Document Type

Thesis

Abstract

Carolina Bays are elliptical to irregular depressions with multiple, single, or no sand rim. These unique features occur only on the Atlantic Coastal Plain of the United States. Chesterfield County, Virginia’s landscape includes the rolling hills of the Piedmont and the terraces of the Coastal Plain. The Coastal Plain morphology in Chesterfield County consists primarily of two Coastal Plain terrace treads, the upper Midlothian Uplands and the lower Richmond Plain, separated by the Chippenham Scarp. More than 165 Carolina Bays are located on broad, flat, horizontal interfluves on the two treads. Carolina Bays occur only on the unconsolidated sediments on both of these terrace treads, not on bedrock or weathered Piedmont rock. Most of the Carolina Bays in the county have never before been delineated or described. Measurements on morphology and long axis orientation show that Carolina Bays in Chesterfield County vary in shape, size, and orientation. All bays in the county contain poorly drained soils even though most are currently being drained naturally or by humans. Salisbury Bay, on the Midlothian Uplands, and Baugh Bay, on the Richmond Plain were selected for field studies. Both bays are similar in texture and mineralology, but Salisbury Bay was slightly coarser grained and contained more varieties of quartz than Baugh Bay. Sediments in both bays resemble the sediments that underlie and surround them. Though many hypotheses attempt to explain the origin of these features (meteorite impact, fish spawning, segmented lagoons, and others), only one (Thom, 1970) comes close to being satisfactory for the bays in Chesterfield County. This one involves depressions forming on flat interfluves, which are then shaped by wind and water, and sand rims accumulate around the depressions.

Date Awarded

2000

Department

Geology

Advisor 1

Gerald H. Johnson

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