Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Geological Sciences

First Advisor

Julio Sepulveda

Second Advisor

Charles Stern

Third Advisor

Eve-LynHinckley

Abstract

The causes and consequences of the Cretaceous-Paleogene mass extinction have long been a source of contention. Several 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 PAH concentration and vegetation proxies for a few thousand years immediately above the K/Pg boundary. These results are like 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 4–5 ringed PAHs is consistent with moderate-high intensity.