Tectonic evolution of early Mesozoic sedimentary basins in the North China block

There have been lots of debates regarding tectonic evolution of sedimentary basins in the North China block during the early Mesozoic. It has been widely held that the North China block was strongly affected by the collision of the North and South China blocks on the south and the terrane accretion on the north, and thus early Mesozoic basins of various scales in the interior and peripheries of the North China block resulted from crustal shortening. Based on extensive and detailed field investigations of stratigraphic sequences, sedimentary processes and basin tectonics, this study shows that the North China block manifested itself in general as a stable domain during the early Mesozoic, with rifting, transcurrent faulting and magmatism occurring mainly in peripheral regions. The North China block behaved as a big intracratonic basin in the Triassic albeit its depositional area shifted to the west in Mid Late Triassic time. The westward migration of depocenter is assumed the consequence of uplifting of the eastern part of the North China block in response to the collision of the North and South China blocks along the Tongbai Dabie Sulu orogenic belt and coeval transpression of the Tanlu fault zone. Sedimentary basins had not developed until the Early Jurassic in the regions north of the Tongbai Dabie orogen, and plausibly formed as the result of crustal stretching related to southeastward exhumation of the Dabie high-pressure metamorphic rocks. The collision of the North and South China blocks led to south-directed displacement of the East Qinling orogen, but few geological records exist indicative of Mid Late Triassic thrusting in the southern margin of the western North China block. Instead, some evidence is suggestive of extensional or transtensional deformations, such as the existence of large normal faults controlling subsidence and sedimentation of Middle Late Triassic basins and the presence of synsedimentary normal faults in basin sequences. Both the East and West Qinling experienced rapid uplifting in the Late Triassic, coeval with large-volume granitic magmatism. Late Triassic uplift and exhumation of the Qinling was considered as the result of asthenospheric upwelling and voluminous granitic injections. Vertical motion of the northern East Qinling might have triggered normal faulting along its northern edge and extensional subsidence of the southern margin of the western North China block. Broad denudation occurred simultaneously in the northern margin of the North China block from the Late Triassic to Early Jurassic in association with magmatism and development of a few small rift basins. Asthenospheric uprising is regarded as the cause for Late Triassic magmatism, regional surface uplift and supracrustal stretching. Triassic subsidence and sedimentation in the interior of the North China block was punctuated by crustal uplifting, possibly driven by mantle up welling at the transition from the Triassic to Jurassic. The whole North China block then resumed low-rate subsidence from the late Early Jurassic and plausibly developed into a broad intracratonic basin in the Middle Jurassic, characterized by widespread distribution of shallow-water lacustrine and meandering river facies associations. The sagging of the whole North China block is thought of as the consequence of thermal contraction in the aftermath of mantle upwelling. Backarc extension related to the Paleo-Pacific plate subduction might have magnified subsidence of the eastern North China block, resulting in relatively thick accumulation of Middle Jurassic strata. This study restores tectonic and sedimentary history of the early Mesozoic basins in different portions of the North China block and advances models to illustrate how the basins of diverse origin were generated and filled in different stages.