Published:January 01, 1978
The Gyre basin is one of the many intraslope basins on the continental slope in the northwestern Gulf of Mexico. This depression, elongate NNW-SSE, is 33 km long and 11 km wide. It srim lies at depths between 900 and 1, 100m, the deepest center of the basin lies just below 1, 650 m. Themorphology of the surrounding slope, and of the sediments recovered in a nearby core hole,suggest that the basin was formed during the late Pleistocene by salt diapir blockage of a submarine canyon system.
High-resolution subbottom profiles depict the disrupted nature of the surficial sediments on the basin rim and slopes.Clear indications of slumping are visible on some of the profiles; and hyperbolic returns probably have masked numerous slump features on the basin flanks.
Gravity and piston cores from the Gyre basin area display large lateral variations in sediment texture. The basin floor and the lower southern slope contain much sand-sized clastic material, displaced shallow-water benthic foraminifers, rock fragments, and shallow-water mollusks that suggest bottom density-current transport. Topographic high sand most slope areas contain no sand sized clastic material. Rates of sediment accumulation are considerably lower and the percentage of carbonate higher in these sections than on the basin floor.
Distribution of clay and heavy minerals is fairly uniform throughout the area. Heavy minerals in the sandstones appear to reflect a mixing of Rio Grande and Mississippi sources. The montmorillonite to illite ratios are lower than those reported for Mississippi and Rio Grande clay-mineral provinces.
Figures & Tables
Framework, Facies, and Oil-Trapping Characteristics of the Upper Continental Margin
The Gulf of Mexico covers an area of more than 1,500,000sq km, has a maximum depth of about 3,700m, 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 guldf and contain avariety of subprovinces distinguished by topographic character and geomorphic history.
The gulf shelf is a relatively smooth, gently sloping surface marked locally bylow-relief featuresformed by sea-level fluctuation during the Pleistocene, reef growth, near-surface movement of diapiric salt and mud, and faulting. Shelf width varies from about 280km off the Florida and Yucatan Peninsulas to less than 10km 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 fault ing in the Straits of Florida and Yucatan Channel; salt diapirism and differential sedimentation in the region off Texas and Louisiana; the largeaccumulation of mainly Pleistocene sediment on a former continental slope seaward of the Mississippi Delta; tectonic uplift and diapirism in theGolfo de Campeche; and shale mobilization of feastern Mexico. In contrast to the greatly varied, irregular topography of the continental slope,thedeep seafloor of the gulf (composed of continental rise and abyssal plainprovinces) is an almost featureless plain smoothed by turbidite and pelagic sedimentation and marked locally bylow-relief knolls, sedimentary aprons, and small-leveed channels.