Introduction
Between 1961 and 1969, Alan Griggs and others conducted fieldwork to prepare a
geologic map of the Spokane 1:250,000 map (Griggs, 1973). Their field observations
were posted on paper copies of 15-minute quadrangle maps. In 1999, the USGS
contracted with the Idaho Geological Survey to prepare a digital version of the Coeur
d’Alene 1:100,000 quadrangle. To facilitate this work, the USGS obtained the field maps
prepared by Griggs and others from the USGS Field Records Library in Denver,
Colorado. The Idaho Geological Survey (IGS) digitized these maps and used them in their
mapping program. The mapping focused on field checks to resolve problems in poorly
known areas and in areas of disagreement between adjoining maps. The IGS is currently
in the process of preparing a final digital spatial database for the Coeur d’Alene 1:100,000
quadrangle. However, there was immediate need for a digital version of the geologic map
of the Coeur d’Alene 1:100,000 quadrangle and the data from the field sheets along with
several other sources were assembled to produce this interim product.
This interim product is the digital geologic map of the Coeur d’Alene 1:100,000
quadrangle, Idaho and Montana. It was compiled from the preliminary digital files
prepared by the Idaho Geological, and supplemented by data from Griggs (1973) and from
digital databases by Bookstrom and others (1999) and Derkey and others (1996). The
resulting digital geologic map (GIS) database can be queried in many ways to produce a
variety of geologic maps. Digital base map data files (topography, roads, towns, rivers
and lakes, etc.) are not included: they may be obtained from a variety of commercial and
government sources. This database is not meant to be used or displayed at any scale
larger than 1:100,000 (e.g., 1:62,500 or 1:24,000). The digital geologic map graphics (of00-135_map.pdf) that are provided
are representations of the digital database.
The map area is located in north Idaho. This open-file report describes the
geologic map units, the methods used to convert the geologic map data into a digital
format, the ArcInfo GIS file structures and relationships, and explains how to download
the digital files from the U.S. Geological Survey public access World Wide Web site on
the Internet
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First posted November 30, 2000
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