Holocene Water Balance Variations in Great Salt Lake, Utah: Application of GDGT Indices and the ACE Salinity Proxy
Holocene Water Balance Variations in Great Salt Lake, Utah: Application of GDGT Indices and the ACE Salinity Proxy
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DOI：
10.1029/2022pa004558
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发表时间：
2023-05
影响因子：
3.5
通讯作者：
Rachel T. So;T. Lowenstein;E. Jagniecki;J. Tierney;S. Feakins
中科院分区：
文献类型：
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作者：
Rachel T. So;T. Lowenstein;E. Jagniecki;J. Tierney;S. Feakins
大盐湖 (GSL) 位于犹他州，是大盆地的一个高盐度终湖，也是晚冰期博纳维尔湖的遗迹。全新世水文气候变化无法从海岸线记录来解释，但可以通过沉积物中存档的代理进行研究。 GLAD1-GSL00-1B 于 2000 年取芯，最近通过全新世部分的放射性碳测年，顶部 11 m 代表距今 7 ka。每 30 厘米（约 220 年）沉积物样本就进行了全套微生物膜脂的研究，包括那些对温度和盐度敏感的膜脂。古菌和卡尔达古菌生态计量 (ACE) 指数检测到，随着盐度的增加，嗜盐古菌的脂质相对于通才有所增加。我们发现全新世 ACE 值范围为 81 至 98，这表明持续的高盐度在 7.2 ka 内的变异性小于 50 g/L。温度代理 MBTʹ5Me 产生的值与过去 5.5 ka 内冰点以上月份 (MAF = 15.7°C) 的现代年平均气温相似。几种甘油二烷基甘油四醚指标显示微生物群落和湖沼学在 5.5 ka 时发生阶跃变化。扩展的考古发现在区域全新世中期干旱期间盐度升高，这在通常接近指数上限的 ACE 记录中不容易检测到。我们推断，全新世中期的 GSL 比全新世晚期更浅、更咸。当前的干燥可能使湖泊恢复到全新世中期以来从未见过的状况。
Great Salt Lake (GSL), Utah, is a hypersaline terminal lake in the 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 Archaeol and Caldarchaeol Ecometric (ACE) index detects the increase in lipids of halophilic archaea, relative to generalists, as salinity increases. We find Holocene ACE values ranged from 81 to 98, which suggests persistent hypersalinity with <50 g/L variability across 7.2 ka. 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 ka. Several glycerol dialkyl glycerol tetraether metrics show a step shift in microbial communities and limnology at 5.5 ka. Extended archaeol detects elevated salinity during the regional mid‐Holocene drought, not readily detected in the ACE record that is often near the upper limit of the index. We infer that the mid‐Holocene GSL was shallower and saltier than the late Holocene. The current drying may be returning the lake to conditions not seen since the mid‐Holocene.