Stability of Continental Shelf and Slope off Louisiana and Texas: Geotechnical Aspects
Published:January 01, 1978
David J. Watkins, Leland M. Kraft, Jr., 1978. "Stability of Continental Shelf and Slope off Louisiana and Texas: Geotechnical Aspects", Framework, Facies, and Oil-Trapping Characteristics of the Upper Continental Margin, Arnold H. Bouma, George T. Moore, James M. Coleman
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Mudflows, faults, surfacescarps, and other deformational features, which indicate that the seafloor may be experiencing continuous or intermittent movements, are present on the outer continental shelf and upper slope offshore Louisiana and Texas. Possible mechanisms causing instability and soil movement include hurricane waves, various forms of gravity-driven slope failure, and other geologic phenomena. The magnitude and rate of soil movements and the forces these movements transmit to structures must be estimated for design of offshore production facilities. Lateral forces on offshore structures due to soil movement can exceed 20 million Newtons(20,000kN). A quantitative analysis of soil deformation and structural loading requires a comprehensive interdisciplinary study of thegeologic and oceanographic environment. Analytic procedures to evaluate the stability of a site include finite-element analyse sand limit-equilibrium methods.Data for these analyses should be based on well-planned geophysical and geotechnical site investigations and engineering laboratory testing.
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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.