Geologic Map of the Southern Half of the Pond Run 7.5 Minute Quadrangle, Scioto County, Ohio

The purpose of this study was to map the bedrock geology of the southern half of the Pond Run 7.5’ Quadrangle. The study area is located in southernmost Ohio, along the Ohio River. The majority of Pond Run mapped is found within Shawnee State Forest. This area has dendritic drainage, moderate relief (750 feet), and is heavily vegetated. Bedrock geology of Pond Run is composed of siliciclastic rocks of Devonian and Mississippian age, which dip to the southeast at less than 1.0 degree per mile. Lithologic units encountered from oldest to youngest are: Cleveland Member of the Ohio Shale (Devonian), Berea Sandstone/Bedford Shale undifferentiated (Devonian), Sunbury Shale (Mississippian), Cuyahoga Formation (Mississippian), and the lower part of the Logan Formation (Mississippian). Additionally, Quaternary alluvial deposits were mapped along the Ohio River. The primary field methodology was the utilization of a Brunton Multi-Navigational System with a built in altimeter to record position of contacts and their elevations. The area was structurally contoured on the base of the Sunbury Shale. No faults or other structural features were noted. Pond Run contains significant slumping in its southwestern corner, especially where the Bedford Shale thickens in the Berea/Bedford interval. Additional slumping occurs in the base of the Cuyahoga Formation where the Henley Shale Member thickens. Slumping is generally triggered by deforestation or over-steepening of these slopes. Key discoveries in this mapping project include neptunian dikes in the Ohio Shale and the first zonal conodont assemblage (Upper duplicata Zone) from the Sunbury Shale. These discoveries exemplify the need for detailed geologic mapping in the field at a 1:24000 scale