Date of Award

5-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Sandra Passchier

Committee Member

Tanya Blacic

Committee Member

Josh Galster

Subject(s)

Eocene-Oligocene boundary—Antarctica--Prydz Bay, Stratigraphic Geology, Eocene Geologic Epoch, Oligocene Geologic Epoch

Abstract

The Eocene-Oligocene transition (EOT) marked a profound shift in the Earth’s climate, as the global greenhouse o f the early Cenozoic gave way to ‘icehouse’ conditions, or a climatic regime influenced by the waxing and waning o f glacial ice. Antarctica was dramatically altered during this time; its formerly cool temperate ecosystems nearly obliterated by the first major episode o f continental glaciation. A record o f this transition appears to be partly preserved in approximately half a kilometer o f sediments recovered from three holes (at ODP Sites 739, 742, and 1166) bored in the continental margin at Prydz Bay, an embayment o f the East Antarctic coast. Until recently, these holes were never completely described with common nomenclature and analysis. This study re-evaluated these cores under a unified regime, using a laser particle sizer to generate matrix grain size distribution profiles for 253 samples collected from the combined sediment column. Additional analysis o f select samples was performed with a scanning electron microscope to classify grain textures, as well as ICP-OES to provide geochemical information. The results o f this study support stratigraphic relationships between the ODP sites that were previously only inferred through seismic acquisition. This provides a much more complete picture o f the sedimentation processes occurring through the EOT. Chemical and microtextural weathering signals also provide a new window into the environment o f Prydz Bay during the EOT. These signals seem to confirm hypotheses from previous researches that the site featured a cool/temperate environment with tidewater glacial systems in the late Eocene that transitioned into near polar glacier conditions dominated by ice sheet growth by the early Oligocene. Crucially, the results o f this investigation suggest that enhanced glaciation o f the Prydz Bay region was already occurring before the start o f the Oligocene, which suggests that an initial step down in global temperature during the late Eocene (proxied from the foraminiferal oxygen isotope record) may be directly related to the initiation o f continental ice expansion.

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