THREE-DIMENSIONAL MAPPING OF SURFICIAL MATERIALS IN OHIO—TECHNIQUES AND APPLICATIONS

Reliable maps and models of surficial and glacial sediments are needed to support planning for a wide range of societal needs, such as groundwater protection and extraction, geotechnical engineering, land use and development, mineral resources, and assessment of risk from geologic hazards. The Ohio Department of Natural Resources, Division of Geological Survey is mapping surficial materials over a range of scales using a variety of qualitative and quantitative techniques. The main focus of this mapping program is to create 1:100,000-scale reconnaissance “stack” maps for the glaciated portion of Ohio. Stack maps consist of two-dimensional polygons attributed with a stratigraphic sequence (the “stack”) representing the generalized lithology and thickness of layers from the surface down to bedrock. The maps are created through the interpretation of digital soil maps, lithologic records from water wells and geotechnical borings, legacy geologic maps, and limited fieldwork. The maps are in a geographic information system (GIS), allowing the quick generation of standard and derivative map products. Custom macros for ArcGIS® were developed by the Ohio Division of Geological Survey to automate common mapmaking tasks. Prototype derivative maps of sand and gravel resources and seismic velocity for earthquake hazard assessment illustrate the potential value of these GIS models. Detailed mapping and modeling is also being conducted at the 1:24,000-scale to support groundwater research (particularly flow simulations) and to assess the quality of the stack maps and parent data. True three-dimensional models allow for the modeling and analysis of complex geology as well as the generation of visualizations that are more easily understood by the public than traditional cross sections and maps. A detailed stratigraphic layer model has been created for the Milan (Ohio) 1:24,000-scale quadrangle, and a stratigraphic model coupled with geostatistical facies simulation has been created for a study area near Ashtabula, Ohio. Overall, the Ohio Division of Geological Survey's mapping work is producing a valuable planning tool for the general public and government agencies while increasing our understanding of the complexity of Ohio's Pleistocene and Holocene sediments.