SURFICIAL GEOLOGIC MAPPING OF EOLIAN SYSTEMS IN THE MOJAVE AND COLORADO DESERTS FOR THE DESERT RENEWABLE CONSERVATION PLAN, CALIFORNIA

The Desert Renewable Energy Conservation Plan (DRECP) is a collaborative interagency action that includes a Natural Community Conservation Plan. The DRECP includes more than 22.5 million acres of land within California. The DRECP utilizes natural community identification as a basis for certain aspects of mapping. The Mojave fringe-toed lizard (Uma scoparia) is a DRECP Covered Species, recognized as a California species of special concern and a Bureau of Land Management sensitive species, and is only found in areas of eolian sand accumulation. Studies have demonstrated the linkage between eolian deposits, dune and sand-based natural vegetation communities, and fringe-toed lizard habitat. This understanding forms the basis for recognizing eolian deposits as areas of higher biological value for terrestrial species, as well as source of unique vegetation communities.

To assist in the identification of potential habitat for species covered under the DRECP, the California Geological Survey (CGS) developed eolian system maps within four areas that needed additional identification of eolian deposits and their associated source and transport areas. The CGS approach included the compilation of existing geologic maps of Quaternary surficial sediments and new mapping where necessary. Using this approach, CGS geologists established the location of eolian sediments and the geomorphic connection with their sources, typically alluvial washes, alluvial fans, lacustrine deposits, and stabilized dune fields. CGS used several lines of evidence to support the interpretation of these relationships. Field reconnaissance provided information on soil development and the relative geologic ages of deposits. Aerial photographic interpretation and field observations were used to define eolian sand transport directions that were compared to regional wind data. These data were used to refine the eolian source and deposit map units with information on the relative state of activity. The resulting four derivative geologic maps cover 2,200 square miles in total. In addition to aiding in the identification of vertebrate species habitat, these maps also may serve as a basis for identifying the general distribution of unique vegetation alliances that have developed based upon the unique characteristics of these geologic units.