Sequence-Based Lithofacies and Paleogeographic Characteristics and Evolution of Permian in South China

Key words: 
• sequence statig raphy /
• sequence -based lithofacies and paleogeog raphy map /
• Permian /
• south China

Abstract: Based on the research on sequence stratigraphy of Permian in the south China with the purpose of oil-gas exploration,11 sequence-based lithofacies and paleogeography maps of Permian in the south china have been drawn up by ways of condensation and instantenity with mapping units of sedimentary systems tracts and key sequence boundary surfaces.In the light of sequence-based lithofacies and paleogeography maps,the characteristics and evolution of Permian sequence-based lithofacies and paleogeography have also been discussed in detail.The authors suggest that the evolution of sequence-based lithofacies and paleogeography of Permian bave obvious characteristics of inheritance,inhomogeneity,phase,orientation and synchronism.Inheritance is that the distrbutive feature of sea and land area.the extension direction and distrbutive precipitation of sedimentary facies zone of each stage of Lower Permian are approximately consistent with the tectonic setting and paleogeographic framework of Devonian and Carboniferous.The inhomogeneity shows that there are different characteristics and development process in different sedimentary basin.The phase indicates that the evolution of sequence-based lithofacies and paleogeography can be divided into 2 phases and 11 stages.The tectonic setting,basin feature and paleogeography of Upper Permian are different from that of Lower Permian,but in different depositional area,the development stags is similar.The paleogeography feature of Upper Permian is related to that of Lower Permian,and the evolution and development of biota approximately keep consistence with that of paleogeography. Compared to traditional lithofacies and paleogeography map sequence-based lithofacies and paleogeography map owns distinct advantages fo accuracy,isochronity,genetic succession and exploratory practicality etc.It deeply reflects the sedimentation,tectonic movement,sea-level change,distribution and evolution of sea and land, volcanic action and oil-formation etc.It also reasonably discloses the relationship of corrosion exposure field of old landmass and the development of sedimentary system with sea-level change and synsedimentary tectonic movement,and vividly describes the special distrbution and evolution of the sedimentary facies zone of coverage area.especially potential oil source,reservoir and cover,Clearly,sequence-based lithofacies and paleogeography map not only objectively and dynamically reflects the basin forming,development and evolution process but also have significant practical significance oil-gas exploration.