INSIGHTS FROM DRIVERS OF THE K-PG MASS EXTINCTION FOR MODERN GLOBAL CHANGE, EXTINCTION RISK, AND AVENUES FOR ADAPTATION (Invited Presentation)

Intergovernmental Panel on Climate Change (IPCC) estimates 25% of Earth’s mammals and 12% of birds are significantly at risk for extinction due to overlapping environmental and habitat pressures. At a high confidence level, rapid climate change greatly increases species vulnerability to extinction, however specific drivers such as shifting climatic zones are difficult to unravel from other anthropogenic drivers of habitat conversion /degradation and introduced (invasive) species. As geologists, we can bring some insight by examining past examples of rapid climate change and its ecological/biological effects where cause and effect are arguably simpler than modern overlapping influences of risk of extinction.

Earth’s last mass extinction event was arguably its most rapid with a ~75% extinction level occurring in < 20 years. This was the Cretaceous-Paleogene extinction event caused by the impact of a 12 km asteroid into the carbonate-evaporite rich stratigraphy of the Yucatán Peninsula forming the Chicxulub impact structure. Drilling results from the International Ocean Discovery Program-International Continental scientific Drilling Program Expedition 364 recovered a nearly complete sequence from uplifted crystalline target rocks in Chicxulub’s peak ring, to 130 m of impact melt rock and suevite (impactoclastic breccia) deposited within the first day of the Cenozoic, to an 80 cm thick “transition unit” deposited on the weeks-to-years time scale ending with the preserved global iridium layer marking the cessation of short term atmospheric effects from the impact. This sequence is then overlain by remainder of the Paleocene deposited under reduced accumulation rates and are in turn overlain by Paleocene-Eocene Thermal Maximum black shale and an expanded Eocene carbonate sequence. Insights from this record for our modern rapid global change include: 1) the ability to compare volumes of climatically active gases produced by Chicxulub with those estimated by the IPCC that yields insight into how the K-Pg extinction was dominantly a rapid global cooling event, 2) opportunity to study ecosystem response and faunal changeover due to rapid climate change and extinction, and 3) assessment of degree of potential global biozone changes and required adaptation/mitigation strategies to preserve diversity.