Abstract
AbstractIncised 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 setting. For this study nineteen sediment cores were drilled through the Holocene succession of the macro‐tidal Ravenglass Estuary in north‐west 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 (ca 11 500 to ca 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 6000 yrs bp). Wave action was dominant, promoting spit formation. The third stage was a highstand at ca 6000 to ca 5000 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 (ca 5000 to ca 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 1 km) reservoir‐equivalent sands belong to the more stable channels.
Highlights
Incised valleys form as a result of basinward migration of the shoreline, inducing exposure of the shelf and promoting enhanced fluvial incision within the lower reaches of the coastal valleys
Estuarine sedimentation within the valley is complex in that the deposits are the product of river, tide and wave action causing a tripartite zonation of facies that corresponds to net bedload transport (Boyd et al, 2011)
This study aims to address the following research questions, in order to summarize the evolution of the Ravenglass Estuary incised valley-fill: 1 What is the stratigraphic organization of infill for the Ravenglass Estuary?
Summary
Incised valleys form as a result of basinward migration of the shoreline, inducing exposure of the shelf and promoting enhanced fluvial incision within the lower reaches of the coastal valleys. A recent study by Wang & et al (2020) demonstrated that 87 Quaternary incised valley fills showed similar stratigraphic organization comparable to the classic conceptual models (Dalrymple et al., 1992b; Allen & Posamentier, 1993; Zaitlin et al, 1994; Heap et al, 2004; Virolle et al, 2019) but displayed significant variability in the stratigraphic architecture of valley fills, related to continental margin type, inherited topography, river size, catchment area and shoreline hydrodynamics. The inner estuarine facies above the sequence boundary in wave-dominated settings can be very muddy compared to sandy facies in the tide-dominated settings
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
