2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 68-12
Presentation Time: 4:25 PM


TOBIN, Thomas S., Geological Sciences, University of Alabama, 201 7th Avenue, Room 2003 Bevill Building, Tuscaloosa, AL 35487-0268 and BITZ, Cecilia M., Atmospheric Sciences, University of Washington, Box: 351640, 4000 15th Ave NE, Seattle, WA 98195, ttobin@ua.edu

The end Cretaceous mass extinction was likely precipitated by a large bolide impact at the Cretaceous – Paleogene (K-Pg) boundary, but a number of studies have suggested a minor to substantial contribution of the Deccan Traps Volcanism (DTV) to the overall extinction (Tobin et al., 2012; Wilson, 2014). DTV generated one of the largest flood basalts in earth history, and similar events have been linked with many of the major mass extinctions of the Phanerozoic (Courtillot and Renne, 2003). Almost all of the DTV occurred within a 700 kyr window around the K-Pg boundary, but the position of the K-Pg boundary within this duration is currently poorly constrained (Schoene et al., 2015). The most likely mechanism for the DTV to affect biology on a global scale is through changing atmospheric chemistry or temperature, either through release of CO2 or SO2 aerosols. We will present modelled global CO2, temperature, and other changes as the result of recent estimates of total eruptive volumes from DTV (Self et al., 2006; Chenet et al., 2009).

We modified and employed a zero-dimensional carbon cycle model, GEOCYC, itself a modification on an earlier GEOCARB III model. CO2 emissions from short (1-100 year) individual eruptive events are unlikely to lead to substantial warming , in contrast to SO2 aerosols which, while not modelled here, may have measureable to severe cooling effects during active emission (Self et al., 2015). Previously, the warming effects of flood basalt carbon emissions have been disregarded due to the length of time between emissions, but our results suggest that despite the episodic nature of flood basalt eruptions, the long lifetime of CO2 causes it to accumulate in the atmosphere and contribute to a global increase in temperature. We modelled a number of emissions scenarios and found that the details of the timing, frequency, and duration of individual eruptions did not materially alter the results, and the overall duration of volcanic activity and total emitted volumes of CO2 are the primary controls on overall warming. Given a range of different published estimates of CO2 release from the DTVP and constraints on its eruptive duration, the eruption the Deccan Traps is capable of generating measurable and significant global warming (~3° or more) in some scenarios, but would have a negligible effect in others.