Oligocene-Early Miocene topographic relief generation of southeasternTibet triggered by thrusting
Kai Cao 1, 2*, Wang G. C. 1, 2, Leloup P.H. 3, Mahéo G. 3, Xu Y. D. 4, 5, van der Beek P.A. 6, Replumaz A. 6, Zhang K. X. 4
1 School of Earth Sciences, Center for Global Tectonics, China University of Geosciences,Wuhan 430074, China
2 State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China
3 Laboratoire de Géologie de Lyon: Terre, Planètes et Environnement, Université Claude Bernard, 2 rue Dapha?l Dubois, Villeurbanne 69622, France
4 School of Earth Sciences, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China
5 Key Laboratory of Sedimentary Basin and Oil and Gas Resources, Ministry of Natural Resources, Chengdu 610081, China
6 Institut des Sciences de la Terre (ISTerre), Université Grenoble Alpes, CNRS, CS 40700, Grenoble 38058, France
Abstract:
The timing and mechanisms of
uplift in southeastern Tibet remain disputed. To address this debate, we conducted structural and morphological analyses
of the Yulong thrust-belt; we also reconstruct the cooling
and exhumation history of the Jianchuan basin in the hanging wall of the thrust system using inverse thermal modeling of
apatite fission-track and (U-Th)/He thermochronology
data. Our results provide evidence for 2.3-3.2 km of rapid exhumation in the Jianchuan basin between ~28 and ~20 Ma,
followed by limited exhumation of less than 0.2 km
since then. The magnitude of basin exhumation is consistent with the present-day topographic step of 1.8-2.4 km across
the Yulong and Chenghai thrust belts, as shown by
morphometric analysis. We thus infer that the present-day morphology of the southeastern margin of Tibet results partly from
thrusting along the Yulong thrust belt during
the Late Oligocene-Early Miocene. This structure may be the southwest
continuation of the Longmen Shan thrust
belt, offset by the Xianshuihe fault in the Late Miocene. On a regional scale, the approximate synchronicity of exhumation
in the hanging walls of the Yalong-Yulong and Longmen Shan
thrust systems indicates that widespread crustal shortening and thickening took place in southeastern Tibet
during the Late Oligocene-Early Miocene.