Geochemical and Particle Size Analysis of East Antarctic Shelf Sediments Through the Eocene Oligocene Transition

• Main Author: Light, Jennifer Joanne
• Format: Text
• Language: unknown
• Published: Montclair State University Digital Commons 2017
• Subjects: Antarctic; East Antarctic Ice Sheet; Powell Basin; Antarc*; Antarctica; Ice Sheet
• Online Access: https://digitalcommons.montclair.edu/etd/15; https://digitalcommons.montclair.edu/context/etd/article/1014/viewcontent/Light_201708_Redacted.pdf

The Eocene Oligocene Transition (EOT) at ~34 million years ago (Ma), marked the global change from greenhouse to icehouse, and the establishment of the East Antarctic Ice Sheet (EAIS). The timing involved with initiation of the EAIS and ice growth during the EOT is still poorly understood due to poor core recovery. The purpose of this study was to expand upon existing knowledge of EAIS dynamics by applying updated age models to geochemical and sedimentological records from three marginal shelf sites that contain Eocene and or Oligocene sediments. This study used inductively coupled plasma optical emission spectrometry and mass spectrometry (ICP-OES/ICP-MS) to determine the bulk chemical composition of samples from marginal east Antarctic shelf sites: ODP Site 1166A [O’Brien et al., 2001] and IODP Site U1360 [Expedition 318 Scientists, 2010]. Particle size analysis was conducted on sediments from west Antarctic ODP Site 696 [Barker et al., 1988], and the distributions were compared to particle size data from Ciarletta [2014] for Sites 1166 and U1360. Overall, Site 696 shows a fining upward sequence indicative of a marine transgression, that could have been caused by depression of continental crust as the EAIS grew or tectonic deepening during the formation of the Powell basin. Major element data was used to calculate various paleoclimate proxies including the Chemical Index of Alteration (CIA), mean annual temperatures, and mean annual precipitation. The paleoclimate of a region can affect the advance and retreat of ice and is therefore important in the study of glaciation in Antarctica. Results show a dominant warm humid environment for the Late Eocene (Site 1166); in contrast, the Lower Oligocene (Site U1360) shows a cooler more arid environment. The provenance of sediments was constrained by calculating Al2O3/TiO2 ratios. Al and Ti are conservative elements and are representative of their source material; therefore, the ratios can be a good indicator of changes in provenance. It was determined that a slight ...