Uplift History of the Cordillera Occidental, Southern Peru, from Canyon Geomorphology

从峡谷地貌看秘鲁南部西科迪勒拉山脉的隆起历史

• 批准号: 0836203
• 负责人: Kip Hodges
• 金额: $ 2.17万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0836203&HistoricalAwards=false
• 关键词: Uplift; History; Cordillera; Occidental; Southern

Massachusetts Institute of Technology (MIT) researchers are studying the uplift history of the Cordillera Occidental of southern Peru, which marks the western boundary of the Altiplano plateau in the central Andes. Their approach is to study the spatial and temporal history of incision of two major river systems (the Colca and Cotahuasi river systems) that transect the range through what are regarded as the two deepest canyons in the Western Hemisphere, each with a total relief in excess of 3200 meters. Although river incision is an imperfect proxy for rock uplift, the behavior of major river systems during tectonic activity is a sensitive indicator of surface uplift relative to sea level. This is true regardless of whether or not steady-state conditions have been met. The geology and geography of these drainages provide four independent ways to estimate the history and pattern of river incision. This circumstance provides an extraordinary opportunity to develop a detailed image of the incision history of the Colca and Cotahuasi river systems, which the MIT researchers are using to deduce the uplift evolution of the western edge of the Altiplano, and to test the implicit assumptions in standard applications of each of the four methods. The MIT researchers are using a combination of the following four methods to decipher the history and pattern of river incision: 1) thermochronologic studies of incised granitic plutons; 2) reconstructions of ancient land surfaces based on preserved remnants of volcanic flows; 3) measurements of the time-integrated rate of river incision using bedrock strath terraces; and 4) reconstructions of the history of valley aggradation and subsequent re-excavation recorded in alluvial fill terraces and remnants of volcanic infills. The information being gleaned from these studies about the incision histories of the Colca and Cotahuasi river systems is essential for evaluating current models of the growth and uplift of the Andes, and for better informing future models.

麻省理工学院（MIT）的研究人员正在研究秘鲁南部西科迪勒拉（Cordillera Occidental）的隆起历史，它标志着安第斯山脉中部Altiplano高原的西部边界。他们的方法是研究两个主要河流系统（科尔卡河和科塔瓦西河系统）切割的时空历史，这两个河流系统穿过被认为是西半球最深的两个峡谷，每个峡谷的总起伏超过3200米。虽然河流切割是岩石隆升的一个不完美的代表，但构造活动期间主要河流系统的行为是相对于海平面的地表隆升的一个敏感指标。无论是否满足稳态条件，这都是正确的。这些流域的地质和地理提供了四种独立的方法来估计河流切割的历史和模式。这种情况为绘制科尔卡河和科塔瓦西河系统切割历史的详细图像提供了一个绝佳的机会，麻省理工学院的研究人员正利用这些图像来推断Altiplano西部边缘的隆起演化，并在四种方法的标准应用中测试隐含的假设。麻省理工学院的研究人员正在使用以下四种方法的组合来破译河流切割的历史和模式：1)切割的花岗岩岩体的热年代学研究；2)基于火山流遗迹的古陆面重建；3)基岩阶地河道切割时间积分速率测量；4)对冲积阶地和火山填充物残余物中山谷沉积历史的重建和随后的重新挖掘记录。从这些研究中收集到的关于科尔卡河和科塔瓦西河系统切割历史的信息，对于评估安第斯山脉生长和隆起的现有模型，以及更好地为未来的模型提供信息至关重要。