Date of Award

5-2010

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

Stefanie A. Brachfeld

Committee Member

Matthew L. Gorring

Abstract

The ANtarctic Geologie DRILLing program (ANDRILL) drilled a sediment core from a sea ice platform in the Ross Sea in southern McMurdo Sound (SMS), Antarctica, in late 2007. The core site is located just to the east of the Transantarctic Mountains (TAM) along the western margin of a half graben and is a site of heavy sedimentation from the TAM, the East Antarctic Ice Sheet (EAIS), the McMurdo Volcanic Group (MVG), and the West Antarctic Ice Sheet (WAIS) and Ross Ice Shelf. The upper 650 m of the core were analyzed for heavy minerals in order to interpret ice sheet drainage patterns and dynamics of the past 17 Myr. Grain mounts of the fíne sand sized (63-250 pm) heavy mineral fraction of 23 intervals were created and approximately 300 grains were identified per slide. The data represents a major change in sediment provenance and indicates the Middle Miocene Climate Transition (MMCT), which was a cooling period 13.8-14.2 Ma. The period before the MMCT is represented by a invariant assemblage of heavy minerals in the interval 300 - 650 mbsf (15-17 Ma), especially static 350 - 550 mbsf, with a provenance of the Koettlitz and Ferrar Glaciers. This suggests a distal ice sheet relative to the SMS core site that is not providing any influence. Between 240 and 300 (13.8 - 15 Ma) mbsf, a change in provenance from local TAM to MVG and southern TAM occurred and mineral assemblages representing these source rocks are more abundant in the upper 240 m. This suggests a cooler environment in which the WAIS is expanding and forces transport and deposition of sediment by the EAIS from further south. This correlates well with clast provenance, wholerock geochemical data, and stratigraphic interpretations performed by other SMS team members.

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