2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 200-5
Presentation Time: 9:10 AM


RICHARDS, Mark1, ALVAREZ, Walter1, SELF, Stephen2, KARLSTROM, Leif3, RENNE, Paul4, MANGA, Michael1, SPRAIN, Courtney J.5, SMIT, Jan6, VANDERKLUYSEN, Loyc7 and GIBSON, Sally8, (1)Department of Earth and Planetary Science, University of California, Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767, (2)US Nuclear Regulatory Commission, Washington DC 20555;, also at Dept. of Earth and Environmental Sciences, The Open University, Milton Keynes, MK76AA, United Kingdom, (3)Department of Geological Sciences, University of Oregon, 1272 University of Oregon, Eugene, OR 97403-1272, (4)Berkeley Geochronology Ctr, 2455 Ridge Rd, Berkeley, CA 94709-1211, (5)Department of Earth and Planetary Science, University of California, Berkeley, 307 McCone Hall, Berkeley, CA 94720, (6)Sedimentology, VU University, Falw, de Boelelaan 1085, Amsterdam, 1018HV, (7)Department of Biodiversity, Earth and Environmental Science, Drexel University, Philadelphia, PA 19104, (8)Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, United Kingdom, mark_richards@berkeley.edu

New constraints on the timing of the Cretaceous-Paleogene (K-Pg) mass extinction and the Chicxulub impact, together with a particularly voluminous and apparently brief eruptive pulse toward the end of the “main-stage” eruptions of the Deccan continental flood basalt province, suggest that these three events may have occurred within less than about a hundred thousand years of each other. Partial melting induced by the Chicxulub event does not provide an energetically-plausible explanation for this coincidence, and both geochronologic and magnetic-polarity data show that Deccan volcanism was underway well before Chicxulub/K-Pg time. However, historical data document that eruptions from existing volcanic systems can be triggered by earthquakes. Seismic modeling of the ground motion due to the Chicxulub impact suggests that the impact could have generated seismic energy densities of order 0.1-1.0 J/m3 throughout the upper ~200 km of the Earth’s mantle, sufficient to trigger volcanic eruptions worldwide based upon comparison with historical examples. Triggering may have been caused by a transient increase in the effective permeability of the existing deep magmatic system beneath the Deccan province, or mantle plume “head.” It is therefore reasonable to hypothesize that the Chicxulub impact might have triggered the enormous Poladpur, Ambenali, and Mahabaleshwar (Wai sub-group) lava flows that account for >70% of the Deccan Traps main-stage eruptions. This hypothesis is consistent with independent stratigraphic, geochronologic, geochemical, and tectonic constraints, which combine to indicate that at approximately Chicxulub/K-Pg time a huge pulse of mantle plume-derived magma passed through the crust with little interaction, and erupted to form the most extensive and voluminous lava flows known on Earth. High-precision radioisotopic dating of the main-phase Deccan flood basalt formations may be able either to confirm or reject this hypothesis, which in turn might help determine whether this singular outburst within the Deccan Traps (and possibly volcanic eruptions worldwide) contributed significantly to the K-Pg extinction.