Spatial Databases for the Geology of the Northern Rocky Mountains - Idaho, Montana, and Washington

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.

[Summary provided by the USGS.]