A Discussion On The Stratigraphic Chronology And Sedimentary Characteristics Of Sibao Group In South China

The Sibao Group in South China is an important part of Jiang Oregenic Belt,it's a “window” to recognize Jiang Oregenic Belt's trench-arc system.we use tectonic stratigraphy,chronology,sedimentology to study its stratigraphic sequence,sedimentary characteristics,SHRIMP zircon U-Pb age,and then combine with these characteristics,determine the prototype basin and tectonic paleogeographic pattern.Based on these works,we have five following understanding:1.Obtain lava zircon U-Pb age in Wentong Formation,Sibao Group.The age is 860±13Ma,indicates that Sibao Group belongs to Neoproterozoic,and the age of Sibao Group shoule be older the 860±13Ma.2.The Sibao Group,in Southeast of Guizhou,is an upward-shallowing sequence.Yaodeng Formation is deep sea-bathyal mudstone and turbidite;The upper of Hecun Formation is neritic clastic,the lower of Hecun Formation is shore facies.Sibao Group,in north of Guilin,are turbidite facies,and the Bouma sequence are developed.3.The rose diagram of inclined bedding in clastic of Sibao Group,in north of Guilin,show that paleocurrent direction Pointing to the south,the provenance is from the north.The research of sedimentaty facies also ptovide evidence for this conclusion.4.Statistical results of skeleton particles show that the tectonic feature of the provenance of Sibao Group is Magmatc Arc.5.Based on the above findings,combined with Fanjingshan Group,we suggest that the tectonic environment of Sibao Group' clastic rocks is forearc basin.