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Exposed Precambrian Bedrock in Part of Dickinson County, Michigan, and Marinette and Florence Counties, Wisconsin

January 19, 2018

The U.S. Geological Survey conducted a program of bedrock geologic mapping in much of the central and western upper peninsula of Michigan and parts of Wisconsin from the 1940s until the late 1990s. Geologic studies in this region are hampered by a scarcity of bedrock exposures because of a nearly continuous blanket of unconsolidated sediments resulting from glaciation of the region during the Pleistocene ice ages. The USGS mapping, done largely at a scale of 1:24,000, routinely recorded the location and extent of exposed bedrock to provide both an indication of where direct observations were made, and as a guide for future investigations to expedite location of observable rock exposures. The locations of outcrops were generally shown as colored or patterned overlays on printed geologic maps. Although those maps have been scanned and are available as PDF files, no further digital portrayal of the outcrops has been done. We have conducted a prototype study of digitizing and improving locational accuracy of the outcrop locations in parts of Dickinson County, Michigan, to form a data layer that can be used with other data layers in GIS applications.