T296 Volcanism, Impacts, and Phanerozoic Mass Extinctions: Discovering a Common Cause and Planning for the 6th Mass Extinction II

Wednesday, 25 September 2019
1:30 PM - 5:30 PM
Room 227ABC, North Building

MERCURY LINKS DECCAN VOLCANISM TO CLIMATE CHANGE AND THE END-CRETACEOUS MASS EXTINCTION

Paper number: T296-5
Program: Technical Sessions
Time: 2:30 PM – 2:45 PM

Authors

Abstract

Deccan volcanism in India and the Chicxulub impact in Mexico are both linked to the Cretaceous-Paleogene (KPB) mass extinction; however, the relative timing of the impact and volcanic eruptions remain controversial, precluding full assessment of their respective roles. Mercury (Hg) anomalies in sediments related to global distribution and atmospheric fallout of Deccan emissions provide a potential tool to directly assess the cause-and-effect relationship between Large Igneous Province (LIP) volcanism, climate change and mass extinctions. We report high-resolution Hg and paleoclimatic records for the most complete and expanded late Maastrichtian - early Danian section at Elles, Tunisia (auxiliary GSSP to El Kef), and correlate this section with similar sequences (e.g., Israel, Spain, France) to assess the global Hg distribution relative to Deccan eruptions. Results confirm Hg as a robust proxy for Deccan volcanism, with large Hg peaks correlated globally. Results also demonstrate maximum global climate warming closely related to peak Hg concentrations at the CF2/CF1 boundary (190 ky pre-KPB) and hyperthermal warming related to maximum Hg concentrations during the last 20 ky before the mass extinction. In contrast, early Danian cooling is associated with low Hg concentrations. We correlate the highresolution, astronomically tuned cyclostratigraphy of Elles with high-resolution U-Pb geochronology of Deccan Trap volcanism at the ca. ±40 ky-level. Results show excellent age correlation for the last 350 ky of the Maastrichtian, with high Deccan eruption rates coincident with global climate warming trends. Volcanically-induced environmental changes led to increased stress on marine life (planktic foraminifera), as evident by reduced species size (Lilliput effect), decreased species populations, and a carbonate crisis that ultimately led to the KPB mass extinction. Threshold life conditions were reached during paroxysmal volcanic eruptions in the last 20 ky before the mass extinction. The timing of the Chicxulub impact relative to Deccan volcanism remains enigmatic in the absence of cosmic evidence in the Deccan and the stratigraphic position of impact breccia in the Chicxulub crater and impact glass spherules in NE Mexico predating the KPB.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-337703

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