Sedimentary Characteristics and Evolution of Jiufotang Formation in Kazuo Basin

Key words: 
• Kazuo Basin /
• Jiufotang Formation /
• sedimentary facies /
• sedimentary evolution /
• Bouma sequence

Abstract: Kazuo basin is Late Mesozoic era rift basin in the west of Liaoning, in which Jiufotang Formation is the filling stratum. On the basis of lithologic character analysis ,such as the color, structure, primary sedimentary structure of field outcrops , and also analysis of the spatial disposition and paleontology fossil combination, as well as drawing and integrated analysis in the laboratory, four sedimentary facies containing braided river delta facies, lake facies, lake gravity flow facies and fan delta facies are recognized from Jiufotang Formation finally.Among them, lake facies is the main body of Jiufotang Formation, which is in the shape of sliver and developing in the middle of each depression; braided river delta facies is formed in the northwest of Siguanyingzi depression and Dachengzi depression; fan delta facies chiefly occurs at southeast of Siguanyingzi depression and Meileyingzi depression; lake gravity flow facies mostly developed in the deep lake area of Kazuo basin. Restricted of the relative relation between sedimentation rate and deposit filling rate, from early to late,the evolution of Jiufotang Formation can be manifested as: lake expansion and retrogradation times, large lake aggradation times and lake atrophy and progradation times.