EAGER: Cosmogenic Nuclide Measurement of Surface Uplift Rate and Paleoelevation

EAGER：表面抬升率和古海拔的宇宙成因核素测量

• 批准号: 1463709
• 负责人: Gregory Hoke
• 金额: $ 14.71万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-01-15 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1463709&HistoricalAwards=false
• 关键词: EAGER; Cosmogenic; Nuclide; Measurement; Surface

Understanding the tectonic forces that drive uplift of large continental plateaus and mountain belts depends on measurement of how fast the surfaces in those physiographic domains have been uplifted and, consequently, how surface elevation has changed with time. Different models of uplift predict different rates or past elevations. Various methods have been used to measure uplift rates and paleoelevation to varying success and with varying degrees of uncertainty. In this project, the research team aims to test a new and novel technique that has the potential to reduce these uncertainties, which could potentially better constrain the understanding of the fundamental forces operating within the Earth that generate these major features. The method relies on precise measurement of cosmogenic nuclides, which are produced in minerals during exposure to cosmic rays. This exploratory project relies on the dependence of cosmogenic nuclide production on elevation to determine uplift rates and paleoelevation in a test on samples from a well-constrained field setting in South America. The engagement of a post-doctoral fellow in the project promotes development of the STEM workforce.This exploratory project develops of a new measure of surface uplift rate using terrestrial cosmogenic nuclides (TCN). Because the method measures uplift rate over a defined timescale, it also yields paleoelevation. The method exploits the well-established dependence of TCN production rates on elevation. The premise is that a stable surface will always have a higher TCN concentration than an otherwise identical surface that has been recently uplifted to the same elevation. Uplifting surfaces exhibit this deficit because most TCN production occurred at a lower elevation - and therefore lower production rate. The size of the deficit depends on the uplift rate and duration of production. The method solves for both erosion rate and surface uplift rate simultaneously over a defined time interval by using multiple samples and multiple isotope pairs, along with independent surface age constraints, in order to gain precision. In order to assess the precision and applicability of this technique, the research team will sample and measure TCN concentrations (21Ne, 10Be, and 26Al) for Miocene to Pliocene ignimbrites of the Atacama Desert (Chile and Peru), where independently determined surface uplift data are available to verify TCN results. The goal is to understand (1) how the method performs at a range of uplift rates; (2) how increasing the number of samples may reduce uncertainty; and (3) whether the approach is internally consistent over different timescales and using different isotope pairs. The research would enhance post-doctoral training thus contributing to the development of a globally competitive STEM workforce and involve the significant international collaboration with the GeoForschungsZentrum in Potsdam, Germany. A successful outcome will be a new novel paleoaltimetry tool that will be widely applicable over much or the Earth?s surface and will transform the ability to determine paleoelevation and surface uplift rates in active orogens or areas experiencing uplift due to dynamic topography or glacial isostatic adjustment.

了解驱动大陆高原和山脉带隆升的构造力取决于测量这些地文域中地表隆升的速度，以及地表高程如何随时间变化。不同的隆起模型预测不同的速率或过去的海拔。已经使用了各种方法来测量抬升速率和古高程，以获得不同的成功，并具有不同程度的不确定性。在这个项目中，研究小组的目标是测试一种新的和新颖的技术，有可能减少这些不确定性，这可能会更好地限制对地球内部产生这些主要特征的基本力量的理解。该方法依赖于对宇宙成因核素的精确测量，这些核素是在矿物暴露于宇宙射线时产生的。该勘探项目依赖于宇宙成因核素产量对海拔的依赖性，在对来自南美洲约束良好的野外环境的样本进行测试中确定隆升速率和古海拔。博士后研究员参与该项目促进了STEM劳动力的发展。该探索性项目开发了一种使用陆地宇宙成因核素（TCN）测量地表隆起率的新方法。由于该方法测量了在规定的时间尺度上的抬升速率，因此也产生了古高程。该方法利用了TCN生产率对海拔高度的既定依赖性。其前提是，稳定的表面总是比最近被抬升到相同高度的其他相同表面具有更高的TCN浓度。隆起表面表现出这种缺陷，因为大多数TCN生产发生在较低的海拔-因此生产率较低。亏损的大小取决于上升速率和生产持续时间。该方法通过使用多个样品和多个同位素对，沿着独立的表面年龄约束，在限定的时间间隔内同时求解侵蚀速率和表面抬升速率，以获得精度。为了评估该技术的精确度和适用性，研究团队将对阿塔卡马沙漠（智利和秘鲁）的中新世至上新世熔结凝灰岩进行采样和测量TCN浓度（21 Ne、10 Be和26 Al），其中独立确定的地表隆起数据可用于验证TCN结果。目的是了解（1）该方法如何在一系列抬升速率下执行;（2）增加样本数量如何降低不确定性;以及（3）该方法在不同时间尺度和使用不同同位素对时是否具有内部一致性。该研究将加强博士后培训，从而有助于发展具有全球竞争力的STEM劳动力，并涉及与德国波茨坦GeoForschungsZentrum的重大国际合作。一个成功的结果将是一个新的新颖的古测高工具，将广泛适用于大部分或地球？表面，并将改变确定活动造山带或因动态地形或冰川均衡调整而经历隆起的地区的古高程和表面隆起率的能力。