Collaborative Research: Recovering Surface Uplift Histories and Climate Dynamics of the Cenozoic N. American Cordillera through Integrated Climate Modeling and Isotopic Studies

合作研究：通过综合气候模拟和同位素研究恢复新生代北美洲科迪勒拉的地表隆升历史和气候动态

• 批准号: 1019420
• 负责人: Christopher Poulsen
• 金额: $ 29.43万
• 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: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1019420&HistoricalAwards=false
• 关键词: Collaborative; Research; Recovering; Surface; Uplift

Previous studies of stable isotopic paleoclimate proxies found in intermontane basins and adjacent metamorphic core complexes suggest that the topography of western North America developed diachronously, obtaining high elevations first in British Columbia at about 50 million years ago and sweeping into Nevada by about 40 million years ago. The stable isotopic studies show that there are rapid and large isotopic shifts that cannot be due to surface uplift alone and call for climatic controls. This research aims to test the hypothesis that relief development and possibly regional scale surface elevation (driven by tectonics) attained threshold values that caused rapid climate and precipitation shifts by actively interfering with atmospheric vapor transport and/or stability. To test this hypothesis, the research team is using a multi-disciplinary approach that involves: (1) collection of stable isotopic data from intermontane basins over discreet time intervals and over a wide geographic area so as to compare with isotope results from climate models; (2) measurement of cooling ages of detrital minerals in an effort to constrain relief and mountain building development within the basin catchments; (3) detailed sedimetological and high-resolution geochronologic studies in basins in order to place the detrital thermochronology and stable isotopic analyses in proper geologic context; and (4) simulation of climate conditions and isotopes of precipitation under different topographic/elevational scenarios using global and regional climate models as a way to interpret the observed stable isotope signals. The goal is to discriminate between two markedly contrasting tectonic models both of which are consistent with current data sets. One calls for the construction of dynamic topography from a moderate elevation low-relief landscape to a north-to-south swell of a high elevation landscape in the Eocene to Oligocene. The other is the north-to-south collapse of a low-relief, high elevation so-called Nevadaplano into region of similar to lower mean elevation but with significantly higher-relief.This proposal addresses a fundamental problem in paleoclimate analysis ? the cause for rapid climatic shifts. It has been proposed that with increased global warming the Earth may undergo rapid reorganization of climate regimes once critical thresholds are reached. Identifying these rapid climate changes during times when the Earth was significantly warmer and had higher concentrations of carbon dioxide is essential for our understanding of how the Earth?s climate behaves during warming episodes. The research team has identified areas in the American West through stable isotope analysis that record rapid climatic shifts when the Earth was significantly warmer (50 to 40 million years ago). What causes these climatic shifts is unknown, however. By combining global climate models with isotope paleo-precipitation measurements it is possible to assess what may have caused these rapid climate shifts. Specifically, the project will test whether they represent regional responses to the rise of mountains or large-scale reorganization of climate.

先前对稳定的同位素古气候代理的研究在跨蒙托坦盆地和邻近的变质核心络合物中发现，西部北美的地形是直言不讳的，在不列颠哥伦比亚省首先在不列颠哥伦比亚省获得了高海拔，大约在5000万年前，在内华达州扫入了大约4000万年前。稳定的同位素研究表明，存在快速和大的同位素移位，不能仅仅是由于表面隆升而引起的，并要求进行气候控制。这项研究旨在检验以下假设：浮雕发展及可能的区域尺度表面升高（由构造驱动）达到阈值值，从而通过积极干扰大气蒸气运输和/或稳定性来导致气候快速和降水转移。为了检验这一假设，研究团队正在使用一种涉及的多学科方法，该方法涉及：（1）从谨慎的时间间隔和广泛的地理区域中收集稳定的同位素数据，以与气候模型相比，以便与同位素进行比较； （2）测量碎屑矿物质的冷却年龄，以限制盆地集水区内的浮雕和山区建筑发展； （3）盆地中详细的静态学和高分辨率的年代学研究，以便将碎屑热量和稳定的同位素分析置于适当的地质环境中； （4）使用全球和区域气候模型在不同的地形/高程场景下模拟气候条件和降水同位素，以解释观察到的稳定同位素信号。目的是区分两个显着对比的构造模型，这两种模型都与当前数据集一致。有人要求建造动态地形，从中等高度低浮雕的景观到始新世至渐新世的高海拔景观的北到南隆起。另一个是低浮雕，高海拔高海拔所谓的内瓦达普拉诺（Nevadaplano）的北到南崩溃，与较低的平均海拔相似，但浮雕明显更高。该提案解决了古气候分析中的基本问题？快速气候变化的原因。有人提出，随着全球变暖，一旦达到临界阈值，地球可能会经历气候政权的快速重组。在地球明显变暖并且二氧化碳浓度更高的时候，确定这些快速的气候变化对于我们了解地球气候在变暖发作期间的行为至关重要。研究小组通过稳定的同位素分析确定了美国西部地区的区域，这些区域在地球明显变暖时（50到4000万年前）记录了迅速的气候变化。但是，导致这些气候变化的原因尚不清楚。通过将全球气候模型与同位素古凝度测量相结合，可以评估可能导致这些快速气候变化的原因。具体而言，该项目将测试它们是代表对山脉兴起还是气候大规模重组的区域反应。