Surficial sedimentology of the Middelkerke Bank (southern North Sea)
Résumé
Detailed surficial investigations over the Middelkerke Bank, a tidal sand bank in the southern North Sea, revealed the relationship between morphology, surficial structures and grain-size parameters. Data from 85 grab samples all over the bank show that on a bank normal profile, the coarser, CaC03 rich and badly sorted sediments are generally located near the highest point of the bank, seaward at the northern end and landward at the southern end. Sedimentary structures were studied from 239 boxcores sampled on ail the morphological units of the bank: crest, flanks and adjacent channels. In the shallower parts, foreset beds are preserved while in the deeper zones, intense bioturbation arises and destroys any structure. The combination between these data and the virtual absence of wave-induced structures indicates that the main agents responsible for the bank shaping are the tidal currents.