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Surficial sediments of the continental rise and slope, Niger Delta, West Africa: properties and geology
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The submarine portions of the Niger Delta, West Africa are undergoing active gravity tectonic deformation due to thick deposits of ductile shale overlain by paralic sands. Because the region is rich in hydrocarbon reserves, the subdermal Niger Delta, and the submarine continental shelf, has been well studied. By comparison the region seaward of the continental shelf has received little attention. A few geophysical studies, and studies addressing the affects of ongoing diapirism on sedimentation, have provided useful, however sparse data on the region. Using a suite of piston cores from the lower continental slope and continental rise, this study set out to describe, illustrate, and analyze the surficial sediments of that region. With the aid of previous studies, it also attempted to shed some light on the effects of the ongoing gravity tectonics, and the region's unique littoral circulation pattern, on surface sedimentation in deep water. To achieve its goals this study employed select geotechnical tests, shear strength, grain size analysis, p-wave velocity data, clay mineralogy by x-ray diffraction, and high resolution imaging by x-radiography. It revealed that much of the study area is blanketed by a Holocene veneer of low shear strength homogeneous clay. It also revealed distinct patterns of deposition and erosion. Mapping of grain size data suggest that sedimentation in the deep water regions of the Niger Delta is influenced to some degree by littoral sand convergence in the eastern and western coastal extremes. A mapping of lost overburden suggests patterns of erosion which overlie, and parallel a zone of clay diapers on the lower continental slope. This suggests that the active gravity tectonics, and its associated diapirism may exert a topographic influence on sedimentation which produces highly localized environments of high erosion, slumping, sliding, and debris and turbidity flows. These environments may be structurally confined and unique to isolated interdiapiric basins. The x-radiographs revealed structures such as debris flow material, and finely graded bedding that were locally confined, and vertically separated by layers of homogeneous clay. It also showed that several structures were not confined to a particular sediment age, but rather appeared to be shear strength transgressive, and thus, owing to the close relationship age bears with shear strength, time-transgressive.
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Includes bibliographical references (leaves 90-94).
Issued also on microfiche from Lange Micrographics.
Kobilka, David William (1999). Surficial sediments of the continental rise and slope, Niger Delta, West Africa: properties and geology. Master's thesis, Texas A&M University. Available electronically from
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