GEOPHYSICAL INVESTIGATION OF THE SOUTH RIVER FLOODPLAIN, BUENA VISTA, VIRGINIA

We conducted resistivity imaging and seismic refraction surveys on the South River floodplain near Buena Vista, VA in fall 2005. The field site is on the South River floodplain underlain by the Conococheague Formation, a Cambrian-Ordovician carbonate unit, and is located near a historic iron furnace and a mill.

Electrical resistivity data revealed an interface at 1 m depth between an upper low-resistivity unit and an underlying higher-resistivity unit. The interface probably represents the boundary between soil and alluvium deposits. There are also lateral variations that include two areas of anomalously high resistivity. Ground truthing revealed a retaining wall and a high concentration of slag in one of the two high resistivity areas. Direct validation of the other high resistivity area was not made, but it may represent a bedrock topographic high.

Seismic refraction data revealed the presence of an upper layer with a velocity of 323-420 m/s, most likely soil and alluvium, and a lower layer with a velocity of 1057-1282 m/s, most likely weathered bedrock. The interface between the alluvium and the bedrock is 4-5 meters below the surface and dips towards the river at 2 degrees.

The results between the two methods of geophysical investigations are consistent with auguring observations. Our investigation revealed information about both the subsurface geology as well as archeological features associated with the nearby iron furnace and the mill