Classification properties of Holocene sediment in Shelikof Strait, Alaska

Abstract

Sediment in Shelikof Strait, which is located between the Kodiak island group and the Alaska Peninsula, varies continuously from muddy sand at the proximal northeast end to silty clay at the distal southwest end. A textural sorting pattern is evident, with pronounced and regular changes in sand content throughout the strait but with consistent separation of silt from clay only at the lowest sand contents. Using data from 74 samples, a strong predictor equation for plasticity index is derived from the amount of clay‐size grains (< 4 μm, geological definition) and grain specific gravity. Vane shear strength values fall in the very soft to medium range. They are best predicted by the amount of silt‐size grains (an indicator of mean grain size); the overburden stress at the shallow sampling depths influences the strength values only slightly. For regressions of plasticity index and vane strength, predictor equations similar to those derived from the total data set can be obtained using as few as 17 samples if...