A GEOLOGIC MAP OF THE POND RUN 7.5 MINUTE QUADRANGLE, SCIOTO COUNTY, OHIO, CONSTRUCTED FROM TWO EDMAP GRANTS

The primary purpose of this study was to map the bedrock geology of the Pond Run 7.5’ Quadrangle in order to establish a Mississippian stratigraphic framework in southern Ohio. The map area is located in southernmost Ohio, along the Ohio River. The majority of Pond Run is found within Shawnee State Forest. This region exhibits dendritic drainage, moderate relief (750 feet), and is heavily vegetated.

The 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, slump deposits and Quaternary alluvial deposits were mapped along the Ohio River. A Brunton Multi-Navigational System (with built-in altimeter) was utilized primarily to ascertain contact elevations and their position. The map was structurally contoured on the base of the Sunbury Shale. No faults or other structural features, (besides jointing) were noted.

The primary result of these two EDMAP Grants was a digital geologic quadrangle map of the Pond Run 7.5’ Quadrangle. Additionally, a Mississippian stratigraphic framework was established through the correlation of these age rocks between southern Ohio and the previously mapped area of northeast Kentucky. Also, Pond Run was found to contain 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, the above mentioned products of the mapping effort, and the training of a new generation of geologists to field map, exemplify the need for EDMAP and detailed geologic mapping in the field at a 1:24000 scale.