Dynamics and sequential analysis of a mesotidal shoal and intershoal channel complex in the Eastern Scheldt (southwestern Netherlands)

Abstract

A detailed survey was carried out on a mesotidal shoal and intershoal channel complex near the mouth of the Eastern Scheldt in the southwestern part of The Netherlands during the summers of 1976 and 1977. The objectives were to establish a relationship between the morphological changes through time and its influence on the development of the preserved sedimentary sequence.

The investigated area is divided into four zones, each one characterized by specific depositional processes and their related bedforms:

(a) the outer channel bend and margin, which is mainly covered by flood-oriented large-scale catenary ripples and sand waves;

(b) the channel thalweg and inner bend, which is dominated by ebb-oriented mega-ripples;

(c) the inner channel margin, which is characterized by a levee wall;

(d) the adjacent shoal areas, which generally are flat but may be covered by patches of flood- or ebb-oriented large-scale ripples.

The preserved vertical sequence of sedimentary structures in each zone is more or less in accordance with the presence of the dominant bedforms within the respective zones. Sequential analysis shows that the net sedimentation within the outer channel margin is much less when compared to the sediment accumulation within the inner channel margin. This means that the lateral accretional units of the inner channel margin are a dominant feature within the preserved sequence of such a shoal and intershoal channel complex, and also that the preservation potential of sedimentary structures in the inner margin sequence is considerable higher as that compared to the outer margin sequence.

Consequently, preservation of the megaripples, a major bedform in a large part of the investigated area, will be limited and will form only a minor part within an ancient analoguous sequence.