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Chemical sediments from the Early Eocene Green River Formation can be used for assessing hydroclimate and basin evolution during their deposition. The Wilkins Peak Member (WPM) of the Green River Formation contains a relatively continuous record of perennial closed-basin saline lake deposition in the Bridger Basin, southwest Wyoming, from approximately 51.6 to 49.8 Ma. The volumes and paragenesis of authigenic chemical sediments in the WPM are intrinsically related to the chemical evolution of basin brines. The geographic distribution of those chemical sediments across the Bridger Basin relates to the syn- and post-depositional tectonic history of the basin. In this study, we integrated thermodynamic modeling of chemical evolution of lake brines with chemostratigraphic and lithostratigraphic interpretations of the basin-center Solvay S-34-1 core to evaluate physical and chemical changes to and within ancient Lake Gosiute during the Early Eocene. Fine-scale X-ray fluorescence (XRF) scanning along the length of the core provides a high-resolution chemical stratigraphy of the WPM. Thermodynamic modeling of the evaporation of hypothetical inflow waters and lake brines yield predicted sequences of evaporite minerals, allowing estimation of the salinities and evaporated volumes of water required to reach saturation with respect to observed mineral deposits from the basin. The spatial distributions of bedded evaporites allow us to investigate tectonic changes to the basin during and after the deposition of the WPM. Here, we integrate these data to interpret changes in lake-level, salinity, and hydroclimate of ancient Lake Gosiute during the Early Eocene. 

Abstract Over the past 50 years, the discovery and initial investigation of subglacial lakes in Antarctica have highlighted the paleoglaciological information that may be recorded in sediments at their beds. In December 2018, we accessed Mercer Subglacial Lake, West Antarctica, and recovered the first in situ subglacial lake-sediment record—120 mm of finely laminated mud. We combined geophysical observations, image analysis, and quantitative stratigraphy techniques to estimate long-term mean lake sedimentation rates (SRs) between 0.49 ± 0.12 mm a–1 and 2.3 ± 0.2 mm a–1, with a most likely SR of 0.68 ± 0.08 mm a–1. These estimates suggest that this lake formed between 53 and 260 a before core recovery (BCR), with a most likely age of 180 ± 20 a BCR—coincident with the stagnation of the nearby Kamb Ice Stream. Our work demonstrates that interconnected subglacial lake systems are fundamentally linked to larger-scale ice dynamics and highlights that subglacial sediment archives contain powerful, century-scale records of ice history and provide a modern process-based analogue for interpreting paleo–subglacial lake facies.