Collaborative Research: Absolute-dated records of Late Quaternary paleohydrology in the Bonneville Basin, western U.S., from novel cave archives

合作研究：美国西部邦纳维尔盆地晚第四纪古水文学的绝对日期记录，来自新颖的洞穴档案

• 批准号: 1103379
• 负责人: William McGee
• 金额: $ 9.41万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1103379&HistoricalAwards=false
• 关键词: Collaborative; Research; Absolute; dated; records

TECHNICAL ABSTRACTWater balance in the U.S. Great Basin largely reflects the position and intensity of the westerly storm track, suggesting that records of past hydrologic changes offer important insights into the behavior of the storm track in different climate states. The limited dating precision and sample resolution of presently available records of past water balance, however, leave scientists unable to address questions about the precise timing and rates of past water balance changes and their relation to abrupt events recorded in other paleoclimate archives. Further, few well-dated records extend past the last glacial period, allowing little understanding of previous interglacials and glacial terminations. This project will use cave deposits to reconstruct past abrupt water balance changes in the Bonneville Basin, the site of the largest of the Great Basin's paleolakes during the last glacial period. The work draws upon both a) lacustrine cave deposits formed in a series of caves flooded by lake waters and b) speleothems from Lehman Cave on the southwestern edge of the basin. Using stable isotope measurements and a combination of U-Th and 14C dating, this group will be able to produce records with unprecedented dating precision and sample resolution covering the most recent glacial termination as well as the previous two interglacials and terminations. Data from lacustrine cave deposits, a novel paleohydrologic archive, indicate that they formed during periods of the last 30 kyr when the lake was both above a given cave?s elevation and hydrologically closed. The deposits thus record the passage of the lake through each cave's elevation and the onset and cessation of basin overflow; they also preserve high-resolution records of the lake's oxygen isotope composition and chemistry. Importantly, the deposits can be precisely dated by U-Th methods, providing the first high-precision, absolute-dated records of Lake Bonneville's water balance changes. Calibrated 14C ages match U-Th ages in lacustrine cave deposits, indicating that 14C reservoir effects were minimal in the lake. As a part of the project, a series of paired U-Th and 14C ages will be used to improve the 14C calibration dataset, focusing on the period between 19 and 25 calendar ka.Lehman Cave speleothems comprise an important complement to the lacustrine cave carbonates, extending back through substantial portions of the last 300 kyr. Stable isotope records from the cave's stalagmites, anchored by U-Th dates, will provide some of the first well-dated archives of regional hydrology during the previous two interglacials and glacial terminations. Together, Lehman Cave and lacustrine cave records promise key insights into the eastern Great Basin's response to both abrupt and orbital-scale climate changes during the last three glacial cycles.NON-TECHNICAL ABSTRACTModels consistently predict that the world's drylands will become drier on average in response to greenhouse warming, but it is unclear how this drying will affect specific regions. In the U.S., there is particular interest in understanding the potential for future drying in the Great Basin, a drought-prone region that has experienced substantial population growth over the last two decades. Records of past water availability provide a key starting point for forecasting future changes in the Great Basin by showing us the region's responses to a wide variety of climates.The balance of precipitation and evaporation in the Great Basin in the western interior of the U.S.A. has changed dramatically over the past 30,000 years, leaving dry lake beds and hypersaline lakes today where extensive lakes existed during glacial times. Water availability in the region largely depends upon precipitation brought by the winter storm track, suggesting that records of past hydrologic changes offer important insights into the behavior of the storm track in different climate states. The limited dating precision and sample resolution of present records, however, leave us with only a general sense of past hydrologic changes, and no well-dated records currently extend to past interglacial warm periods.This project will use cave deposits to reconstruct past water balance changes in northern Utah's Bonneville Basin, the site of the largest of the Great Basin's paleolakes. These deposits record changes in precipitation in the basin over much of the past 300,000 years and are able to be precisely dated, offering us the opportunity to construct a detailed and extended picture of past climate changes in the region. Importantly, stalagmites from Lehman Cave on the western edge of the basin record the last two interglacial warm periods, allowing us the opportunity to study the mean state and variability of the region's hydrology during times when the region was as warm as or slightly warmer than at present. This work represents an important contribution to our understanding of past climate changes and will help calibrate models seeking to reproduce past changes in order to better forecast the future. In addition, these records will assist us in interpreting past ecological changes in the basin and the history of early human occupation in the region.

技术摘要美国大盆地的水平衡在很大程度上反映了西风风暴路径的位置和强度，这表明过去水文变化的记录为不同气候状态下风暴路径的行为提供了重要的见解。然而，目前可用的过去水平衡记录的测年精度和样本分辨率有限，使得科学家无法解决有关过去水平衡变化的精确时间和速率及其与其他古气候档案中记录的突发事件的关系的问题。此外，很少有日期明确的记录可以延续到末次冰期之后，因此人们对之前的间冰期和冰期终止了解甚少。该项目将利用洞穴沉积物来重建博纳维尔盆地过去突然的水平衡变化，该盆地是末次冰期期间大盆地最大的古湖泊所在地。该作品利用了a）由湖水淹没的一系列洞穴形成的湖泊洞穴沉积物和b）盆地西南边缘雷曼洞穴的洞穴沉积物。利用稳定同位素测量以及 U-Th 和 14C 测年相结合，该小组将能够以前所未有的测年精度和样本分辨率生成记录，涵盖最近的冰川终止以及前两次间冰期和终止。湖相洞穴沉积物（一种新的古水文档案）的数据表明，它们是在过去 30 年间形成的，当时湖泊既高于特定洞穴的海拔，又在水文上关闭。因此，沉积物记录了湖泊通过每个洞穴海拔的通道以及盆地溢流的开始和停止；他们还保存了该湖氧同位素组成和化学成分的高分辨率记录。重要的是，这些沉积物可以通过 U-Th 方法精确测定年代，从而提供了邦纳维尔湖水平衡变化的第一个高精度、绝对日期记录。校准后的 14C 年龄与湖相洞穴沉积物中的 U-Th 年龄相匹配，表明 14C 水库对湖泊的影响很小。作为该项目的一部分，一系列配对的 U-Th 和 14C 年龄将用于改进 14C 校准数据集，重点关注 19 至 25 历卡之间的时期。雷曼洞穴洞穴化石是对湖相洞穴碳酸盐岩的重要补充，向后延伸通过最后 300 kyr 的大部分。洞穴石笋的稳定同位素记录以 U-Th 日期为基础，将提供前两次间冰期和冰期末期期间区域水文学的一些最早的日期明确的档案。雷曼洞穴和湖泊洞穴记录共同为了解大盆地东部在过去三个冰川周期中对突然和轨道尺度气候变化的反应提供了重要见解。非技术性摘要模型一致预测，世界旱地平均将因此变得更加干燥温室变暖，但目前尚不清楚这种干燥将如何影响特定地区。在美国，人们特别有兴趣了解大盆地未来干旱的可能性，该盆地是一个干旱多发地区，在过去二十年中经历了人口大幅增长。过去可用水量的记录向我们展示了该地区对各种气候的反应，为预测大盆地未来的变化提供了一个关键起点。美国西部内陆大盆地的降水和蒸发平衡已经发生了变化在过去的三万年里，气候发生了巨大的变化，留下了今天的干湖床和高盐湖，而冰河时期存在着广阔的湖泊。该地区的可用水量很大程度上取决于冬季风暴路径带来的降水，这表明过去水文变化的记录为了解不同气候状态下风暴路径的行为提供了重要的见解。然而，现有记录的测年精度和样本分辨率有限，使我们只能对过去的水文变化有一个大致的了解，并且目前没有日期明确的记录延伸到过去的间冰期温暖时期。该项目将利用洞穴沉积物来重建过去的水平衡犹他州北部博纳维尔盆地的变化，该盆地是大盆地最大的古湖泊所在地。这些沉积物记录了该盆地过去 30 万年大部分时间的降水变化，并且能够精确测定年代，为我们提供了对该地区过去气候变化详细而广泛的了解的机会。重要的是，盆地西缘雷曼洞的石笋记录了最后两个间冰期的温暖时期，使我们有机会研究该地区在与 2017 年一样温暖或略温暖的时期的水文平均状态和变化。展示。这项工作对我们了解过去的气候变化做出了重要贡献，并将有助于校准试图重现过去变化的模型，以便更好地预测未来。此外，这些记录将有助于我们解释该流域过去的生态变化以及该地区早期人类占领的历史。