METHODOLOGY OF INTEGRATING SUBSURFACE SEDIMENT DISTRIBUTION AND GEOMORPHOLOGY INTO REGIONAL CONCEPTUAL MODELS: BELLEFONTAINE AND SOUTHWESTERN CLARK COUNTY, OHIO

The link between subsurface sediment distribution and geomorphic landforms requires additional consideration. Thus, the objective of this research is to incorporate both detailed geomorphic mapping and subsurface data sets to understand that link. This methodology is developed for two study areas in southwestern Ohio: Bellefontaine and southwestern Clark County.

The production of a detailed geomorphic map of the Bellefontaine study area was completed using ground transverses, a topographic map base, and aerial photograph interpretation. For southwest Clark County, an existing geomorphic map was employed. In both study areas, Ohio Department of Natural Resources (ODNR) water well logs were augmented with additional borings conducted specifically for this research. From these efforts, reconstruction of multiple cross sections provides the basis for a regional conceptual model.

Subsurface logs of each landform type were analyzed by determining the percentage length of till, sand/gravel, and lacustrine sediments for each landform. Distinct distributions are apparent. For example, within the Bellefontaine study area, several hundred feet of drill logs record that moraines contain 75.3% till and 24.7% sand/gravel; whereas kame moraines contain 52.4% till and 47.6% sand/gravel. These sediments may represent deposition during more than one glacial cycle.

This research suggests that landform type provides clues to the subsurface sediment distribution, but that developed conceptual models are unique to each study area. Thus a combined landform-subsurface approach must be employed concurrently.