Analysis of simulated advanced spaceborne thermal emission and reflection (ASTER) radiometer data of the Iron Hill, Colorado, study area for mapping lithologies

The advanced spaceborne thermal emission and reflection (ASTER) radiometer was designed to record reflected energy in nine channels with 15 or 30 m re solution, including stereoscopic images, and emitted energy in five channel s with 90 m resolution from the NASA Earth Observing System AM1 platform. A simulated ASTER data set was produced for the Iron Hill, Colorado, study a rea by resampling calibrated, registered airborne visible/infrared imaging spectrometer (AVIRIS) data, and thermal infrared multispectral scanner (TIM S) data to the appropriate spatial and spectral parameters. A digital eleva tion model was obtained to simulate ASTER-derived topographic data. The mai n lithologic units in the area are granitic rocks and felsite into which a carbonatite stock and associated alkalic igneous rocks were intruded; these rocks are locally covered by Jurassic sandstone, Tertiary rhyolitic tuff, and colluvial deposits. Several methods were evaluated for mapping the main lithologic units, including the unsupervised classification and spectral c urve-matching techniques. In the five thermal-infrared (TIR) channels, comp arison of the results of linear spectral unmixing and unsupervised classifi cation with published geologic maps showed that the main lithologic units w ere mapped, but large areas with moderate to dense tree cover were not mapp ed in the TIR data. Compared to TIMS data, simulated ASTER data permitted s lightly less discrimination in the mafic alkalic rock series, and carbonati te was not mapped in the TIMS nor in the simulated ASTER TIR data. In the n ine visible and near-infrared channels, unsupervised classification did not yield useful results, but both the spectral linear unmixing and the matche d filter techniques produced useful results, including mapping calcitic and dolomitic carbonatite exposures, travertine in hot spring deposits, kaolin ite in argillized sandstone and tuff, and muscovite in sericitized granite and felsite, as well as commonly occurring illite/muscovite. However, the d istinction made in AVIRIS data between calcite and dolomite was not consist ently feasible in the simulated ASTER data. Comparison of the lithologic in formation;produced by spectral analysis of the simulated ASTER data to a ph otogeologic interpretation of a simulated ASTER color image illustrates the high potential of spectral analysis of ASTER data to geologic interpretati on.