When did the Altiplano Form? A Coupled Thermochronometer and Numerical Model Test

高原何时形成？

• 批准号: 0409289
• 负责人: Todd Ehlers
• 金额: $ 29.89万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409289&HistoricalAwards=false
• 关键词: When; did; Altiplano; Form; Coupled

Understanding the timing, rates, and deformation associated with mountain belt plateau formation is central to quantifying relationships between plateaus, plate tectonics, and climate. Computer models of plateau development invoke variations in crustal temperatures and strength as the main mechanism of plateau formation. Strength variations are important because as tectonic processes shorten and thicken the crust the lower crust weakens and flows laterally, preferentially supporting plateau formation over a narrow mountain belt. However, tests of these computer models are hampered by a lack of knowledge about the kinematic history of plateau formation. This project is using rock cooling histories, field-constrained structural analysis, and computer models to delineate the tectonic evolution of the Bolivian fold and thrust belt to infer the formation process and surface uplift chronology of the Andean Plateau.Apatite fission track (AFT) and zircon (U-Th)/He (ZHe) ages are being collected and analyzed along two transects in the Bolivian fold and thrust belt to determine rock cooling histories. The AFT and ZHe data are being used to define the timing and rates of uplift along each sampling transect. Coupled two dimensional thermal, tectonic, and erosion computer models are being used to quantify the history of the Bolivian fold and thrust belt by predicting cooling ages and comparing them with the AFT and ZHe data. The coupled computer models aid in the interpretation of data through several steps: (1) the tectonic history of the thrust belt is prescribed using the 2DMove software, restored structural cross-sections, and geologic maps along both profiles, (2) the tectonic model then drives advective heat transfer in the thermal model and surface uplift in the erosion model, (3) for each tectonic and erosion history simulated across the fold and thrust belt the thermochronometer ages exposed at the surface are computed using apatite fission track annealing and zircon He diffusion algorithms. Model predicted and observed ages are compared with statistical methods to identify the range of permissible tectonic and erosion histories for Andean Plateau formation and surface uplift. The data and computer models are being integrated to quantify the timing, rate, and duration of motion on each thrust fault across each sampling transect. Combining the deformation and erosion history of all the faults across each transect will provide constraints on (1) the timing and history of Andean Plateau formation, and (2) temperature and strength dependent computer models of plateau formation.

了解与山地带高原形成相关的时间、速率和变形，对于量化高原、板块构造和气候之间的关系至关重要。高原发展的计算机模型将地壳温度和强度的变化作为高原形成的主要机制。强度变化很重要，因为随着构造过程缩短和挤压地壳，下地壳变弱并横向流动，优先支持高原形成而不是狭窄的山脉带。 然而，这些计算机模型的测试是阻碍了缺乏知识的高原形成的运动学历史。该项目使用岩石冷却历史，场约束结构分析，本文通过对玻利维亚褶皱冲断带的构造演化过程的研究，结合计算机模拟，探讨了安第斯高原的形成过程和地表隆升年代学。在玻利维亚褶皱和冲断带的两个断面上，正在收集和分析年龄，以确定岩石冷却的历史。AFT和ZHe数据用于定义沿着每个采样样带的抬升时间和速率。耦合二维热，构造和侵蚀计算机模型被用来量化的历史玻利维亚褶皱和冲断带预测冷却年龄和比较它们与AFT和ZHe数据。耦合的计算机模型通过以下几个步骤帮助解释数据：（1）使用2DMove软件、恢复的构造横截面和沿着两个剖面的地质图来描述冲断带的构造历史，（2）构造模型然后驱动热模型中的平流热传递和侵蚀模型中的表面隆起，（3）对褶皱冲断带各构造和剥蚀史，采用磷灰石裂变径迹退火法和锆石He扩散法计算出地表出露的热时年龄。模型预测和观察到的年龄进行了比较，统计方法，以确定安第斯高原形成和表面隆起的允许的构造和侵蚀历史的范围。数据和计算机模型正在整合，以量化每个采样样带上每个逆冲断层的运动时间、速率和持续时间。将每个断面上所有断层的变形和侵蚀历史结合起来，将对（1）安第斯高原形成的时间和历史以及（2）高原形成的温度和强度依赖的计算机模型提供约束。