DYNAMIC SEQUENCE STRATIGRAPHY OF PERIPHERAL FORELAND BASINS

The general concepts of dynamic sequence stratigraphy are proposed based on the de-tailed studies of sequence stratigrapy of the latest Ladinian(late Middle Triassic)and Car-nian(early Late Triassic)peripheral foreland basins on the western margin of the Upper Yangtze platform.These peripheral foreland basins may be classified into Zones A and B corresponding to those by Posamentier et al.(1993),where there exist distinctive apparent sea-level cycles during a same apparent eustatic period.In Zone A,the rate of subsidence always exceeds the rate of eustatic fall.Consequently,relative sea-level rises continuously during a eustatic cycle,albeit at varying rates.The accommodation spaces are chiefly con-strained by the overthrusting of the peripheral thrust sheets.In Zone B,the rate of eustatic fall periodically exceeds the rate of subsidence,resulting in an interval of relative sea-level fall during a eustatic cycle.It follows that the dynamic sequences in Zone A are made up of the flexural deformation systems tract(FST)and viscoelastic deformation systems tract (VST).The transition from FST to VST reflects the constant increase in the accommoda-tion spaces of the sediments,formation and development of the basin-range transformation systems,and architecture of the dynamic sequence stratigraphy of these transformation systems.The results of research in this paper will assist in the basin-wide basin analysis and allow the rational assessment of the fluid and solid mineral resources.