Preliminary Digital Database for the Portola 30' x 60' Geologic and Geophysical Map, California

This geospatial dataset compiles, in digital form, geologic and geophysical data for the Portola 30’x 60’ quadrangle, located in the northern Sierra Nevada, California. This geologic map of the Portola 30’x 60’ quadrangle integrates decades of published and unpublished mapping in the northern Sierra Nevada. In conjunction with geophysical data, including more than 1000 new gravity measurements and new detailed aeromagnetic data, the map seamlessly depicts a complex region at the intersection of the Sierra Nevada and Basin and Range provinces. All geologic data were compiled as a GeMS digital database; geophysical data were converted to a GeMS schema. This digital geologic database is a companion dataset to a USGS Scientific Investigation Map. The dataset includes a geographic information system geodatabase that contains mapped contacts and faults, map unit polygons, orientation points of recorded field observations, and polyline features of mapped intrusive dikes. Vector data are attributed according to the USGS National Cooperative Geologic Mapping Program’s GeMS digital geologic map schema. The spatial data are accompanied by non-spatial tables that describe the sources of geologic information, a description of geologic map units, a glossary of terms, and a Data Dictionary that duplicates the Entity and Attribute information contained in the metadata file. To maximize usability, spatial data are also distributed as shapefiles and tabular data are distributed as ascii text files in comma separated values (CSV) format.