Thermo‐Kinematic Constraints on Restoration of the Eastern Sichuan Fold‐And‐Thrust Belt, South China

Abstract

AbstractKinematic restoration of the eastern Sichuan fold‐and‐thrust belt (ESFTB) in South China is calibrated with a new thermo‐kinematic model combining analog models, discrete element method, and thermochronology data. Thermo‐kinematic analysis provides constraints on the onset, rate, and lateral variation of deformation and exhumation. Results show that the ESFTB experienced a northwestward thrusting and periodic exhumation. Its evolution was characterized by five major stages based on the deformation characteristics; (a) Shortening above a basal decollement and formation of large imbricates separated by narrow synclines during 170–130 Ma; (b) Transition stage during 130–100 Ma; (c) Stepping up of deformation to shallow decollement levels and shaping of the thick‐skinned domain during 100–70 Ma; (d) Shaping of the thin‐skinned domain during 70–20 Ma; and (e) Continuous exhumation and structural modification from 20 Ma to present. The changes in the exhumation rate have been tectonic responses to the subduction retreat of the Paleo‐Pacific Plate and the eastward growth of the Tibetan Plateau. The westward subduction of the Paleo‐Pacific Plate resulted in northwestward shortening across South China, progressive deformation of the ESFTB, and rapid exhumation from the Late Jurassic to the Late Cretaceous. The crustal extension associated with the rollback of the Paleo‐Pacific slab accounted for the Mesozoic exhumation rate decrease until the Miocene. The accelerated cooling of the thin‐skinned domain of the ESFTB since the Miocene was a response to the eastward growth of the Tibetan Plateau, while the continuous slow exhumation in the thick‐skinned domain was related to the continuous crustal extension in South China.