Southernmost Arkansas and northernmost Louisiana are dominated by two regional positive features, the Sabine and Monroe uplifts. Between them (and extending at least partly across the latter) is a system of normal faults along which movement took place during deposition of Late Jurassic clastics. North of the study area is the South Arkansas graben system, part of the great peripheral fault system which essentially marks the updip (north) limit of thick salt and other Jurassic and Lower Cretaceous sediments of the Gulf coastal province. Still farther north is a series of grabens or half-grabens in which were deposited redbeds and other detritus of probable Triassic age which were intruded by diabase. Far south of the study area are the systems of Tertiary contemporaneous aults of the Texas and Louisiana Gulf coast.

Jurassic contemporaneous faults generally parallel regional structural and depositional strike and are slightly younger basinward (south). Most are downthrown toward the basin, but locally, and regionally in one place, compensating down-to-north faults are present. Beds on downthrown sides are greatly thickened, correlation of individual units is usually impossible, and throws increase with depth. Because the downthrown blocks are tilted, sediments are thickest adjacent to the fault. Fault planes are believed to be curved, and although they are of high angle (60-70°) near the top, they may flatten with depth. As a result of this flattening, together with flowage of underlying Jurassic salt away from downthrown blocks, faults are not known to extend below the salt. They do not cut beds younger than Jurassic and die out upward in a conformable section.

Studies of better known (peripheral-graben and Tertiary) fault systems of the Gulf coastal province are plentiful and offer a variety of explanations regarding causes of contemporaneous faults. These are briefly reviewed in the text and include basement faulting, flexures, differential compaction, gravity creep, and salt flowage. It is concluded that gravity creep of the Late Jurassic sedimentary blanket down the gently dipping slope between the coastal shelf on the north and the basin on the south initiated faulting in the study area. Important facies changes across the area of contemporaneous faults suggest that active differential subsidence facilitated movement, as did the presence of an underlying plastic medium (salt). Sediment loading on downthrown blocks caused salt flowage aw y from them; movement was maintained and increased by this process, but ceased when the supply of salt was exhausted.