Sediment erosion thresholds and characteristics of resuspended aggregates on the western European continental margin

Sediment erosion thresholds and characteristics of resuspended aggregates w ere experimentally determined on cores from the western European continenta l margin with a ship-borne erosion chamber augmented by image analysis. Bot tom sediments (212-4940 m water depth) had a thin surface layer that was re suspended as aggregates (median diameter 125-2403 mu m) under critical shea r velocities (u(*c)) of 0.4-1.2 cm s(-1). For the underlying sediments, ero ded as primary particles, u(*c) increased with water depth from 0.7 cm s(-1 ) (sandy shelf sediments) to 2.1 cm s(-1) (lower slope sediments). A two-la yer concept of the sediment interface is discussed which distinguishes betw een an underlying sediment layer, bound by both physico-chemical and biolog ical adhesion and a more easily resuspendable surface aggregate layer. The surface layer consists mainly of aggregates in the 140-450 mu m size range and is resuspended at mean thresholds u(*c) of 0.8-0.9 cm s(-1). These aggr egates can subsequently be transported in tide-related resuspension-deposit ion loops over long distances. (C) 2000 Elsevier Science Ltd. All rights re served.