SURFICIAL GEOLOGIC MAPPING ALONG THE OHIO RIVER, WESTERN KENTUCKY – PRELIMINARY RESULTS

The Kentucky Geological Survey (KGS) is currently conducting surficial geologic mapping along the Ohio River Valley in western Kentucky. The purpose of this study is to characterize the three-dimensional valley fill architecture of the Ohio River Valley and develop lithologically based surficial geologic maps. These digital geologic maps will incorporate landforms, subsurface lithologies, and interpretations of surficial processes. This study is designed to develop digital geologic map products and databases that support geohazard, geotechnical, land-use planning, and hydrologic investigations. The proximity of the New Madrid and Wabash Valley Seismic Zones, increased development in the region, and hydrologic issues provide the need for updated surficial geologic maps.

This project consists of mapping 7.5-minute quadrangles along the Ohio River, and is funded by the U.S. Geological Survey's STATEMAP program. Four quadrangles were mapped in 2004, seven in 2005, and seven are in progress for 2006.

Sources of surface data for this project include field mapping using standard geologic mapping techniques, process geomorphology, and digital elevation data. Subsurface data from KGS databases containing information on oil and gas, coal, and water; KGS seismic investigations; and geotechnical reports from external agencies are used for creating bedrock topography maps, cross sections, and characterizing the valley-fill architecture of mapped units.

Preliminary results from field mapping and outcrop investigations reveal outwash sand and gravel derived from receding Pleistocene glaciers to the north that are overlain by modern deposits of the meandering Ohio River. Landforms present along the river valley include a modern floodplain and relic terraces that represent the extent of the ancient Ohio River. Rapid outwash aggradation led to deposition of slackwater sediment in tributary valleys. The upland areas adjacent to the river valley are underlain by bedrock that is covered with a veneer of loess.