The Study On Lithofacies And Origin Analysis Of Sha4 Upper Member Of Paleogene Shahejie Formation Fine-grained Sedimentary Rocks In The Dongying Sag

Upper sections of Sha 4 in Fanyel and Niuye 1 in Dongying Sag of Jiyang Depression of Bohai Bay Basin were selected to study the Palaeogene fine-grained facies were selected and studied.The results are as follows,1.The samples evaluated by fine description of the core,rock thin section,scanning electron microscopy,effectively identifying the diagenetic mineral.The diagenetic minerals generally contain calcareous mudstone,argillaceous limestone and mudstone,limestone,dolomite,siltstone,paste rock.The shape of lamina in fine grained sedimentary rocks samples mainly are horizontal,slow wavy,intermittent,foreset,turbidite.The compositions of the lamina mainly are organic matter,calcite,clay,silt.2.Based on colour,mineral composition,organic matter,sedimentary structure of fine-grained sedimentary rocks,we put forward a lithofacies division scheme,which include 21 fine-grained facies and 33 subfacies accordingly to the bedding shape and forming mechanisms.Based on the lithofacies division scheme,we come to 4 sedimentary cycle.The environmental change between deep lacustrain facies,semi-deep lacustrain facies and shore-shallow lacustrain facies,which represent evolutionary process of the basin.3.We try to reveal the paleoclimate control to the lithofacies from the Milankovitch cycle study on the Upper Sha4 Section.It was found that the long eccentricity cycle played a key role in climate control.The lithofacies dominated by organic matter lamina and a small amount of calcite lamina were formed in the hot and humid conditions,and the lithofacies whose lamina contents are mainly calcite lamina with a few organic,silty and gypsum laminas were formed in the dry and cool conditions.