Using organic biomarker paleohypsometry to reconstruct the punctuated uplift history of the Northern Tibetan Plateau

青藏高原长期以来一直是研究与大陆碰撞有关的极端地形的天然实验室。北方青藏高原是了解印度-亚洲碰撞如何在距离构造板块边界1,000公里的大陆内部产生高地形的关键地点。该项目将利用新发展的定量方法重建青藏高原北方过去地形的历史。该项目产生的数据将揭示青藏高原北方何时以及如何上升到现在的高度，并将有助于区分构造模型。该项目的主要影响包括：1。两名早期职业调查员的支持，2。培训研究生和本科生在现场和实验室分析，3。加强美国和加拿大机构之间的国家和国际合作，4.将分析技术纳入本科课程，以及5.社区外展活动，如指导未被充分代表的少数民族学生进行科学项目，提供演示和实地视频，并在当地特许学校检查地质标本。了解远离板块边界的造山高原是如何形成的，长期以来一直是大陆动力学中一个充满活力和争议的话题。高地形是地壳和地幔作用的表现形式，本项目旨在了解何种机制（俯冲、地幔动力学、背驮式盆地充填或地壳流动）控制着青藏高原北缘高地形的形成，以及它对印度-亚洲碰撞的影响。该项目将检验一个假设，即青藏高原北方的高地形是在1500万至800万年前的向外扩张过程中形成的。项目研究人员将首先开发一种综合方法，将沉积地质学、有机地球化学和地貌学的技术结合起来。研究人员将用祁连山地区三个选定河流集水区的全新世沉积物测试这种方法，并使用有机地球化学指标，即，陆地高等植物叶蜡中正构烷烃的氢同位素和土壤中微生物甘油四醚的分布，以校准代用指标与河流集水区高程分布之间的关系（高程测量）。研究人员将校准的代用指标应用于河西走廊前陆盆地和柴达木盆地山间的沉积岩，以限制两个盆地之间祁连山山脉的海拔历史。这种方法将在美国西部造山带、安第斯山脉和青藏高原其他地区的类似气候条件下得到广泛应用。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Tibetan Plateau has long served as a natural laboratory for the study of extreme topography related to continent-continent collisions. The northern Tibetan Plateau is a key location for understanding how the India-Asia collision produced high topography in the continental interior 1,000 km away from the tectonic plate boundary. This project will reconstruct the history of past topographies of the northern Tibetan Plateau by using a newly developed quantitative approach. Data generated from this project will reveal when and how the northern Tibetan Plateau was uplifted to the present elevation and will help to differentiate between tectonic models. Broader impacts of this project include: 1. support of two early-career investigators, 2. training of graduate and undergraduate students in field and laboratory analyses, 3. enhancement of national and international collaborations between institutions in the United States and Canada, 4. incorporation of analytical techniques into undergraduate courses, and 5. community outreach events, such as mentoring underrepresented minority students with science projects, delivering presentations and field-based videos, and examining geology specimens at local charter schools.Understanding how an orogenic plateau formed far away from a plate boundary has long been a dynamic and controversial topic in continental dynamics. High topography is the manifestation of crustal and mantle processes, and this project aims at understanding which mechanism (underthrusting, mantle dynamics, infilling of ‘piggy-back’ basins, or crustal flow) controls the construction of high topography at the north margin of the Tibetan Plateau and what implications it bears for the India-Asia collision. The project will test the hypothesis that high topography in northern Tibetan Plateau has been constructed during a pulse of outward expansion from 15 to 8 million years ago. The project investigators will first develop an integrated approach that combines techniques in sedimentary geology, organic geochemistry, and geomorphology. The investigators will test the approach with Holocene sediments from three selected river catchments within the Qilian Shan region and use organic geochemistry proxies, i.e., hydrogen isotopes of n-alkanes derived from terrestrial higher-plant leaf waxes and distribution of microbial glycerol tetraethers produced in soils, to calibrate the relationships between proxies and the elevation distributions of river catchments (hypsometry). The investigators will apply the calibrated proxies to well-dated sedimentary rocks in the foreland basin of Hexi Corridor and the intermontane Qaidam Basin to constrain the elevational history of the Qilian Shan range between the two basins. This approach will be of broad use in similar climatic regimes in orogenic belts in the western United States, the Andes, and other parts of the Tibetan Plateau.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.