Surface sediments and sequence models in the ebb-tidal delta of Texel Inlet, Wadden Sea, The Netherlands

Abstract

Grain size and primary sedimentary structures in the ebb-tidal delta of Texel Inlet are described with the emphasis on the relations with tidal and wave processes. Grain size distribution curves represent two major types, wave-dominated (very well sorted sand with dominantly saltation population) and tide-dominated (less well sorted with relatively large suspension and traction populations). Areal distribution of mean grain size, sorting and different distribution curves is closely related to sediment transport patterns. The deep inlet channel and the offshore area serve as source areas for the ebb-tidal delta and have coarse, relatively poorly sorted sediments. Deposition of very well sorted fine sand occurs on the shallow ebb-delta shoal. The size and sorting of the sands are the result of selective transport and wave processes. Sedimentary structures formed by waves and tidal currents are distinctly distributed over the shallow ebb-delta shoal, the channels and the adjacent inner shelf. The areal distribution of mud drapes in the ebb-tidal delta is a combined effect of the local tidal current pattern and the related locally high concentrations of fine-grained suspended sediment. Alternation of tidal current dominance, during and immediately after storms, with wave dominance during fair weather conditions, results in the formation of “storm” deposits at specific locations in the ebb-tidal delta, i.e. seaward of the main ebb channel. On the basis of this study, sequential models are proposed for the migrational inlet channel, the progradational ebb-delta lobe, and the landward migrating ebb-delta shoal (the transgressive sequence formed after abandonment of the ebb-delta lobe).