THE GEOLOGIC AND GEOMORPHIC EVOLUTION OF THE MOJAVE DESERT, CALIFORNIA: INSIGHTS FROM A GEOINFORMATICS APPROACH

Information technologies provide geologists with tools of unlimited dimension to construct and test scientific hypotheses regarding the tectonic and landscape evolution of regions. Recent studies using digital elevation data demonstrates that the topography is spatially and structurally well correlated with the patterns of deformation produced by the current tectonic regime (Eastern California shear zone [ECSZ]). A related unanswered question is: Does the distribution and type of landscape elements of the Mojave Desert also reflect the current tectonic setting? To examine this general question, we mapped the Mojave Desert region (~150,000 km2) and constructed a digital GIS containing ~20,000 mapped polygons attributed with information on age, landform type, and composition. Mapping was accomplished using a combination of spectral image analysis, airphoto interpretation, and geological field techniques. The result is a regionally uniform GIS whose accuracy and precision are high, known, and verified.

The results of our study are consonant with hypothesis for extensive tectonic control on the landscape. Landforms in active areas of the ECSZ are generally much smaller in comparison to adjacent areas. The higher density of polygons in active areas are likely due to comminution by shear and erosional dissection driven by local uplift. Active mountain fronts within the ECSZ portion of the Mojave have narrower debris aprons than inactive ranges to the west and east. Inactive mountains within the ECSZ and the Eastern Mojave are typically rimmed with large bajadas. Young fronts within the ECSZ commonly have multiple generations of alluvial fans. In contrast, the western Mojave contain low relief bedrock plain-pediment systems of great antiquity (pre-8 Ma).