Sedimentary Characteristics And Tectono-paleogeographic Implications Of The Luojiamen Formation,Shuangxiwu Area,Zhejiang,China

Research on the high-quality chronological data and the sedimentary tectonic environment has a direct impact on the research of formation and evolution of the Jiangnan orogenic belt.Recently,although we have basically mastered the high-precision isotope chronological data of the Luojiamen Formation and the Shuangxiwu Group,there are still lacking research on sedimentary facies and sedimentary source analysis,which is resulting in a huge controversy on tectonic settings of the Luojiamen Formation and the significance of “Shengong Movement plane of unconformity”.By discussing the stratigraphic sequence,sedimentary facies,skeletal grains of clastic rock,and the analysis of correction of oblique bedding and flute cast data,we conclude that,1)There are four types of sedimentary facies in Luojiamen Formation;2)The rose diagram is indicating that the paleocurrent directs to the northwest;3)The Q-F-L ternary diagram shows that the provenance is a volcanic arc zone;4)The clastic rocks in Fuyang Luojiamen Formation is probably a set of marginal marine deposition.5)Through the study,we hold the opinion that the angular unconformity between the Heshangzhen Group-Loujiamen Formation and the Shuangxiwu Group-Zhangcun Formation is not the collision orogenesis relic of the Cathaysia plate and the Yangtze plate,but the transformation interface of tectonic units.