T200 Mass Extinctions: Volcanism, Impacts, and Catastrophic Environmental Change II
Tuesday, 21 October 2014
8:00 AM - 12:00 PM
223/224
TRIGGERING OF THE LARGEST DECCAN ERUPTIONS BY THE CHICXULUB IMPACT
Paper number: T200-6
Program: Technical Sessions
Time: 9:10 AM – 9:25 AM
Authors
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Sally GibsonUniversity of Cambridge, Cambridge, N/A
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Walter AlvarezUniversity of California, Berkeley, CA
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Stephen Selfalso at Dept. of Earth and Environmental Sciences, The Open University, Milton Keynes
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Leif KarlstromUniversity of Oregon, Eugene, OR
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Paul RenneBerkeley Geochronology Ctr, Berkeley, CA
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Michael MangaUniversity of California, Berkeley, Berkeley, CA
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Courtney J. SprainUniversity of California, Berkeley, Berkeley, CA
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Jan SmitVU University, Amsterdam, N/A
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Loyc VanderkluysenDrexel University, Philadelphia, PA
Abstract
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.