Stratigraphy Sequence Of Diaokou Lobe In The Modern Yellow River Delta

Delta region is the most developed region of the human civilization and economic activity since ancient time. The study of modern delta not only has important realistic meaning for economic construction such as beach reclamation, harbor approach selection, silting prevention and trail channel regulation, but also provides identification marks and contrast model for understanding the ancient delta, and can then guide the exploration and development of sedimentary minerals, such as hydrocarbon, of ancient delta.The Yellow River changed its course to Diaokou river in 1964 which lasted 12 years and four months until 1976. In the estuary, it has experienced complete natural evolution process of modern Yellow River delta and has formed a complete set of modern Yellow River delta depositional system, its historical data record is the most detailed. Therefore, this article relies on co-operation project "Deposition Processes and Styles of Modern Yellow River Delta" of the Ocean University of China and the ExxonMobil Upstream Research Company. Our study focused on the Diaokou delta lobes. Ten geological cores were laid onshore, with a total length of more than 170m, laid 108km of the shallow stratigraphic section offshore, which formed a three-dimensional delta model. Catalog of all drilling and geological profile and interpretation work were completed in door, and a total of 3372 samples were obtained for grain size analysis and dating. The whole project has obtained full and reliable data for in-depth study of modern Yellow River Delta.Grain size analysis results show that modern Yellow River delta sediment consist mainly fine fraction sediment, clayey silt and silt are its main sediment types. The main sedimentary features are poor sorting, extremely positive skew and kurtosis sharp. It mainly consists of two parts: saltation load and suspension load and bed load is missing. The Yellow River fluid belongs to the category of gravity flow, which has its own particularity due to its high concentration of suspended sediment and fine particle. So there are large differences among it and the ordinary traction current, turbidity and mudslides.Modern Yellow River delta basically is in accordance with the ternary structure of multiplicative delta, the grain size gradually gets bigger from the bottom to the top. It primarily shows a regression sedimentary sequence, however at the delta margin, the phenomenon of transgressive deposition also exists; vertically its type can be classified as estuarine sand bar and delta lateral margin, it can also be treated as main stream channel type and distributary channel type, transverse cross section shows the overlapping of estuarine sand bar and delta lateral margin, the estuarine sand bar appears at interval. So the sedimentary model of modern Yellow River delta can be summarized as"one long mouth, two sheet of mud, lapping each other, complex structure".Hydrodynamic conditions, the coming water and sediment of the Yellow River delta have significant seasonal characters. Combining its evolution model and influence factors, the Yellow River delta is not just a simple river-dominated delta or wave-dominated delta, the huge amount of sediment in the flood season makes it in a period of high speed construction that is a characteristics of river-dominated delta but strong waves in winter have intense damage effect on most part of delta sediment which makes it like a wave-dominated delta. Fast depositional speed, frequent swinging of watercourse and overlapping of each delta lobe forms the unique depositional model of Yellow River delta, it is this Yellow River delta depositional model that makes the presence of large amounts of geological weak layers. The unstable internal geological structure has led to the frequent occurrence of geological disasters like undersea slump, landslides and also caused great threats to ocean engineering facilities.The Yellow River shaped the republic's youngest land - the Yellow River delta. She not only gives Chinese people rich resources and vast lands, but also brings the people besides Yellow River heavy disaster. The Yellow River is renowned for its huge sand concentration and different sources of the sand and water. The high sediment fluid of Yellow River makes its delta high depositional speed, serious siltation, frequent occurrence of course changing and bursting and endless geological disasters, thus forms the unique depositional model and geological features of modern Yellow River delta. Therefore, Yellow River delta study can not only improve the theoretical level of delta research system, but also can help the local economy development and the social construction.