Internal structure of some tidal mega-ripples on a shoal in the Westerschelde estuary, the Netherlands: report of a preliminary investigation

Abstract

Ebb mega-ripples on a sandy shoal in the Westerschelde\nestuary (SW-Netherlands) were studied in crossseCtion.\nThe internal structure is dominated by large scale\nebb-directed cross-stratification of a particular type showing flood induced erosional and/or depositional modifications.\nThe characteristics betraying the tidal origin of the crossstratified structure are:\n1. Erosional unconformities (diastems) between the successive cross-stratal bundles that build one large scale set.\n2. Regular alternations between such bundles and conformably\ninclined solitary trains of small scale sets containing\nupslope directed cross-strata.\n3. The isolated occurrence of a ± 1 dm-thick coset of small\nscale cross-strata conformably intercalated between two\nof the above mentioned bundles.\n4. (Sub)horizontal cosets, of small scale cross-stratification erosively separating vertically successive large scale ebbsets.\nThe above mentioned features confirm the subordinate\nand rather erosional, activity of the flood currents as compared with that of the ebb.