Mid-Miocene initiation of exhumation in the Mangkang area, eastern Tibet: constraints from (U-Th)/He thermochronology
Abstract
The edges of the Tibetan Plateau are characterized by extremely steep topographic fronts, such as the Himalayan arc to the south, the Altyn Tagh to the north, and the Longmen Shan to the east. However, the northeastern and southeastern plateau margins are prominent exceptions, which are characterized by diffuse and low-gradient topography, and no obvious topographic boundaries are present. Knowledge of the timing of initiation of rapid exhumation in the southeastern margin of the Tibetan Plateau is essential to test or formulate new models for how plateau edges evolve. As the initiation age of accelerated river incision can be used as a proxy for the timing of surface uplift, we selected the Mangkang area in the eastern margin of the Tibetan Plateau to perform apatite (U-Th)/He analyses to further constrain the age of the onset of exhumation in the Mangkang area. The Mangkang area is in the northern segment of the Jinsha-Red River Shear zone, where the Mekong River dissects the southeastern margin of the Tibetan Plateau and forms numerous steep river gorges. New (U-Th)/He analyses on apatites from granodiorites and diorites from the Mangkang transect indicate that rapid river incision began at or prior to ca. 20 Ma. Our new result from this area is not consistent with the inferences from the lower crust flow model.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.T51D2371Y
- Keywords:
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- 1115 GEOCHRONOLOGY / Radioisotope geochronology;
- 8002 STRUCTURAL GEOLOGY / Continental neotectonics;
- 8104 TECTONOPHYSICS / Continental margins: convergent;
- 8175 TECTONOPHYSICS / Tectonics and landscape evolution