DIGITAL TECHNIQUES SUPPORTING QUATERNARY GEOLOGIC MAPPING IN THE OHIO RIVER VALLEY, WESTERN KENTUCKY
Geologic field work consists of traditional landform and map-unit delineation, outcrop investigation, soil description, and soil-core drilling. Field-observation and drilling locations are recorded using handheld GPS receivers. Digital topographic (DRG) and elevation (DEM) data support landform mapping and are used as base maps. DOQ files provide aerial imagery to support mapping. The USDA digital soil-map databases (SSURGO) support landform interpretation and extrapolation of map units into inaccessible areas. KGS has recently completed digital conversion of 1:24,000-scale geologic maps for the entire state. These digital maps typically focus on bedrock features and generalize unconsolidated deposits, and are used as a starting point for the Quaternary mapping.
Subsurface data used to delineate bedrock topography and lithologic trends include extensive KGS databases of water, coal, and oil and gas data, which are also available to the general public via the Internet. Well data from these non-Quaternary databases are examined to extract the relevant information to support the mapping, and transferred to a new Quaternary database. Contributed geotechnical data from state highway and local municipalities are also integrated into the Quaternary database. Seismic reflection and refraction data from KGS and other sources are also used to identify trends in bedrock topography or general variation in lithologic and stratigraphic architecture. Because of the diverse nature of the compiled databases, a relative confidence is assigned to each data value entered into the Quaternary database.
Map-unit delineations and attributes, field-observation locations, well data, and base-map layers are stored in a geographic information system. Use of the GIS software allows for rapid editing and redrafting of maps, development of print-on-demand products, supports Web delivery of data, and assists in the production of derivative analytical products such as seismic hazard assessments or geotechnical planning maps.