Spectral mapping of quaternary geomorphic surfaces in the Whipple and Piute Mountains of southeastern California using visible and near infrared datasets

Landscape evolution within the Mojave Desert of southern California records a complex interaction between regional and local tectonic events and climatic variations. Identification and correlation of geomorphic surfaces can provide information about regional as well as local tectonic and climate histories. Geomorphic surfaces may be discriminated on the basis of their spectral signatures as recorded by instruments sensitive to visible and near-infrared radiation. Surfaces covered wholly or in part by clasts which have a veneer of desert varnish are especially recognizable in this wavelength range. The number of geomorphic surfaces that may be distinguished by remote sensing are comparable to those recognized in the field. However, surfaces with varnished clasts may be further subdivided using spectral information. Topographic differences among surfaces are less distinguishable by remote sensing techniques than by field measurements.; The chemistry of rock varnish has been investigated in order to determine how variations in bulk composition affect spectral response curves. SEM measurements identified nine major elements: Mn, Fe, Ti, Ca, K, Si, Al, Mg, and Na. These elements displayed both horizontal and vertical variations in the varnish layers. Using TOF-SIMS, three different elemental distribution patterns have been recognized: (1) uniform distribution of elements across the surface; (2) non-uniform distribution of elements across the surface; and (3) non-uniform patterns in which the highest concentration is associated either with the microtopographic highs or lows on the surface.; Remote sensing techniques provide a fast and efficient way to make correlations of geomorphic surfaces among ranges within the desert provinces of southwest United States. The criteria previously developed for field mapping and identification of geomorphic surfaces are topography, the amount of rock varnish present, the degree of desert pavement development, and the type of soil present. Of these criteria, topography and combined rock varnish and desert pavement, development, can be observed using visible and near-infrared datasets. Variations among different geomorphic surfaces record tilting and elevation changes which may reflect tectonism and/or climatic shifts.