DISTRIBUTION AND CHARACTER OF LATE PLEISTOCENE LACUSTRINE AND SPRING DEPOSITS PANAMINT VALLEY, CALIFORNIA

Panamint Valley, Ca consists of two depositional basins with playas at ~469m and ~317m elevation separated by a 521m divide. Late Pleistocene lacustrine deposits representing at least 2-3 pluvial highstands occur between ~609 and 353m. Preliminary mapping and age control suggests that the divide between the two basins in Panamint Valley was not breached during the last highstand. Varying ages and water chemistries indicated by radiometric dating and ostrocode taxa provides information about the last highstand and timing of the hydrologic exchange through the topographic divide. Gastropod-bearing tufa that forms a discontinuous bathtub ring at ~476m elevation around a bedrock hill (Lake Hill) which protrudes from the upper playa surface returned a 11,880 +/- 70 ka 14C. Mollusc and ostrocode fauna from shallow bucket auger samples suggests around 10,500 ka the late stage alkaline and saline lake was followed by a freshwater wetland. Groundwater carbonates occur near 500m elevation along the south flank of the divide at about the last highstand elevation of the lower basin lake. Eleven new 14C ages on charophytic and(or) other algae tufa ranging in elevation from 384 to 512m in the lower basin give ages that range from about 24,000 to 17,000 ka. Isolated remnants of late Pleistocene gravel and cobble beach deposits locally associated with prominent strandlines are commonly underlain by 1 to 3 m marly deposits with ostrocodes indicative of spring discharge and (or) wetlands environments suggesting a high water table was associated with the highstands and groundwater discharge occurred along the shoreline. At some localities these deposits contain ostrocode taxa suggesting divergent water chemistries mixed at the discharge-shoreline interface that would facilitate tufa formation.