MODELING OF THE OHIO RIVER VALLEY IN WESTERN KENTUCKY USING THE KGS SUBSURFACE DATABASE

The Ohio River Valley in western Kentucky consists of Pleistocene glacial outwash, whereas the tributary valleys consist of lacustrine or slackwater deposits. Loess mantles much of the upland areas. A generalized model of bedrock topography of the Ohio River Valley can be constructed by using depth-to-bedrock values from a surficial subsurface database in a GIS environment. Other applications of this data include creating a three-dimensional geologic model by incorporating the lithology data of the subsurface database. These data should also be useful for seismic hazard assessments for the region.

The Kentucky Geological Survery is currently creating a subsurface database of surficial deposits along the Ohio River Valley in western Kentucky. This database has been created to augment the STATEMAP-funded Quaternary geologic mapping project conducted by KGS in this area. A Web-based data-entry application allows for easy entry of subsurface data into a relational database. The primary source data used in the creation of the database include coal boreholes, oil and gas wells, and water wells from existing databases. Other sources of data include drilling in the area to support KGS Quaternary geologic mapping, seismic-refraction and -reflection surveys, USGS cone-penetration tests, Kentucky Department of Transportation drilling data, and data from published sources in the area.

The new relational subsurface database includes tables to characterize bedrock depth and lithologies of unconsolidated materials. A confidence level is assigned to bedrock data depending on the type of data derived from the source databases, so that questionable data and wells that do not reach bedrock can be properly attributed. Lithology tables include depth values, as well as descriptions of unlithified or unconsolidated sediments and the uppermost bedrock lithology. Each line of lithologic text associated with a well record is classified as soil, unconsolidated sediment, bedrock, or no description. Using this classification scheme, a stratigraphic thickness for each well can be readily obtained.