Study On Basic Characteristics And Evolution Trend Of Final Filling Period In The Sanshui Basin

The Sanshui Basin is closer to the South China Sea.The study on the relationship between the development of the Cenozoic Sanshui Basin and the early evolution of the South China Sea is a trend worthy of attention.The predecessors have relatively few studies on the Baoyue Formation and the Huayong Formation in the final stage of the Sanshui Basin.It is of great significance to regional geological research and is an indispensable part of geological development process to the basic characteristics and evolution characteristics of the basin's final closure stage of the Sanshui Basin.Through the study of predecessor data,field observations,indoor petrography,sedimentology analysis,combined with microscopic observation,the following conclusions are drawn:1 The Sanshui Basin entered the extension stage in the Cenozoic,and the Buxin Formation reached the peak of development.After the Baoyue Formation,the basin showed a shrinking trend.The sedimentary facies of the Huayong Formation showed a trend of water receding and evolution.No other strata develop on it,marking the basin from atrophy to complete closure.2.The Huayong Formation represents the final stage of basin evolution.There are still many types of sedimentary facies,such as the shallow lake phase,the fan delta facies,the meandering facies and the braided river,and the filling process of the basin is contracted from the periphery to the center.The eastern part of the basin is gentle,and the relative height difference in the west is obvious.Finally,the filling process is completed in the Jinxinggang area with the remaining river phase.3.The new volcanic geochronology data indicates that there is still magmatic activity in the Sanshui continental basin since the beginning of the expansion of the South China Sea basin,but the sedimentation has stopped.It shows that the regional extension center has been seriously moved southward,and the Sanshui Basin has ceased to exist as a sedimentary depression,indicating that the Sanshui area has ceased to respond to the expansion of the South China Sea in addition to volcanism.