Extensional Fault Systems in the Ama Drime Range, Southern Tibet

近年来对喜藏造山系的研究主要集中在季风气候对其发育的影响上。在一个有争议的假设中，侵略性的季风降水目前吸引了从青藏高原下面向南流动的中间地壳通道到喜马拉雅造山带。在这个项目中，亚利桑那州立大学的一个研究小组与中国科学院的科学家合作，正在测试一个最近活跃的拆离在青藏高原南部边缘的预测，在西藏南部阿玛原山中新世藏南断层系统的大致位置。这一横向范围具有变质核杂岩的整体形式，并在东部和西部受到正断层系统的束缚，这些正断层系统直接进入先前绘制的藏南断层系统链。该团队正在绘制这些断层系统之间的关键交叉点，这些断层系统在喜马拉雅雨影的高海拔地区引人注目地暴露出来。利用构造地质学、构造地形学、低温热年代学、宇宙成因核素定年等技术，建立了阿玛原岩晚新生代的发掘历史，并与阿玛原岩东西向藏南断裂下盘的发掘历史进行了比较。这些结果将用于评估第四纪河道挤压的情况，或者对其进行证伪，或者建立与挤压河道上限结构相关的变形的结构和地貌后果。河道流的概念是构造学领域中一个新的、有争议的概念。这表明气候和构造之间存在强烈的耦合。河道流动挤压假说的原始版本认为，早中新世至中中新世的河道南向挤压是由两个北倾构造（中央主逆冲构造和藏南断裂体系）的滑动所调节的。这项研究探讨了季风引起的河道流动至今仍在继续的观点。这项工作的结果将成为正在进行的关于喜马拉雅地区变形风格、侵蚀程度和构造耦合的辩论的核心。

Recent research on the Himalayan-Tibetan orogenic system has focused on the role of monsoon climate in its development. In one controversial hypothesis, aggressive monsoon precipitation currently attracts the southward flow of a channel of middle crust from beneath the Tibetan Plateau to the Himalayan orogenic front. In this project, an Arizona State University research team, in collaboration with scientists from the Chinese Academy of Sciences, is testing the prediction that a recently active detachment occurs along the southern edge of the Tibetan Plateau at the approximate position of the Miocene South Tibetan fault system in the Ama Drime Range of southern Tibet. This transverse range has the overall form of a metamorphic core complex and is bound on the east and west by normal fault systems that strike directly into previously mapped strands of the South Tibetan fault system. The team is mapping critical intersections among these fault systems that are spectacularly exposed in this high-elevation region within the Himalayan rain shadow. They are also using the techniques of structural geology, tectonic geomorphology, low-temperature thermochronology, and cosmogenic nuclide dating to establish the late Cenozoic exhumation history of the Ama Drime massif and compare it with the exhumation history of the South Tibetan fault footwall east and west of the massif. These results will be used to evaluate the case for Quaternary channel extrusion and either falsify it or establish the structural and geomorphic consequences of deformation related to the upper bounding structure of the extruding channel.The concept of channel flow is a new and controversial idea in the field of tectonics. It suggests a strong coupling between climate and tectonics. The original version of the channel flow-extrusion hypothesis envisioned that Early-Middle Miocene southward extrusion of the channel was accommodated by slip on two north-dipping structures: the Main Central thrust and the South Tibetan fault systems. This study explores that idea that monsoon-induced channel flow continues today. The results of this work will be central to the ongoing debate over the style of deformation and the degree of erosion and tectonics coupling in the Himalaya.