Date of Award
Master of Science (MS)
College of Science and Mathematics
Earth and Environmental Studies
Thesis Sponsor/Dissertation Chair/Project Chair
The Eocene-Oligocene Transition (EOT) approximately 34 million years ago (Ma) marks the shift from the warm greenhouse conditions of the Eocene to today’s icehouse, and was accompanied by the establishment of the East and West Antarctic Ice Sheets. Details surrounding the timing, magnitude, and regional expansion of glaciation are poorly constrained primarily due to low core recovery and lack of reliable age models, and therefore warrant continued investigation. A recently updated age model applied to Ocean Drilling Program (ODP) Site 696, located in the northwest sector of the Weddell Sea, indicates Core 55R represents a high-recovery succession encompassing the EOT. This project presents a high-resolution, multimethod analysis of this sediment core.
Laser particle size analysis was performed throughout the core, and inductively coupled plasma mass spectrometry and optical emission spectrometry are used to quantify major, trace, and rare earth elemental concentrations on samples with >80% mud. Paleoclimate proxies are calculated to characterize the dominant weathering regime and degree of glacial influence on sediment. Results indicate a cool, dry climate and sediment with a strong glacial signature, as evidenced by low chemical index of alteration (CIA) values and significant contribution of glacial rock flour. Trace and REE ratios do not suggest major changes in source material, and felsic versus mafic plots indicate 55R sediment is felsic to intermediate in composition. Sediment remains well sorted throughout, and therefore elemental enrichments are likely related to grain-size partitioning.
Results of this study have implications for the investigation into continental glacial history of Antarctic through the EOT; 55R sediments reflect a similar climate to shelf sediments retrieved from Prydz Bay and Wilkes Land Margins and are consistent with significant terrestrial cooling across East Antarctica during the late Eocene. Studies from West Antarctica, however, suggest a later onset with less glacial stability. Similar high-resolution studies are thusly needed to further improve our understanding of Antarctic ice dynamics in response to climate perturbations.
Lepp, Allison Paige, "Geochemical and Sedimentological Analysis of Marine Sediments from ODP Site 696 and Implications for the Onset of Antarctic Glaciation" (2018). Theses, Dissertations and Culminating Projects. 140.