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A regionally-consistent and integrated geologic spatial database for the Northern Rocky Mountains of Montana, Idaho, and eastern Washington, brings together forty-three 1:100,000-to 1:250,000-scale digital geologic maps into a common database format. The regional geologic database is an ArcInfo® coverage (NR_GEO) that contains spatial data for both lines (contacts, faults, fold axes, dikes, sills, veins, garnet isograd, boundaries) and polygons (geologic units). The database represents the original content of the published maps and provides easily-used and consistent attribute content. We have also added information based on our interpretations of published reports. In particular, we have added attribute information that 1) classifies igneous rocks by age, composition, and name, and 2) allows the creation of derivative maps based on lithology. Three schemes are used to classify polygons and lines in this spatial database. The first scheme is based on the original map units defined in the source maps used to compile this database. The second approach uses the age, composition, and mode of occurrence to define igneous map units. The last approach uses the names of igneous intrusions and volcanic units to define map units. This database can be queried to address an assortment of geological questions and to produce a variety of derivative geological maps. Digital themes derived from these digital spatial geologic databases will be used by the U.S. Department of Agriculture Forest Service (USFS) for planning and research purposes and by the U.S. Geological Survey (USGS) to facilitate research and conduct mineral-resource assessments. We would like to thank Reed S. Lewis and Loudon R. Stanford with the Idaho Geological Survey and Karen Porter, Dick Berg, and Patrick Kennelly with the Montana Bureau of Mines and Geology for their cooperation in our effort to make this compilation. They worked with us to produce several new digital geologic maps and provided digital files of geologic maps and map-unit descriptions. They also answered numerous geologic questions that came up during the compilation process. Eastern Washington University students Rebecca Pitts, David Cleveland, Mike Koenig, and Richard D. West helped compile data. Ellen Burch, Information Systems Support, Inc., scanned map-unit descriptions and converted them to text format. Karen Lund and Mike O'Neill with the U.S. Geological Survey provided unpublished data for the database.

This report compiles selected results from 13 U.S. Geological Survey (USGS) mineral resource assessment studies conducted in Idaho and Montana into consistent spatial databases that can be used in a geographic information system. The 183 spatial databases represent areas of mineral potential delineated in these studies and include attributes on mineral deposit type, level of mineral potential, certainty, and a reference. The assessments were conducted for five 1° x 2° quadrangles (Butte, Challis, Choteau, Dillon, and Wallace), several U.S. Forest Service (USFS) National Forests (including Challis, Custer, Gallatin, Helena, and Payette), and one Bureau of Land Management (BLM) Resource Area (Dillon). The data contained in the spatial databases are based on published information: no new interpretations are made. This digital compilation is part of an ongoing effort to provide mineral resource information formatted for use in spatial analysis. In particular, this is one of several reports prepared to address USFS needs for science information as forest management plans are revised in the Northern Rocky Mountains.