Date of Award

1-1-2011

Document Type

Campus Access Thesis

Department

Earth and Ocean Sciences

Sub-Department

Geology

First Advisor

Douglas F Williams

Second Advisor

Camelia Knapp

Abstract

Ground Penetrating Radar, radiocarbon dating and core analyses were combined within this investigation to determine the shallow geologic framework and the recent depositional history of Thousand Acre Marsh. Analyses of these data revealed the role of Thousand Acre Marsh as a record keeper of subsurface sediments and the effects of adjacent environments, North Inlet Marsh system, Winyah Bay estuary, river migration and North Island spit, on the formation of this present day brackish marsh.

Brackish marshes are dynamic and important coastal ecosystems, both for habitats to flora and fauna and economically for state tourism. The knowledge of present day and past changes within these environments is important to future management of these coastal environments. Thousand Acre Marsh is located 5 miles east of Georgetown, SC along the South Carolina lower coastal plain. Recent changes to local geology such as the uplift of the Cape Fear Arch, the migration of the Pee Dee River and the elongation of the North Island spit have all played a part in the formation of Thousand Acre Marsh and their impacts can be identified within the shallow subsurface environments. The construction of a stratigraphic framework from lithological analyses and radiocarbon dating shows a laterally continuous trend of environments that portray the depositional history of this marsh. The trend begins with a swale between two relict dune ridge systems which slowly transitions to a forest environment, evidence from roots and root systems in sand facies, to a freshwater swamp suggested from dense clay with wood fragments. Next there is evidence of an alternating mudflat and freshwater marsh environments suggested from identification of alternating peat and clay layers which were formed by the migration of the Pee Dee River, to the modern day brackish marsh due to effects of sea level rise and tidal exchange within the Winyah Bay estuary. All of these environments have been identified within sediment cores, identification of geophysical reflectors and correlated with radiocarbon dating. The identified environmental changes correlate with timing of local changes in geology as suggested above. Thousand Acre Marsh is an evolving brackish marsh, due to sea level rise and influence from adjacent environments. These changes should be further investigated and continued into the future, to gather knowledge of the changing environment and to benefit coastal managers in preserving our coastal environments for the future.

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