Fluvial Sequence Stratigraphy Division And Facies Evolution Of Qigu Formation,Baijiahai Bulge,Basin Junggar

Sequence stratigraphy has been widely used in terrestrial formation Because of its complex time-space evolution,the division and correlation of the fluvial facies has always been a difficulty in sequence stratigraphy.The aim zone locate in the high point of Baijiahai bump,eastern Basin Junnar study on which is far less than it is needed now.Based on previous studies,outcrop data,3D seismic data and 604 wells' logging data,this paper carefully analyzed characters of strata sequences and sedimentary facies in the aim zone and studied deeply on the relevant sedimentary features and high resolution sequence stratigraphy and discussed the stratigraphic cycle partition and the interface identification in meandering river facies.Use medium-term cycle sequence as framework,short-term sequence cycle as isochronous contrast unit,the isochronous stratigraphic framework is builded and in which the sand correlation work is carried out.At last,the sedimentary distribution and evolution of Qifu formation is clearly known The main resuts achieved are as followed:1.The Qigu formation is meandering river facies formed under arid,semi-arid climatic conditions.Based on the study of outcrop data,logging data and seismic data,one long cycle and three medium-term cycles are recognized.The top surface of the long cycle is a category? interface,it is an angle unconformity surface between Qigu famation and the overlaid Qingshuihe famation;the bottom surface of the long cycle is a category ? interface which:is the integration interface between Qigu and the underlying Toutunhe formation.The interface of the inner medium-term cycle is all lithofacies transition surfaces.2.Guided by the principle of high resolution sequence stratigraphy,the configuration and superposition pattern of short-term cycles within an medium-term cycle is studied.It is believed that:there are two short-term cycle forms in meandering river facies-the deeping-up asymmetrical type(type A)and the symmetrical(type B)which are differently distributed within a medium-term cycle.3.Combining previous research,the formation sand ratio and seismic attributes,the double provenance are confirmed.The carat beautiful mountain one which loc ate in northwest area is the main source of the MSC1 and then became weaker and weaker,at the same time the one from northeast is more and more strong.For the change in A/S,the river form had changed from middle sinuosity meandering river to high sinuosity meandering river and then changed back to middle sinuosity meandering river during the whole sedimentary period.