Sedimentary microfacies in the first member of the Liushagang Formation in southwestern Weizhou depression, Guangxi

Two types of sedimentary facies have been distinguished in the light of core examination, grain-size data, well logs and seismic data, including the transgressive fan delta and delta facies. The fan delta facies may be subdivided into the mid-fan and proximal fan subfacies, and the delta facies may be subdivided into the delta front and prodelta subfacies. There are eleven sedimentary microfacies altogether involved in the above-mentioned facies zones. The emphasis in this paper is placed on the characteristics, planar distribution and vertical evolution of the sedimentary microfacies in four submembers of the first member of the Liushagang Formation in the Weizhou-11 district, southwestern Weizhou depression, Guangxi. The fan delta deposits appeared during the deposition of the lower part ofthe first member of the Liushagang Formation, while till the deposition of the upper part of it, the progradational delta deposits were accentuated.