Coastal geomorphology of eastern Nigeria: beach-ridge barrier islands and vegetated tidal flats : Allen J.R.L., 1965. Geol. en Mijnbouw., 44 (1): 1–21.

Abstract

Within the 2.5 km thick Late Proterozoic Lyell Land Group of the Eleonore Bay Supergroup in East Greenland, numerous successions of stacked sheet sandstone bodies, 10–70 m thick occur. Each succession consists of several, 5–50 m thick multistorey sand sheets, separated from each other by 0.2–2 m thick heterolithic mudstone, or sandstone beds. Individual sand sheets are 0.2–3.0 m thick. They have highly erosive lower contacts, show a rough fining-upward trend and are capped by a thin mudstone veneer containing desiccation cracks. Dominant sedimentary structures within the sand sheets are sets of planar cross-bedding showing a range of characteristic tidal features, such as successive bundles of foresets, herringbone cross-stratification, ebb and flood caps and numerous reactivation surfaces. Horizontal lamination is abundant and may in some instances comprise more than half of the structures within a sand sheet. The sand sheets represent high energy tidal channels, with the multistorey sand sheets constituting larger tidal channel complexes. The heterolithic beds represent mixed tidal flat sediment, deposited during periods of tidal channel complex abandonment, probably caused by channel aggradation and changing drainage patterns. The tidal channels were wide, shallow and very sandy, with a very poorly developed channel morphology, caused by lack of fine-grained sediments and vegetation. Most likely they evolved within a meso- to microtidal, sandy back-barrier setting where the channels migrated swiftly across tidal flats and reworked most interchannel sediment. An architecture was developed consisting of stacked sand sheets interbedded with rare heterolithic mudstone beds. The model presented incorporates sedimentary parameters and processes characteristic of a pre-vegetative landscape and it has no direct modern analogue.