Seismic Stratigraphy and Global Changes of Sea Level: Part 9. Seismic Interpretation of Clastic Depositional Facies: Section 2. Application of Seismic Reflection Configuration to Stratigraphic Interpretation

Depositional facies are predictable from seismic data through an orderly approach to the interpretation of seismic reflections. We term this approach "seismic facies analysis." Seismic facies analysis procedures are discussed in detail in Part 6, Vail et al, this volume. Seismic facies types generated by sand-shale strata vary mostly as a function of water depth at the time of deposition. Therefore, a regional environmental framework of shelf, shelf margin, and basin slope and basin floor, provides a useful gross subdivision for classification of clastic seismic facies units. Shelf environments are characterized by general parallelism of reflections. Changes in reflection amplitude, frequency, continuity, interval velocity, and broad, low-relief mounds are the principal factors in defining seismic facies units. The shelf-margin and prograded-slope environment typically contains thick marine sediments and has water depths sufficient for the development of complex arrangements of sigmoid and oblique prograding reflection patterns. The basin slope and floor environment includes a variety of deep basin facies as well as nonprograding slope facies and facies that extend from the slope into the basin deep.