Geosciences Division Seminar
Title : Palaeoceanographic implications of single planktonic foraminiferal isotopic analysis
Date : 01-07-2025
Time : 16:00:00
Speaker : Dr. Sanchita Banerjee
Area : Geosciences Division
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..
Title : Sediment Connectivity in India’s Large River Basins under Climate and Human-Induced Stress
Date : 08-07-2025
Time : 16:00:00
Speaker : Dr. Abhishek Dixit
Area : Geosciences Division
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.
Title : Chemical compositions of the Ganga, Yamuna, Narmada and Tapi Rivers: An assessment of spatial and temporal variability
Date : 22-07-2025
Time : 16:00:00
Speaker : Dr. Rakesh Kumar Tiwari
Area : Geosciences Division
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.