DECCAN VOLCANISM, IMPACTS AND THE K-T MASS EXTINCITON

Could Deccan volcanic eruptions in India be the real cause for the KT mass extinction? Several recent discoveries strongly suggest this possibility, including the main phase (80%) of Deccan Trap eruptions in C29r in a series of rapid megapulses with SO2 emissions equal or exceeding that of the Chicxulub impact (Chenet et al., 2007, 2008) and ending coincident with the KT mass extinction (Keller et al., 2008, 2009a,b). The short duration of volcanic eruptions and rapid, repeated massive SO2 injections may have caused a deadly runaway effect that led to the KT mass extinction. Sediments buried 2500-3500 m deep in the Krishna-Godavari (K-G) Basin of SE India, recovered a series of cores drilled by the Oil and Natural Gas Corporation of India (ONGC) with up to 9 megaflows that span over 1500 km across India and mark the world’s longest and largest eruptions (Keller et al., 2008; Self et al., 2008). Four to five of these megaflows occurred in rapid succession marking the end of the main Deccan volcanic phase. Preliminary results show that after the first megaflow more than 50% of the species disappeared and with each new megaflow more species died out culminating in the mass extinction coincident with the last megaflow at or near the KT boundary. In Meghalaya, NE India, over 1000 km from the Deccan volcanic province the biotic and environmental effects of twin catastrophes – volcanism and an extraterrestrial impact - can be observed. At this locality, extreme stress conditions and near extinction of planktic foraminifera began well below the KT boundary, similar to the K-G Basin of SE India. The KT boundary is marked by a major Ir anomaly (12 ppb) that suggests a second impact struck a world that had already suffered a devastating mass extinction caused by volcanism. Just like the Chicxulub impact that predates the KTB and caused no mass extinction (Keller et al., 2007, 2009c) this second impact caused no mass extinction, but may have exacerbated already devastating environmental conditions.

Chenet et al., 2007 EPSL 263: 1-15; 2008 JGR 113: BO4101. Keller et al., 2007 EPSL 255: 339-356; 2008 EPSL 268:293-311; 2009a EPSL 282: 10-23; 2009b JFR 39:40-55; 2009c JGS 166: 393-411. Self et al., 2008 JVGR 172: 3-19.