BASMAP (BASEMENT AGE AND STRUCTURE MAP): PROTOTYPE GIS DATABASE OF CRUSTAL GEOLOGY IN THE SOUTHERN ROCKY MOUNTAIN REGION

Exposed crystalline basement rocks provide the most detailed information available on the structure and evolution of the continental crust of the western United States. In the coming decade Earthscope and other regional- to continent-scale geophysical experiments will provide an unprecedented image of the deeper structure of the crust and mantle. The interpretation of these geophysical data will depend, to a large degree, on integrating large geophysical datasets with local to regional geologic mapping, structural observations, geochemical data, and geochronologic ages. The BASMAP project is designed to rapidly meet the pressing need for a consistent, dynamic, and extensible spatial database of crystalline basement rocks in the western U.S. that is compatible with large geophysical datasets. The scope of the BASMAP project is crustal rocks throughout the western U.S. although the prototype is limited to the southern Rocky Mountains of Wyoming, Colorado, and New Mexico. The initial implementation of BASMAP comprises: (1) an object-oriented database of structural, petrologic, geochemical, and geochronologic data, (2) a GIS spatial database with a range of scale/resolution, and (3) a set of tools for accessing, analyzing, and plotting data. The prototype incorporates geologic mapping at a variety of scales and demonstrates dynamic retrieval and plotting of structural, geochemical, and geochronologic, and geophysical data. Preliminary results of three geologic/geophysical applications of BASMAP are presented: (1) analysis of ⁴⁰Ar/³⁹Ar data from Colorado and New Mexico, (2) spatial relationships between pseudotachylyte and ultramylonite zones in the Homestake shear zone Colorado, (3) integration of geologic observations and geophysical data from the Continental Dynamics of the Rocky Mountains (CD-ROM) transect. Continued development and dissemination of BASMAP will facilitate geophysical interpretation of the crustal structure of the western U.S. utilizing consistent and current geologic, geochemical, and geochronologic data.