ABSTRACT

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.

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