GEOLOGIC MAPPING LOWER MISSISSIPPIAN LITHOSTRATIGRAPHY OF SCIOTO, PIKE, JACKSON AND VINTON COUNTIES OF OHIO AIDED BY LIDAR-DERIVED MICROTOPOGRAPHY

Geologists from the Ohio Department of Natural Resources, Division of Geological Survey previously mapped the lower Mississippian lithostratigraphy of Scioto, Pike, Jackson and Vinton Counties, Ohio, during the 1980s and 1990s. Staff geologists mapped the Mississippian-age strata as a single, undifferentiated lithostratigraphic map unit. In these counties, the lower Mississippian section consists of approximately 400 feet-thick of fine-grained, horizontally bedded, clastic sedimentary strata. Lithologic correlation among Mississippian-age units is difficult owing to unconformities and river valley development, which eroded strata and widened the distance between correlatable outcrops. LiDAR-derived microtopography illustrated how each lithologic unit was affected differently by mass wasting, weathering, fracture distribution, and hydrology. Field visits verified that most lithologic members could be recognized by their microtopographies. For example, microtopographies of the Mississippian-age Cuyahoga and Logan Formations presented a clear distinction between the rutted and rilled Cuyahoga Formation’s shales and the steeply sloping, smooth surfaces of the Logan Formation’s consolidated sandstones. LiDAR-derived microtopography has added value to geologic mapping because it has allowed mapping of inaccessible field areas. During mapping, geologic contacts lines were drawn between contrasting microtopographies that demonstrated lithologic change. These contacts were converted into polygons and symbolized during map drafting. Field mapping validated polygon extents and provided key elevation and lithologic information. Mapping LiDAR-derived microtopographic extents, in combination with field verification, improved mapping resolution and aided in the understanding of Ohio’s Mississippian-age lithostratigraphy.