Abstract
Sequence stratigraphy is a study of genetically related strata within a chrono-stratigraphic framework, which is defined by erosion or nondeposition surfaces, or their correlative conformities. The fundamental unit of the sequence stratigraphy is the depositional sequence, bounded by unconformities and their correlative conformities. A depositional sequence is interpreted to be deposited between an eustatic fall and the next in a subsided basin. Depositional sequences have a hierarchical internal structure. A bed is the fundamental building block, and successions of beds form sedimentary facies. Assemblages of process-related facies make up depositional systems. A linkage of contemporaneous depositional systems is the systems tract. During the interactions of subsidence, sediment input, and sea level change, systems tracts are progressively stacked forming depositional sequences. The systems tracts are identified and correlated on the basis of their facies and bounding discontinuities. Most of the discontinuities form as aresult of fluctuations in relative sea level. The unconformities (subaerial erosion surfaces) and regressive surfaces of erosion are formed during relative sea level falls. The ravinement surfaces (tansgressive surfaces of erosion) are formed during relative sea level rise. In many cases, the unconformities are destroyed by successive transgression and are replaced by ravinement surfaces. The recognition and discussion of the facies and discontinuities are important for the sequence stratigraphic analysis. The reconstruction of the hierarchical structure from outcrops or well cores, leads us to the detail discussion of eustasy and tectonics.
