Biomarker and Pollen Evidence for Late Pleistocene Pluvials in the Mojave Desert
Biomarker and Pollen Evidence for Late Pleistocene Pluvials in the Mojave Desert
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DOI：
10.1029/2022pa004471
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发表时间：
2022-09
影响因子：
3.5
通讯作者：
M. Peaple;Tripti Bhattacharya;T. Lowenstein;D. McGee;K. Olson;J. Stroup;J. Tierney;S. Feakins
中科院分区：
文献类型：
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作者：
M. Peaple;Tripti Bhattacharya;T. Lowenstein;D. McGee;K. Olson;J. Stroup;J. Tierney;S. Feakins
过去 200 凯里，北美西南部的气候经历了干湿阶段的深刻变化。为了更好地限制这些水文气候变化的时间、幅度和古环境影响，我们对从加利福尼亚州塞尔斯湖钻探的一个新的 77 m 沉积物岩心 (SLAPP-SRLS17) 收集的样本进行了多代理生物标志物研究。在这里，我们使用生物标志物和花粉来重建植被、湖泊状况和气候。我们发现长链正构烷烃的 δD 值主要由冰期到间冰期的变化主导，这与附近的 Devils Hole 方解石 δ18O 变化相匹配，表明这两个档案主要反映了降水同位素。然而，降水同位素并不简单地与植被和湖泊条件的干湿变化证据相一致，这表明降水同位素跟踪的大规模大气环流与景观水分可用性之间存在部分脱节。裂痕菌产量的增加和甲烷循环证据的减少揭示了在第二次终结期间有一个10凯尔间隔的新鲜、多产和混合良好的湖泊，证实了在倒数第二次（塔霍）冰川（140-130ka）末期，海岸线存在古湖高位以及下游帕纳明特盆地和死亡谷的溢出沉积物的证据。同时，brGDGT 产生了 200 Kyr 记录中的最低温度估计值（冰点以上的平均月份 = 9°C ± 3°C）。这些湖泊学条件在 200 凯尔记录中的其他地方没有重复，这表明海因里希 11 号高位比末次盛冰期和海因里希 1 号（18-15 ka）更湿润。
The climate of the southwestern North America has experienced profound changes between wet and dry phases over the past 200 Kyr. To better constrain the timing, magnitude, and paleoenvironmental impacts of these changes in hydroclimate, we conducted a multiproxy biomarker study from samples collected from a new 77 m sediment core (SLAPP‐SRLS17) drilled in Searles Lake, California. Here, we use biomarkers and pollen to reconstruct vegetation, lake conditions, and climate. We find that δD values of long chain n‐alkanes are dominated by glacial to interglacial changes that match nearby Devils Hole calcite δ18O variability, suggesting both archives predominantly reflect precipitation isotopes. However, precipitation isotopes do not simply covary with evidence for wet‐dry changes in vegetation and lake conditions, indicating a partial disconnect between large scale atmospheric circulation tracked by precipitation isotopes and landscape moisture availability. Increased crenarchaeol production and decreased evidence for methane cycling reveal a 10 Kyr interval of a fresh, productive, and well‐mixed lake during Termination II, corroborating evidence for a paleolake highstand from shorelines and spillover deposits in downstream Panamint Basin and Death Valley during the end of the penultimate (Tahoe) glacial (140–130 ka). At the same time brGDGTs yield the lowest temperature estimates (mean months above freezing = 9°C ± 3°C) of the 200 Kyr record. These limnological conditions are not replicated elsewhere in the 200 Kyr record, suggesting that the Heinrich stadial 11 highstand was wetter than the last glacial maximum and Heinrich 1 (18–15 ka).