Physiography of Gulf of Mexico: 1. The Setting

The Gulf of Mexico covers an area of more than 1,500,000 sq km, has a maximum depth of about 3,700 m, and includes many of the geomorphic features of large oceans. The continental shelf, slope, rise, and abyssal plain comprise the major physiographic provinces of the gulf and contain a variety of subprovinces distinguished by topographic character and geomorphic history. The gulf shelf is a relatively smooth, gently sloping surface marked locally by low-relief features formed by sea-level fluctuation during the Pleistocene, reef growth, near-surface movement of diapiric salt and mud, and faulting. Shelf width varies from about 280 km off the Florida and Yucatan Peninsulas to less than 10 km at the Mississippi Delta. The continental slope consists of a considerable variety of physiographic subprovinces and individual features that encircle the deep gulf floor. The distinctive subprovinces of the gulf slope have evolved in response to reef building and constructional sedimentation on the Florida and Yucatan carbonate platforms; erosion, nondeposition, slumping, and faulting in the Straits of Florida and Yucatan Channel; salt diapirism and differential sedimentation in the region off Texas and Louisiana; the large accumulation of mainly Pleistocene sediment on a former continental slope seaward of the Mississippi Delta; tectonic uplift and diapirism in the Golfo de Campeche; and shale mobilization off eastern Mexico. In contrast to the greatly varied, irregular topography of the continental slope, the deep seafloor of the gulf (composed of continental rise and abyssal plain provinces) is an almost featureless plain smoothed by turbidite and p lagic sedimentation and marked locally by low-relief knolls, sedimentary aprons, and small-leveed channels.