Deccan volcanic eruptions occurred in three phases with the main phase-2 in chron 29R at the end of the Maastrichtian accounting for 80% of the entire 3500 m thick Deccan lava pile. Four of Earth's longest lava flows span over 1000 km across India and out into the Bay of Bengal ending with the Cretaceous-Tertiary (KT) mass extinction (Keller et al., 2008, 2009a,b). Still unknown in KT studies is the potential cause-and-effect relationship of Deccan volcanism and the mass extinction. This project addresses this problem. The main objective is to investigate the biological and environmental consequences of these longest lava flows and their effects upon marine life. This has been problematic because Deccan eruptions are largely continental. We have discovered marine sequences in eastern, central and southwestern India. For this project we plan to investigate outcrops as well as drill two 50 m deep wells in two quarries of Rajahmundry, Andhra Pradesh, to recover the last 1 m.y. record of the Maastrichtian. In addition, we plan fieldwork in Gujarat to collect upper Maastrichtian sediments deposited in an estuarine environment. These records will be analyzed in a multidisciplinary international collaboration project that includes US, Indian and Swiss scientists and students who will be collaborating in all phases of this research, from fieldwork to analyses, interpretation and writing papers for publication. Specific topics to be investigated include the biological and environmental effects of volcanism upon benthic and planktic foraminifera, calcareous nannofossils, ostracods and palynomorphs, as well as changes in climate, productivity and oxygen based on stable isotopes, sedimentology, microfacies, bulk and clay mineralogy. The database collected under this project will be the first direct evaluation of the effects of a large igneous province (LIP) upon life and the methods are potentially applicable to other mass extinctions associated with LIPs. This project is supported with cofunding from the Office of International Science and Engineering's India Program.
This project set out to investigate the role of Deccan volcanism in India as potential cause for the end-Cretaceous mass extinction. Deccan volcanism occurred in three major phases with phase-2 eruptions accounting for ~80% of the total lava pile that still today form mountains as high as 3000 m covering a major part of India. The precise age of phase-2 eruptions and its relationship to the mass extinction of dinosaurs was the major focus of this investigation. Our investigations concentrated on fieldwork in the Deccan Traps as well as in nearby areas across India based on outcrops and deep wells drilled to a depth of 3000 to 4000 m by the Oil and Natural Gas Corporation of India (ONGC). These investigations were very successful. In Meghalaya, NE India, one of the world’s most complete Cretaceous-Tertiary (KT) sections is only about 800 km from the Deccan Volcanic Province and reveals a well-defined KT boundary with large Ir anomaly (12ppb), carbon isotope shift, and mass extinction. But during the 100,000 to 200,000 years prior to the mass extinction, extreme high-stress conditions prevailed with the disaster opportunist Guembelitria cretacea dominating (>95% of the assemblages). Similar high-stress conditions have now been observed worldwide. A direct cause-and-effect relationship between the mass extinction and Deccan volcanism was demonstrated between phase-2 eruptions and the mass extinction particularly in the basalt quarries of Rajahmundry and nearby deep wells from the Krishna-Godavari Basin, SE India. In this region phase-2 eruptions ended with Earth’s longest and largest lava megaflows reaching 1500 km across India and out into the Bay of Bengal. On land the dinosaurs disappeared at the onset of this eruption phase. In the marine realm the mass extinction began with 50% species extinctions in planktic foraminifera a short time prior to the arrival of the first of four megaflows, followed by another 50% extinctions after the first megaflow. No recovery occurred between megaflows 2 and 3 and the mass extinction was complete with the last megaflow at the KTB boundary. The lack of recovery in between the lava megaflows suggests that eruptive events followed each other rapidly, preventing ecosystem recovery and leading to detrimental runaway effects. This rapid succession of massive volcanic eruptions resulted in extreme climate changes due to sulfur dioxide and greenhouse gases (CaCO2) causing acid rain on land and ocean acidification that prevented shell growth in calcium carbonate secreting organisms in the oceans leading to their extinction. From beginning to end the mass extinction may have occurred over just a few tens of thousands of years to at most 100,000 years. Prevailing high-stress conditions preceding the mass extinction on a global basis include dwarfing of species, decreased species diversity and blooms of the disaster opportunist Guembelitria cretacea. In the marine realm high-stress conditions prevailed for about 500,000 years after the mass extinction even though no significant volcanic eruptions occurred over this time until the end when the last phase-3 volcanic eruptions occurred, which account for about 14% of the total Deccan lava pile. Full marine recovery occurred only after the end of phase-3 volcanism in paleomagnetic chron 29N. This indicates that Deccan volcanism and its environmental effects were the major contributors, if not major cause, for both the end-Cretaceous mass extinction as well as the long delayed marine recovery. The Chicxulub impact, which occurred about 100-150 kyr before the mass extinction, contributed to the detrimental climatic and environmental conditions leading up to the mass extinction through CO2 and SO2 emissions, which are estimated to be of the same magnitude as one single major Deccan eruption (one megaflow). However, because an impact is a single event this permitted ecosystem recovery and would not cause mass extinctions. The results of this project contribute significantly to the over three decades long controversy over the end-Cretaceous mass extinction. In particular, it provides the first solid data that shows the mass extinction is directly tied to the main phase-2 Deccan volcanism and the extinctions were rapid and directly tied to the major lava megaflows across India. These results demonstrate that the KTB mass extinction scenario is much more complex than a single impact event as commonly believed. Volcanism is the likely main cause for the KTB mass extinction, just as massive volcanic eruptions are the most likely main cause for the end-Devonian, end-Permian, and Jurassic/Triassic mass extinctions.
