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

摘要我们试图通过测定欧文斯河流域倒数第二个流域帕纳明特流域的洪积海岸线特征来确定美国西部大盆地最大湿度时期的时间。在更新世的大部分时间里，欧文斯河在Searles盆地（帕纳明特上游）终止，形成了一个复杂的叠加海岸线和石灰华沉积网络。然而，在相对罕见的最潮湿的时期，当所有的上游盆地（欧文斯，中国和塞尔）溢出，洪积湖高达310米深的形成在帕纳明特山谷。构造隆起保留了界限分明的海岸线，其特征是碳酸盐凝灰岩沉积（在靠近海岸线的浅水中就地形成）、浪蚀阶地和近岸湖泊沉积。我们建议采用两种新的改进技术，以日期在帕纳明特谷的显着大风海岸线。盖尔海岸线代表了欧文斯河从帕纳明特流入死亡谷的最新时期，但它还没有可靠的日期。通过测量宇宙成因的氯-36（36 Cl）积累来确定凝灰岩的年代，这种技术已被证明在内华达州和其他地方的冰碛物年代测定中是成功的，但尚未广泛应用于碳酸盐凝灰岩矿床。与海岸线相关的细粒浅水湖泊沉积物的年龄将通过光激发光测年确定，与海岸线相关的冲积扇物质中的36 Cl深度剖面将提供额外的年龄控制。我们相信，这些综合技术将有信心地确定海岸线的年龄，从而确定欧文斯河系统的最大湿度时期，到目前为止，这只能从沉积物岩心代理间接推断。明确识别最潮湿的时间间隔将提供一个共同的基准，欧文斯、西尔斯和死亡谷岩心中现有的沉积物代用品可以标准化，从而为大盆地地区提供了一个更连贯的区域古气候重建。大盆地最大湿度的确定时期可以与冰芯和海洋沉积物记录进行比较，以评估该地区的温度和水分输送情况。大陆环境对全球气候变化的反应。该项目将在每个阶段涉及本科生，帮助培养未来的研究人员和科学教育工作者。来自代表性不足群体的学生将积极从汉普郡和霍利奥克山学院招募，PI将从纽约市的学校为汉普郡学院招募高中生。主要研究者主要从事本科教育，该项目的研究成果和经验将纳入其理科专业和非理科专业的本科课程，以及向公众社区观众介绍气候变化。作为一个积极的NSF赞助的研究人员，PI将能够更好地传达全球变化研究的性质，通过拟议的研究活动开发重要的新知识，并通过增加PI的知名度和可信度。

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.