Paper No. 104-6
Presentation Time: 3:00 PM
MERCURY LINKS DECCAN VOLCANISM TO CLIMATE CHANGE AND THE END-CRETACEOUS MASS EXTINCTION
Deccan volcanism in India is intimately linked to long-term global climate warming during the last 350 ky of the Maastrichtian ending in hyperthermal warming and the end-Cretaceous mass extinction. Recently, we tested the first direct link between Deccan eruptions and climate change for the 550 ky prior to the mass extinction based on the global distribution of Mercury (Hg) fallout and the stable isotope record of climate change at Elles, Tunisia and Hor Hahar, Israel. In both localities, high Hg fallout correlates with climate warming. The correlation with Deccan volcanism in India was achieved based on U-Pb chronology of Deccan eruptions and at Elles based on bio- and Hg- stratigraphy plus orbital cyclicity. The direct correlation with Deccan volcanism is unequivocal with an error margin of two precession cycles (±20 ky). A total of 20 extreme event (EE) eruption pulses were identified over 550 ky but the onset of climate warming began with EE4 ~340 ky prior to the mass extinction. A short cool event occurred between 50-20 ky prior to the onset of hyperthermal warming. By far the ten most extreme eruptions occurred during the last 20 ky prior to the mass extinction and resulted in hyperthermal warming, ocean acidification and toxicity ending in the mass extinction within a few thousand years.
We report similar Hg and stable isotope analyses from global Deccan emissions in Texas and half a dozen localities in northeastern Mexico to assess the link to the mass extinction. These data revealed similar Hg pulsed extreme events during the Maastrichtian, including the short climate cooling with the topmost reworked spherules 20-50 ky pre-KPB. Most significantly, the primary Chicxulub impact spherule layer in NE Mexico coincided with the major pulsed eruption EE6 dated about ~200 ky prior to the mass extinction. This finding confirms earlier reports and estimated biostratigraphic age of 200-300 ky prior to the KPB. The new timing of the Chicxulub impact relative to Deccan volcanism calls for reconsideration of the impact theory as cause for the end-Cretaceous mass extinction.