Identifier

etd-11182010-134832

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

The changing extents of the West Antarctic Ice Sheet (WAIS) and the manifestation of meltwater discharge on the outer shelf during the Miocene were deduced using seismic stratigraphy and seismic facies interpretations. Deep Sea Drilling Project (DSDP) Leg 28 drill sites were used for chronologic constraints of the outer continental shelf (OCS) seismic stratigraphy to establish correlations to coeval strata at the inner shelf SMS-ANDRIL drill site. The evidence indicates that grounded ice sheets periodically existed on the OCS during the early and middle Miocene and in section inferred to have been deposited in the late-Miocene. Large-scale grounding events occurred between 18.2 - 14.1 Ma when ice occupied the Central Trough, the North and South Central Highs (N/SCHs), and the rims of the Eastern Basin ramp. The grounding events resulted in widespread erosion of the Outer Continental Shelf (OCS) and deposition of thick packages (>50m) of ice proximal seismic facies within the Central and Eastern Ross Sea. High amounts of sediment discharge, of both glacial-marine and ice-proximal sources, converted the Eastern Basin ramp to a shelf platform, which created a larger area across which grounded ice could advance by Late Miocene time. Comparison of the OCS record with the inner continental shelf SMS-Andrill Site suggests that units interpreted as full glacial cycles must reflect small-scale translations of grounded ice that did not affect the OCS. A large-scale meltwater discharge episode occurred between 13.8-14.1 Ma is well-preserved on the OCS. Seismic evidence indicates that grounded ice occluded Ross Sea at the time of melt discharge on the outer shelf. The general lack of similar distributions of meltwater features in the overlying section is consistent with the view of a shift to dry polar climatic conditions at sea level during the middle Miocene but the absence of similar features in the underlying section is not consistent with the view that similar climatic warmth existed during the early Miocene.

Date

2010

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Bart, Philip

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