Abstract

The Oligocene age Buck Hill volcanic group consists of several rock types including: basalt, welded tuff and non-welded tuffaceous units. This study uses spectral analysis and principal component analysis of Landsat 7 Enhanced Thematic Mapper Plus (ETM+) data to delineate spectral differences between the various volcanic units as well as other nearby units. The five volcanic units analyzed in this study are the Pruett Formation, Cottonwood Springs Basalt, Duff Formation, Mitchell Mesa Tuff and the Tascotal Formation. Also, spectra were taken from the nearby Cretaceous Boquillas Formation and from Quaternary alluvial sediments. Imagery for this study was gathered by the Landsat 7 ETM+ on November, 9 2002 and was downloaded from the archives at www.texasview.org. The image covering the study area is designated path 31 row 39. ERDAS Imagine 9.2 was used to composite the original image and convert the raw digital number values to reflectance. The spectral analysis and principal component analysis was preformed using ESRI ArcMap 9.3. Reflectance spectra for each unit were generated by plotting the average reflectance for each band over a uniform area. Also, the average values for each principal component were similarly plotted. Applications of this study range from general geologic mapping to mineral exploration.