GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 335-5
Presentation Time: 9:00 AM-6:30 PM


GROSS, Michael A., University of Colorado at Boulder, Boulder, CO 80310, SEPULVEDA, Julio, Department of Geological Sciences, University of Colorado Boulder, Boulder, CO 80309, ALEGRET, Laia, Dept. Ciencias de la Tierra & IUCA, University of Zaragoza, Zaragoza, 50009, Spain and SUMMONS, Roger E., Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, MIT, E25-633, 77 Massachusetts Ave, Cambridge, MA 02139,

The causes and consequences of the Cretaceous-Paleogene mass extinction have long been a source of contention. A number of models predict that enough thermal radiation from the bolide impact was produced to ignite wildfires at least regionally and possibly on a global scale, raising average temperatures by up to ~10°C, and releasing large amounts of CO2 and CO. However, the role of regional versus global wildfire events as an environmental stressor, as well as the sources of the fire (land vegetation vs. hydrocarbon reservoirs) and its expression in terrestrial and marine archives, remains controversial. Typically, wildfires are preserved in the geologic record by features such as charcoal and soot deposition. Additionally, molecular fossils (biomarkers) like polycyclic aromatic hydrocarbons (PAHs) and long-chain n-alkanes preserved in marine sedimentary sequences can be diagnostic of biomass burning (including sources and temperature of combustion) and terrestrial input to the marine realm, respectively. Using Gas Chromatography- Mass Spectrometry, we investigated the abundance of these biomarkers in the K/Pg global stratotype and section point (GSSP) of El Kef, Tunisia. Our results indicate the occurrence of a spike in PAHs concentration and long-chain n-alkanes for a few thousand years immediately above the K/Pg boundary. These results are similar to those found in the marine section of Caravaca, Spain and demonstrate that wildfires and enhanced terrestrial input following the K/Pg may have been more widespread features of this event than previously recognized. Finally, a dominance of 2–3 ringed PAHs is consistent with low-moderate intensity rather than high temperature wildfires. We will provide a comparison with other marine and terrestrial records using similar approaches, and will discuss the potential sources of paleo-wildfires.