Geosciences Division Seminar
Title : The Evolution of Granite-Greenstone Belts of the Western part of Dharwar Craton, Dharwar Craton, South India
Date : 02-12-2025
Time : 16:00:00
Speaker : S V Balaji Manasa Rao
Area : Geosciences Division
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.
Title : Marine Microbes at the Air–Sea Interface: From SML Ice-Nucleating Bacteria to Microbial Aerosols in the Indian Ocean
Date : 08-12-2025
Time : 11:00:00
Speaker : Prof. Koji Hamasaki
Area : Geosciences Division
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.
Title : Size-resolved Sources, Composition and Optical Characteristics of Brown Carbon Aerosols
Date : 16-12-2025
Time : 16:00:00
Speaker : Garima Verma
Area : Geosciences Division
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.
Title : N₂ Fixation in Inland Water Ecosystem
Date : 16-12-2025
Time : 16:30:00
Speaker : Md. Fahad Alam
Area : Geosciences Division
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.
Title : Novel Tools to assess the Health Risks from Outdoor and Indoor Air Pollution
Date : 23-12-2025
Time : 16:00:00
Speaker : Dr. Vishal Verma
Area : Geosciences Division
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.
Title : Role of ocean anoxia in the Permian–Triassic crisis: Evidence from geochemical and isotopic data
Date : 26-12-2025
Time : 11:00:00
Speaker : Nilima Mishra
Area : Geosciences Division
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.
Title : Assessing environmental microplastics using FTIR
Date : 26-12-2025
Time : 11:30:00
Speaker : Maitri Maheshwari
Area : Geosciences Division
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.
Title : Investigating the Chautang-Drishadvati-Harappan connection
Date : 30-12-2025
Time : 16:00:00
Speaker : Aditya Vikram Mishra
Area : Geosciences Division
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.
Title : Geochemical Investigation of Neoproterozoic Bhander Shales: Implications towards Provenance
Date : 30-12-2025
Time : 16:30:00
Speaker : Deependra Singh
Area : Geosciences Division
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.