Studies in the tectonics of China: Extensional tectonics of the northern margin of the South China Sea; amalgamation and uplift of the Tian Shan; and wedge extrusion model for the Altyn Tagh Fault

Rift-onset ages for the south China margin obtained by construction of balanced cross-sections from seismic and well data indicate that rifting started at {dollar}approx{dollar}50, {dollar}approx{dollar}43-40, and {dollar}approx{dollar}50 Ma in the Beibu Gulf, QDN, and PRM basins, respectively, all younger than conventionally assigned. Extension/time curves indicate continuous rifting prior to sea-floor spreading from 32-15.5 Ma in the SCS. Seismic profiles demonstrate diachronous cessation of rifting, from {dollar}approx{dollar}30 Ma in the east to {dollar}approx{dollar}23 Ma in the west, which might be coupled with the beginning of the sea-floor spreading at 32 Ma in the east and 23 Ma in the west. Those relations support a new kinematic model which combines the mechanism of slab-pull, leading to {dollar}approx{dollar}1000 km of N-S extension, and extrusion of {dollar}{dollar}10 km).; Apatite fission-track data from the Chinese west Tian Shan indicate unroofing of {dollar}<{dollar}2 km during the Cenozoic except along the NTS fault zone where unroofing exceeded 3-4 km. Late Jurassic-Early Cretaceous unroofing was recorded in the south and north Tian Shan. Part of the Central Tian Shan retains late Paleozoic fission-track ages indicating {dollar}<{dollar}2 km of post-Paleozoic unroofing. The results support the existence of a Mesozoic ancestral Tian Shan.; A new wedge extrusion model for the Altyn Tagh region solves a dilemma of North China-Tarim-Qaidam relations created by previous palinspastic reconstructions by correlating two mid-Paleozoic sutures: Qilian Shan and Beishan. This model respects crustal mass balance during deformation and predicts net right-slip along the presently left-slip Altyn Tagh Fault.