Identifier

etd-11042011-080759

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

Previously acquired geological and geophysical data from the eastern Ross Sea outer shelf support the view that the West Antarctic Ice Sheet (WAIS) deposited three large-volume grounding zone wedges (GZWs) during the relatively short time since the onset of ice sheet retreat began at approximately 11 ka 14C BP. Here, GZW sediment volumes were estimated from seismic data correlations to evaluate the different possible durations of the individual grounding events. The two end-member fluxes used correspond to 1) a modern flux active at Whillans Ice Stream and 2) a larger flux accounting for the larger size of the drainage basin at LGM. Two basic experiments were conducted. In the first experiment, calculations of grounding-event durations were based on 2D estimates of GZW volumes from a regional dip-oriented seismic transect. The second experiment focused on 3D-volume estimates for the youngest GZW on middle shelf, which is referred to as the Gray Unit. The 3D volume of the Gray Unit was used to calculate Gray Unit grounding-event duration. The results from the 2D experiment are invalid for this study because the analysis showed that the study requires a 3D approach. The grounding-event durations calculated for the 3D experiment suggests that the three GZWs could not have been deposited within the short time elapsed since the onset of post-LGM ice-sheet retreat. Instead, the long duration needed to deposit the Gray-Unit GZW favors the alternate view that each wedge was deposited during at least part of the advance phase of the last glacial cycle. Following this line of reasoning suggests that Gray Unit GZW corresponds to deposition beginning in OIS 3 and ending during OIS 2 i.e. the last glacial maxima, whereas the older GZWs must represent deposition during successively older pre-LGM glacial maxima.

Date

2011

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Bart, Philip J

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