Wave-dominated nearshore sedimentation and ‘forced’ regression: post-abandonment facies, Great Limestone Cyclothem, Stainmore, UK

Abstract

Investigation of sedimentary successions and depositional structures from the post-abandonment phase of the Great Limestone Cyclothem (Upper Carboniferous), Stainmore, UK suggests that deposition occurred in a sand-dominated coastal setting. Recognition of sedimentary structures produced by storms and interpretation of palaeocurrent and palaeowave data indicate that a W—E oriented, southwardly prograding, high-energy shoreline system existed in the Stainmore region. Two equally plausible interpretations suggest that the trough cross-stratified facies lying towards the top of the shoreface succession may either represent: (1) upper shoreface deposits formed by high energy fairweather waves, or (2) the deposits of a tidally influenced deltaic distributary or incised valley fill estuarine system. These interpretations contrast significantly with the N-S oriented, transgressive barrier island model proposed in an earlier study. The sharp contact between lower shoreface and underlying offshore facies suggests that progradation of the shoreline occurred during a relative sea-level fall (‘forced’ regression). Palaeocurrent evidence indicates that deposition occurred within a system in which sediment was periodically flushed from a contemporary delta lobe and subsequently transported to the Stainmore shoreline by longshore currents.