Deep-Sea Sedimentation

Eocene Porcellanites and Early Cretaceous Cherts from the Western North Atlantic Basin

“…Biogenic Origin Attributed to Enhanced Preservation According to Berger (1974) and Fischer and Arthur (1977), silica deposition and retention is favored not only by high supply but also by high sediment accumu¬ lation rates, high organic carbon contents, and silicarich or silica-saturated bottom waters. During thalassocratic or polytaxic times (such as the Eocene), warm equable climates with low vertical and latitudinal tem¬ perature gradients produced a sluggish deep circulation with silica-saturated and oxygen-depleted bottom wa¬ ters (Fischer and Arthur, 1977).…”

Structural framework, stratigraphy, and petroleum geology of the area of oil and gas lease Sale No. 49 on the U.S. Atlantic continental shelf and slope

“…The thickness of these inferred Jurassic and Lower Cretaceous sedimentary rocks indicates that they were deposited at high sedimentation rates of 100-300 m/10 6 yrs. These rates are one to two orders of magnitude higher than normal hemipelagic or pelagic sedimentation rates of red clays, siliceous oozes, or calcareous oozes (for example of sedimentation rates, see Berger, 1974) but are in line with normal rates of terrigenous-mud and turbidite deposition (Fischer, 1969). The low velocity (4-5 km/s) at which seismic waves travel through these deeply buried sediments indicates a scarcity of carbonate rocks and possibly good porosity throughout the entire section.…”

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“…En general, las tasas de sedimentación obtenidas para estas rocas a partir de la comparación de las relaciones MnO/A1 2 0 3 con el diagrama de Matsumoto e lijima (1983) son altas, si se comparan con los valores usuales de la sedimentación de barros silíceos pelágicos, que oscilan entre 2 y 10 mm/10 3 años (Berger, 1974). Sin embargo, son normales si se considera el registro de la sedimentación diatomítica de otras zonas de corrientes ascensionales costeras como es la Formación Monterey (California).…”