Seismic Stratigraphy and Global Changes of Sea Level: Part 6. Stratigraphic Interpretation of Seismic Reflection Patterns in Depositional Sequences: Section 2. Application of Seismic Reflection Configuration to Stratigraphic Interpretation

Seismic stratigraphy is the study of stratigraphy and depositional facies as interpreted from seismic data. Seismic reflection terminations and configurations are interpreted as stratification patterns, and are used for recognition and correlation of depositional sequences, interpretation of depositional environment, and estimation of lithofacies. Seismic sequence analysis subdivides the seismic section into packages of concordant reflections, which are separated by surfaces of discontinuity defined by systematic reflection terminations. These packages of concordant reflections (seismic sequences) are interpreted as depositional sequences consisting of genetically related strata and bounded at their top and base by unconformities or their correlative conformities. Reflection terminations interpreted as stratal terminations include erosional truncation, toplap, onlap, and downlap. Seismic facies analysis interprets environmental setting and lithofacies from seismic data. Seismic facies units are groups of seismic reflections whose parameters (configuration, amplitude, continuity, frequency, and interval velocity) differ from adjacent groups. After seismic facies units are recognized, their limits defined, and areal associations mapped, they are interpreted to express certain stratification, lithologic, and depositional features of the deposits that generated the reflections within the units. Major groups of reflection configurations include parallel, subparallel, divergent, prograding, chaotic, and reflection-free patterns. Prograding configurations may be subdivided into sigmoid, oblique, complex sigmoid-oblique, shingled, and hummocky clinoform configurations External forms of seismic facies units include sheet, sheet drape, wedge, bank, lens, mound, and fill forms. Seismic facies units are interpreted in terms of the depositional environments, the energy of the depositing medium, and the potential lithologic content of the strata generating the seismic facies reflection pattern.