APPLICATION OF REMOTE SENSING TECHNIQUES TO THE STUDY OF GEOLOGY IN JOSHUA TREE NATIONAL PARK, CALIFORNIA

Joshua Tree National Park is located at the boundary between the Mojave and Colorado Deserts in southeastern California. The rugged terrain and harsh environmental conditions in this area make typical field methods for geologic mapping difficult. However, due to the sparse vegetation, this is an ideal area to utilize remote sensing technology. Previously published maps of the area have been pieced together from data supplied by multiple sources. This research uses remote sensing imagery of Joshua Tree National Park and the surrounding area, in association with field data to produce a geologic map of the area from a single source. An image was acquired from the USGS/NASA Landsat7 satellite on September 6, 1999. This image was processed using a “four component image processing” technique (Crippen, 1990). The image processing uses three band ratios emphasizing ferric iron, ferrous iron, and carbonate and clay concentrations in the landscape. The fourth component is an average of the reflectance in bands 1, 3 and 4, which emphasizes the topography. This technique causes certain rock types to be depicted as specific colors in the image. Lines have been digitized on the image at color changes, which signify rock unit boundaries. From this image, previously unmapped rock units have been found. Field data, including rock type, detailed descriptions and GPS coordinates, has been collected in the less rugged portions of the research area. This field data in association with rock age data collected by other researchers and the geologic map produced from the satellite image are all being used to decipher the geologic history of the area. Rock units that have been mapped include Cenozoic (?) basalt, at least three granites with Mesozoic formation ages, and Early Proterozoic pelitic and granitic gneiss.