Contourites of the Ordovician Pingliang Formation in southern margin of Ordos Basin
Li Hua1, 2, 3, He Youbin1, 2, 3, Huang Wei3, Liu Zhuruizhi3, Zhang Jin3
1 Key Laboratory of Exploration Technologies for Oil and Gas Resources,Ministry of Education, Yangtze University,Wuhan 430100,Hubei 2 Research Center of Sedimentary Basin,Yangtze University,Wuhan 430100,Hubei; 3 School of Geosciences,Yangtze University,Wuhan 430100,Hubei
Abstract：The contourites,gravity flow deposits and deep water autochthonous deposits, consisting of limestone,mudstone with sandstone with radiolarian chert and volcanic tuff interbeds, were developed in the Ordovician Pingliang Formation in the southern margin of Ordos Basin. Contourites were divided into calciruditic contourites,calcarenitic contourites,calcisiltitic contourites,calcilutitic contourites and silt-sandy contourites. Ripples and bioturbation were well shaped on top of calcisiltitic contourites. The ripples,with wave length 1-5,cm and wave height 0.2-0.5,cm,were asymmetric and showed migration direction obviously. The complete and incomplete sedimentary sequences were composed of superimposed calcarenitic contouritse,calcisiltitic contourites and calcilutitic contourites,and displayed upward fine-coarse-fine trend with thickness several millimeters to centimeters. The sequences consisted of not only superimposed multilayer,but also single layer,or appeared between two adjacent muddy layers or stylolites;and the thickness of the upward￣coarsening sequences and the upward￣fining ones were asymmetrical. Contour current moved from the east to the west with path subparallel to the slope. The deep water autochthonous deposits and gravity flow deposits were developed in the lower part of the Lower Pingliang Formation; by contrast,the deep water autochthonous deposits and contourites were favored in the upper part. The contourites were mainly influenced by tectonic movements,relative sea-level rise,current energy,palaeotopography and motion path.
基金资助:国家自然科学基金项目(批准号:41472096、41502101)、湖北省创新群体基金项目(编号:2015CFA024)及长江青年基金项目(批准号:2015cqn26)联合资助; [Co￣funded by the National Nature Science Foundation of China(Nos.41472096,41502101),Group innovation fund of Hubei(No.2015CFA024)and the Yangtze Youth Fund(No; 2015cqn26)]
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