Discussion on Mesozoic-Cenozoic Evolution of Tian Shan and Its Adjacent Basins
FANG Shihu 1),2) GUO Zhaojie 1) ZHANG Zhicheng 1) WU Chaodong 1) ( 1)Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, Peking University,Beijing,100871; 2)The Research Institute of Petroleum Exploration and Development,PetroChina,Beijing,100083)
This paper discussed the main Mesozoic-Cenozoic tectonic-events, basin evolution, thermochronology and crustal shortening of Tian Shan and its adjacent basins.The basins of south and north Tian Shan have underwent various dynamics stages in Mesozoic-Cenozoic era.The Mesozoic-Cenozoic strata in the basins of south and north Tian Shan showed much information about tectonic evolution. Conglomeratic sedimentation of the latest Jurassic-earliest Cretaceous is consistent with the amalgamation at south margin of Eurasia block, and that of late Cenozoic is related to the India-Asia collision during late Oligocene to early Miocene. So far, the thermochronology data about Mesozoic-Cenozoic cooling events can be divided into three stages: early cretaceous, late Oligocene-Miocene and after Pliocene. These thermochronology data is the direct notes of tectonics events in the latest Jurassic-earliest Cretaceous and late Cenozoic. Tian Shan rose quickly during these two periods. Sedimentologic and thermochronological information proved that Tian Shan Area was active in tectonics during the latest Jurassic-earliest Cretaceous and late Cenozoic, which were the signs of transformation of basin types. Tarim basin and Junggar basin have the same evolution history: intra-continent faulted-depression basin in Jurassic, intra-continent depression basin from Cretaceous to Eocene, and Rejuvenated foreland basin form Neocene to Quaternary. The deformation of Tian Shan was propagating form west to east, which have illustrated by rate of crustal shortening, time-transgression of Xiyu Conglomerate, and GPS observations. The differential deformation of Tian Shan was related to northward extrusion of Pamir Syntaxis.