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Evolution and Effects of Sequence Stratigraphy

Abstract

In many ways, sequence stratigraphy's effect on stratigraphic interpretation is comparable to that of plate tectonics on structural geology. After 40 years, stratigraphic concepts that seem self-evident to today's students faced painful periods of ridicule and resistance, both within Exxon and in industry, 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. In the early 1950's, Peter Vail, John Sangree and Robert Mitchum became graduate students at Northwestern University under the tutelage of Larry Sloss, whose ideas of cratonic sequences had a strong influence, especially on Vail. The Exxon era started in the mid ‘50's when all three students joined Carter Oil Company, the ExxonMobil precursor. Early ideas on chronostratigraphy were first developed in bedding patterns in well logs and outcrops. Despite criticism and ridicule, Vail transferred to the Geophysical Division and almost single-handedly demonstrated that seismic reflection patterns are chronostratigraphic surfaces. In 1965, he was allowed to start a seismic stratigraphic group that quickly blossomed with ideas on worldwide sea-level cycle documentation, seismic facies analysis, computer applications, mapping techniques, and improved biostratigraphic analysis. In 1977, AAPG Memoir 26 was published. Following that, an accommodation model was developed that integrated the effects of eustatic sea level, tectonics and sediment supply. Systems tracts – lowstand, transgressive, and highstand – occur within a cycle of relative change of sea level. Recognition in well logs and outcrops led to the name change to sequence stratigraphy. In the late 1980's, Vail became a professor at Rice, and Sangree and Mitchum became consultants and teachers for industry in general. About this time, the use of 3D seismic on workstations exploded in industry, greatly affecting sequence interpretation. Ingenious uses of 3D imagery, such as Henry Posamentier's seismic geomorphology, show more and more details of what earlier 2D imaging had only imagined. Through all these changes, however, the sequence model has proven to be astonishingly robust in predicting facies and environment in a wide variety of basins and tectonic settings.