The paper summarizes the results and conclusions of a structural study covering the western Gulf Coast of the United States. The various structural types of this area are described and their possible genesis discussed.

During late Paleozoic or early Mesozoic, subcrustal movements initiated a regional subsidence in the Gulf Coastal Plains, which reached definite geosynclinal proportions during the Tertiary. In connection with the formation of this geosyncline, local gravity and some igneous activity occurred, giving origin to various structural types within the subsiding area.

The igneous activity, in the form of plutonic intrusions, created regional as well as local uplifts. In southern Arkansas a graben of the rift-valley type is associated with one of these uplifts.

The gravity activity formed regional and local subsidence structures. The regional features, such as regional dip, flexures, arches, and embayments are the direct result of differential regional subsidence. The local subsidence structures, represented by anticlinal, synclinal, and piercement folds, however, are believed to result from gravity flow of sedimentary beds deposited in the geosynclinal area. Gulf Coast faulting originated in connection with this gravity-flow folding and is considered to be a near-surface expression of the deeper-seated folding.