The Litang fault system that crosses the Litang Plateau, a low relief surface at high elevation
(~4200–4800m above sea level) that is not affected by regional incision, provides the opportunity to study
exhumation related to tectonics in the SE Tibetan Plateau independently of regional erosion. Combining
apatite and zircon fission track with apatite (U-Th)/He thermochronologic data, we constrain the cooling
history of the Litang fault system footwall along two transects. Apatite fission track ages range from 4 to
16 Ma, AHe ages from 2 to 6 Ma, and one zircon fission track age is ~99 Ma. These data imply a tectonic quiet
period sustained since at least 100 Ma with a slow denudation rate of ~0.03 km/Ma, interrupted at 7 to 5 Ma
by exhumation at a rate between 0.59 and 0.99 km/Ma. We relate that faster exhumation to the onset of
motion along the left-lateral/normal Litang fault system. That onset is linked to a Lower Miocene important
kinematic reorganization between the Xianshuihe and the Red River faults, with the eastward propagation
of the Xianshuihe fault along the Xiaojiang fault system and the formation of the Zhongdian fault. Such
strike-slip faults allow the sliding to the east of a wide continental block, with the Litang fault system
accommodating differential motion between rigid blocks. The regional evolution appears to be guided by
the strike-slip faults, with different phases of deformation, which appears more in agreement with an “hidden
plate-tectonic” model rather than with a “lower channel flow” model.
Tectonics, 2015, DOI: 10.1002/2014TC003671.
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Insigths from Tertiary deformation of SE Asia |