Title: The Sediments and Sedimentary Geochemistry of the Southeastern Atlantic Shelf
Abstract: The sediment and geochemical data collected by the M/V Gill on the southeastern Atlantic shelf display both single station and areal variability that can be resolved through multiple non-linear regression to obtain meaningful regional and local relationships. The shelf sediments are composed chiefly of sand-sized quartz and mollusk shell debris with minor phosphorite and quartz gravel. From Georgia to Cape Hatteras quartz predominates almost to the shelf-slope break, while to the south shell debris dominates the shelf except for a narrow coastal belt of reworked quartz sand. The outer shelf, slope, and rise are floored with contemporary foraminiferal oozes with glauconite, pteropod tests, bryozoan and coraline algal fragments, and terrestrial silt and clay. The regression surfaces show the following: (1) the mean grain size of both the terrestrial and carbonate fractions decreases seaward with the larger decrease occurring in the former; (2) the sorting of the carbonate fraction decreases seaward while the terrestrial fraction becomes less well sorted to the south; (3) the percentage of carbonate increases linearly to the southeast with the aragonite content decreasing as it is replaced by magnesian calcite; (4) the organic content increases linearly seaward and maintains an almost constant C/N ratio of 15 to the base of the slope; (5) the heavy mineral content decreases linearly southeasterly, with igneous hornblende increasing seaward, and metamorphic minerals increasing southerly. The data support an ineffective southerly longshore drift since Pleistocene low sea level stands. The regional sedimentary geochemical relationships of Ca, Sr, K, P, Al, Mg, Fe are quadratic; Mn is cubic. The regression surfaces increase seaward following the orientation of the shelf and shore. The geometry of the structure and geomorphology of the shelf and shore appear to be controlling the regional textural, mineralogical, and geochemical relationships. Similar controls should be expected from other areas.
Publication Year: 1967
Publication Date: 1967-11-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 9
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