USING LAKE SEDIMENTS TO INFER THE LATE-GLACIAL HYDROLOGIC CONDITIONS OF PLUVIAL LAKE MOJAVE, CALIFORNIA

Silver Lake is an intermittent playa located in the Mojave Desert of Southern California. Silver Lake’s predecessor is Lake Mojave, a pluvial lake that occupied the basin during the late Pleistocene (ca. 25 ka) through the Early Holocene (ca. 8 ka). The hydrologic setting and depositional history of Lake Mojave makes it well suited to record past winter precipitation variability in the San Bernardino Mountains and possibly late summer/early fall North American Monsoon precipitation in the Mojave Desert. The Mojave River is the primary source of inflow for Silver Lake. With headwaters in the San Bernardino Mountains, the river drains the surrounding desert drainage basin and terminates in the Lake Mojave basin. The hydrologic and climatic conditions necessary to sustain Lake Mojave are significantly different than the prevailing modern climatic conditions. Thus, lacustrine sediments deposited in the basin present an opportunity to reconstruct the variable states (e.g., deep vs. shallow) of Lake Mojave. A newly acquired 23 m sediment core from the lake’s depocenter serves as the basis for a paleohydrologic investigation of this site. Detailed analyses were applied to a 4.2 m section of mud positioned 7.6-12.2 m below the modern playa surface. AMS ¹⁴C dates for 15 ostracod and 6 bulk organic matter samples constrain the timing of an inferred lake level depth model for Lake Mojave from ca. 16 to 12.2 ka. Results indicate a dry period characterized by low, variable lake levels sustained from 16 to 14.7 cal ka BP transitions to a wet period characterized by high lake levels between 14.7 and 12.2 cal ka BP. The timing of this transition at 14.7 cal ka BP is regionally and hemispherically correlative suggesting a common climate forcing.