Timing and Kinematics of Cenozoic of E-W Extension in Central Tibet Transition in the Strain Field of the Tibetan Plateau

青藏高原应变场中藏中过渡新生代东西向伸展的时间和运动学

• 批准号: 0309976
• 负责人: Daniel Stockli
• 金额: $ 22.99万
• 依托单位: University of Kansas Center for Research Inc
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0309976&HistoricalAwards=false
• 关键词: Timing; Kinematics; Cenozoic; Extension; Central

0309976StockliCenozoic extension within the Tibetan Plateau is expressed as a series of prominentN-S trending rift valleys. Recent GPS studies show that these graben systems and associated conjugate strike-slip systems accommodate a significant portion of internal N-S shortening and E-W expansion of the Tibetan Plateau. The development of these structures represents a significant shift in deformational style and marks the transition to a constrictional strain field within the Tibetan crust. Determining the timing of the formation of these structures is a critical step in understanding the evolution of the plateau. In order to test existing hypotheses proposed to explain these N-S trending rifts and to understand the geodynamic significance of Cenozoic E-W extension in Tibet, the PI needs to answer two fundamental questions. (1) What is the timing of initiation and spatial distribution of E-W extension in Tibet? (2) What is the temporal and kinematic interplay between conjugate strike-slip deformation and E-W extension within central Tibet? A regionally synchronous versus diachronous onset of rifting or progressive migration versus discrete episodes of fault initiation have very different implications for the evolution of the intraplate strain field and the driving forces responsible for rift formation. Currently, the different geodynamic models for the Cenozoic evolution of Tibet are difficult to evaluate due to the lack of sufficient temporal constraints on the onset of rifting. The PI proposes to use an integrated approach, combining structural mapping with apatite (U-Th)/He and fission track dating, to elucidate the timing and magnitude of faulting associated with the Cenozoic strain pattern across central Tibet. Thermochronological methods directly dating the cooling of rocks in exhumed fault blocks will complement field-based kinematic analysis of the rift systems and should help resolve outstanding questions regarding the timing and geodynamic significance of the Tibetan rifts. This proposed study will have far-reaching implications for our understanding of how the lithosphere behaves during continent-continent collision. New data will yield insights into the fundamental problem of how and when Tibet extended after thickening, information that is critical for evaluating the many different tectonic models for this entire region. Furthermore, results will shed light on the hotly debated question of whether there is a temporal link between E-W extension and surface uplift of the Tibetan plateau. Given the implications of the uplift of the Tibetan plateau for regional and global climate, the PI expects his results to be of interest to a wide spectrum of geoscientists. This project also has substantial educational and societal merit. The proposed international collaboration with scientists from the Chinese Academy of Science will permit an exchange of scientific ideas and knowledge. This exchange will greatly benefit KU students, exposing them to the classic Himalayan-Tibetan orogenic system. Two KU graduate students will be deeply involved in several mapping expeditions and will work closely with scientists from UCLA and the Chinese Academy of Science.

确定这些构造形成的时间是了解高原演化的关键一步。裂谷的区域同步或跨时开始或渐进迁移与断层起始的离散事件对板内应变场的演化和裂谷形成的驱动力有着非常不同的含义。这项研究将对我们理解大陆与大陆碰撞时岩石圈的行为产生深远的影响。这个项目也有很大的教育和社会价值。拟议中的与中国科学院科学家的国际合作将允许科学思想和知识的交流。两名堪萨斯大学的研究生将深入参与几次测绘探险，并将与加州大学洛杉矶分校和中国科学院的科学家密切合作。