A NEW DIGITAL GEOLOGIC MAP OF BIG BEND NATIONAL PARK, TEXAS

The USGS is compiling a new 1:100,000-scale digital geologic map of Big Bend National Park in cooperation with the National Park Service. The map will incorporate existing mapping by academic groups, the Texas Bureau of Economic Geology, and other agencies. New mapping by the USGS and academic partners will be added in areas where data gaps exist. This new work will emphasize detailed geologic mapping of volcanic units, areas of plutonic rocks, and surficial units throughout the park. Much of the existing mapping is available only as hardcopy; therefore, early phases of compilation will focus on scanning and digitizing these maps to develop GIS databases and combining these databases with new mapping in ArcInfo (ESRI, Redlands, CA). New bedrock mapping in digital format will likely be ArcView (ESRI, Redlands, CA) shapefiles requiring conversion into ArcInfo coverages. Surficial units mapped on the PG-2 plotter will produce digital files in dxf format also requiring conversion into ArcInfo coverages prior to merging with bedrock geology. Adjacent and overlapping map datasets will be compared to check for consistency of geologic interpretations, particularly along map boundaries. Additional field work will be directed to resolve the anticipated inconsistencies. Initial work in converting existing mapping to digital format has concentrated on the eastern part of the park. Expansion of the database through 2005 will add new mapping of bedrock geology in areas along the western park boundary and integrate the new detailed surficial mapping. Final phase of development will incorporate bedrock and surficial mapping completed through 2005 and 2006 for central portions of the park. New bedrock mapping in the central portions will contribute to a more detailed stratigraphy by including newly subdivided strata of sedimentary and volcanic units. A more detailed stratigraphy will contribute to a better understanding of the geologic processes and their temporal relationships that produced the diverse geology within the park. (Mention of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government.)