Sequence and seismic stratigraphy of the Jurassic strata in northeastern Gulf of Mexico

The Upper Jurassic section in the northeastern Gulf of Mexico includes the Norphlet and Smackover Formations (Oxfordian), considered as one of the most prolific oil and gas producers in the area, the Haynesville Formation (Kimmeridgian), and the Cotton Valley Group (Tithonian to Berriasian/Lower Valanginian). The study area, located in the onshore-offshore southwest Alabama, consists of mixed siliciclastic and carbonate deposits representing continental, marginal marine, and marine environments. Well log, core and two-dimensional reflection seismic data were used to provide a sequence stratigraphic framework for the Jurassic section through identification of transgressive-regressive sequences and their associated key stratigraphic surfaces.; Three transgressive-regressive (T-R) sequences were identified in the Upper Jurassic-Lower Cretaceous strata onshore Alabama, using well log and limited core data. In the offshore area, four transgressive-regressive sequences were recognized on well logs. Stratigraphic analysis of the reflection seismic data yielded three T-R sequences. Sequence boundaries and marine flooding events were identified on seismic sections through interpretation of reflection termination patterns of seismic reflectors. The reflection seismic data were eventually integrated with well log data using check-shot surveys and synthetic seismogram.; The recognized transgressive-regressive sequences have utility for regional stratigraphic correlation of the Jurassic sediments across the northern Gulf of Mexico. The Oxfordian (Smackover), the Late Kimmeridgian (Haynesville), and the Berriasian (Cotton Valley) marine flooding events have potential for global correlation. Sequence boundaries and marine flooding surfaces were identified as major events in the geohistory of the northern Gulf of Mexico.; Several approaches to sequence stratigraphy have been established. The three most popular approaches are the depositional sequence, the genetic stratigraphic sequence, and the T-R sequence. The T-R approach is thought to have the greatest utility in the study area. An evaluation of the merits and limitations of each approach was performed considering a number of factors such as applicability to the study area, compatibility with the basic definition of a sequence, complexity and amount of terminology associated with each approach, type of available data, geographic location and geologic setting of the study area, and nature of stratigraphic section in question.