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Holocene Salinity Variations in Great Salt Lake, Utah: Application & Calibration of the ACE Salinity Proxy
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  • Rachel So,
  • Tim Lowenstein,
  • Elliott Jagniecki,
  • Jessica Tierney,
  • Sarah Feakins
Rachel So
University of Southern California

Corresponding Author:[email protected]

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Tim Lowenstein
Binghamton University
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Elliott Jagniecki
Utah Geological Survey
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Jessica Tierney
University of Arizona
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Sarah Feakins
University of Southern California
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The Great Salt Lake (UT) is a hypersaline terminal lake in the US Great Basin, and the remnant of the late glacial-pluvial Lake Bonneville. During the Holocene, hydroclimate variations have been more subtle in the basin. These variations can be investigated by organic geochemical methods within the sediment core GLAD1-GSL00-1B, cored in 2000 and recently well-dated by radiocarbon for the Holocene section (Bowen et al., 2019) with 11 meters representing 8 ka to present. Sediment samples every 30 cm (~200 years) were extracted and the total lipid extracts were analyzed by HPLC-MS to detect the full suite of microbial membrane lipids, including those responsive to temperature and salinity. Modern samples were also collected to provide local calibration for the archaeol-caldarchaeol ecometric (ACE) salinity proxy, where ACE = archaeol/(archaeol + caldarchaeol). ACE detects the increase in lipids of halophilic archaea, relative to generalists, as salinity increases. From currently analyzed data and calibrations, we find Holocene lake salinity estimates ranged from 239 to 283 psu, suggesting persistent hypersalinity with < 50 psu variability across 8 kyr. For comparison, the modern salinity of the lake ranges from 100 to 160 psu in the southern half, and 240 to 270 psu in the north. From ~7-6 ka, salinity estimates were relatively high at 270 to ~280 psu. Following 6 ka, salinity decreases and reaches its lowest value of 239 psu at 4.8 ka. Afterwards, salinity increases and varies between ~250 to ~270 psu, remaining at 270 psu in the last 1 kyr. This new salinity record is compared to available shoreline reconstructions and regional climate records. The temperature proxy, MBT’5Me,­ as calibrated by BayMBT, suggests mean annual air temperature estimates ranged from 12°C to 24°C (compared to modern mean temperature of 13°C). This indicates a substantial, variable complication from salinity in this consistently hypersaline lake, as recently reported for the MBT’5Me­ proxy.