RESOLVING THE DRIVER OF THE END-CRETACEOUS MASS EXTINCTION USING SEDIMENTARY MERCURY GEOCHEMISTRY: VOLCANISM VERSUS IMPACT

Sedimentary mercury (Hg) enrichments have been used to link the emplacement of the Deccan Traps, a large volcanic province, to the end-Cretaceous mass extinction (ECME) at the Cretaceous-Paleogene (K/Pg) boundary. This is in potential conflict with the leading hypothesis that the ECME was caused by an extraterrestrial impact event and subsequent environmental change. Mercury accumulation in sediments can be enhanced as an outcome of volcanic outgassing, impacts, or during biogeochemical feedbacks to climate change (e.g., wildfires, soil destabilization, and changes in precipitation and dust deposition). To test the hypothesis that the Deccan Traps caused the ECME sedimentary Hg enrichments, we have generated Hg concentrations from a suite of study sites located in the North American Interior spanning a large latitudinal gradient that contain the K/Pg boundary. Mercury concentrations from biostratigraphically and U-Pb constrained paleosols in outcrop and core locations from multiple basins in New Mexico, Colorado, Wyoming, Montana, and North Dakota display large increases surrounding the K/Pg boundary and in Cretaceous and Paleogene lignites. These new data suggest strong local controls on ECME Hg accumulation, including but not limited to depositional setting and diagenesis.