Preliminary geologic map of Fort Irwin basin, north-central Mojave Desert, California

Abstract

Surficial geologic units commonly exist as thin (<1 m) veneers over older units. In areas where this relationship is common the unit designators are shown on the map as being separated by a slash (/). The younger, or overlying, unit is indicated first Thus, Qya/Qoa indicates an area where a veneer of young alluvial fan deposits overlies old alluvial deposits and Qya/Kpg indicates an area where a veneer of young alluvial fan deposits overlies Cretaceous porphyritic granite. For those areas of veneer deposits, the map color is that of the underlying unit and a pattern designates the age and type of veneer deposit The lateral extent of individual deposits is commonly so small that each deposit cannot be shown individually at the published map scale. Where areas are made up of deposits too small to show individually, the designators of deposits present are separated by a plus sign (+), with the most common deposit listed first Thus, Qyai + Qya2 indicates an area with both Qyai and Qya2 deposits and associated surfaces, and that Qyai is more common than Qya2. For the combined units, the color of the youngest unit is displayed on the map.