Sediments are deposited along with dead remains of organisms unique to the time and environment of deposition (usually hard parts of organisms e.g. shells, bones). Over time, these parts get preserved as fossils. In an undisturbed sedimentary sequence, the lower layers of sediment are older and the overlying sediments are of progressively younger age. The evolution of organisms (and the corresponding fossils) is also a function of time. Therefore the order of sediment deposition and the fossil content  record 'relative time'!! 

Foraminifera are microscopic calcium carbonate shells of marine unicellular organisms that fossilize. Shells of dead 'planktonic' foraminifera record the evolution of species through geologic time. Therefore these shells (particularly of certain index species characteristic of a certain historic time interval) prove very important to constrain the age of sediments and to time-correlate distant sedimentary sections. Their small size allows for higher temporal resolution ie. better sampling of time. Their high abundance in marine sediments also allows statistically valid population studies. 

 Planktic foraminifera have diverse ecologies and occupy a wide range of niches in the water column, enabling the reconstruction of water-mass stratification and paleoecology through geologic time. Their high sensitivity to changes in climate, temperature, salinity, pH and oxygen makes them ideal proxies for environmental changes.

Mass extinctions and faunal turnover intervals from the geologic past have acted as evolutionary bottlenecks and help understand the underlying mechanisms that govern natural selection. I am interested in understanding the possible triggers, time scales (of perturbations and feedbacks), rates of biodiversity loss and recovery of life in the aftermath of such events. Such time-intervals therefore provide excellent case studies to assess the tolerance and resilience of past ecosystems to climatic/environmental perturbations. The possibility of a future anthropogenic mass extinction due to rapid climate change makes such an effort imperative.

 I have worked with planktic foraminifera (and supporting geochemical proxies) of the Cretaceous-Tertiary boundary interval. My dissertation research was carried out under the guidance of Prof. Gerta Keller at Princeton University. Some important contributions of this work were: (1) a time-correlation between biotic stress and the major phases of large-scale Deccan volcanism of India, (2) global nature of these stress events, (3) first ever confirmation of an ocean acidification event immediately preceding the mass extinction. These new insights improve our perception of the nature and mechanism of this extinction event.

Apart from ongoing research on the late Maastrichtian (Cretaceous) leading up to the end-Cretaceous (KTB) mass extinction at 66 million year ago (Ma), I am interested in events such as the extreme rapid warming Paleocene-Eocene Thermal Maximum (PETM) of 55.8 Ma and the Cenomanian/Turonian anoxic event of ~93 Ma ago. I hope to explore a few of these critical intervals of global climate and faunal change, particularly in the Indian subcontinent. Correlations with sections worldwide will help to establish a regional/global bigger picture.