BEDROCK GEOLOGIC MAP OF THE NORTHERN HALF OF NINETY SIX 7.5 MINUTE QUADRANGLE, SOUTH CAROLINA

This is the third report of an on-going project to map in detail the bedrock geology of the Ninety Six 7.5 minute quadrangle for National Park Service and the USGS Geologic Resources Inventory. Ninety Six National Historic Site lies in the SE quadrant of the Ninety Six 7.5 minute quadrangle, South Carolina. This report provides a digital bedrock geologic map for the northern half of the quadrangle. Rocks in the quadrangle are part of the Charlotte terrane, the uplifted plutonic infrastructure of the Carolina terrane, remnants of a Neoproterozoic to Early Paleozoic exotic volcanic island arc accreted to southeastern North America during formation of Pangaea. The topography consists of gently rolling hills with up to 180 ft. of relief. The bedrock is deeply weathered, overlain in most places by a thick layer of soil. The NW quadrant is dominated by spectacular large-boulder exposures of the Coronaca granite. In hand samples the Coronaca is unfoliated light gray to tan, fine to medium grained biotite metagranite with a xenomorphic equigranular texture and at least 20% quartz. Lake Greenwood obscures the geology in the NE corner of the quadrangle. As in the southern half of the quadrangle, the bedrock in the NE quadrant is deeply weathered. The predominant rock type is unfoliated biotite metagranite that is cut in numerous places by small plugs and dikes of unfoliated hornblende metadiorite. Cross-cutting relationships suggest the metadiorite is younger than the metagranite. Both rock-types have a xenomorphic-equigranular texture, which suggests they are metamorphic rocks. Aphanitic-textured white volcanic ash crops out in numerous places in the NE quadrant. The ash overlies metagranite or metadiorite where contact relations are observable. Limited exposures of strongly sheared quartz muscovite schist suggest the presence of several NE-trending shear zones. They could be traced only short distances.