed wind fields show better skill in reproducing the observed spatio-temporal pattern of rainfall and its delta-18-O. A large discrepancy is observed in the magnitude of the simulated amount effect over the Indian subcontinent between the models and observation, probably because models simulate the spatial distribution of monsoon precipitation differently. Nudged simulations show that interannual variability of rainfall delta-18-O at proxy sites are controlled by either regional (rather than local) rainfall or upstream rain out. Interannual variability of rainfall delta-18-O over the East Asian region is well correlated with ENSO, while it is only weakly correlated over the Indian sub-continent.

Late Quaternary sedimentation in the western India: A geochemical provenance study

Date: 2015-07-22
Speaker: Mr. Anirban Chatterjee
Venue: Nanosims Meeting Hall

Abstract

The western part of Indian sub-continent is home to a unique repository for Quaternary sedimentary deposits, representing different climatic and geomorphic regimes. One of the important steps to understand the landform evolutionary processes is to decipher the source and transport pathways of the sediments deposited in these basins. Rare Earth Element (REE) geochemistry and Sr-Nd isotopic signatures are important tools to decipher sediment provenance. In this talk I would present results of our study carried out in this regard, from Luni river basin, Thar Desert and Ghaggar River.

Speleothem based reconstructed monsoon during Early-Holocene and Late-Pleistocene

Date: 2015-07-14
Speaker: Ms. Shraddha Band
Venue: Nanosims Meeting Hall

Abstract

Speleothems which are cave carbonate deposits occurring in limestone areas can be used to reconstruct past climatic variations, often providing a high-resolution continuous record covering a long-period of time. As ratio of stable isotopes of oxygen in rainfall is amount dependent in tropical sites, for speleothems it is a robust proxy of past monsoon variations. With this motive, stalagmites from two caves having different geographical locations were studied. A stalagmite from Dandak cave that grew between 10 to 9 kyr shows persistent intensification of monsoon since the early part of Holocene, in addition to switching over to a few drought like events for short intervals of time. Another stalagmite from Belum cave covering a time span of 100 kyr (between 190 to 80 kyr) has rather interesting depositional history in accordance with the Marine Isotope Stages-6 to 4. Results from these two caves will be discussed in the seminar.

Understanding the evolution of the Marwar basin: A geochemical perspective

Date: 2015-06-30
Speaker: Mr. Bivin Geo George
Venue: Ground Floor Lecture Hall

Abstract

The Late Neoproterozoic to Early Cambrian (750Ma- 500Ma) witnessed remarkable events in the Earth?s history such as the break-up of supercontinent Rodinia, evolution of multi-cellular life, an oxygenation event and the evolution of a climate system that is similar to the present day. These global events often leave their imprints in the contemporaneous sedimentary rocks. In the talk, I shall discuss some of the results from our study aimed at understanding the provenance, paleogeography and tectonic setting of the sedimentary rocks of the contemporaneous Marwar basin.

In situ petrological evidence from ophiolite suggest that mantle upwelling in spreading center initiated from mantle transition zone (>410 - 660 km).

Date: 2015-06-23
Speaker: Dr. Souvik Das
Venue: Ground Floor Lecture Hall

Abstract

Ophiolites are generally considered as relics of spreading center. Geoscientists strongly believe that, spreading center rocks are derived from shallow upper mantle (<90 km). But geophysical studies have shown that the root of the mantle upwelling beneath a spreading centre is at much greater depths (>100 ? 410 km). To fill this knowledge gap present research has been carried out on mantle part of a well preserved Tethyan ophiolite (Nidar valley, SE Ladakh) along Indus Suture Zone. Finding of ultra high pressure minerals infer that some part of the Nidar ophiolite have evolved from the mantle transition zone.

Decoding Crustal Evolution

Date: 2015-06-16
Speaker: Dr. Shrema Bhattacharya
Venue: Ground Floor Lecture Hall

Abstract

The Earth is thought to have been formed about 4.6 billion years ago from solar nebula. By the early igneous differentiation processes two types of crust have been generated, namely oceanic and continental. These crusts and upper mantle, which is known as lithosphere was broken up into number of tectonic plates. Oceanic crust reconcile the ages only up to 200 million year from today, in contrast continental crust are the oldest rocks on Earth formed during 3.7 to 4.6 billion years ago and provide the details of earth’s differentiation processes. New continental crust is mostly linked to the intense orogenic cycles of super continent formation such as, Rodinia, Pangea and Gondwana by the amalgamation of old micro-continents, their destruction and recycling. This talk will give a glimpse of the two orogenic cycles and how the continental crust formed using whole rock geochemistry, U-Pb isotope geochronometre and Lu-Hf Isotopic tracer in the mineral zircon.

Influence of solar activity on rainfall-indications from speleothems

Date: 2015-06-09
Speaker: Dr. M. G. yadava
Venue: Ground Floor Lecture Hall

Abstract

High-resolution proxy based rainfall records show that there are rhythmic changes which shall be attributed to solar activity. Interestingly, the rhythmicity is not persistent; it appears for a certain period of time as observed in two speleothems studied so far. Some plausible explanations on a physical link between sun and Indian monsoon will be discussed.

Application of Accelerator Mass Spectrometry (AMS) in study of Cosmogenic Isotopes

Date: 2015-05-26
Speaker: Dr. Ravi Bhushan
Venue: Ground Floor Lecture Hall

Abstract

Accelerator Mass Spectrometry (AMS) is an advanced ultrasensitive mass spectrometry technique for measurement of cosmogenic radionuclides in extremely small quantity of samples with a much reduced analysis time. The advent of AMS not only facilitated orders of magnitude lower requirement of sample quantity and analysis time, but also opened new avenues of research in earth sciences. The low energy (MeV) Accelerator Mass Spectrometer (AMS) being procured by PRL is a universal compact AMS which can effectively measure several cosmogenic radionuclides that include ¹⁴C, ¹⁰Be and ²⁶Al. AMS has found extended application in archaeology, oceanography, hydrology, geology, biomedical research and paleoclimatology. AMS would not only provide new opportunities in application of cosmogenic isotopes in earth, atmosphere and planetary sciences, but would also serve as a long lasting requirement for a geochronological facility.In this talk, some applications of AMS in earth sciences would be discussed.

Characterization of secondary organic aerosols present in the ambient atmosphere

Date: 2015-05-12
Speaker: Mr. Satish R. V.
Venue: Ground Floor Lecture Hall

Abstract

Aerosols are of central importance for atmospheric chemistry and physics, biosphere, climate, and public health. Organic aerosols (OA) constitute about half of the total sub-micrometer particulate mass in the troposphere. These OA can be emitted to the atmosphere directly as particles (primary OA, POA) and/or formed in the atmosphere through oxidation of volatile organic carbon (secondary OA, SOA). Evidences suggest that SOA is often dominant component of OA, and majority of SOA is water soluble. Some of the water-soluble organic aerosols (known as brown carbon) absorb sunlight, which causes additional direct/indirect climatic effects of OA. In this talk, various characteristics of ambient SOA will be discussed.

Microbial cycling of nitrogen in agriculture: Great acceleration and its impacts

Date: 2015-05-05
Speaker: Dr. B. Ramakrishnan
Venue: Ground Floor Lecture Hall

Abstract

"Presentations by First Year Students"

Date: 2015-04-28
Speaker: Ms. Niharika Sharma; Mr. Wriju Chowdhury; Mr. Raghwendra N. Shandilya; Mr. Sachin Gupta; Mr. Anil Patel; Mr. P. Kiran Kumar
Venue: Ground Floor Lecture Hall

Abstract

Ions in water: Implications to safe water, food and environment

Date: 2015-04-23
Speaker: Dr. T. Pradeep
Venue: Ground Floor Lecture Hall

Abstract

Clumped isotopes in air CO2 and carbonates: implications to global carbon cycle and paleoclimate studies

Date: 2015-04-21
Speaker: Dr. A. H. Laskar
Venue: Ground Floor Lecture Hall

Abstract

Molecules containing two rare isotopes (e.g. ¹³C¹⁸O¹⁶O in CO₂),called clumped isotopes are powerful tools to independently constrain the sources of CO₂ in the atmosphere and paleo temperature reconstruction. This is due to their unique physical and chemical properties such as the abundance of ¹³C-¹⁸O bond is purely temperature dependent and is independent of the oxygen isotopic composition of parent material unlike oxygen isotope thermometry in which oxygen isotopic composition of original water must be known for any kind of paleoclimate study. In this talk I will briefly discuss the principles and applications of clumped isotopes in CO₂. I will also present our recent results on identifying sources of CO₂ in the atmosphere, quantifying anthropogenic fractions of CO₂ in urban and industrial areas, paleo temperature reconstruction using various carbonate archives and endothermic/ectothermic thermoregulations of dinosaurs using clumped isotopes. Also I will discuss some advanced applications and future prospects of clumped isotopes.

Biochemical modeling of tree ring cellulose isotope data for Paleo-reconstructions.

Date: 2015-03-31
Speaker: Dr. Trina Bose
Venue: Ground Floor Lecture Hall

Abstract

One of the primary sources of climatic variability information in recent past are the tree ring cellulose isotope datasets due to their stable temporal resolution. However the reconstructions produced from such data have variable dependabilities due to their site and species specificness in terms of parameter reconstructed and the calibration correlation. Cellulose formation in all of the trees (including the ring bearing ones) is mostly the same basic physiochemical process as they all undergo C₃ metabolic process.This process and resultant isotopic fractionation have been modeled from experimental information on live trees. In presence of basic meteorological data i.e. temperature and humidity estimates, pCO₂ has been reconstructed from carbon isotope data from tree ring cellulose.The processes involving oxygen and hydrogen isotope fractionations provide information about humidity, temperature and source water isotopic compositions. Some of these process based reconstruction models will be discussed.

THE GRAND CHALLENGES IN EARTH SURFACE PROCESS STUDIES WITH ILLUSTRATIONS FROM FLOOD STUDIES

Date: 2015-03-24
Speaker: Prof. R. J. Wasson
Venue: PRL GUEST HOUSE

Abstract

The grand challenges (according to the National Research Council of the USA, 2010) are: 1. Interacting Landscapes and Climate 2. Quantitative Reconstruction of Landscape Dynamics Across Time Scales 3. The coevolution of Ecosystems and Landscapes 4. The Future of Landscapes in the ?Anthropocene? These challenges should involve geoscientists, ecologists, atmospheric scientists, physicists, chemists, mathematicians, historians, social scientists, and engineers. Each of these grand challenges will be illustrated using the reconstruction of flood histories from India and Thailand.

Multi-elemental and Isotopic (87Sr/86Sr) Characterization and Authentication of the Indian Basmati Rice

Date: 2015-03-17
Speaker: Dr. Rupali Anant Lagad
Venue: Ground Floor Lecture Hall

Abstract

Globalization of agricultural products has increased risk of adulteration of premium quality food products. In order to protect loyal producers and consumer’s right for safe and healthy food, Geographical Indication (GI) is an effective activity, which is developed especially for protecting the geographical authenticity of food stuffs. Multi-elemental profiling, REEs pattern, isotopic composition of food plays important role in checking quality, safety and authenticity of GI protected food stuff. In the present research work, globally demanded, premium cost, Indian GIs protected agricultural product, authentic Basmati rice samples were analyzed for its multi-elemental profiling and 87Sr/86Sr ratio fingerprinting. The results obtained for same will be discussed in the seminar.

Long term records of the Indian monsoon as revealed by 3 recent papers

Date: 2015-03-10
Speaker: Prof. R. Ramesh
Venue: Ground Floor Lecture Hall

Abstract

Three recent papers have tried to reconstruct the Indian monsoon on various timescales and with different resolutions. The first, concentrates on the last two millennia (from north India), the second the last glacial period (south India), and the third (China) covers the full glacial interglacial cycle. In this seminar I will present these papers and discuss their relative merits and demerits. I will also highlight our continuing efforts to fill gaps in the Holocene monsoon records and show how recent ocean records verify our earlier conclusions.

Seasonality in Secondary Aerosol Formation over the Indo-Gangetic Plain

Date: 2015-03-03
Speaker: Dr. Neeraj Rastogi
Venue: Ground Floor Lecture Hall

Abstract

Understanding the secondary aerosol formation is among most important topics in the field of aerosol research because its poor understanding leads to large uncertainty in the assessment of aerosol effects on air quality and climate. The Indo-Gangetic Plain (IGP) receives large amount of primary particles and precursors of secondary particles from the emissions from vehicles, industries, thermal power plants, large-scale post-harvest biomass burning, and bio-fuel burning; however, knowledge on secondary aerosol abundances and characteristics is sparse. Based on the year-round day and night time sampling of atmospheric fine particles from Patiala, this talk will discuss the temporal characteristics of primary and secondary aerosols over the IGP, and their implications. The importance of time resolved measurements in understanding the secondary aerosol formation processes will also be discussed.

146Sm-142Nd systematics in some Indian carbonatites and alkaline rocks: challenges and observations

Date: 2015-02-17
Speaker: Ms. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

Geochemical and isotopic studies of Sm-Nd have contributed significantly to our knowledge of evolution of Earth?s mantle. Whereas the conventional isotopic system of these elements (147Sm-143Nd, t1/2=103Ga) is key to our understanding of evolution of the mantle over the geologic time, the short-lived 146Sm-142 Nd (t1/2=68 Ma) systematics helps us to zoom into the early history of evolution of the silicate Earth. The latter though requires high-precision mass spectrometry (< 10 ppm precision in 142 Nd/144Nd measurements), which became available only recently. In my talk I shall briefly discuss analytical challenges in 142 Nd/144Nd measurements, our efforts/progress in this direction, and preliminary results from some carbonatites and alkaline rocks of India ? aimed at locating the early enriched mantle reservoir.

Geochemistry of continental shelf waters and sediments, south east coast of India, Bay of Bengal.

Date: 2015-02-10
Speaker: Dr. Nisha V.
Venue: Ground Floor Lecture Hall

Abstract

Continental shelf studies are important in order to understand the physico-chemical properties of sea water as well as biogeochemical systems existing in the marine environment. Lying within the tropical zone the east coast India receives strong monsoonal rains and hence any variation in the intensity and amount of precipitation would reflect in the seawater and sediment deposition characteristics along the continental shelf. This study quantifies the spatial and vertical heterogeneity in the distribution of seawater properties and geochemical parameters that influence their distributional trends in seafloor sediments during the 2009 post North East (NE) and South West (SW) monsoon periods along the east coast Tamilnadu continental shelf. In this talk, I would present some of the results on the distribution and monsoonal fluctuations of various physico-chemical and geochemical parameters of seawater and seafloor sediments spatially and vertically along the continental shelf East Coast Tamilnadu.

Oxygenation of Earth's atmosphere-ocean system

Date: 2015-02-03
Speaker: Prof. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

We take our oxygenated world for granted and expect to find breathable oxygen everywhere - after all, O₂ makes up 21% of the modern atmosphere. However, free oxygen, at levels mostly less than 0.001% of that of present atmosphere, was anything but plentiful during the first half of Earth?s 4.5-billion-year history. Its rise to modern levels and impact on early biological evolution is one of the most interesting stories in Earth?s history. In this talk, I shall review the current status and discuss new methods of research on the topic

What controls the atmospheric abundances of dicarboxylic acids over the open ocean: Insights from the Western North Pacific

Date: 2015-01-29
Speaker: Dr. Bikkina Srinivas
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric dicarboxylic acids (DCA), a ubiquitous and important component of secondary organic aerosols (SOA), play a crucial role in cloud condensation nuclei activity of aerosols, affecting the Earth’s climate. Despite the high abundances of oxalic acid and other DCA in the marine boundary layer, there is no consensus on what controls their atmospheric distributions over the open ocean. Although it is hypothesized that marine biological productivity is responsible for the production of DCA in the remote marine atmosphere, there were no substantial evidences to support the hypothesis based on field observations. Here, we present the unequivocal evidence for the marine source of DCA and related polar compounds whose concentrations showed several times higher in more biologically influenced aerosols (MBA) than in less biologically influenced aerosols (LBA). Their main sources are proposed as isoprene and unsaturated fatty acids emitted from the ocean surface during high biological activity as inferred by high abundances of isoprene-SOA tracers and azelaic acid. The measured concentrations of isoprene-SOA tracers in MBA show ca. 40 times higher than in LBA. These results demonstrate that marine derived isoprene and unsaturated fatty acids control the spatial distributions of water-soluble diacids and related compounds over the high biological productivity ocean, suggesting requirement for the reassessment of feedbacks of marine-derived SOA on climate forcing over the remote oceanic regions.

Particulate Organic Carbon export from upper Indian Ocean using 234Th/238U and 210Po/210Pb disequilibria

Date: 2015-01-27
Speaker: Dr. R. Rengarajan
Venue: Ground Floor Lecture Hall

Abstract

Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in persistent organic pollutants. Most of these perturbations are tied to ocean warming, acidification and coastal eutrophication and change the type and magnitude of organic carbon exported to the ocean’s interior. 234Th238U and 210Po210Pb pair has been widely utilized in the quantification of particulate scavenging and cycling of lithogenic and biogenic particulate matter in marine system. I will present preliminary results on carbon export to the deep oceans using 234Th/238U and 210Po/210Pb disequilibria in the water column obtained from recent ocean cruises under GEOTRACES and SIBER programmes.

Petrological, Geochemical and U-Pb Zircon Geochronological Studies of the Bundelkhand Granitoid Complex, Central India: Constraints on Archean Crustal Evolution

Date: 2015-01-20
Speaker: Dr. Batuk Kumar Joshi
Venue: Ground Floor Lecture Hall

Abstract

This study investigates the major and trace element compositions and zircon U-Pb ages (SIMS) of granitoids from Bundelkhand Craton, Central India and draws conclusions on their petrogenesis, emplacement ages and evolution. The secular and geochemical diversity of the granitoids in the complex ranges from sodium-rich TTGs (3.3-2.5 Ga) to calc alkaline, potassium-rich granitoids (2.57-2.52 Ga), which points towards a change in the source of granitoids from meta-basaltic material (TTGs) to variable sources with inputs from mantle-derived material and recycled crustal lithologies (calc alkaline granitoids). The U-Pb geochronology of the granitoids indicate that evolution of the craton was episodic and started as early as Paleoarchean. At 2.57-2.52 Ga, Bundelkhand experienced a rapid period of voluminous magmatic activity that produced a variety of plutonic rocks deriving from enriched mantle (e.g. sanukitoids) as well as crustal sources (intracustal granites). In conclusion, the Bundelkhand craton grew intensively due to a new type of tectono-magmatic event near the Archean-Proterozoic boundary and was stabilized by 2.5 Ga.

Global signatures of Little Ice Age and Medieval Warm Period in the climatic records from the southern Saurashtra Coast during the last two Millennia

Date: 2015-01-13
Speaker: Ms. Upasana Banerji
Venue: Ground Floor Lecture Hall

Abstract

The climate during the last two millennium witnessed both warming and cooling periods in the form of Medieval Warm Period (MWP) and Little Ice Age (LIA). These past global climate changes have strong regional expression. Studies from Indian subcontinent have highlighted the existence of MWP and LIA. However, there remains a knowledge gap regarding such global event from the western India. In view of this, mudflats from the southern Saurashtra coast, Gujarat were selected for the climatic reconstruction. The study aims to reconstruct the climatic variability observed during the last two millennia and to correlate the present finding with the global climatic events such as MWP and LIA. On the basis of geochemical proxies supported by C-14 dating, the preliminary results suggest that the Saurashtra region also responded to global climatic events such as MWP and LIA.

Recent developments in the marine N2 fixation studies: New results from the North Atlantic Ocean

Date: 2015-01-06
Speaker: Dr. Arvind Singh
Venue: Ground Floor Lecture Hall

Abstract

Global N2 fixation results might have been hampered by the use of inadequate methodology. Recent studies have highlighted various problems in the previous methods. In addition, some impurities have been detected in the tracer used to estimate N2 fixation. In this seminar, we shall discuss all such issues along with some new results from the North Atlantic Ocean.

2014

Isotopic tracing of atmospheric mineral dust over Oceans

Date: 2014-12-30
Speaker: Dr. Ashwini Kumar
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric mineral dust has been recognized as an important constituent in the earth climate system because of their significant impact on various atmospheric and oceanic processes. In order to assess the impact of dust on climatic processes, it is very important to identify the sources of transported dust. Recently, radiogenic isotopes have been efficiently used for tracing atmospheric dust provenance and its transport over the oceans. In this talk, I will highlight on the transatlantic dust transport using radiogenic isotopes (Pb, Sr and Nd).

Dissolved inorganic carbon (DIC) and its delta-13C in the Ganga(Hooghly) river estuary: Evidence of DIC generation via organic carbon degradation and carbonate dissolution.

Date: 2014-12-26
Speaker: Dr. Tarun Kumar Dalai
Venue: Ground Floor Lecture Hall

Abstract

A geochemical perspective of the Mid-Holocene sedimentation in the Great Rann of Kachchh.

Date: 2014-12-23
Speaker: Mr. Anirban Chatterjee
Venue: Ground Floor Lecture Hall

Abstract

The low lying salty wasteland of the Great Rann of Kachchh is a unique Quaternary terrain of Western India. It has witnessed complex interplay of tectonics and sea-level change, within the short span of Holocene. In addition, many scholars believe it to be a delta complex of a paleo-river system fed by Himalayan glaciers during the mid-Holocene period. This hypothesis is interwoven with the evolutionary history of the Harappan Civilisation. Thus, decoding of the sedimentary history of the Great Rann of Kachchh is not only geologically significant, but also has profound geo-archaeological importance. In this talk I would present results of our geochemical study in the basin, carried out in an effort to decipher the sediment sources and understand the depositional pathways.

Time-resolved aerosol inorganic chemical composition and precursor gases over Ahmedabad: Gas-aerosol Equilibrium Characteristics.

Date: 2014-12-16
Speaker: Mr. A.K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Chemical composition of ambient aerosol exhibits large variability on a diurnal cycle and it requires high time-resolved measurements in order to study factors influencing the composition. We measured aerosol water-soluble ionic constituents and related trace gases, viz HCl, HNO₃ and NH₃ with a time resolution of one hour at Ahmedabad using Ambient Ion Monitor System. The aerosol composition and trace gas concentrations were used to verify gas-aerosol equilibrium over this urban environment using an equilibrium model. The results and implications will be discussed in this talk.

Biogeochemical study of freshwater ecosystems in India.

Date: 2014-12-09
Speaker: Ms. Rupa Mukerjee
Venue: Ground Flooe Lecture Hall

Abstract

Freshwater ecosystems are necessary to sustain life. Humans rely on freshwater systems not only for drinking water, but also for agriculture, transportation, energy production, industrial processes, and the extraction of fish and other products. Excess reactive nitrogen from anthropogenic sources such as fertilizers, industrial sewage, and other terrestrial inputs has led to large changes in aquatic biogeochemical cycles which, in turn, led to eutrophication and hence, water quality degradation, oxygen deficiency, fish killing and shift in species composition. Therefore, mechanisms by which freshwater systems can reduce local and downstream nutrient concentrations are becoming increasingly important and for that we need to first identify the source of these excess nutrients. In this talk, I will briefly discuss biogeochemistry of some of the lakes and wetlands in India and proposed plan for my PhD work

Holocene environments of the Great Rann of Kachchh, Western India.

Date: 2014-12-02
Speaker: Dr. Niteshkumar N. Khonde
Venue: Ground Floor Lecture Hall

Abstract

The Great Rann of Kachchh (GRK) basin is a dried up floor of the former Arabian Sea gulf in the northern extremity of the Kachchh paleorift. GRK has remained one of the enigmatic terrains for geologists due to its unique inundation pattern and geomorphic settings. The seasonal inundation/drying cycles always generated interest for common man and earth scientists. The GRK has also played an important role in Harappan flourishment and provided transport pathways for the maritime activities. Geologically, GRK has served as a Holocene depocenter which accumulated huge pile of sediments preserving past records of environmental changes and climatic history. It is believed that the GRK has gone through the complex interplay of the climate-tectonic forces throughout its geological past. Despite several scientific issues the geological evolution of the GRK basin still remains to be understood. Some of the preliminary outcomes from the inundation pattern in Rann, surface sediments, exposed cliff sections along the island margins and subsurface sediments of Rann basin would be discussed.

Atmospheric Mineral Dust: Long-range transport and chemical processing.

Date: 2014-11-25
Speaker: Prof. M. M. Sarin
Venue: Ground Floor Lecture Hall

Abstract

This talk will highlight some of our recent results on atmospheric transport of mineral dust from the Indo-Gangetic Plain to the Bay of Bengal. The atmospheric supply of mineral dust, a dominant source of iron (Fe) to the ocean surface, has been asubject of major debate over the past two decades. The chemical form of soluble Fe and its bioavailability are the major issues in this debate and in assessing the impact on marine biogeochemistry. In vast areas of open ocean waters (Subarctic Pacific, Equatorial Pacific, and Southern Ocean: High Nutrient Low Chlorophyll (HNLC) regions), productivity is limited by the availability of this micronutrient (Fe). The studies carried out in HNLC regions have highlighted dust-mediated glacial-interglacial CO₂ changes and emphasizethe need to further understand the atmospheric transport and deposition of mineral dust to the open ocean. In this context, several modelling studies have relied on the transport of mineral dust from arid and semi-arid regions as a dominant source of soluble iron to the open ocean. One of the important parameters in the atmospheric supply of Fe to sea water is the solubility of mineral dust. The significance of chemical processing of mineral dust by anthropogenic acidic species (H₂SO₄, HNO₃) in enhancing the fractional solubility of aerosol iron has been suggested as a vital factor.

Nitrogen dynamics in forest soils.

Date: 2014-11-18
Speaker: Dr. Sanjeev Kumar
Venue: Ground Floor Lecture Hall

Abstract

High resolution precipitation record from a stalagmite from Kotumsar cave, Chhattisgarh.

Date: 2014-11-11
Speaker: Ms. Shraddha Band
Venue: Ground Floor Lecture Hall

Abstract

Caves in India are used extensively to reconstruct past monsoon conditions. A stalagmite sample (KOT-1) collected from Kotumsar cave that grew between 5000 to 4000 yr BP, has been sub-sampled for stable isotope analysis using high resolution micromill technique. As the stalagmite banding is annual, the objective of the study was to find the traces of seasonal variability. Although in this particular sample the variability was not found other interesting results have come up. Contemporaneous to the stalagmite formation, archaeological evidences of burnt charcoal, millets were found. These interdisciplinary results can help in understanding man-climate relationship

Nutrient Variability in a Tropical Monsoonal Estuary.

Date: 2014-10-14
Speaker: Mr. Subha Anand S
Venue: Ground Floor Lecture Hall.

Abstract

Monsoonal estuaries are highly dynamic and unique ecosystems. Materials transported through rivers undergo various biogeochemical transformations here before reaching the sea.The processes occurring in estuaries are very rapid and vary with time and space. Intra- and inter seasonal variability of dissolved oxygen and nutrients were studied in a tropical monsoonal estuary (Zuari, Goa, India). A dual sampling approach was adopted by monitoring the changes (daily/alternate day) at a fixed location and at ten stations from upstream to mouth during spring and neap tides for about a year. This study evaluates the strength of biogeochemical and physical processes in regulating the variability in the estuary. Another goal of this study is to see the retention of anthropogenic inputs in the estuary. The results will be discussed in detail.

Climate Change - IPCC versus Indian Research- a perspective

Date: 2014-10-07
Speaker: Prof. R Ramesh
Venue: Ground Floor Lecture Hall

Abstract

Reconstructing the paleoredox conditions using Delta-98 / 95 Mo in Black Shales

Date: 2014-09-30
Speaker: Ms. Sneha Sawant
Venue: Ground Floor Lecture Hall

Abstract

Ocean anoxia is preserved in Black Shale due to their formation under euxinic settings. Molybdenum (Mo) stable isotope system is a valuable tool for investigating ocean paleoredox conditions. Mo isotopic composition of seawater is determined by its relative removal in oxic and anoxic sinks. Mo isotopes fractionates during its removal from seawater under oxic conditions whereas it remains invariable during its precipitation in reducing sediments. Hence, Mo isotope composition of reducing sediments can be used to track the temporal variation in redox condition of the global ocean. The Mesoproterozoic-Early Cambrian period in the early history of the earth witnessed important evolutionary changes such as rise in atmospheric oxygen and changes in the biosphere. An attempt is being made to reconstruct the redox conditions during this period using Mo isotopes in black shales. Mo isotope composition of black shales was determined by double spike technique to correct isotope fractionation during sample purification and instrumental mass bias on MC-ICP-MS. In this talk, mechanisms of molybdenum fractionation under oxic-anoxic settings and some results on black shales from different Eras will be discussed.

Role of Saline-alkaline soils in estimation of silicate erosion rate in the Ganga plain

Date: 2014-09-09
Speaker: Ms. Jayati Chatterjee.
Venue: Ground Floor Lecture Hall

Abstract

Silicate erosion is one of the major sinks of atmospheric CO₂ in million year time scale. Contemporary silicate erosion of all major global rivers including Ganga has been studied extensively. Major ion composition and Sr isotopic ratio of the rivers have been used as tools for this purpose. But, presence of saline-alkaline soils in the Ganga basin complicates the use of these tools, as they act as a source of dissolved ions to the river water. These soils have been chemically and isotopically characterized in the present study. Dissolved budget of the Ganga river system has been apportioned to various sources, e.g.,silicates, carbonates, saline-alkaline soils etc, by inversion of chemical and Sr isotopic data. The results will be presented in this talk. I will also discuss couple of papers from Goldschmidt 2014.

Mo isotopes in rivers, estuaries and the Indian Ocean: Implications to its fractionation and internal cycling.

Date: 2014-09-02
Speaker: Dr. Sunil Kumar Singh
Venue: Ground Floor Lecture Hall

Abstract

Molybdenum (Mo) isotopes are being used as a proxy to trace paleo-redox condition of oceans. Quantitative interpretation of Mo isotope records in marine sediment deposits to derive redox conditions of ancient oceans requires representative data on Mo input and its isotope composition to the oceans. This information is important to refine the contemporary isotope budgets of Mo and for using this isotope system to determine variability in the spatial extent of redox conditions of the ancient oceans. Mo concentration and its isotope composition have been measured in dissolved and particulate phases of the Indian rivers, estuaries and in the northern Indian Ocean to (i) assess the impact of physical/chemical weathering on the isotope fractionation of Mo, (ii) constrain its flux and delta-98Mo to the northern Indian Ocean (iii) its internal cycling in the northern Indian Ocean. Mo isotopes fractionate significantly during weathering and transport in rivers and estuaries. Sinking particles and bottom sediments could supply significant amount of lighter Mo isotopes to the water columns in the northern Indian Ocean. Detail results will be discussed in the seminar.

Understanding carbon and nitrogen cycling in the Cochin estuary and coastal Arabian Sea.

Date: 2014-08-26
Speaker: Ms. Bhavya. P. S
Venue: Ground Floor Lecture Hall

Abstract

Estuaries and coastal waters are a few of many victims of eutrophication caused by excessive nutrient loading due to anthropogenic interferences. Estuarine C and N assimilations are mainly controlled by C: N: P ratios rather than individual nutrient concentrations. Along with the nutrient ratio, the increasing pCO2 is also a major factor in regulating the photosynthesis in the estuarine waters. delta-13CDIC is used for identifying the sources of dissolved inorganic carbon (the substrate for photosynthesis) and also to understand the presence of anthropogenic CO2 in the ocean surface waters. In this talk, these interesting topics will be addressed on basis of our study conducted in the Cochin estuary, one of the eutrophic estuaries in India, and adjacent coastal Arabian Sea with special emphasis on the anthropogenic involvements

Dissolved major ions, Sr and 87Sr/86Sr and sigma-Nd of the Godavari river system: Implications to chemical weathering rates and 87Sr and 143Nd fluxes to the ocean

Date: 2014-08-19
Speaker: Mr. K. Damodararao
Venue: Ground Floor Lecture Hall

Abstract

Rivers are the principal pathways by which dissolved and particulate matters from continental weathering are transported to the oceans. The river water chemistry and elemental flux transported by them to the oceans are needed to understand the major process at the surface of the Earth. The present study deals with the Godavari River Basin, the largest river system of the peninsular India, by studying the chemical and Sr, Nd isotope compositions in the both dissolved and particulate phases. This study provides not only the estimates of the weathering fluxes from this basin to the Bay of Bengal but also evaluate the role of two distinct lithology, the Deccan basalts and Archean geniesses in controlling these fluxes. These results will be discussed in detail in the seminar.

delta-D and delta-18-O of rainfall over India: model vs. observation.

Date: 2014-08-05
Speaker: Mr. Midhun M
Venue: Ground Floor Lecture Hall

Abstract

Stable isotopologues of water (HDO and H218O) are widely used to trace the processes in hydrological cycle, as well as to reconstruct paleoclimate. In India, due to the lack of sufficient observation, the spatial and temporal variability of stable isotopologues of water are poorly known. General Circulation Models (GCM) fitted with stable isotope physics are widely used to understand the processes influencing the distribution of stable isotopologues of water. A 32 year long simulation from an isotope enabled GCM (IsoGSM) is compared with the available observations over India and will be discussed in the talk.

18-O depletion in monsoon rain relates to large scale organized convection rather than the amount of rainfall

Date: 2014-07-22
Speaker: Ms. Lekshmy P. R.
Venue: Ground Floor Lecture Hall

Abstract

Oxygen isotopic variations in rainfall proxies such as tree rings and cave calcites from South and East Asia have been used to reconstruct past monsoon variability, mainly through the amount effect: the observed 18-O depletion of rain with increasing amount, manifested as a negative correlation of the monthly amount of tropical rain with its delta-948;18-O both measured at the same station. This relation exhibits a significant spatial variability, and at some sites (especially North-East and peninsular India), the rainfall proxies are not interpretable by this effect. We show here that relatively higher 18-O-depletion in monsoon rain is not related necessarily to its amount, but rather, to large scale organized convection. Presenting delta-18-O analyses of ~654 samples of daily rain collected during summer 2012 across 9 stations in Kerala, southern India, we demonstrate that although the cross correlations between the amounts of rainfall in different stations is insignificant, the delta-948;18-O values of rain exhibit highly coherent variations (significant at P = 0.05). Significantly more 18-O-depletion in the rain is caused by clouds only during events with a large spatial extent of clouds observable over in the south eastern Arabian Sea.

Silicon isotopic approach for the paleoclimatic reconstruction in the northern Indian Ocean

Date: 2014-07-15
Speaker: Ms. Chandana K. R
Venue: Ground Floor Lecture Hall

Abstract

The drop in atmospheric CO2 during glacial periods has been interpreted as sequestration of CO2 in the deep oceans. Another theory supporting the drop in atmospheric CO2 concentrations is consumption of nutrients by phytoplankton during glacial period. The biogeochemical cycling of silicon in the ocean is controlled by diatom production. The silicon isotopic composition of the diatom / biogenic opal can help in reconstructing the nutrient utilisation patterns and test the hypothesis of atmospheric CO2 drop during glacials. The silicon isotope can be used to ascertain the silicic acid utilization by the diatoms on a regional scale over glacial and interglacial cycles of the Quaternary period. The northern Indian Ocean being the most dynamic region which experiences seasonal monsoon, high biological productivity resulting in extreme oxygen minimum zone has attracted great attention. Few studies from Southern ocean based on silicon isotope have revealed that under iron stressed conditions, diatoms shows enrichment in delta30Si which implies a greater fraction of nutrient utilisation. In the tropical region such as the northern Indian Ocean where iron limitation is not a constraint, behaviour of silicon isotope as a function of nutrient utilisation pattern during the glacial and interglacial cycles in sediments still needs to be realised.

Understanding the distributions of dissolved iron in the Northern Indian ocean

Date: 2014-07-08
Speaker: Mr. Venkatesh Chinni
Venue: Ground Floor Lecture Hall

Abstract

Chronology and geochemistry of dry land fluvial system, western India.

Date: 2014-07-01
Speaker: Dr. Anil D. Shukla
Venue: Ground Floor Lecture Hall

Abstract

Dry land fluvial system in western India emanates from the Aravalli ranges and drains into the Gulf of Cambay and the Gulf of Kachchh. The sedimentary characteristics and textural attributes of the incised alluvial sequences in various river basins of western Indian indicate significant variability in the palaeohydrological conditions. Considering that the region is dominated by the Indian Summer Monsoon (ISM), the temporal changes in sedimentation pattern can be ascribed to the changing strength of the ISM. In the present study, we investigated the Banas River which drains through the transitional climatic zone viz. the arid northwest and semi-arid southeast.

Understanding the Neoproterozoic Earth

Date: 2014-06-24
Speaker: Mr. Bivin Geo George
Venue: Ground Floor Lecture Hall

Abstract

Proterozoic Eon (2500 – 541 Ma) in the Earth’s history is marked by significant chemical, biological and geological events such as the oxygenation of the atmosphere, evolution of multi-cellular life, assembly and breaking up of the supercontinent Rodinia and at least three global glaciations. The end of this Eon, known as the Neoproterozoic Era (1000-541 Ma), witnessed some of the most important events in the Earth history: e.g., the snowball Earth and the first appearance of animal life. In this talk I shall deal with some of these events that had permanently changed the surface of the Earth and the chemical/geological evidences that teach us about the timing and extent of such events. I shall also discuss where in India one can find such evidences and how these can be studied to understand the Neoproterozoic Earth.

Causes and consequences of June 2013 devastation in the Bhagirathi and Alaknanda valleys

Date: 2014-04-29
Speaker: Dr. Navin Juyal
Venue: Ground Floor Lecture Hall

Abstract

During June 15th to 17th 2013, unprecedented devastation engulfed the entire Uttarakhand in general and Alaknanda and Bhagirathi valleys in particular. The disaster was attributed to an integrated effect of heavy rainfall intensity, sudden outburst of a lake (Chorabari) and very steep topographic condition (natural calamity). However, there are suggestions that the magnitude of the tragedy was amplified due to human intervention in the fragile Himalayan ecosystem. The presentation will focus on ascertaining the causes of the June 2013 tragedy with emphasize on how best we can protect the terain and the people from such devastation in future.

Dissolved silicon and its isotopes in water column of the Bay of Bengal: Internal cycling versus lateral transport.

Date: 2014-04-22
Speaker: Dr. Satinder Pal Singh
Venue: Ground Floor Lecture Hall

Abstract

Tracing Geographical Origin of Food with Application of Isotope Analysis.

Date: 2014-03-25
Speaker: Dr. Rupali Anant Lagad
Venue: Ground Floor Lecture Hall

Abstract

Geochemical and geological constraints on the composition of marine sediment pore fluid: Possible link to gas hydrate deposits.

Date: 2014-03-18
Speaker: Dr. Aditya Peketi
Venue: Ground Floor Lecture Hall

Abstract

Dissolved Sr and its Isotope in estuaries of eastern coast of India: Impact of submarine groundwater discharge.

Date: 2014-03-04
Speaker: Mr. Damodararao Karri
Venue: Ground Floor Lecture Hall

Abstract

The Importance of long Histories for Flood Disaster Management.

Date: 2014-02-13
Speaker: Prof. Robert James Wasson
Venue: Ground Floor Lecture Hall.

Abstract

Long records of floods are needed to estimate return periods, document the envelope of natural variability, determine if present-day floods are outside this envelope, understand the relationship between floods and key climate drivers, and identify extreme floods as examples of what may be necessary for mitigation and adaptation. Gauged flood histories are usually short and therefore incapable of providing the data and information required. In addition, disasters are not natural but are the result of human vulnerability that is created over time. Therefore, histories of vulnerability are also needed to understand how disasters are generated. The focus of this seminar will be the construction of flood histories using geologic archives over centuries in N Thailand, the central Himalaya, and N Australia. Early results from Thailand suggest a random occurrence of large floods during the past 200 years that is likely to be the result of random occurrences of typhoons and tropical storms, and the recognition of an example of an extreme flood in the 1830’s that would have devastating consequences if it occurred today. In India and Australia large flood magnitude and frequency appear to have moved outside the envelope of variability for the past 1000 years, and frequency is non-random. Also, there are correlations between flood frequency, climate changes, and ENSO variability over the past half millennium in N Australia and India. The implications of these findings for large flood management will be explored.

Carbon-14 and Iodine-129 as Tracers: Regional, Cosmic and Anthropogenic Effects

Date: 2014-02-11
Speaker: Dr. T. J. Jull
Venue: Ground Floor Lecture Hall

Abstract

Use of environmental isotopes to distinguish and estimate the sources of runoff: a case study of Kashmir Himalaya

Date: 2014-01-28
Speaker: Dr. Gh. Jeelani,
Venue: Ground Floor Lecture Hall

Abstract

Oxygen and hydrogen isotopes have been used as a tool to estimate the contributions of various components to the runoff of Liddar River in Kashmir Himalaya. Discrete seasonal variability of isotopes in precipitation and streams was found in the study area. The stable isotopes were found to be lighter at higher altitudes and in winter season. The isotopes were heavier at lower altitudes and in summer. In the present study the isotopes were also used to study the role of snow-melt and glaciers in controlling the regional hydrology.

On maximizing entropy in constraining the distribution of radiogenic heat in the crust.

Date: 2014-01-17
Speaker: Dr. R. N. Singh
Venue: Ground Floor Lecture Hall

Abstract

Paleoseismology using Corals

Date: 2014-01-15
Speaker: Mr. Kaustubh Thirumalai
Venue: Ground Floor Lecture Hall

Abstract

Delta-18 O and Delta-D of Atmospheric Water Vapor over Bay of Bengal.

Date: 2014-01-07
Speaker: Mr. Midhun M.
Venue: Ground Floor Lecture Hall

Abstract

Causes And Patterns of Seismic Events In Gujarat.

Date: 2014-01-03
Speaker: Dr. K. S. Misra
Venue: Ground Floor Lecture Hall

Abstract

2013

Atmospheric Brown Carbon: New results from Bay of Bengal.

Date: 2013-12-31
Speaker: Prof. M. M. Sarin
Venue: Ground Floor Lecture Hall

Abstract

The relevance of chemical composition of atmospheric particulate matter is of prime concern in the present-day climate change scenario. In particular, a considerable mass of organic aerosols remains unidentified, leading to a large degree of uncertainty in assessing their impact on climate change. Recent studies have highlighted the importance of light absorbing organic aerosols, referred as brown carbon (BrC),ubiquitous and abundant over rural, urban and remote continental and marine locations. This talk will present the first field measurements of light absorbing organic aerosols (BrC) in the marine atmospheric boundary layer of the Bay of Bengal.

Decoding the geological history of the Andaman Islands.

Date: 2013-12-17
Speaker: Dr. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Regionalities in geo-hydrological and hydro-meteorological processes discerned from Isotopic characteristics of Indian water sources

Date: 2013-11-26
Speaker: Dr. R. D. Deshpande
Venue: Ground Floor Lecture Hall

Abstract

It has been possible to recognize some of the characteristic isotopic(oxygen and hydrogen) patterns in various water resources of India, and their spatio-temporal variations, due to a collaborative national initiative for isotope fingerprinting (IWIN Programme). A huge volume of new isotope data from IWIN enables examining regionalities in hydrological processes and provides a unique tool to understand the ongoing geo-hydrological and hydro meteorological processes. Snap-shots of some of these processes will be presented in this talk.

Origin of Sediments deposited in the Andaman accretionary prism

Date: 2013-11-19
Speaker: Dr. Neeraj Awasthi
Venue: Ground Floor Lecture Hall

Abstract

Dissolved Nd in the Ganga river system and its flux to the Bay of Bengal.

Date: 2013-11-12
Speaker: Ms. Jayatee Chatterji
Venue: Ground Floor Lecture Hall

Abstract

PAHs and Dicarboxylic Acids in ambient atmospheric aerosols from Biomass Burning Emissions in Northern India.

Date: 2013-11-05
Speaker: Dr. Prashant Rajput
Venue: Ground Floor Lecture Hall

Abstract

Organic aerosols (OA) constitute significantly (~ 20 – 90%) to the total fine particulate matter in the troposphere. They have potential to, impact aerosol composition in totality through water uptake and, interact with atmospheric traceconstituents (O3, NOX and OH radical). Thus how, they have a potential role to acting as cloud condensation nuclei (CCN). Furthermore, the impact of OA on radiative forcing and atmospheric deposition of nutrients to the open ocean have been an interesting area of the atmospheric research. In this talk, two important classesof organic species: referred as polycyclic aromatic hydrocarbons (PAHs; 2–6 rings) and dicarboxylic acids (C2–C9) will be presented.

Recent revisions in the radiocarbon calibration database.

Date: 2013-10-15
Speaker: Dr. M. G. Yadava
Venue: Ground Floor Lecture Hall

Abstract

Environmental services: Need for more science.

Date: 2013-10-08
Speaker: Prof. R. N. Singh
Venue: Ground Floor Lecture Hall

Abstract

Role of volatiles (H2O, CO2) in deep mantle.

Date: 2013-10-01
Speaker: Dr. Sujoy Ghosh
Venue: Ground Floor Lecture Hall

Abstract

Understanding Evolution of Silicate Earth using Sm-Nd systematics.

Date: 2013-09-17
Speaker: Ms. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

Isotope Applications in Hydrology: Results from IWIN and Emergent Perspectives

Date: 2013-09-11
Speaker: Dr. R. D. Deshpande
Venue: Ground Floor Lecture Hall

Abstract

Land Sea interaction during last 5.5 ka around Diu Island, Western India.

Date: 2013-09-10
Speaker: Ms. Upasana Banerji
Venue: Ground Floor Lecture Hall

Abstract

The Science of Geoengineering

Date: 2013-08-27
Speaker: Dr. Govindaswamy Bala
Venue: Ground Floor Lecture Hall

Abstract

Geochemistry and Petrogenesis of Bundelkhand Granite, Central Indian Shield

Date: 2013-08-21
Speaker: Ms. Saweeta Kumari
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric Processing of Ambient Aerosols: Implications

Date: 2013-08-06
Speaker: Dr. Neeraj Rastogi
Venue: Ground Floor Lecture Hall

Abstract

Landform Evolution and Glaciers of Ladakh: Response to Climate Change

Date: 2013-07-29
Speaker: Dr. R. K. Ganjoo
Venue: Ground Floor Lecture Hall

Abstract

Synoptic controls of rainfall δ18O over Kerala, India

Date: 2013-07-23
Speaker: Ms. Lekshmy P. R.
Venue: Ground Floor Lecture Hall

Abstract

Mr. A. K. Sudheer

Date: 2013-07-16
Speaker: Mr. A. K. Sudheer
Venue: Ground Floor Lecture Hall

Abstract

Effects of anthropogenic inputs on nitrogen dynamics of a tropical estuary and adjacent coastal waters.

Date: 2013-07-02
Speaker: Ms. Bhavya P. S.
Venue: Ground Floor Lecture Hall

Abstract

Reconstruction of past carbon dioxide levels from Tree-ring cellulose δ13C.

Date: 2013-06-25
Speaker: Ms. Trina Bose
Venue: Ground Floor Lecture Hall

Abstract

Ambient mass spectrometry for systematic study of chemicals and pesticides in vegetables and herbs

Date: 2013-04-23
Speaker: Dr. Amzad Hussain Laskar
Venue: Ground Floor Lecture Hall

Abstract

Early Differentiation of the Silicate Earth

Date: 2013-04-09
Speaker: Ms. Ikshu Gautam
Venue: Ground Floor Lecture Hall

Abstract

Subsurface imaging - challenges and opportunities

Date: 2013-04-02
Speaker: Prof. Mrinal Sen
Venue: Ground Floor Lecture Hall

Abstract

Dr. Aditya Peketi

Date: 2013-03-19
Speaker: Dr. Aditya Peketi
Venue: Ground Floor Lecture Hall

Abstract

High resolution Paleoclimatic Reconstruction and Speleothem dating

Date: 2013-03-12
Speaker: Ms.Shraddha Band
Venue: Ground Floor Lecture Hall

Abstract

Harmful Algal Blooms in the Arabian Sea

Date: 2013-03-05
Speaker: Dr. Arvind Singh
Venue: Ground Floor Lecture Hall

Abstract

Did Sarasvati flow into the Great Rann of Kutch 5000 years ago?

Date: 2013-02-19
Speaker: Mr. Anirban Chatterjee
Venue: Ground Floor Lecture Hall

Abstract

The Cretaceous Volcanic Episode in and around Peninsular India

Date: 2013-01-29
Speaker: Dr. K. S. Misra
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric outflow from the Indo-Gangetic Plain

Date: 2013-01-01
Speaker: Dr. M. M. Sarin
Venue: Ground Floor Lecture Hall

Abstract

2012

Particle export during the iron fertilization experiment LOHAFEX

Date: 2012-12-18
Speaker: Dr. R. Rengarajan
Venue: Ground Floor Lecture Hall

Abstract

Indian Summer Monsoon in the Late Pleistocene: Reconstruction from a Speleothem from P. India

Date: 2012-12-11
Speaker: Dr. Timmy Francis
Venue: Ground Floor Lecture Hall

Abstract

Paleoclimatic Records from the Northern Indian Ocean

Date: 2012-12-04
Speaker: Dr. Ravi Bhushan
Venue: Ground Floor Lecture Hall

Abstract

Atmospheric dry deposition of mineral dust and anthropogenic trace metals to the N. Indian Ocean

Date: 2012-11-27
Speaker: Dr. Bikkina Srinivas
Venue: Ground Floor Lecture Hall

Abstract

A High-precision Measurement System for Carbon Isotopic Ratios of Atmospheric Methane

Date: 2012-11-06
Speaker: Mr. D. K. Rao
Venue: Ground Floor Lecture Hall

Abstract

Lamont-Doherty Earth Observator

Date: 2012-10-23
Speaker: Prof. R. F. Anderson
Venue: Ground Floor Lecture Hall

Abstract

Solid Earth Geophysics in India Since Independences

Date: 2012-10-16
Speaker: Prof. R. N. Singh
Venue: Ground Floor Lecture Hall

Abstract

Generation,emplacement and preservation of carbonatites: a story from Rajasthan, India

Date: 2012-10-09
Speaker: Dr. J. S. Ray
Venue: Ground Floor Lecture Hall

Abstract

Advances in radiocarbon detection methods

Date: 2012-09-04
Speaker: Dr. M. G.Yadav
Venue: Ground Floor Lecture Hall

Abstract

Cosmogenic radioactivity in Indian Meteorites collected in last two decades

Date: 2012-08-28
Speaker: Dr. A. D. Shukla
Venue: Ground Floor Lecture Hall

Abstract

Radiocarbon dating of groundwater

Date: 2012-08-14
Speaker: Mr. Balaji D.
Venue: Ground Floor Lecture Hall

Abstract

Molybdenum isotopes in the Indian Estuaries: Implication to biogeochemistry of Mo

Date: 2012-08-07
Speaker: Dr. Sunil Kumar Singh
Venue: Ground Floor Lecture Hall

Abstract

Towards understanding the pattern of Late Quaternary Glaciations in Indian Himalaya

Date: 2012-07-31
Speaker: Dr. Sheikh Nawaz Ali
Venue: GROUND LECTURE HALL