LATE PLEISTOCENE LAKES AND GROUNDWATER DISCHARGE, PANAMINT VALLEY, CALIFORNIA

Panamint Valley is intermittently occupied by perennial water bodies linked to two fundamentally different sources, the Owens River system (ORS) and the regional groundwater aquifer (RGA). The bedrock of the different flow paths is sufficiently unique to influence the water chemistry, which in turn influences the ostracode assemblages. Previous Sr isotopic studies indicated the presence of two chemically distinct water sources. Likewise, microfaunal studies of the ORS demonstrated faunal variations that respond to climate-driven variation in water chemistry.

Lacustrine deposits within Panamint Valley extend through an elevation range over 360 m. During glacial periods, ostracode assemblages indicate high total carbonate alkalinity to calcium ratio (alk/Ca) and a cold, dilute lake with variable salinity fed by surface flow from the ORS. During interglacials, the assemblages indicate high total dissolved solids (brine) and very low alk/Ca ratios fed by the RGA. Deposits and archived core suggest large lakes and surface flow by the ORS during marine oxygen-isotope stages (OIS) 2 and 6, while saline marsh or wetlands supported by the RGA persisted during some of OIS 3 and most of OIS 4.

Lacustrine and wetland deposits that range in elevation between 415 - 512 m contain Limnocythere sappaensis, indicating a saline lake with ORS flow; 14C dates from associated tufa give OIS-2 ages. Ostracodes, including Cyprideis beaconensis, occur between about -34 to -78 m depth in DH-1 core and have amino acid racemization ratios (AAR) and a single 14C age of 40,710 +/- 670 BP suggesting OIS-3 age or older for the section. The fauna, brine shrimp pellets and the foraminifera Elphidium sp. in two samples, indicates a saline to briny wetland or shallow lake fed by the RGA. Comparison of DH-1 with DH-3 and Owens Lake core suggests the interval spans much of OIS 4. The high stand deposits lying 320 to 260 m above the playa at elevations of 550 to 610 m indicate ORS flow. AAR from ostracodes and snails in these deposits indicate one lacustrine period. An OIS-6 age for this period can be inferred by comparison of the high stand AAR with the archived core AAR results that underlie the 14C age cited above. Ostracodes and foraminifera indicate that Panamint Valley was used by Pacific migrant shorebirds during OIS-3 and 4, and by Gulf of Mexico migrants during OIS-6.