Late Pleistocene Geologic History of Texas Outer Continental Shelf and Upper Continental Slope
Published:January 01, 1978
BruceR. Sidner, Stefan Gartner, WilliamR. Bryant, 1978. "Late Pleistocene Geologic History of Texas Outer Continental Shelf and Upper Continental Slope", Framework, Facies, and Oil-Trapping Characteristics of the Upper Continental Margin, Arnold H. Bouma, George T. Moore, James M. Coleman
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Integrated high-resolution seismic and core data from the Texas outer continental shelf and upper continental slope were used to reconstruct the late Pleistocene geologic history of the area. Paleoclimatic fluctuations, determined with foraminifers and correlated with the aid of seismic data, indicate that the late Pleistocene-Holocene sequence represents five cool/warm fluctuations. Correlation of the sefluctuations with the generalized paleotemperature curve generated from oxygen isotope data serves as a basis for placing both paleoclimatic and sedimentary events into a time framework. Seismic profiles over core sites allow the dating of seismic reflecting horizons and extension of the chronologic framework over most of the area.
Two major phases of shelf-edge outbuilding occurred during the late Pleistocene. Both phases began with the development of shelf-margin deltas during lowstands of sea level. The deposition of these shallow-water clays and sandy clays within the shelf-slope transition zone was accompanied by active growth faulting. Large slide masses are present on the adjacent continental slope where the progradation of shelf-margin deltas extended beyond the previously existing shelf break. Active gas generation appears to be associated with the slide masses and greatly alters the seismic character of the surrounding sediments.
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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.