Sequence Lithofacies Paleography of Leikoupo Formation,Sichuan Basin
Li Ling1,Tan Xiucheng1,2,Zhou Suyan3,Zou Chun4 1.School of Engineering and Resources,Southwest Petroleum University,Chengdu,Sichuan 610500,China 2.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu,Sichuan 610500,China 3.Exploration and Exploitation Research Institution,Dagang Oil Field,PetroChina,Dagang,Tianjin 300284,China 4.Geological Institute,No.5 Oil Extraction Plant,Zhongyuan Oil Field,SINOPEC CORP,Puyang,Henan 457001,China
The inconsistence in different mining areas of the stratigraphic division schemes of Leikoupo Formation,Sichuan Basin,and the fact that on the karst zone strata sloughed off effected by Early Indosinian movement,brings about a problem of stratigraphic classification and lithofacies paleographic reconstitution.Guided by sequence stratigraphy theories and methods,this paper collates and stipulates the stratigraphic division schemes of Leikoupo Formation on the basin interior and reconstructs stratic lithofacies paleography by using quarternary bedding as constructive units.High precision lithofacies paleographic study demonstrates that Sichuan Basin of Leikoupo stage was in restricted-evaporated sea environment and that platform edge developed near Songpan-Ganzi oceanic trough in northwest Sichuan,where the grain bank of platform internal and fringe constitutes the main prospecting parts of Leikoupo Formation.The evolution of lithofacies paleography indicates that the bed form of basin transformed from dipping eastward to westward by the way of"seesaw"in the period of Leikoupo Formation deposition.Even in the early stage of sequence Ideposition,it still remained what the topographic configuration took on as in early Triassic,which was high westward and low eastward,while the eastward dipping trend disappeared gradually in sequenceIII depositional period.Yet,after that period there presented a miniature of uplift-hollow framework in the sequence IV—V depositional period on the basin interior.From sequence VI on,the bed form uplift-hollow framework differentiated intensively accompany with the intensity of the tectonic compression movement,forming macro-thick gypsolyte basin,whose depocencer had an apparent westward dipping trend in the depositional period of sequence VI—X.
【Fund】： 国家重点基础研究发展计划项目“973”计划(2012CB214803);; 中国石油科技创新基金研究项目(2011D-5006-0105);; 四川省重点学科建设项目(SZD0414)
【CateGory Index】： P618.13
【CateGory Index】： P618.13