This is an Arc/Info database version of USGS Map I-2395 from

A.B. Wilson and Betty Skipp, 1994, Geologic Map of the eastern part of the 
Challis National Forest and vicinity, Idaho
  
The original stable base printing sheets were digitized and attributed for 
Nancy Shock by TechniGraphic System, Inc. of Fort Collins Colorado.  Greg Green
edited and prepared the digital version for release as a gis database.