GEOPHYSICAL AND ARCHAEOLOGICAL INVESTIGATIONS OF CIVIL WAR SITES NEAR RADFORD, VIRGINIA

MONTGOMERY, Sarah Beth, Radford University, 1015 Calhoun St. Apt. G, Radford, VA 24141, HERMAN, Rhett, Physics, Radford University, Department of Physics, PO Box 6983, Radford, VA 24142, WHISONANT, Robert C., Geology, Radford University, Geology Program, PO Box 6939, Radford, VA 24142 and BOYD, Charles C., Anthropology, Radford University, Anthropological Sciences, PO Box 6939, Radford, VA 24142, smontgomery@radford.edu

In the summer of 2013 geophysical techniques were used to investigate two Civil War earthwork forts near Radford, Virginia. An initial study was conducted at one of the sites using magnetometry (cesium vapor) and ground penetrating radar (GPR) to search for possible artifacts. To our surprise a map of the magnetic field revealed a line of higher field strength conspicuously following the earthen walls at that site. This led the group to perform the same type of magnetic survey at the second site, with similar high magnetic field readings outlining the walls. Our interest was then directed to understanding what could cause our magnetic signal to align with the walls. Follow-up surveys using electrical resistivity and GPR were performed at both sites. The resistivity surveys indicated areas of low resistivity within the earthen walls aligning with the locations of the magnetic anomalies. The GPR surveys were inconclusive in that they did not show any anomalous structures within the walls. Archeological test trenches were dug in a number of areas at the initial site to explore possible physical sources of the magnetic anomalies. These trenches transected the walls of the fort and have yielded rock samples that are undergoing analysis for possible sources of the magnetic signals. Samples of fresh bedrock from the trenches are dolomite belonging to the Elbrook Formation and do not show magnetization. Other rocks in the trenches are limonite-encrusted fragments of weathered dolomite and fine-grained quartzites, the latter possibly brought into the area by the nearby New River. Individual samples of the limonite-rich rocks from the trenches were found to be magnetized using the magnetometer. One preliminary explanation for the magnetic anomalies is that enough iron is concentrated in the limonite-bearing rocks to create the magnetization. More excavations are ongoing to attempt to decisively determine the reason for the magnetic anomalies.

Session No. 13

T8. Geohazards: Methods for Mapping, Monitoring, and Mitigating

Thursday, 10 April 2014: 1:00 PM-5:00 PM

Solitude (Inn and Conference Center at Virginia Tech)

Geological Society of America Abstracts with Programs. Vol. 46, No. 3, p.22

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Southeastern Section - 63rd Annual Meeting (10–11 April 2014)

GEOPHYSICAL AND ARCHAEOLOGICAL INVESTIGATIONS OF CIVIL WAR SITES NEAR RADFORD, VIRGINIA