Sedimentary Characteristics Of The Shuangqiaoshan Group In Northwest Jiangxi And Its Tectonic Palaeogeography

As an important part of Jiangnan Orogenic Belt, Shuangqiaoshan Group is aseries of terrigenous clastic-volcanic sequence with the characteristics of Shallowmetamorphic, Strong deformed Flysch sedimentary formation, which is emerged inthe southeast of Yangze block. At the base of Structural geology, Sedimentary geologyand Tectonic history, the following major progress was made after the research abouttectonic stratigraphic framework and tectonic paleogeographic characteristics:1. Reshape the stratigraphic sequence of Shuangqiaoshan Group in the northwestof Jiangxi, which can be divided into the Kengkou Formation, Shatan Formation,Shangli Formation and Yishan Formation.2.Identify a fan subfacies and an Outer fan subfacies. The depositional sequenceof the focus study area is of upward change from coarse to fine and coarse in Particlesize, which reflects a process of transgression and regression the sedimentaryenvironment has had.3.As The data of small oblique bedding of Kengkou Formation, ShatanFormation and Yishan Formation have shown, paleocurrent direction of theShuangqiaoshan Group changes in the vertical direction. That of Kengkou directs toNE, Shantan is SSW, but Yishan is predominantly NE or NNE.4. As the statistics analysis of the detrital framework mode of the sandstone inShuangqiaoshan Group shows, the type of its provenance may be recycled orogenprovenances. Combining the main and trace tectonic discrimination diagrams ofShuangqiaoshan Group, recommend that the xx is formed in peripheral foreland basinin active continental margin, whose source is mainly from cycle orogenic belt.In short，According to the above data, the prototype basin of Shuangqiaoshangroup experienced two stages: back-arc basin and peripheral foreland basin. Kengkouformation develops in back-arc basin on the mainland side, Shatan on the side bycontinental island arc, Yishan in the peripheral foreland basin. This suggests that theJiangnan orogenic belt is on the verge of convergent plate during this period.