Analysis Of Late Cretaceous Sedimentary Facie S In The Western Jinjiang Basin,jiangxi Province

Jiangxi Province,located in southeastern China,is affected by the subduction of the Pacific Plate,many NE-trending faults have been developed,along which many fault basins have been formed.Previous studies on these basins mostly focused on several large and relatively high-level red-bed basins in the province,such as Guangfeng Basin,Xinjiang Basin,Guixi Basin and so on.In these studies,basin types,sedimentary characteristics,stratigrap hic division and paleontology are the main aspects.The study of the western part of Jinjiang Basin is of great significance to the improvement of the sedimentary characteristics,provenance characteristics and the analysis of sedimentary environment of Jinjiang Basin and the sedimentary basins in Jiangxi Province.On the basis of field investigation and collation of predecessors' data,this paper studies the sedimentary facies in the western part of Jinjiang Basin,Jiangxi Province.The main research are as follows:(1)By investigating and studying the measured profiles,it is concluded that the sedimentary system of the late Cretaceous Zhoutian Formation in the western part of Jinjiang Basin is lake sedimentary system,which can be divided into three sub-facies sedimentary units,namely,shore lake subfacies,shallow lake subfacies and sub-deep Lake subfacies.The sedimentary system of the Late Cretaceous Hekou Formation is an alluvial fan,which can be divided into two sub-facies sedimentary units: fan root and fan middle.(2)By using Gazzi-Dickinson method to analyze the detrital grains of sandstone samples from Zhoutian Formation and Hekou Formation,the Q-F-L diagrams show that the samples of Zhoutian Formation and Hekou Formation are from uncut magmatic arcs.The Qp-Lv-Ls diagrams show that the samples of Zhoutian Formation and Hekou Formation both have the characteristics of island arc orogenic belts,indicating that the samples of Zhoutian Formation and Hekou Formation tend to be the source of island arc orogenic belts.(3)Based on the statistics,classification and calibration of a-axis trend and ab-axis occurrence of gravels in Xialancun and Hekou Formations of Zhoutian Formation,Grapher 10 is used to plot the paleocurrent rosette map.It is concluded that the source of Xialancun gravels in Xialancun Formation of Western Jinjiang Basin is mainly from the east-north direction of the basin,while the source of Tianyin Cave gravels in Hekou Formation is mainly from the west-north direction of the basin.(4)Through U-Pb dating of sandstone clastic zircon samples from Zhoutian Formation and Hekou Formation,it is concluded that the zircons from Zhoutian Formation are derived from early Jurassic magmatism,Caledonian intrusion movement,Neoproterozoic island arc magmatism and Paleoproterozoic magmatism of Yangtze Plate,respectively.The zircons of Hekou Formation are derived from early Jurassic magmatism,Caledonian intrusion movement and Neoproterozoic island arc magmatism.