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 Evidence for an MIS M2 Glacial‐Pluvial in the Mojave Desert Before Warming and Drying in the Late Pliocene

“…Searles Valley contains a dry lake bed with evaporite deposits spanning the Holocene, atop deposits of lake muds deposited during Pleistocene pluvials and evaporites formed during drier periods (Knott et al., 2021; Olson & Lowenstein, 2021; Olson et al., 2023; Smith, 2009). The wettest times of the last 200 ka coincided with terminations T2 and T1 following the last two glacial maxima of marine isotope stages (MIS) 6 and 2 (Peaple, Bhattacharya, Lowenstein, et al., 2022; Stroup et al., 2023). Plant wax δD data (Peaple, Bhattacharya, Lowenstein, et al., 2022) corroborate independent evidence from cave carbonate δ 18 O for precipitation isotopes (Lachniet et al., 2014; Moseley et al., 2016), lending confidence to these archives of past precipitation change.…”

A >200 ka U‐Th Based Chronology From Lacustrine Evaporites, Searles Lake, CA

“…Sample materials were identified by XRD and visual inspection. Sample mineralogies are indicated in the data archived at the NOAA paleoclimatology database (Stroup et al., 2022). XRD was performed on most samples used for dating.…”

“…Data files are archived at the NOAA paleoclimatology database (https://doi.org/10.25921/wrk3-tj55; Stroup et al., 2022).…”