A high-precision U-Pb age model for the Deccan Traps

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A high-precision U-Pb age model for the Deccan Traps PI: Asst. Prof. Blair Schoene, Princeton Univ., bschoene@Princeton.EDUThe Office of International and Integrative Activities/International Science co-funded the proposal with Sedimentary Geology and Paleobiology. ABSTRACTThis proposal focuses on an international collaboration with U.S. faculty and students travelling to India to work with their Indian collaborators, conduct fieldwork, and engage in subsequent analysis of samples to attempt high-precision eruption dates for the Deccan Traps and compare those dates with the independent timeline provided by biostratigrpahy. The ~66 Ma end-Cretaceous mass extinction is the most recent and publicly visible catastrophe in Earth history, encompassing the demise of dinosaurs and other large animals. Despite widespread scientific consensus that the extinction was caused solely by the Chicxulub asteroid impact (Yucatán, Mexico), additional evidence suggests that large, contemporaneous volcanic eruptions may have contributed significantly to this ecological disaster. These volcanic rocks are exposed in India and known as the Deccan Traps and comprise 1.3 km3 of basalt. This proposal focuses on providing high-precision eruption ages for the Deccan Traps in order to better compare them with the independent timeline of extinction and recovery across the Cretaceous-Paleogene boundary (KPB). By determining rates of volcanic eruptions through the Deccan stratigraphy, the investigators will estimate the volume of volcanic gasses emitted as a function of time. These estimates can be incorporated into models of late-Cretaceous climate change and compared with geochemical proxy and fossil records to better understand the potential contribution of the Deccan Traps to biologic turnover at the KPB.To achieve these goals, the investigators will apply chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) to zircons extracted from within the Deccan basalts and from volcanic ashbeds between basalt flows. Their initial results show this approach to be successful, producing uncertainties on flow deposition to ±20-30 thousand years. These initial data include estimates of the onset and termination of the main phase of Deccan volcanism and show it to bracket the KPB with a duration of ~750 kyr; their new data will include a high-resolution timeline for the eruptions throughout the entire 3 km thick volcanic sequence, which is critical for assessing volatile release through time. These dates can be compared to recently published estimates for the timing of the KPB extinction and Chicxulub impact, and further compared to increasingly bolstered records of ecological and environmental change both leading up to and following the main extinction event. The resulting age model for the Deccan Traps will be an essential component of a holistic approach towards understanding late-Cretaceous ecological change and the subsequent rebuilding of Earth's biosphere.