Geological and Geophysical Investigations of Continental Margins
Knowledge of continental margins advanced rapidly during the 1970s. Multichannel seismic reflection whose cost formerly restricted its use largely to the immediate vicinity of shallow-water prospects has become more common in deeper waters. The use of the technique by government and academic groups helped solve basc structural and evolutionary problems of rocks of the deeper offshrore. Better sources and more sophisticated processing yielded better and deeper resolution of the data. To better disseminate new knowledge of continental margins, AAPG held three meetings in 1977 to review the current status of knowledge. The papers presented at those meetings are contained in this volume. There are 32 chapters divided into the following sections: Rifted Margins; Convergent Margins; Small Basin Margins; and Resources, Comparative Structure, and Eustatic Changes in Sea Level.
Structure and Development of the Southeast Georgia Embayment and Northern Blake Plateau: Preliminary Analysis1
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Published:January 01, 1979
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CiteCitation
William P. Dillon, Charles K. Paull, Richard T. Buffler, Jean-Pierre Fail, 1979. "Structure and Development of the Southeast Georgia Embayment and Northern Blake Plateau: Preliminary Analysis", Geological and Geophysical Investigations of Continental Margins, Joel S. Watkins, Lucien Montadert, Patricia Wood Dickerson
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Abstract
Multichannel seismic reflection profiles from the Southeast Georgia Embayment and northern Blake Plateau show reflectors that have been correlated tentatively with horizons of known age. The top of the Cretaceous extends smoothly seaward beneath the continental shelf and Blake Plateau, unaffected at the present shelf edge. A reflector inferred to correspond approximately to the top of the Jurassic section onlaps and pinches out against rocks below. A widespread smooth reflector probably represents a volcanic layer of Early Jurassic age that underlies only the northwestern part of the research area. A major unconformity beneath the inferred volcanic layer is probably of Late Triassic or Early Jurassic age. This unconformity dips rather smoothly seaward beneath the northern Blake Plateau, but south of a geological boundary near 31ºN, it has subsided much more rapidly, and reaches depths of more than 12 km. Development of the continental margin north of the boundary began with rifting and subsidence of continental basement in the Triassic. An episode of volcanism may have been due to stresses associated with a spreading center jump at about 175 million years ago. Jurassic and Cretaceous deposits form an onlapping wedge above the inferred early Jurassic volcanics and Triassic sedimentary rocks. During Cenozoic times, development of Gulf Stream flow caused a radical decrease in sedimentation rates so that a shelf that was much narrower than the Mesozoic shelf was formed by progradation against the inner edge of the stream. South of the 31°N geological boundary, the basement probably is semi-oceanic and reef growth, unlike that in the area to the north, has been very active at the outer edge of the plateau.