Sequence Stratigraphy: Evolution and Effects

R.M. Mitchum: Consultant, Houston, Texas; P.R. Vail: Rice University, Houston, Texas; and J.B. Sangree: Consultant, Corpus Christi, Texas

Abstract

In many ways, the effect of sequence stratigraphy on stratigraphic interpretation is comparable to that of plate tectonics on structural geology. These are markers in the history of geology upon which talented minds can build the next advances. However, concepts that seem self-evident to today's students faced painful periods of ridicule and resistance when first systematized by Peter Vail in the 1960's. The history of this slow acceptance is marked by a gradual evolution of concepts that bring basin tectonics, sea-level fluctuations, and sediment supply into an integrated stratigraphic solution.

One basic idea is the time-significance of stratal surfaces and surfaces of discontinuity, and of the seismic reflections generated by them. Another concept is that cyclic sedimentary sequences form in response to varying rates of eustatic changes, tectonic subsidence, and sedimentary supply. The sequence model is highly variable but astonishingly robust in predicting facies and environments in a wide variety of basin and tectonic settings.

Applications in industry and academia are widespread, especially in predicting deep-marine sands, seals and source rocks in offshore settings. Other specific applications include sequence stratigraphy of carbonates, estuarine sands, incised valleys, forced regressions, well-log, and outcrop analysis. Development of eustatic cycle charts needs high-quality biostratigraphy for dating and environmental analysis. The advent of 3-D seismic data opens a myriad of uses involving attributes of the seismic signal. No matter how specialized, however, the good interpreter always starts with a rigorously defined chronostratigraphic framework of sequences and systems tracts for proper interpretation.