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Silver Bluff - Savannah River DoE

 

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Geophysical Survey Silver Bluff Plantation (38AK7), Aiken County, South Carolina

Silver Bluff is located on the Savannah River in Aiken County, South Carolina. The bluff is about 15 miles downstream of Augusta, Georgia, and rises approximately nine meters above the river. The plantation, an area of 1,275 hectares, is part of a site owned by the National Audubon Society. The property is managed to demonstrate the compatibility of agriculture with wildlife and environmental concerns. Approximately 324 hectares are under cultivation while most of the area is comprised of woods and swamp. Little is known of the early history of Silver Bluff. William Bartram, the pioneer naturalist, visited the site in 1776 and noted the presence of ‘various monuments, terraces, areas, as well as traces of fortresses of regular formation.' George Galphin purchased the plantation in 1752 and established a trading post in the area. In 1975, after years of deterioration, the property was willed to the National Audubon Society. It was placed on the National Register of Historic Places in 1977.

Six different average amplitude

This image presents the results of six different average amplitude
time slices. The estimated depth of each slice is given at the top of each
plot (using a 0.1 m/ns velocity estimate). The units of all GPR data are micro Volts. The GPR images are clipped at plus and minus 2 standard
deviations from the mean value.


The image below compares resistance data, magnetic data, and a GPR time slice.

Comparing resistance data, magnetic data, and a GPR time slice.
 

The green polygon shows the GPR survey area in relation to resistance and magnetic survey areas. The blank areas in the resistance data represent the location of trees (blanks surrounded by relative lows), or, blanks surrounded by relative highs represent areas were the soil was over-range (2047.5) or we were unable to get a reading due to high
contact resistance. Note: the blanks surrounded by highs can be replaced with a high threshold value for aesthetic purposes in the final report.

Some general comments concerning the results: The extremely high electrical resistance of the soil at this site was somewhat problematic. Survey speed was reduced due to high contact resistance problems, and, as mentioned above, we were unable to get valid data in some locations. The high resistance (low conductivity) of the background soil did, on the other hand, create a nearly ideal medium for the GPR. Tree roots appear to be the main source of GPR signal clutter. The magnetic results are fairly typical for historic archaeological sites, with TRM fields from historic iron artifacts, fired bricks, and fired ceramics dominating the signal response. There are some low amplitude anomalies of interest (both positive and negative) that will be more rigorously investigated in the final report.