Date of Award

Spring 2006

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

Donald J. P. Swift

Committee Member

G. Richard Whittecar

Committee Member

George F. Oertel

Committee Member

Thomas Royer

Call Number for Print

Special Collections LD4331.O35 S386 2006

Abstract

Late Pleistocene sediments mapped along Virginia's southeastern coastal plain record deposition by high-frequency cycles during isotope stages 5 to 1. Correlations between several geologic units both south (S) and east (E) of the Chesapeake Bay have proven difficult due to insufficient dating methods. To improve these regional correlations, two members of the Tabb Formation on Virginia's southside and two formations on the southern Delmarva Peninsula were selected for stratigraphic analyses. Ground penetrating radar provided geologic details in areas where samples were collected for optically stimulated luminescence (OSL) dating. The stratigraphically older units, Sedgefield Member of the Tabb Formation (S) and the Butlers Bluff Member of the Nassawadox Formation (E), yielded OSL dates of approximately 50 ka (stage 3) and 70 ka (stage 4; 5a assignment), respectively. The Butlers Bluff data match previous dates from coral in the Sedgefield; however, the dates from the Sedgefield were discarded due to a high concentration of U and Th indicating post-deposition migration into the sample site. The younger units, Poquoson Member of the Tabb Formation (S) and the Wachapreague Formation (E), yielded OSL dates of approximately 43 ka and 42 ka (stage 3), respectively. Maximum altitudes of marine depositional surfaces for these units range from +12 to +3 m. However, established glacial-eustatic sea-level curves, along with these dates and others reported for these units, suggest the units were deposited when sea level oscillated between +3 to -25 m. If both the sea-level curves and the dates are correct, then an uplift of at least 10 to 15 m must have occurred in order to explain the altitudes of these units. These discrepancies may arise from isostatic adjustments of the fore bulge peripheral to the Laurenti de Ice Sheet that would have been at maxima during isotope stages 6 and 2. If peripheral bulges develop and decay more slowly than eustatic sea-level responds to high-frequency climate change, then these depositional units might mark times when a minor spike of sea level occurred while the bulge was relatively relaxed.

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DOI

10.25777/1xb0-1c44

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