Differential growth of the northern Tibetan margin: evidence for oblique stepwise rise of the Tibetan Plateau

Fei Wang,Liekun Yang,Yinzhi Wang,Wenbei Shi,Lin Wu,Weibin Zhang,Rixiang Zhu

doi:10.1038/srep41164

Abstract

Models of how high elevations formed across Tibet predict: (a) the continuous thickening of a “viscous sheet”; (b) time-dependent, oblique stepwise growth; and (c) synchronous deformation across Tibet that accompanied collision. Our new observations may shed light on this issue. Here, we use 40Ar/39Ar and (U-Th)/He thermochronology from massifs in the hanging walls of thrust structures along the Kunlun Belt, the first-order orogenic range at the northern Tibetan margin, to elucidate the exhumation history. The results show that these massifs, and hence the plateau margin, were subject to slow, steady exhumation during the Early Cenozoic, followed by a pulse of accelerated exhumation during 40–35 Ma. The exhumation rate increases westward (from ~0.22 to 0.34 and 0.5 mm/yr). The two-fold increase in exhumation in the western part (0.5 mm/yr) compared to the eastern part suggests westward increases in exhumation and compressional stress along the Kunlun Belt. We relate these observations to the mechanisms responsible for the oblique stepwise rise of Tibet. After collision, oblique subduction beneath Kunlun caused stronger compressional deformation in the western part than in the eastern part, resulting in differential growth and lateral extrusion.

Highlights

Cenozoic terrains along the northern margin of the Tibetan Plateau are considered to be the consequence of the far-field effects of continued Eurasia–India convergence[2] and can be regarded as ideal locations to test the growth models
Low temperature geochronological studies are lacking, and existing constraints on the exhumation and cooling history of the western part of the Kunlun Belt are very poor. It is the first-order orogenic belt of the northern Tibetan margin and has great potential to reveal the evolution of the plateau, systematic research and direct evidence of the couplings between tectonics and surface processes are still lacking, and the modes of uplift and exhumation needs to be better quantitatively constrained
We present results using the K-feldspar 40Ar/39Ar and apatite (U-Th)/He thermochronological systems in Figs 3 and 4 and Supplementary Tables S3 and S4, respectively

Summary

OPEN Differential growth of the northern

Tibetan margin: evidence for oblique stepwise rise of the Tibetan received: 16 September 2016 accepted: 14 December 2016. The onset time of growth is still elusive, most studies suggest that the thickened crust and high topography in central Tibet and its northern margin were built up by 40–50 Ma4–12 (Fig. 1), which is close to the commonly suggested collision time of ~47–55 Ma2,13–15 These data appear to contradict the notion of initiation and propagation of strain away from the collision boundary. Low temperature geochronological studies are lacking, and existing constraints on the exhumation and cooling history of the western part of the Kunlun Belt are very poor It is the first-order orogenic belt of the northern Tibetan margin and has great potential to reveal the evolution of the plateau, systematic research and direct evidence of the couplings between tectonics and surface processes are still lacking, and the modes of uplift and exhumation needs to be better quantitatively constrained. The exhumation history of the range provides an important constraint on the manner of mountain-building along the northern Tibetan margin and can potentially inform models of the growth of the plateau

Results

Mean age Included replicate Excluded replicate

Methods

Author Contributions

Additional Information