A > 200 ka U-Th based chronology from lacustrine evaporites, Searles Lake, CA

Abstract

Well-dated lacustrine records are essential to establish the timing and drivers of regional hydroclimate change. Searles Basin, California records 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 based on dating of evaporite minerals. 98 dated samples comprising 9 different minerals were evaluated based on stratigraphic, mineralogic, textural, chemical and reproducibility criteria. After application of these criteria, a total of 37 dated samples remained as constraints for the age model. A lack of dateable minerals between 145-110 ka left the age model unconstrained over the penultimate glacial termination (Termination II). We thus established a tie point between plant wax δD values in the core and a nearby speleothem δ18O record at the beginning of the Last Interglacial. 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 that correspond with prior work. The new dating is broadly consistent with previous efforts but provides more precise age estimates and a detailed evaluation of evaporite depositional history. We also offer a substantial revision of the age of the Bottom Mud-Mixed Layer contact, shifting it from ˜130 ka to 178±3 ka. The new U-Th chronology documents the timing of mud and salt layers and lays the foundation for climate reconstructions.

Biomarker and Pollen Evidence for Late Pleistocene Pluvials in the Mojave Desert

“…Sediment cores SLAPP-SRLS17-1A and 1B (35.7372°N, 117.33°W, 495 m asl) were drilled from Searles Lake in 2017 with 95% recovery extending to 76.7 m below the lake floor (Figure 1b). U/Th dating of evaporite minerals (Stroup et al, 2022) indicate the recovered sediments span 200 ka BP. Stroup et al (2022) use 37 U-Th ages to construct a Bayesian age model using BACON (Blaauw & Christeny, 2011).…”

“…U/Th dating of evaporite minerals (Stroup et al, 2022) indicate the recovered sediments span 200 ka BP. Stroup et al (2022) use 37 U-Th ages to construct a Bayesian age model using BACON (Blaauw & Christeny, 2011). The model considers the mineralogy, stratigraphic superposition, and boundaries between lithological units.…”