MAPPING THE OUTER MARGINS OF THE SERPENT MOUND IMPACT STRUCTURE TO ASSES THE EXTENT OF DEFORMATION, ADAMS, PIKE, AND HIGHLAND COUNTIES, OHIO

The Serpent Mound impact structure, located in Adams, Highland, and Pike counties in south central Ohio, is a heavily eroded complex impact structure which occurred between 350 and 250 Ma (Milam 2010a). The structure is characterized by a highly faulted and fractured central uplift surrounded by a ring graben. In 1975 Stephen Reidel mapped the structure and concluded that the extent of deformation is approximately 4 km from the crater center. Keith Milam (2010b) proposed that the extent of deformation, based on complex crater morphometry, be within 10 – 25 km in diameter, that downward displaced strata suggest a minimum deformed area of 14 km in diameter, and that digital elevation models of the area also support the 10 – 25 km range. Here by way of field mapping we test the hypothesis put forth by Milam (2010b) that the extent of deformation of the Serpent Mound impact structure is between 10 and 25 km in diameter.

Field mapping 5 – 12.5 km from the central uplift revealed no evidence of structural deformation. All of the strata follow regional trends dipping very gently to the east. Offset contacts did not exceed nor approach their associated maximum amount of relief. The current extent of faulting remains to be ~8 km in diameter and the extent of downward displaced strata remains to be ~14 km in diameter (Reidel 1975, Milam 2010b). Further analyses of possible rim fault influenced superimposed drainage will be necessary to more accurately establish the true extent of deformation.

Despite a lack of structural evidence in the mapping area, the high resolution geologic map and cross-sections produced provide an updated record of the geology and mineral resources in the study area.