Mesozoic sedimentary basin development and tectonic implication, northern Yangtze Block, eastern China: record of continent-continent collision

摘要

A Mesozoic foreland-basin complex formed along the northern Yangtze plate during subduction of this plate under the Qinling-Dabieshan erogenic belt along the Mianlue suture. As the Yangtze plate moved northwestwards and was obliquely subducted under the Qinling-Dabieshan (Middle-Late Triassic), a flysch foredeep developed in the Diebu-Songpan in the western part of the northern Yangtze plate. During the Late Triassic, a nonmarine molasse basin first formed in the eastern part of the northern Yangtze plate in response to initial collision there. This molasse clastic wedge prograded over the former marine basin and was accompanied by a change from high-sinuosity river systems flowing into basinal lakes, to higher gradient braidplains. Complete oceanic closure along the Mianlue suture during the Middle Jurassic produced a more extensive east-west molasse basin with rivers, deltas and lakes. During Late Jurassic through Early Cretaceous, the depocenter of the nonmarine molasse basin migrated continually from east to west because of intracontinental deformation associated with clockwise rotation of the Yangtze plate relative to the North China plate. In this time interval, the basin was again dominated by fluvial and lake-delta deposition and rivers continued to disperse sediments southwards into the basin.