12 Coastal Processes and Geologic Framework: Insights from Geological and Geophysical Surveys across the Continental Margin (Posters)

Thursday, 31 March 2016
8:00 AM - 5:30 PM
Exhibit Hall

STRATIGRAPHY AND GEOCHRONOLOGY OF THE PLEISTOCENE PALEO-STRAND PLAIN IN THE COAST OF NORTHEASTERN SOUTH CAROLINA

Paper number: 12-8
Program: Theme Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

The surface geology of the central US Atlantic coastal plain is a sand-dominated coast with paleo-beach ridge complexes formed parallel to previous shorelines. These paleo-beach ridges can give valuable insight into relative sea-level (RSL) in the past. The chronology of these ridges, however, has been a subject of controversy. This study investigates the stratigraphy and chronology of these paleo-beach ridges.

The paleo-beach ridges of interest for this study are located in the Hobcaw Barony, northeast of Georgetown, South Carolina. The Hobcaw Barony paleo-strand plain is composed of prograding beach ridges. Stratigraphy of the strand plain was determined using vibracoring and ground penetrating radar (GPR). Subsamples from cores were analyzed for water content and loss on ignition (LOI) and samples taken from representative cores were also analyzed for optical stimulated luminescence (OSL) dating to determine age of deposition.

The stratigraphy in this study area consists of three major units. The top unit is 1-2 m thick and consists of well to moderately sorted fine to medium sands with humate. This unit is interpreted as dune deposits affected by pedogenesis. The next unit is poorly sorted medium to coarse sands with interbedded gravel layers that transitions downwards to a third unit of shelly sand with common well-rounded shell fragments. The lower two units together form foreshore deposits. The maximum height of these foreshore deposits constrains the upper limit of relative sea level during the formation of the strand plain. Water content varies from 11.9% to 20.6% while LOI is from 0.1% to 5.2%. High LOI values correlate to sands enriched in humate. OSL results will be gathered from the luminescence dating laboratory at the University of Liverpool and be compared with other studies to help understand chronological development of the strand plain. As results from this study bring clarification on the formation of the strand plain, they will give insight into how sea-level change and the geomorphology of this region have evolved in the past.

Geological Society of America Abstracts with Programs. Vol. 48, No. 3

doi: 10.1130/abs/2016SE-273526

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