The Research Of Basin Structure And Filling Characteristics Of Palaeogene In Dongying Depression

Dongying depression is a typical fault-sag bilayers structure terrestrial lacustrine basin. The palaeogene rift depositional stage has undergone several evolution stages including early initial rift stage, late initial rift stage, rift extension stage, and rift converge stage etc.. The tectonic movement intensity, climate change, and sediments supply etc. elements of every evolution stage are different. These differences cause the discrepancies of basin structure, reservoir genesis types and distribution characteristic. So the oil-gas enrichment degree and pool forming model of sedimentary formation of different evolution stage are different. The thesis discusses the sedimentary basin structure characteristics and evolution of palaeogene in Dongying depression, comprehensive using the theory and method of tectonic geology, experiment simulate analysis and sedimentology. Combining the analysis of facies marks in different sedimentary systems, the sedimentary systems genesis types and distribution of different structure types sedimentary basins in palaeogene depositional evolution is recovered.The formation processes of the rotation half-graben controlled by plate fault, the rolling half-graben controlled by listric fault and the compound half-graben controlled by slope-flat fault are discussed separately based on geological structure physical simulation. The basin structure type has closed relationship with the shape of basin-controlling faults. The shape evolution of basin-controlling boundary faults in Dongying depression palaeogene basin exist three stages. Generally, basin-controlling fault of early palaeogene (sedimentary period of the Kongdian Formation (Ek)) is plate fault. Basin-controlling boundary fault of middle palaeogene (sedimentary period of the Fourth Submember (Es₄) to the Early Third Submember (Es₃) of Shahejie Formation) is listric fault. Bain-controlling boundary fault of late palaeogene (sedimentary period of the Second Submember of Shahejie Formation(Es₂) to Dongying Formation (Ed)) is slope-flate fault.The basin-controlling fault activity of Dongying Depression presents left-lateral character. The maximum principal stress of sedimentary period of Ek is N-E, which of sedimentary period of Es₄ is N-S, which of sedimentary period of Es₃ to First submember of Shahejie Formation(Es₁) is mainly N-W, and which of sedimentary period of Ed is N-S. The forming time of N-W fault is obviously earlier than N-E fault in Dongying Depression. The development stage peak time of N-W normal faults is Es₃. The intensity is big, above 80m/Ma. The stop time of activities of Shicun Fault and Chennan Fault (east section) are separately Ng and Nm. The beginning time of activity of N-E (N-EE) faults except Chennan Fault (west section) is generally early period of Ek, and the decline time of which is the sedimentary of Ng (Guangtao Formation).The palaeogene basin subsidence center of Dongying Depression basically behaves as the characteristic of anticlockwise migration. The sedimentary period of Ek, the basin structure is N-W direction fault basin controlled by N-W fault. The sedimentary period of Es₄, it is E-W direction sedimentary basin controlled by closed E-W fault or closed N-EE fault. The sedimentary period of Es₃ to Ed, it is N-E direction sedimentary basin controlled by N-E fault.Dongying depression of palaeogene sedimentary stage develops the sedimentary facies including alluvial fan, fan delta, delta, beach and bar, nearshore subaqueous fan, sub-lacustrine fan, slump turbidite fan, and playa etc.. The rotation half-graben basin structure develop in sedimentary period of Ek, which display characteristic of shallow water salt lake depsition. The rolling half-graben basin structure develop in sedimentary period of Es₄ to Es₂x, which display characteristic of deep water extensive basin and large-scale delta. The compound half-graben basin structure develop in sedimentary period of Es₂s to Ed, which display characteristic of extensive water and basin.