MAPS OF THE SURFICIAL GEOLOGY FROM SURFACE TO BEDROCK FOR PORTIONS OF OHIO

A new series of 1:100,000-scale maps depicting the lateral distribution, thickness, and type of unconsolidated surficial materials, from surface down to bedrock, are being produced for portions of Ohio by the Ohio Department of Natural Resources, Division of Geological Survey. Surficial deposits have been mapped in this manner for 41% of the state as represented by the Ohio portions of 12 30 x 60 minute quadrangles (Bellefontaine, Canton, Cincinnati/Falmouth, Cleveland North, Cleveland South, Dayton, East Liverpool, Lorain/Put-in-Bay, Newark, Springfield, Toledo, and the western portion of Lancaster). Surficial materials were mapped at 1:24,000 scale on 321 7.5-minute quadrangles, digitally compiled using GIS technology, and converted into a full-color, print-on-demand, 1:100,000-scale, surficial-geology maps. Data sources include field mapping, county soil surveys, water-well logs, Ohio Department of Transportation and Ohio EPA boring logs, engineering logs, theses, and published and unpublished geologic and hydrogeologic reports.

An easy-to-read map format using letters, numbers, and modifiers has been developed to allow three-dimensional surficial information to be indicated on a two-dimensional map. Map polygons are attributed using stack-unit designators that indicate the thickness and stratigraphic sequence of major material units (e.g., till, gravel, sand, silt, clay, and organic materials), from the surface down to and including the uppermost bedrock unit. A GIS Geodatabase contains spatial information on each polygon. Attributes of the stack units can be queried on the basis of material types and thickness to quickly create derivative maps. Potential queries for derivative maps might include identifying clay and silt deposits for mapping of potential geologic hazards, identifying sand and gravel deposits for aggregate exploration, or depicting areas of thick till for identification of favorable solid-waste disposal sites.