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Holocene water balance variations in Great Salt Lake, Utah: application of GDGT indices and the ACE salinity proxy
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  • Rachel T So,
  • Tim Lowenstein,
  • Elliot Jagniecki,
  • Jessica E. Tierney,
  • Sarah J Feakins
Rachel T So
University of Southern California

Corresponding Author:[email protected]

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Tim Lowenstein
Binghamton University
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Elliot Jagniecki
Utah Geological Survey
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Jessica E. Tierney
University of Arizona
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Sarah J Feakins
University of Southern California
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Great Salt Lake (UT) is a hypersaline terminal lake in the US Great Basin, and the remnant of the late glacial Lake Bonneville. Holocene hydroclimate variations cannot be interpreted from the shoreline record, but instead can be investigated by proxies archived in the sediments. GLAD1-GSL00-1B was cored in 2000 and recently dated by radiocarbon for the Holocene section with the top 11 m representing ~7 ka to present. Sediment samples every 30 cm (~220 years) were studied for the full suite of microbial membrane lipids, including those responsive to temperature and salinity. The ACE index detects the increase in lipids of halophilic archaea, relative to generalists, as salinity increases. We find Holocene ACE values ranged from 81-98, which suggests persistent hypersalinity with <50 g/L variability across 7.2 kyr. The temperature proxy, MBTʹ5Me,­ yields values similar to modern mean annual air temperature for months above freezing (MAF = 15.7°C) over the last 5.5 kyr. Several GDGT metrics show a step shift at 5.5 ka before which temperature estimates are unreliable due to the shift in lake ecology and likely shallow depth. The step change in lake conditions at 5.5 ka and additional variations within the late Holocene are compared to regional climate records. We find evidence for a dry mid-Holocene in GSL, corroborating other records.