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Dives in 240-250 m water depths were made by the submersible Alvin in the northwest and central parts of the Wilkinson basin in July 1971. The submersible was instrumented with a probe consisting of a nuclear transmission densitometer, which directly measured bulk density and, indirectly, water content at 0.8-cm intervals, and with a static cone penetrometer, which indirectly measured shear strength at 2.5-cm intervals. The probe was pushed at a constant rate to a maximum depth of 1.45 m by means of a rack and pinion drive actuated by the Alvin's mechanical arm. Three sites, located several hundred meters apart, were occupied on each of the 2 dives.

Previously measured geotechnical properties in the Wilkinson basin, a postglacial sedimentary basin of lutite, indicated relatively uniform areal and vertical (to 3 m below the bottom) conditions. The Alvin studies showed a horizontal and vertical heterogeneity much greater than expected. The presence in limited areas of high shear strength strata, not directly correlatable with bulk density or water content, and other apparent small-scale anomalies are not easily reconciled with conventional depositional patterns generally believed present in marine sedimentary basins.

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