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.

美国的技术摘要水平衡在很大程度上反映了西风风暴轨迹的位置和强度，这表明过去的水文变化的记录为在不同气候状态下风暴轨迹的行为提供了重要的见解。然而，有限的约会精度和样本解决了过去的水平平衡记录，这使科学家无法解决有关过去水平衡变化的准确时机和速度的问题，以及它们与其他古气候档案中记录的突然事件的关系。此外，很少有良好的记录延伸到最后一个冰川时期，从而几乎没有了解以前的冰川间和冰川终止。该项目将使用洞穴沉积物来重建Bonneville盆地的过去突然水平变化，Bonneville盆地是最后一个冰川时期大盆地古湖中最大的地点。这项工作借鉴了a）湖泊洞穴的沉积物，这些洞穴矿床是在湖水湖和b）盆地西南边缘的雷曼洞穴中淹没的一系列洞穴中形成的。使用稳定的同位素测量以及U-TH和14C约会的组合，该组将能够以前所未有的约会精度和样品分辨率产生记录，涵盖了最新的冰川终止以及前两个冰川间和终止。来自湖泊洞穴沉积物的数据是一种新型的古水域档案，表明它们在湖泊的最后30个KYR期间形成，当时该湖都高于给定的洞穴高度且封闭。因此，沉积物记录了湖中每个洞穴海拔的通道以及盆地溢出的开始和停止；他们还保留了湖泊氧同位素组成和化学的高分辨率记录。重要的是，这些存款可以通过U-Th方法准确地进行，提供了第一个高精度，绝对的日期记录，记录了Bonneville湖水平衡的变化。经过校准的14C年龄与湖间洞穴沉积物中的U级相匹配，这表明湖中14C的储层效应很小。作为该项目的一部分，一系列配对的U-Th和14C年龄将用于改善14C校准数据集，重点是19至25个日历KA.Lehman Cave Speleothems之间的时期，这是对Lacustrine Cave Cave碳酸盐群的重要补充，并通过最后300 kyr的实质性部分扩展了。由U-th日期锚定的洞穴稳定的同位素记录将在前两个冰川间和冰川终止期间提供一些最早的区域水文学档案。雷曼洞穴和湖泊洞穴的记录共同承诺，在过去三个冰川周期中，东部大盆地对突然和轨道尺度气候变化的反应的关键见解始终如一地预测，对于温暖的温暖而言，这对绿色的温暖而言，这会使这种干燥的区域平均响应，这将变得更加干燥。在美国，人们特别感兴趣地了解大盆地的未来干燥的可能性，这是一个容易发生干旱地区，在过去的二十年中，人口增长巨大。过去的水可用性记录通过向我们展示该地区对各种气候的反应，为预测大盆地的未来变化提供了关键的起点。在过去的30,000年中，美国西部内部大盆地的降水量和蒸发之间的平衡发生了巨大变化，使当今的葡萄湖时期存在于当今的葡萄湖时期。该地区的水利用性在很大程度上取决于冬季风暴轨道带来的降水，这表明过去的水文变化记录为在不同气候状态下风暴轨迹的行为提供了重要的见解。然而，目前记录的约会精度和样本分辨率有限，但是，我们只给我们带来了过去的水文变化的一般感，目前没有良好的记录扩展到过去的冰川间温暖的时期。该项目将使用洞穴沉积物来重建过去的水平水平的北部北部邦纳维尔盆地的水平变化，这是大流域最大的古代古代古代古代的大型古代。这些沉积物记录了过去30万年的盆地降水变化，并能够精确过时，为我们提供了构建该地区过去气候变化的详细和扩展图片的机会。重要的是，从盆地西部边缘的雷曼洞穴（Lehman Cave）记录了最后两个冰川间温暖时期，这使我们有机会研究该地区水文学的平均状态和可变性，当时该地区的温暖或比目前的温​​度较高或稍温暖。这项工作代表了我们对过去气候变化的理解的重要贡献，并将有助于校准寻求重现过去变化以更好地预测未来的模型。此外，这些记录将有助于我们解释盆地的过去生态变化以及该地区早期人类职业的历史。