Collaborative Research: Cenozoic Tectonics and Surface Uplift in North-Central Tibet

合作研究：西藏中北部新生代构造与地表隆起

• 批准号: 0633891
• 负责人: Xixi Zhao
• 金额: $ 38.31万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-01 至 2011-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0633891&HistoricalAwards=false
• 关键词: Collaborative; Research; Cenozoic; Tectonics; Surface

The collision between India and Asia has forcefully raised the Tibetan plateau, the most extensive region of elevated topography and thick crust on the Earth's surface. The uplift of the plateau may also have played a major role in controlling global climate during Cenozic time. Understanding the uplift history of the Tibetan plateau is one of the main challenges in earth sciences today. Despite more than three decades of active research, there is little consensus regarding the timing of plateau uplift and the tectonic processes by which the plateau was raised. In this collaborative study, researchers from the University of California at Santa Cruz and Indiana University are carrying out an integrated research program combining paleomagnetism (magnetostratigraphy and tectonics), sedimentology (facies descriptions, and paleocurrent and provenance studies), isotopoic dating, and paleoaltimetry (basalt vesicularity and oxygen isotopes) in a series of three latitudinally spaced basins in North-Central Tibet. The primary goals are to reconstruct the Paleogene tectonic history of north central Tibet, assess the relative contribution of upper crustal processes to plateau growth and maintenance, and assess the relative roles of tectonic models that predict early (e.g., approximately 40 million years ago) gradual uplift and those that predict more recent (less than 15 million years ago) abrupt uplift. To achieve these goals, lithostratigraphy and depositional environments in each basin are being compared using standard basin-analysis techniques to characterize the tectonic setting of sedimentation. The detailed new magnetostratigraphic results and radiometric dates will clarify the age of and correlation between these basins. The new paleomagnetic results will also provide pole positions and paleolatitudes to constrain the calculation for the Indo-Asian convergence rate and the amount and timing of tectonic rotation between tectonic blocks in the region. Times series of oxygen isotopes from these basins will provide quantitative information on their topographic development and climatic history. Comparison with vesicularity paleoaltimetry of the lavas may provide an independent check on elevation and remove ambiguity as to whether low oxygen-isotope values signal high paleoelevation of the basins themselves or of regions downwind along the vapor transport path. This research will improve understanding of the tectonic processes of intracontinental deformation related to the India-Asia collision. A definitive uplift history of northern Tibet is important for understanding climate change during Cenozoic time and will place fundamental constraints on the mechanism(s) of plateau formation, which interests a broad scientific community. This project forms the basis for two graduate students' PhD studies, and parts of the project are suitable for undergraduate research theses.

印度和亚洲之间的碰撞有力地抬升了青藏高原，这是地球表面最广泛的高地地形和厚地壳区域。高原的隆起也可能在新生代控制全球气候方面发挥了重要作用。了解青藏高原的隆升历史是当今地球科学的主要挑战之一。尽管进行了三十多年的积极研究，但对于高原隆升的时间和高原隆起的构造过程仍没有达成共识。在这项合作研究中，来自加州大学圣克鲁斯分校和印第安纳大学的研究人员正在开展一项综合研究计划，结合古地磁学（磁地层学和构造学）、沉积学（相描述、古水流和物源研究）、同位素测年和古测温法。西藏中北部一系列三个纬度间隔盆地的玄武岩囊泡性和氧同位素）。主要目标是重建西藏中北部的古近纪构造历史，评估上地壳过程对高原生长和维持的相对贡献，并评估预测早期（例如大约4000万年前）逐渐形成的构造模型的相对作用。隆起和那些预测最近（不到 1500 万年前）突然隆起的预测。为了实现这些目标，正在使用标准盆地分析技术对每个盆地的岩石地层和沉积环境进行比较，以表征沉积的构造环境。详细的新磁性地层结果和辐射日期将阐明这些盆地的年龄和相互关系。新的古地磁结果还将提供极位置和古纬度，以约束印度-亚洲收敛速度以及该地区构造块之间构造旋转的数量和时间的计算。这些盆地的氧同位素时间序列将提供有关其地形发展和气候历史的定量信息。与熔岩的泡状古海拔测量进行比较可以提供对海拔的独立检查，并消除低氧同位素值是否表明盆地本身或沿着蒸汽输送路径的顺风区域的高古海拔的模糊性。这项研究将增进对与印度-亚洲碰撞有关的陆内变形构造过程的理解。明确的藏北隆升历史对于理解新生代时期的气候变化非常重要，并将对高原形成的机制产生根本性的限制，这引起了广大科学界的兴趣。该项目构成了两名研究生博士研究的基础，该项目的部分内容适合本科生研究论文。