Effects of Deccan volcanism on paleoenvironment and planktic foraminifera: A global survey

Abstract

Deccan volcanism, one of Earth’s largest fl ood basalt provinces, erupted ~80% of its total volume (phase 2) during a relatively short time in the uppermost Maastrichtian paleomagnetic chron C29r and ended with the Cretaceous-Tertiary boundary mass extinction. Full biotic recovery in the marine realm was delayed at least 500 k.y. or until after the last Deccan eruptions in C29n (phase 3, 14% of the total Deccan volume). For over 30 yr, the mass extinction has been commonly attributed to the Chicxulub impact, and the delayed recovery remained an enigma. Here, we demonstrate that the two phases of Deccan volcanism can account for both the mass extinction and delayed marine recovery. In India, a direct correlation between Deccan eruptions (phase 2) and the mass extinction reveals that ~50% of the planktic foraminifer species gradually disappeared during volcanic eruptions prior to the fi rst of four lava megafl ows, reaching ~1500 km across India, and out to the Bay of Bengal. Another 50% disappeared after the fi rst megafl ow, and the mass extinction was complete with the last megafl ow. Throughout this interval, blooms of the disaster opportunist Guembelitria cretacea dominate shallow-marine assemblages in coeval intervals from India to the Tethys and the Atlantic Oceans to Texas. Similar high-stress environments dominated by blooms of Guembelitria and/or Globoconusa are observed correlative with Deccan volcanism phase 3 in the early Danian C29n, followed by full biotic recovery after volcanism ended. The mass extinction and high-stress conditions may be explained by the intense Deccan volcanism leading to rapid global warming and cooling in C29r and C29n, enhanced weathering, continental runoff, and ocean acidifi cation, resulting in a carbonate crisis in the marine environment. *jpunekar@princeton.edu Punekar, J., Mateo, P., and Keller, G., 2014, Effects of Deccan volcanism on paleoenvironment and planktic foraminifera: A global survey, in Keller, G., and Kerr, A.C., eds., Volcanism, Impacts, and Mass Extinctions: Causes and Effects: Geological Society of America Special Paper 505, p. 91–116, doi:10.1130/2014.2505(04). For permission to copy, contact editing@geosociety.org. © 2014 The Geological Society of America. All rights reserved. on August 25, 2014 specialpapers.gsapubs.org Downloaded from