LAUSR

Incised valley fills are complex as they correspond to multiple sea-level cycles which makes interpretation and correlation of stratigraphic surfaces fraught with uncertainty. Despite numerous studies of the stratigraphy of incised valley fills, few have focused on extensive core coverage linked to high fidelity dating in a macro-tidal, tide-dominated settings. Here, we have drilled nineteen sediment cores through the Holocene succession of the macro-tidal Ravenglass Estuary in northwest England, UK. A facies and stratigraphic model of the Ravenglass incised valley complex was constructed, to understand the lateral and vertical stacking patterns relative to the sea-level changes. The Ravenglass Estuary formed in five main stages. First, incision by rivers (~11,500 to ~10,500 yrs BP) cutting through the shelf during lowstand, which was a period of fluvial dominance. Secondly, a rapid transgression and landward migration of the shoreline (10,500 to 6,000 yrs BP). Wave action was dominant, promoting spit formation. The third stage was a highstand at ~6,000 to ~5,000 yrs BP, creating maximum accommodation and the majority of backfilling. The spits narrowed the inlet and dampened wave action. The fourth stage was caused by a minor fall of sea-level (~5,000 to ~226 yrs BP), which forced the system to shift basinward. The fifth and final stage (226 yrs BP to present) involved the backfilling of the River Irt, southward migration of the northerly (Drigg) spit and merging of the River Irt with the Rivers Esk and Mite. The final stage was synchronous with the development of the central basin. As an analogue for ancient and deeply buried sandstones, most of the estuarine sedimentation occurred after transgression, of which the coarsest and cleanest sands are found in the tidal inlet, on the foreshore and within in-channel tidal bars. The best-connected (up to 1km) reservoir-equivalent sands belong to the more stable channels.