Oligocene-early Miocene rapid exhumation along the Xianshuihe fault system: Implications for the growth of the Southeastern Tibetan Plateau

Abstract

• 24 new thermochronometric ages from the bend section of the Xianshuihe fault system are reported. • New data indicate migration of the locus of fast exhumation towards the fault zone from ∼25 to ∼10 Ma. • Oligocene-early Miocene fast exhumation along the fault system resulted from crustal shortening. • southeastern Tibetan Plateau; Xianshuihe fault; low-temperature thermochronology; • Oligocene-Early Miocene; rapid exhumation; Plateau growt. Large-scale strike-slip faults in the southeastern Tibetan Plateau are considered to have accommodated significant crustal extrusion and deformation during the plateau growth. However, the long-term deformation and exhumation history along the large-scale strike-slip faults is still unclear. Here, we present new thermochronological datasets from the near-field of the bend section of the Xianshuihe fault system, they reveal migration of the loci which show rapid exhumation between ∼25 Ma and ∼10 Ma towards the fault zone. Our new results clearly show a phase of rapid Oligocene-early Miocene basement exhumation, indicating contemporaneous crustal shortening along the fault. Through synthesizing the evidence of Oligocene-early Miocene fast exhumation along the Xianshuihe fault system, and synchronous deformation along adjacent strike-slip and thrust faults in the region, we propose that the southeastern Tibetan Plateau may have reached a remarkable high-elevation topography during this period. This was accompanied by significant crustal shortening under a contractional regime, with northeastward advance of the eastern Himalayan syntaxis and southeastward crustal extrusion originated from the plateau hinterland. Our findings are generally in agreement with sedimentary records in the marginal sea basins and paleo-altimetry studies.