The palaeoenvironments and dynamics of the Rannoch—Etive nearshore and coastal succession, Brent Group, northern North Sea

Abstract

Abstract This paper investigates the palaeoenvironments and dynamics of the Rannoch Formation in the East Shetland Basin and the sedimentology of the Etive Formation in one particular part of the basin, the southern Cormorant area. The study utilizes core and well data from the North Sea as well as comparative outcrop data from Utah, western USA. Rannoch Formation facies, coupled with a slight coarsening and cleaning upward of sand-dominated profiles above offshore shales and below channelized delta top sediments, are indicative of a prograding shoreface. The middle shoreface is dominated by hummocky cross-stratified fine sand characterised by horizontal to very low angle, planar to undulatory laminations, often cut by steeper scour features. The Etive Formation is characterized in the southern Cormorant area by development of a microtidal, wave-dominated barrier cut by associated inlet channels. These associations are consistent with an interpretation of the Rannoch Formation as a high energy, storm-dominated environment, with strong wave oscillatory motion accompanied by weak translatory currents as the most likely depositional setting. In the overlying Etive Formation, shoreline characteristics are those of a dissipative coastal system with a complex three-dimensional inshore topography and at least one nearshore bar system developed during fairweather periods.