T55 Multidisciplinary Approaches to Studying the Causes and Consequences of Mass Extinction: Geochemistry, Paleoecology, and Paleoenvironments II

Sunday, 9 October 2011
1:30 PM - 5:30 PM
Room 200H-J

DECCAN TRAPS DIRECTLY LINKED TO KTB MASS EXTINCTION AND DELAYED RECOVERY

Paper number: T55-11
Program: Technical Sessions
Time: 4:00 PM – 4:15 PM

Authors

Abstract

In magnetochron C29R prior to the Cretaceous-Tertiary boundary (KTB) mass extinction massive Deccan Trap eruptions (80% of total volume) in India covered an area the size of Texas and produced the world’s largest and longest lava mega-flows reaching 1500 km across India. Here we report on the multi-disciplinary investigation, including paleontology, lithology, mineralogy, stable isotopes, geochemistry and e-logs of eleven wells from the K-G Basin. Results reveal four mega-flows with the last mega-flow ending at the KTB. The biologic response to these massive volcanic eruptions was swift and devastating. Just prior to the first mega-flow, planktic foraminifera suffered 50% species extinctions due to Deccan volcanism preceding the mega-flows. Survivors suffered another 50% extinctions after the first mega-flow eruption leaving just 7 to 8 survivor species. No recovery occurred between the next three mega-flows and the mass extinction was complete with the last mega-flow at the KTB. The mass extinction was likely the consequence of rapid and massive volcanic CO2 and SO2 gas emissions, leading to high continental weathering rates, global cooling, acid rain, ocean acidification and a carbon crisis in the marine environment.

After the KTB mass extinction, high-stress conditions persisted for at least 300-500 ky in India and globally, as indicated by the evolution of low diversity (<20% of pre-KTB diversity) stress tolerant small species. The last major Deccan eruptions (14% of total volume) occurred in the early Danian base of C29N about 300-500 ky after the mass extinction and produced three to four mega-flows, similar to those of C29R. The global effects of this volcanic phase were comparable to the KTB with a major negative carbon isotope excursion, organic-rich clay deposition, and faunal assemblages dominated by the disaster opportunist Guembelitria cretacea but few species extinction. Full recovery of the marine ecosystem occurred only after this last volcanic phase. Deccan volcanism thus appears to be the main cause for the KTB mass extinction and the long delayed marine recovery that has remained an enigma for the past 30 years.