Sedimentary record of Mesozoic intracontinental deformation in the eastern Junggar Basin, northwest China: response to orogeny at the Asian margin

A nonmarine Mesozoic succession is exposed along the flanks of the Kelameili Shan, eastern Junggar Basin. Three angular unconformities occur within Upper Triassic to Lower Cretaceous strata: at the Triassic-Jurassic boundary, between the Lower Jurassic Badaowan and Sangonghe formations, and at the base of the Lower Cretaceous Tugulu Group. Localized landscape unconformities also mark the base of the Middle Jurassic Xishanyao Formation and the Middle to Upper Jurassic Shishugou Group. All of the unconfonnity surfaces are overlain by alluvial conglomerate. Unconformity generation resulted from the episodic reactivation of the Paleozoic west-northwest-orientated Kelameili Shan fault zone and other north-south-orientated intrabasinal faults during the Jurassic. Previous interpretations of the Mesozoic stratigraphy of northwest China have linked pulses of clastic sedimentation to continent-continent and arc-continent collisions at Asia’s southern margin, namely the collision of the Qiangtang Block in the Late Triassic, the Lhasa Block in the latest Jurassic, and the Kohistan-Dras island arc in the Late Cretaceous. The Kelameili Shan stratigraphy contains too many unconformities, deformation events, and conglomeratic pulses for a one-to-one correlation to be made. Additional deformation events might have been caused by the collision of other smaller continental blocks at the southern side of Asia and phases of retroarc compressional deformation.