MAPPING OHIO'S SURIFICIAL GEOLOGY-TOOLS, TECHNIQUES, AND APPLICATIONS TO GROUNDWATER

The ODNR, Div. of Geological Survey (ODGS) has had an ongoing program of mapping Ohio’s surficial geology for over 10 years. Mapping is done at a scale of 1:24,000 with final reconnaissance level maps of USGS 30 x 60 minute quadrangles produced at a scale of 1:100,000. This final map is colorized based upon the uppermost surficial unit. Mapping features the use of labeled polygons that captures the lithology, sequence, and thickness of all the drift units plus the lithology of the uppermost bedrock unit. This labeled “stack’ also is attributed in the GIS layers which allows for custom mapping done by means of querying and selecting specific lithologies and thicknesses. Derivative maps can be created and illustrated for a number of applications including aggregate resources and waste disposal.

The mapping process has been very dynamic and has adapted to new technologies. What began initially as hand drawn maps on mylar has migrated to a completely on-screen digital process utilizing GIS. A number of custom tools, techniques, and applications have helped to both expedite the process and greatly increase the accuracy of the mapping. Applications such as LiDAR-based DEMs and SSURGO soil layers allow for a level of mapping simply not imaginable a dozen years ago. The ability to view water well log records and ODOT soil borings/engineering logs on-screen represents another dynamic application that facilitates mapping.

The “stack maps” being created by the ODGS serve as a tremendous framework for evaluating and mapping unconsolidated aquifers in Ohio. Knowing the thickness and lithology of specific units is critical in helping to determine their potential as aquifers. The ability to query and select the various lithologies and thicknesses can also serve as another tool for helping to determine viable aquifers.