A >200 ka U‐Th Based Chronology From Lacustrine Evaporites, Searles Lake, CA
A >200 ka U‐Th Based Chronology From Lacustrine Evaporites, Searles Lake, CA
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DOI：
10.1029/2022gc010685
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发表时间：
2023-03
期刊：
影响因子：
3.7
通讯作者：
J. Stroup;K. Olson;T. Lowenstein;A. Jost;Hayley M. Mosher;M. Peaple;S. Feakins;Christine Chen;S. Lund;D. McGee
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文献类型：
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作者：
J. Stroup;K. Olson;T. Lowenstein;A. Jost;Hayley M. Mosher;M. Peaple;S. Feakins;Christine Chen;S. Lund;D. McGee
年代久远的湖泊记录对于确定区域水文气候变化的时间和驱动因素至关重要。加利福尼亚的Searles盆地记录了欧文斯河系统终端盆地中一个波动的盐碱湖的沉积历史，该盆地排干了东部的内华达山脉。本文基于蒸发岩矿物的年代测定，对2017年采集的~ 76 m长的SLAPP - SLRS17岩心建立了U - Th年代学。根据地层学、矿物学、质地、化学和可重复性标准，对包含9种不同矿物的98个年代样品进行了评估。在应用这些标准之后，总共37个日期样本仍然作为年龄模型的约束。145 - 110 ka之间可测定年代的矿物的缺乏，使得年龄模型不受倒数第二个冰期末期（末期II）的约束。因此，我们在岩心中的植物蜡δD值与末次间冰期开始时附近的岩洞δ18O记录之间建立了一个连接点。我们构建了一个贝叶斯年龄模型，允许地层学告知沉积速率的变化。我们发现>210 ka SLAPP‐SRLS17记录包含与先前工作相对应的五个主要单元。新的年代测定与以前的研究大体一致，但提供了更精确的年龄估计，并能够详细评估蒸发岩的沉积历史。我们还对底部泥浆-混合层接触的年龄进行了实质性修订，将其从~ 130 ka移至178±3 ka。新的U - Th年表记录了泥层和盐层形成的时间，为气候重建奠定了基础。
Well‐dated lacustrine records are essential to establish the timing and drivers of regional hydroclimate change. Searles Basin, California, records the depositional history of a fluctuating saline‐alkaline lake in the terminal basin of the Owens River system draining the eastern Sierra Nevada. Here, we establish a U‐Th chronology for the ∼76‐m‐long SLAPP‐SLRS17 core collected in 2017 based on dating of evaporite minerals. Ninety‐eight dated samples comprising nine different minerals were evaluated based on stratigraphic, mineralogic, textural, chemical, and reproducibility criteria. After the application of these criteria, a total of 37 dated samples remained as constraints for the age model. A lack of dateable minerals between 145 and 110 ka left the age model unconstrained over the penultimate glacial termination (Termination II). We thus established a tie point between plant wax δD values in the core and a nearby speleothem δ18O record at the beginning of the Last Interglacial. We construct a Bayesian age model allowing stratigraphy to inform sedimentation rate inflections. We find that the >210 ka SLAPP‐SRLS17 record contains five major units that correspond with prior work. The new dating is broadly consistent with previous efforts but provides more precise age estimates and enables a detailed evaluation of evaporite depositional history. We also offer a substantial revision of the age of the Bottom Mud‐Mixed Layer contact, shifting it from ∼130 ka to 178 ± 3 ka. The new U‐Th chronology documents the timing of mud and salt layers and lays the foundation for climate reconstructions.