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》(Public Law 111-5)资助的。大型走滑断层在喜马拉雅-西藏造山带演化中的作用是一个持续争论的话题，主要集中在阿尔金·塔格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，已经出现了两个主要的模型家族，它们预测这些断裂是：1)喜马拉雅-西藏造山带中目前活跃的、过去曾相互作用以适应大陆地壳侧向挤压的一级、长期存在的特征；或2)具有复杂历史的二级特征，其性质可能是瞬变的，可能没有相互作用。由于缺乏分别来自喀喇昆仑和阿尔金·塔格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，这些断层位于山谷中，彼此相距不到50公里，这些山谷保存了数代新近系至第四纪的地表沉积。这项由美国、加拿大和中国的科学家和学生开展的合作研究项目是：1)通过对基岩地质和地表沉积物的详细野外填图、景观分析，以及通过陆地宇宙成因核素地表暴露和第四纪冰川冰川、河流阶地和黄土沉积的光激发发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；2)通过对两条断层以及目前已识别的断裂带之间的区域进行详细的构造填图，研究两条断层系统之间的可能相互作用。这项研究将提供新的信息来解决大陆碰撞带中大型走滑断层的作用、演化和相互作用的问题。地质界的一个普遍问题是大陆碰撞带中大型走滑断层的作用。这个问题对于喜马拉雅-藏区尤其令人感兴趣。喜马拉雅-藏区是世界上最大的活动大陆碰撞带？S，它有几条长达1000多公里的走滑断层。两个相互矛盾的普遍假设是，这些断层要么在碰撞带的演化中发挥重要的长期作用，容纳数百公里的位移，并相互作用，使地壳在相对于亚洲向北移动时偏离印度的方向；要么是瞬时特征，容纳相对较小的位移(约100-150公里)，彼此不相互作用。对印度-亚洲碰撞带最大的走滑断裂--帕米尔山脉东南部的阿尔金·塔格和喀喇昆仑断裂的研究，将评估这些断裂的近期活动，它们在碰撞带中所起的作用，以及它们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，这一研究成果将为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.