RUI: Direct Determination of Late Pleistocene Periods of Maximum Wetness in the Owens River System: Shoreline Dating in Panamint Valley, California

我们试图通过测定欧文斯河系倒数第二个盆地Panamint山谷的洪水岸线特征来确定美国西部大盆地最潮湿时期的时间。在更新世的大部分时间里，欧文斯河终止于瑟尔斯盆地(Panamint上游)，形成了一个叠加的海岸线和凝灰岩沉积的复杂网络。然而，在相对罕见的最潮湿的时期，所有上游盆地(欧文斯、中国和瑟尔斯)都泛滥，帕纳明特山谷形成了深达310米的雨积湖。构造抬升保存了明确的海岸线，以碳酸盐凝灰岩沉积(原地形成于海岸线附近的浅水)、波浪切割台地和近岸湖泊沉积为标志。我们建议应用两种最新改进的技术来确定帕纳明特山谷突出的盖尔海岸线的年代。大风海岸线代表了欧文斯河从帕纳明特流入死亡谷的最近一段时间，但它还没有可靠的日期。凝灰岩的年代将通过测量宇宙成因的氯-36(36Cl)积累量来确定，这一技术已被证明在内华达山脉和其他地方的冰川冰雹测年中取得了成功，但尚未广泛应用于碳酸盐凝灰岩矿床。与海岸线有关的细粒浅水湖泊沉积的年龄将通过光激发发光测年确定，与海岸线有关的冲积扇材料中的36Cl深度剖面将提供额外的年龄控制。我们相信，这些组合技术将自信地确定海岸线的年龄，从而确定欧文斯河水系的最潮湿时期，到目前为止，这些时期只是从沉积物岩心替代物间接推断出来的。对最潮湿时间间隔的明确识别将提供一个共同的基准，使欧文斯、西尔斯和死亡谷核心现有的沉积物指标得以标准化，从而为大盆地地区提供更一致的区域古气候重建。大盆地明确定义的最高湿润时期可以与冰芯和海洋沉积物记录进行比较，以评估该大陆环境中的温度和水分输送如何响应全球气候变化。该项目将涉及每个阶段的本科生，有助于为未来的研究人员和科学教育工作者做好准备。来自代表性不足群体的学生将从汉普郡和芒特霍利奥克学院积极招收，国际学生联合会将从纽约市的学校为汉普郡学院招收高中生。该项目的研究成果和经验将被纳入他的理科和非理科专业本科课程，以及面向公众的关于气候变化的演讲。作为国家科学基金会赞助的积极研究人员，国际和平研究所将能够更好地传达全球变化研究的性质，这既是通过拟议的研究活动发展重要的新知识，也是通过增加国际和平研究所的可见度和可信度。

ABSTRACTWe seek to establish the timing of periods of maximum wetness in the western U.S. Great Basin by dating pluvial shoreline features in Panamint Valley, the penultimate basin in the Owens River system. During most of Pleistocene time, the Owens River terminated in Searles basin (upstream from Panamint), forming a complex network of superimposed shorelines and tufa deposits. However, during the relatively rare wettest periods when all the upstream basins (Owens, China, and Searles) overflowed, pluvial lakes up to 310 meters deep formed in Panamint Valley. Tectonic uplift has preserved well-defined shorelines, which are marked by carbonate tufa deposits (which formed in situ in shallow water near shorelines), wave-cut benches, and near-shore lacustrine deposits. We propose to apply two newly refined techniques to date the prominent Gale shoreline in Panamint Valley. The Gale shoreline represents the most recent period of overflow of the Owens Rivers from Panamint into Death Valley, but it has not been reliably dated. Tufa will be dated by measuring cosmogenic chlorine-36 ( 36Cl) buildup, a technique that has proven successful in dating glacial moraines in the Sierra Nevada and elsewhere, but has not been extensively applied to carbonate tufa deposits. Ages of fine-grained shallow water lacustrine deposits associated with the shoreline will be determined by optically- stimulated luminescence dating and a 36Cl depth profile in alluvial fan materials associated with the shoreline will provide additional age control. We believe these combined techniques will confidently identify the ages of the shorelines and therefore periods of maximum wetness in the Owens River system, which so far have only been indirectly inferred from sediment core proxies. Clear recognition of the wettest time intervals will provide a common benchmark to which the existing sediment proxies in Owens, Searles, and Death Valley cores could be standardized, thus providing a more coherent regional paleoclimate reconstruction for the Great Basin region.Well-defined periods of maximum wetness in the Great Basin can be compared with ice core and marine sediment records to assess how temperature and moisture transport in this continental setting responded to global climate changes.This project will involve undergraduate students in every phase, helping to prepare future researchers and science educators. Students from underrepresented groups will be actively recruited from Hampshire and Mount Holyoke Colleges, and the PI will be recruiting high school students from schools in New York City for Hampshire College. The PI is principally involved in undergraduate education and the research results and experiences from this project will be incorporated into his undergraduate courses for science majors and non-science majors, as well as into presentations on climate change for public community audiences. As an active NSF-sponsored researcher, the PI will be better able to convey the nature of global change research, both by virtue of developing important new knowledge through the proposed research activities and also by increasing the visibility and credibility of the PI.