NOAA/WDS Paleoclimatology - Searles Lake California, U-Th chronology and Grayscale Data for SLAPP-SRLS17-1A/B, Late Pleistocene

Well-dated lacustrine records are essential to establish the timing and drivers of regional hydroclimate change. Searles Basin, California contains the depositional history of a fluctuating saline-alkaline lake in the terminal basin of the Owens River system draining the eastern Sierra Nevada. Here, we establish a U-Th chronology for the ~76-m-long SLAPP-SLRS17 core collected in 2017. Alternating layers of salt and mud indicate dry and wet conditions, respectively. We selected syndepositional evaporite materials that precipitated in the water column or near the sediment-water interface for U-Th dating. 98 dated samples comprising 9 different minerals were evaluated based on stratigraphic, mineralogic, textural and chemical information. A lack of dateable minerals between 145–110 ka left a critical time period unconstrained, thus we establish a tie point between plant wax dD values in the same core and a nearby speleothem ?18O record to date the penultimate glacial termination (Termination II). We construct a Bayesian age model allowing stratigraphy to inform sedimentation rate inflections. We find the >210 ka SLAPP-SRLS17 record contains five major units. The base of the core includes alternating mud and salt layers (210-177.5 ka), muds record a lake throughout 177.5-38.5 ka including Termination II, followed by seven mud-salt lake evaporation cycles between ~38.5-22.5 ka. Lake muds were deposited across the Last Glacial Maximum and early deglaciation (~22.5-15.6 ka), and salt deposits record a dry basin in the last ~15.6 ka. The new U-Th chronology documents sedimentation rate changes between muds and salts and lays the foundation for climate reconstructions.