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.

马萨诸塞州理工学院（MIT）的研究人员正在研究秘鲁南部的西方科迪勒拉山脉的隆起历史，该山脉标志着安第斯山脉中部阿尔蒂普拉诺高原的西部边界。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，这两个河流系统通过被认为是西半球最深的两个峡谷横切山脉，每个峡谷的总地形超过3200米。虽然河流下切是一个不完美的岩石隆起的代理，在构造活动期间的主要河流系统的行为是一个敏感的指示器相对于海平面的表面隆起。无论是否满足稳态条件，这都是正确的。这些水系的地质和地理提供了四种独立的方法来估计河流下切的历史和模式。这种情况提供了一个非常好的机会来开发一个详细的图像的切口历史的科尔卡和科塔瓦西河系统，麻省理工学院的研究人员正在使用它来推断的隆起演变的西部边缘的高原，并测试隐含的假设在标准的应用程序的四种方法。 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）切割花岗岩岩体的热年代学研究; 2）基于保存的火山流遗迹重建古代陆地表面; 3）使用基岩斯特拉特阶地测量河流切割的时间积分速率;（4）恢复冲积充填阶地和火山充填残体中记录的河谷加积和随后的再开挖历史。从这些研究中收集到的关于科尔卡河和科塔瓦西河流域的切割历史的信息对于评估安第斯山脉的生长和隆起的当前模型以及更好地为未来模型提供信息至关重要。