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。青藏高原北部是了解印度-亚洲碰撞如何在远离构造板块边界1000公里的大陆内部产生高地形的关键位置。本项目将使用一种新开发的定量方法重建青藏高原北部过去的地形历史。该项目产生的数据将揭示青藏高原北部何时以及如何被抬升到现在的高度，并将有助于区分构造模型。本项目更广泛的影响包括：1。支持两名早期职业调查员，2。2 .对研究生和本科生进行实地和实验室分析方面的培训；3 .加强美国和加拿大机构之间的国内和国际合作；4 .将分析技术纳入本科课程；社区外展活动，例如用科学项目指导未被充分代表的少数民族学生，发表演讲和实地视频，以及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，一直是大陆动力学中一个动态的、有争议的话题。高地形是地壳和地幔过程的表现，本项目旨在了解青藏高原北缘高地形构造的控制机制（逆冲、地幔动力学、“背驮式”盆地填充或地壳流动）及其对印度-亚洲碰撞的影响。该项目将验证青藏高原北部的高地形是在1500万至800万年前向外扩张的脉冲中形成的假设。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技术结合起来。研究人员将对祁连山地区三个选定的河流流域的全新世沉积物进行测试，并使用有机地球化学代用物，即陆生高等植物叶蜡中正构烷烃的氢同位素和土壤中产生的微生物甘油四醚的分布，来校准代用物与河流流域海拔分布之间的关系（假设）。将标定后的代用物应用于河西走廊前陆盆地和柴达木山间盆地的定年沉积岩，以限定两盆地之间祁连山山脉的抬升史。这种方法将广泛应用于美国西部造山带、安第斯山脉和青藏高原其他地区类似的气候条件。该奖项反映了美国国家科学基金会的法定使命，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.