Channel, dune and sand sheet architectures of strait-adjacent deltas

Sea strait geographies amplify tidal currents, which can result in the formation of tidal strait deposits with a symmetrical facies arrangement. It can be problematic to distinguish such confined tidal strait deposits from strait systems that developed in less constricted settings. To push a more robust differentiation between the confined tidal strait model and a model for less constricted tidal deposits, this study presents an example of a strait-adjacent delta and compares it to the existing model of confined tidal straits. The strait-adjacent delta interpretations are based on an exposed succession in Northern Morocco, that formed in the Miocene Rifian Corridor. The multi-km, seismic-scale exposures at the Ben Allou locality, formed in a region with a largely unconstrained coastline. Clayey and silty portions dominate the distal offshore and prodelta facies, while the proximal delta front and delta plain are comprised of carbonate-rich sandstones. These sandstones exhibit complex architectures of stacked channels and dunes in the delta front, and mud drape-bearing sand sheets on the delta plain. It is shown that the strait-adjacent delta model that is presented herein, is different from a confined tidal strait deposit as it has an asymmetric facies arrangement, and a basinward reduction in depositional energy.