Paleoenvironment Of The Upper Submember Of Member 3 Of Paleogene Shahejie Formation In The Dongpu Depression

The upper sub-section(Es₃¹)of the third member of the Shahejie Formation of the Paleogene in the Dongpu Sag was selected as the research object,and the core sediments with a depth of 2209m-3434.06m were sampled.The contents of main and trace elements and rare earth elements were determined by X-ray fluorescence spectrometer and plasma mass spectrometer(ICP-MS),and the sheets prepared from the sediment samples of the study area were observed under the microscope by a Zeiss polarizing microscope.The research contents include element content and occurrence characteristics,edimentary facies and sedimentary structures in the study area of the Upper Paleozoic in the Dongpu Sag.On this basis,the environmental factors such as paleoclimate,paleo-depth and paleo-salinity were discussed,the correlation with sediment types and the source of sediments by studying the horizontal and vertical distribution characteristics of the elements;inferring by studying the species and species of micro-fossils and judging their living environment The characteristics of the times and the environment;combined with sedimentary sedimentary features to carry out comprehensive environmental analysis,inferred the paleoenvironmental evolution process of the Upper Paleozoic Shahejie Formation in the Dongpu Sag,providing for stratigraphic division and comparison and oil and gas exploration in the study area.Scientific basis.The study shows that the Upper Sha-3 of the Dongpu Sag is a typical salted lake or a transgressive event.The sedimentary environment is characterized by lake water salinization or sea-land interaction,and the climate changes from hot and dry at the beginning to warm and the temperature is lowered.The lake level drops,the salinity of the water body decreases,and the oxidized environment changes to the reducing environment.The sediment particle size gradually becomes thinner and the deposition rate decreases.As these environmental factors change,the sedimentary environment and sedimentary facies also change accordingly.Figure42;Table11;Reference 116...