Abstract
We use stratigraphic, sedimentological, and borehole data and seismic profiles from the western Tarim Basin to document its Mesozoic tectonic evolution. A nearly 60-km-wide, Triassic fold-and-thrust belt along the southwestern margin of Tarim Basin is unconformably overlain by a Jurassic-Cretaceous sedimentary sequence along a regional angular unconformity. The Lower-Middle Jurassic strata consist mainly of an upward-fining sequence ranging from terrestrial conglomerates to turbidite deposits, which represent the products of an initial rift stage. Palaeocurrent analyses show that sediments for these rift deposits were derived from the paleo-Kunlun and paleo-Tienshan Mountains to the southwest and northern, respectively. The overlying Upper Jurassic-Cretaceous series consist of coarse-grained, alluvial fan to braided river deposits in the lower stratigraphic member, and lagoonal mudstones and marine carbonates in the upper member. These finer-grained rocks were deposited in a subsiding basin, indicating that a significant change and reorientation in the drainage system should have occurred within the basin during the Early Cretaceous. The western Tarim Basin evolved from a syn-rift stage to a post-rift stage during the Jurassic-Cretaceous. A post-orogenic stretch developed due to the evolution of the Paleo-Tethyan orogenic belt in Central Asia is a likely geodynamic mechanism for this major tectonic switch from a contractional episode in the Triassic to an extensional deformation phase in the Jurassic-Cretaceous.
Highlights
Central Asia comprises an intricate collage of many crustal blocks and discrete geological domains, such as high orogenic plateaus, mountain ranges and sedimentary basins, which are separated by crustal- or lithospheric-scale faults (Figure 1A)
In Tibetan Plateau, the Early Cimmerian orogeny was driven by the convergence between Tarim and Qiangtang block (Matte et al, 1996; Yin and Harrison, 2000; Zhu et al, 2013; Song et al, 2015)
Previous analyses proposed that the northward subduction of the Paleo-Tethys ocean floor beneath the South Kunlun has initiated by Late Permian-Early Triassic, producing an accretionary prism at the margin of South Asia, and it was followed by the resultant collision in the Late Triassic (Mattern and Schneider, 2000; Xiao et al, 2003)
Summary
Central Asia comprises an intricate collage of many crustal blocks and discrete geological domains, such as high orogenic plateaus, mountain ranges and sedimentary basins, which are separated by crustal- or lithospheric-scale faults (Figure 1A) This geological collage was built up through progressive accretion of continental fragments and terranes into the south Asian margin throughout the Phanerozoic (Watson et al, 1987; Windley et al, 1990; Allen et al, 1993; Matte et al, 1996; Mattern and Schneider, 2000; Xiao et al, 2005, 2015). The validity of these models remains to be tested These Jurassic-Cretaceous tectonic deformations occurred after the Paleozoic-Early Mesozoic amalgamation history along the paleo-south Asian margin, and since they played a firstorder role in the localization and evolution of the Cenozoic intracontinental deformation along the northern edge of the Tibetan Plateau (Ritts and Biffi, 2001; Jolivet et al, 2010; Jolivet, 2015; Tong et al, 2020). Previous studies have found benthic foraminifers, ostracods and abundant bivalves, which indicate the steady high-energy lagoons or estuarine environments (Xi et al, 2016)
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