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  1. 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. Ninety‐eight dated samples comprising nine different minerals were evaluated based on stratigraphic, mineralogic, textural, chemical, and reproducibility criteria. After the application of these criteria, a total of 37 dated samples remained as constraints for the age model. A lack of dateable minerals between 145 and 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 that 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 enables 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.

     
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  2. Abstract

    The climate of the southwestern North America has experienced profound changes between wet and dry phases over the past 200 Kyr. To better constrain the timing, magnitude, and paleoenvironmental impacts of these changes in hydroclimate, we conducted a multiproxy biomarker study from samples collected from a new 77 m sediment core (SLAPP‐SRLS17) drilled in Searles Lake, California. Here, we use biomarkers and pollen to reconstruct vegetation, lake conditions, and climate. We find that δD values of long chainn‐alkanes are dominated by glacial to interglacial changes that match nearby Devils Hole calcite δ18O variability, suggesting both archives predominantly reflect precipitation isotopes. However, precipitation isotopes do not simply covary with evidence for wet‐dry changes in vegetation and lake conditions, indicating a partial disconnect between large scale atmospheric circulation tracked by precipitation isotopes and landscape moisture availability. Increased crenarchaeol production and decreased evidence for methane cycling reveal a 10 Kyr interval of a fresh, productive, and well‐mixed lake during Termination II, corroborating evidence for a paleolake highstand from shorelines and spillover deposits in downstream Panamint Basin and Death Valley during the end of the penultimate (Tahoe) glacial (140–130 ka). At the same time brGDGTs yield the lowest temperature estimates (mean months above freezing = 9°C ± 3°C) of the 200 Kyr record. These limnological conditions are not replicated elsewhere in the 200 Kyr record, suggesting that the Heinrich stadial 11 highstand was wetter than the last glacial maximum and Heinrich 1 (18–15 ka).

     
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