A spectral reflectance study of the sedimentary paleozoic rocks around Racetrack Valley in Death Valley National Monument

Abstract

Sedimentary rocks from the Racetrack Valley area of Death Valley National Monument were sampled, and spectral reflectance data in the wavelengths 0.40 to 2.50 microns were obtained to study the possibility of distinguishing different carbonate rocks using the spectral data. Of the 49 samples which were analyzed, 12 were primarily limestone, 25 were primarily dolomite, 7 were primarily quartzite and one was a calcareous shale. Spectra were obtained from pieces of the weathered rock surfaces of the sample using a Beckmann Lab Spectrophotometer. This study shows that it is possible to discriminate among carbonate rock types in this study area using differing reflectivities, position of various absorption bands and the presence of, or lack of, different absorption bands such as carbonate, water and hydroxyl. Dolomite absorption bands were at slightly shorter wavelengths than th9se of limestones. The exact position of the absorption bands depended on other impurities in the rock. The spectral reflectance of the quartzites varied depending on the amount of desert varnish covering the surface of the sample. Different formations were discriminated as well, using differing reflectivities, position of various absorption bands and the presence of, or lack of, different absorption bands such as carbonate, water and hydroxyl bands. The ability to discriminate both rock carbonate types and rock formations will prove invaluable to the field and exploration geologist. Previously unaccessible territories will become accessible using spectral reflectivity data and remote sensing techniques. This will allow the mapping and exploration of unexplored areas to be more cost and time effective than previously possible.