The Cenozoic Evolution of Crustal Shortening and Left-Lateral Shear in the Central East Kunlun Shan: Implications for the Uplift History of the Tibetan Plateau

Abstract

The timing of crustal shortening and strike-slip faulting along the East Kunlun Shan provides insight into the history of surface uplift and may constrain the time at which the Tibetan Plateau reached high elevations. We investigate a series of extensional basins and restraining bends along the Xidatan strand of the Kunlun strike-slip fault, which provide an ideal setting to unravel the tectonic history of the northern plateau margin. We present new apatite (U-Th)/He, apatite fission track, and zircon (U-Th)/He ages and QTQt thermal modeling, 40Ar/39Ar fault gouge dating, and structural mapping from the central East Kunlun Shan. Our data suggest that the East Kunlun Shan experienced slow to negligible exhumation until late Cretaceous time, followed by an increase in rate by 65–50 Ma. Along with a ~47 Ma fault gouge age, we posit that the Paleocene–early Eocene was a time of crustal shortening along the northern plateau. Rapid exhumation along transpressional portions of the Xidatan fault initiated by 23–20 Ma, which we interpret as the local onset of strike-slip faulting. An early Miocene transition from north-south crustal shortening to left-lateral shear along the East Kunlun Shan, the onset of normal and strike-slip faulting in central and southern Tibet by 18 Ma, and lower crustal flow in eastern Tibet by 13 Ma suggest the establishment of orogen-wide east-west oriented extension and extrusion by the middle Miocene. The plateau-wide shift in stress accommodation implies that high gravitational potential energy, and likely high elevation, was attained by the middle Miocene.