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

Louisiana State University, Baton Rouge LA

Investigators

Abstract

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.