Geotechnical properties of continental upper rise sediments—Veatch Canyon to Cape Hatteras

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Abstract
Geotechnical properties and brief core descriptions are given for 17 high‐quality gravity cores collected on the continental upper rise between Veatch Canyon and Cape Hatteras. Eleven of the cores were taken on four transects across the upper rise perpendicular to the continental slope. Six other cores were recovered from the axis and periphery of the outer Hudson Canyon. The upper 1m of sediment from the upper rise (not associated with the canyon) is generally bioturbated, olive‐gray silty clays containing few, if any, primary sedimentary structures. The cores peripheral to the outer Hudson Canyon contain numerous thin‐bedded mud turbidite sequences, indicating that the canyon's levees were built up by over‐bank deposition of turbidity currents, particularly on the south side of the canyon. Geotechnical properties of the sediments from the upper rise display a reasonably high degree of uniformity over the expanse of the study area. Within‐core variation is often high and can be attributed to slight textural differences, bioturbation, and normal consolidation. Comparison of the mass physical properties (average values) of the upper rise sediments with those of the continental slope shows surprising similarities in all properties except water content, which is slightly higher for the rise deposits. However, the slope cores display considerably higher variability in their geotechnical properties. The upper rise sediments display higher values of water content, shear strength, sensitivity, and Atterberg limits, and slightly lower values of wet unit weight than do the sediments from the North Atlantic as a whole. The Atlantic basin sediments also show a much greater variability of geotechnical properties, due to their different sedimentological provinces and varying sediment types, than do the upper rise deposits. Significant differences exist between the geotechnical properties of the upper rise cores and those associated with the outer Hudson Canyon. This is attributed to the higher variability of coarse material (sands and silts) in the canyon sediments and a presumed much greater rate of deposition for some areas of the canyon.