Abstract

Three transgressive-regressive sequences have been recognized on two dimensional reflection seismic data in the Mobile Area, offshore Alabama, and northeastern Gulf of Mexico. The three T-R sequences (transgressive-regressive J1, transgressive-regressive J2, and transgressive-regressive LK1) are of Upper Jurassic (Oxfordian) to Lower Cretaceous (Lower Valanginian) in age, averaging about 2–11 million years in duration.

These sequences represent continental, coastal, marginal marine and marine strata of the shelfal areas of the Gulf of Mexico basin, in which low frequency, tectonic-eustatic events are the main driver behind such stratal patterns. Each sequence consists of a backstepping transgressive section and an infilling regressive section. A surface of maximum transgression separates the two systems tracts. Four sequence boundaries and three surfaces of maximum transgression were recognized on seismic sections.

The transgressive-regressive J1 sequence is Oxfordian to Kimmeridgian in age, and includes beds of the Norphlet, the Smackover, and the lower Haynesville. The transgressive-regressive J2 sequence is Kimmeridgian to Berriasian in age and consists of strata of the upper Haynesville and the lower Cotton Valley. The transgressive-regressive LK1 sequence is Berriasian to Early Valanginian in age. It is composed of the upper Cotton Valley Knowles Limestone. These Upper Jurassic to Lower Cretaceous transgressive-regressive sequences and their associated sequence boundaries and surfaces of maximum transgression (downlap surfaces) have utility for regional correlation across the northeastern Gulf of Mexico.