Biomarker Evidence for an MIS M2 Glacial‐Pluvial in the Mojave Desert Before Warming and Drying in the Late Pliocene
Biomarker Evidence for an MIS M2 Glacial‐Pluvial in the Mojave Desert Before Warming and Drying in the Late Pliocene
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DOI：
10.1029/2023pa004687
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发表时间：
2024-01
影响因子：
3.5
通讯作者：
M. Peaple;Tripti Bhattacharya;J. Tierney;Jeffrey R. Knott;T. Lowenstein;S. Feakins
中科院分区：
文献类型：
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作者：
M. Peaple;Tripti Bhattacharya;J. Tierney;Jeffrey R. Knott;T. Lowenstein;S. Feakins
莫哈韦沙漠中的古代湖泊沉积物表明，这个目前干燥的地方的水循环与过去的气候截然不同。在这里，我们重新审视 55 年前从加利福尼亚州塞尔斯谷钻探的 700 m 岩心，该岩心发现了上新世晚期湖泊相的证据。我们更新了古地磁年龄模型，并从湖泊沉积物（3.373–2.706 Ma）中提取了气候条件的新生物标志证据。 MBT′5Me 温度代理首先检测当前条件（21 ± 3°C，n = 2），然后从 3.268 Ma 开始，到 2.734 Ma 结束，检测到比当前条件更温暖的条件（25 ± 3°C，n = 17）。细菌和古细菌生物标志物显示，3.268 Ma 后湖泊盐度增加，可能反映了因温度升高而导致的蒸发增加。植物蜡的 δ13C 值（−30.7 ± 1.4‰，n = 28）与当地 C3 类群一致，可能是雨季期间扩大的针叶林地，其 C4 含量低于更新世。植物蜡的δD值（−174±5‰，n=25）表明上新世晚期降水δD值（−89±5‰，n=25）与晚更新世降水δD在同一范围内。微生物生物标志物识别出一个深淡水湖和与海洋同位素阶段 M2（3.3 Ma）北半球主要冰川作用开始相对应的冷却。在上新世晚期（3.268-2.734Ma）随后的温暖时期，一个盐度更高的湖泊持续了约0.6Ma，然后在更新世北半球冰川作用加剧时湖泊干燥。
Ancient lake deposits in the Mojave Desert indicate that the water cycle in this currently dry place was radically different under past climates. Here we revisit a 700 m core drilled 55 years ago from Searles Valley, California, that recovered evidence for a lacustrine phase during the late Pliocene. We update the paleomagnetic age model and extract new biomarker evidence for climatic conditions from lacustrine deposits (3.373–2.706 Ma). The MBT′5Me temperature proxy detects present‐day conditions (21 ± 3°C, n = 2) initially, followed by warmer‐than‐present conditions (25 ± 3°C, n = 17) starting at 3.268 and ending at 2.734 Ma. Bacterial and archeal biomarkers reveal lake salinity increased after 3.268 Ma likely reflecting increased evaporation in response to higher temperatures. The δ13C values of plant waxes (−30.7 ± 1.4‰, n = 28) are consistent with local C3 taxa, likely expanded conifer woodlands during the pluvial with less C4 than the Pleistocene. δD values (−174 ± 5‰, n = 25) of plant waxes indicate precipitation δD values (−89 ± 5‰, n = 25) in the late Pliocene are within the same range as the late Pleistocene precipitation δD. Microbial biomarkers identify a deep, freshwater lake and a cooling that corresponds to the onset of major Northern Hemisphere glaciation at marine isotope stage marine isotope stages M2 (3.3 Ma). A more saline lake persisted for ∼0.6 Ma across the subsequent warmth of the late Pliocene (3.268–2.734 Ma) before the lake desiccated at the Pleistocene intensification of Northern Hemisphere Glaciation.