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: 1019648
• 负责人: C. Page Chamberlain
• 金额: $ 20.86万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1019648&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.

先前对山间盆地和邻近变质核复合体中发现的稳定同位素古气候代理的研究表明，北美西部的地形是历时发展的，大约5000万年前在不列颠哥伦比亚省首先出现高海拔，并在大约4000万年前席卷内华达州。稳定同位素研究表明，存在快速且大的同位素变化，这不能单独归因于地表隆起，需要气候控制。本研究旨在检验以下假设：地势发展和可能的区域尺度地表海拔（由构造驱动）达到阈值，通过主动干扰大气水汽输送和/或稳定性而导致气候和降水快速变化。为了验证这一假设，研究小组采用了多学科方法，其中包括：（1）在谨慎的时间间隔和广泛的地理区域内收集山间盆地的稳定同位素数据，以便与气候模型的同位素结果进行比较； （2）测量碎屑矿物的冷却年龄，以限制流域内的救济和造山活动； (3) 详细的盆地沉积学和高分辨率地质年代学研究，以便将碎屑热年代学和稳定同位素分析置于适当的地质背景中； (4) 使用全球和区域气候模型模拟不同地形/海拔情景下的气候条件和降水同位素，作为解释观测到的稳定同位素信号的方法。目标是区分两种截然不同的构造模型，这两种模型都与当前数据集一致。一种方法是建立动态地形，从始新世到渐新世的中等海拔低地势景观到从北到南隆起的高海拔景观。另一个是所谓的内华达普拉诺（Nevadaplano）的低地势高海拔地区从北向南塌陷到与较低平均海拔相似但地势明显更高的地区。该提议解决了古气候分析中的一个基本问题？气候快速变化的原因。有人提出，随着全球变暖的加剧，一旦达到临界阈值，地球可能会经历气候状况的快速重组。在地球明显变暖且二氧化碳浓度较高的时期识别这些快速的气候变化对于我们了解地球气候在变暖期间的表现至关重要。研究小组通过稳定同位素分析确定了美国西部的一些地区，这些地区记录了地球显着变暖时（50至4000万年前）的快速气候变化。然而，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降水测量相结合，可以评估导致这些快速气候变化的原因。具体来说，该项目将测试它们是否代表了对山脉上升或大规模气候重组的区域反应。