Stable Isotopes in Unstable Times: A geochemical investigation of the end Cretaceous mass extinction

• Main Author: Tobin, Thomas Steven
• Other Authors: Ward, Peter D
• Format: Thesis
• Language: English
• Published: 2014
• Subjects: Clumped Isotope; Cretaceous; Mass Extinction; Paleogene; Paleotemperature; Stable Isotope; Geology; Geochemistry; Paleontology; earth and space sciences; Antarctic; The Antarctic; Antarctic Peninsula; Antarc*
• Online Access: http://hdl.handle.net/1773/26014

Thesis (Ph.D.)--University of Washington, 2014 This primary goal of this dissertation is to increase understanding of the end Cretaceous (or Cretaceous - Paleogene or K-Pg) mass extinction through the use of light stable isotope geochemistry. These studies attempt to examine any climatic and environmental changes that occurred around the K-Pg boundary, and might have contributed to the K-Pg mass extinction, specifically by examining isotopic records at high stratigraphic resolution around the boundary. Studies are completed in two field areas, the Antarctic Peninsula and eastern Montana, USA, both of which preserve the K-Pg boundary. While these works, like most scientific studies, lead to further questions that warrant investigation and confirmation, they generally support the idea the end Cretaceous mass extinction was more complicated than a simple asteroid strike. This dissertation is comprised of five scientific chapters as well as short introductory and concluding sections. The introduction explains the background and context behind each study, and the process by which I ultimately worked with a wide variety of co-authors to complete the various projects. The conclusion begins the process of examining the differences and similarities of each study, and explores further avenues of research to test some of the proposed hypotheses or reconcile potentially contradictory data. Four of the chapters are written as scientific manuscripts, while a fifth chapter details the work done as part of my astrobiology rotation. Chapter 1 (Tobin et al., 2011) outlines the discovery of analytical errors in the typical process of measuring carbonate stable isotopes (δ 13 C and δ 18 O) on small sample sizes of powder. Carbonate material is typically prepared using one of two methods, either by drilling using a high speed drill or micromill, or by crushing a sample using a mortar and pestle. Drilling produces a finer grain size of material, which is consequently more prone to being altered in its δ 18 O value during a typical ...