Collaborative Research: Continuation and Termination of Karakorum and Karakax Faults in Western Tibet: Implications for the Role of Regional Strike-slip Faults in Orogenic Belts

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。大型走滑断层在喜马拉雅-青藏造山带演化中的作用是一个持续争论的话题，其中相当大的焦点是阿尔金和喀喇昆仑断层系统。关于这些断裂在造山带中的重要性和作用，出现了两种主要的模式，它们预测这些断裂是：1）喜马拉雅-青藏造山带中的一级、长期特征，这些特征目前是活动的，过去曾相互作用，以适应陆壳的侧向挤压;或2）具有复杂历史的二阶特征，其本质上可能是瞬时的并且可能没有相互作用。由于缺乏喀喇昆仑和阿尔金断裂系统西北部和西部的数据，区分这些模型一直很困难。在帕米尔山脉东南部，这些断层位于山谷内，彼此相距不到50公里，保存了许多代新近纪至第四纪的表层沉积物。这个合作研究项目是由美国，加拿大和中国的科学家和学生是：1）通过详细的基岩地质和表层沉积物的野外测绘、景观分析以及通过陆地宇宙成因核素表面暴露和第四纪冰碛、河流阶地和黄土沉积物的光释光测年确定活动变形速率，确定两条断层的第四纪滑动历史，以及2）通过对两个断层以及当前识别的断层链之间的区域的详细结构映射来研究两个断层系统之间的可能的相互作用。这项研究将提供新的信息，以解决有关的作用，演化和大型走滑断层在大陆碰撞带的相互作用的问题。地质学界普遍存在的一个问题是大型走滑断层在大陆碰撞带中的作用。这个问题是特别感兴趣的关于喜马拉雅-西藏地区，世界？中国大陆最大的活动大陆碰撞带，它有几条长度超过1000公里的走滑断层。两个相互竞争的一般假设是，这些断层要么1）在碰撞带的演变中发挥重要的长期作用，容纳数百公里的位移，并相互作用，使地壳横向运动，使印度相对于亚洲向北移动，或2）是容纳相对少量的位移（大约100-150公里）的瞬态特征，它们彼此不相互作用。本文以印度-亚洲碰撞带最大的走滑断裂--帕米尔东南部的阿尔金断裂和喀喇昆仑断裂为研究对象，评价它们的近期活动性、在碰撞带中的作用以及它们之间是否存在或正在相互作用。阿尔金断裂和喀喇昆仑断裂是大陆碰撞带大型走滑断裂的典型代表，其研究成果将为认识这些构造的作用和演化提供重要的新信息。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The role of large strike-slip faults in the evolution of the Himalayan-Tibetan orogen is a topic of continued debate, with considerable focus on the Altyn Tagh and Karakorum fault systems. Two primary families of models have emerged regarding the importance and role of these faults in the orogen that predict that these faults are either: 1) first order, long lived features in the Himalayan-Tibetan orogen that are currently active and have interacted in the past to accommodate lateral extrusion of continental crust; or 2) second order features with complicated histories that may be transient in nature and may not have interacted. Differentiating these models has been difficult due to the lack of data from the northwestern and western portions of the Karakorum and Altyn Tagh fault systems, respectively. In the southeast Pamir Mountains these faults lie within 50 kilometers of each other within valleys that preserve numerous generations of Neogene to Quaternary surficial deposits. This collaborative research project between U.S., Canadian, and Chinese scientists and students is: 1) determining the Quaternary slip histories of the two faults through detailed field mapping of the bedrock geology and surficial deposits, landscape analysis, and determination of rates of active deformation through terrestrial cosmogenic nuclide surface exposure and optically stimulated luminescence dating of Quaternary glacial moraine, fluvial terrace, and loess deposits, and 2) investigating possible interactions between the two fault systems though detailed structural mapping of the two faults as well as the region between the currently identified fault strands. This research will provide new information to address questions regarding the role, evolution, and interaction of large strike-slip faults in continental collision zones. A general question within the geologic community is the role of large strike-slip faults in continental collision zones. This question is of particular interest in regards to the Himalayan-Tibetan region, the world?s largest active continental collision zone, which has several strike-slip faults over 1000 km in length. Two competing general hypotheses are that these faults either 1) play a significant long-term role in the evolution of the collision zone accommodating hundreds of kilometers of displacement and interacting to allow lateral motion of crust out of the way of India as it moves northward relative to Asia, or 2) are transient features accommodating relatively small amounts of displacement (approximately 100-150 kilometers) that do not interact with each other. This study of the largest strike-slip faults in the India-Asia collision zone, the Altyn Tagh and Karakorum faults in the southeast Pamir Mountains, will evaluate the recent activity of these faults, the role of they have played in the collision zone, and whether they have or are interacting with each other. As the Altyn Tagh and Karakorum faults are type examples of large strike-slip faults in continental collision zones, the results from this study will provide important new information on the role and evolution of these structures.