Siliciclastic sediments of the Cotton Valley and Haynesville groups prograded over an Upper Jurassic carbonate ramp and are overlain by the Knowles Limestone. These carbonates bracket siliciclastics sediments deposited on a shallow shelf adjacent to the De Soto Canyon Salt Basin. Five depositional environments are defined in Federal and State waters of Mississippi, Alabama, and Florida on the basis of log curves and lithology.

Delta-plain beds comprise red/brown sandstone and siltstone displaying blocky spontaneous potential (SP) curves. The prodelta environment contains interbedded red/brown siltstone and white sandstone with spiky SP curves. Interbedded lagoonal sediments are characterized by white sandstone and gray micrite with spiky SP curves and poorly developed SP curves respectively. Barrier islands exhibit white sandstone and red/brown siltstone with blocky SP curves. Open-marine environments are characterized by interbedded black shale and gray thin sandstone exhibiting poorly developed SP curves.

Knowles Limestone deposition began along the shelf-edge penecontemporaneously with a basin-filling clastic wedge during the Late Jurassic / Early Cretaceous. Three Lower Cretaceous platforms developed over the clastic wedge with the uppermost platform extending 161 km (100 mi) landward of the shelf edge. This extensive marker was later subaerialy exposed.

Petroleum exploration of the Cotton Valley / Haynesville groups is sparse, but gas shows occur in both clastics and carbonates within the Mississippi Sound, Mobile, Viosca Knoll, and Main Pass areas. The nearest onshore Cotton Valley production is found in barrier island sands at the Catahoula Creek Field, Hancock County, Mississippi. Such sands extend from southern Mississippi to offshore Destin Dome area, offering future exploration targets.