Late Paleozoic oroclinal bending, arc amalgamation, and large-scale transcurrent tectonics in the western Central Asian Orogenic Belt: termination of accretionary orogenesis and initiation of aridification in Central Asia?

Abstract

<p>The western Central Asian Orogenic Belt (CAOB) underwent the prolonged accretion from Neoproterozoic to latest Paleozoic, and evolved into an intracontinental orogenic environment in the Mesozoic to Cenozoic, which was accompanied by significant changes of climatic environments. To constrain earlier accretion mechanisms and processes of the CAOB is fundamentally important given its control on the orogenic architecture and paleogeography, which inevitably affects the subsequent intracontinental orogeny. Here, I focus on the late Paleozoic tectonic reconstruction of the western CAOB with an aim to understand the role of oroclinal bending, arc amalgamation, and large-scale transcurrent tectonics in shaping the orogenic architecture of the western CAOB. My results show that the development of the U-shaped Kazakhstan Orocline in the western CAOB may have been controlled by the along-strike variation of the trench retreat, which was accompanied by the consumption of the Junggar Ocean in the core area of the orocline. The subsequent amalgamation of multiple arcs in the western CAOB may further amplify the oroclinal structure, and I emphasize that the orogen-parallel extension plays a significant role in arc amalgamation of the western CAOB. In the Permian, the large scale of strike-slip faults characterized the western CAOB with sinistral shearing in the north (Chinese Altai) and dextral kinematics in the south (Tianshan), which together indicates the eastward migration of orogenic materials (current coordinate). Following the termination of accretionary orogeny, the western CAOB was in an intracontinental environment with relatively arid climate in the early to middle Triassic as indicated by the widespread occurrence of red beds, which may mark the initiation of aridification in Central Asia.</p><p>Acknowledgements: this study was financially supported by the Hong Kong Research Grant Council (HKU17302317), the international partnership program of the Chinese Academy of Sciences (132744KYSB20200001), the National Key Research and Development Program of China (2017YFC0601205), the National Natural Science Foundation of China (41872222) and a project from Guangdong Province (2019QN01H101).</p>