Transgressive coastal systems (1st part): barrier migration processes and geometric principles

Coastal processes during transgression have been explored through morpho-kinematic simulations using the Shoreface Translation Model (STM). Our STM experiments show that the landward migration of coastal system is controlled by the rate of sea level rise (SLR), the rate of sediment supply (Vs), the shelf slope (?), and the morphology of the coastal profile (M). Additionally, the geometric relationships between shoreface and plane of translation govern three kinematic modes of coastal barrier migration: (1) roll-over, (2) hybrid, (3) encroachment. Each mode exhibits differences along the coastal profile in relation to zones of erosion (cut) and redeposition (fill) and to the consequent sediment exchanges across the profile (from the cut to the fill). Each mode produces distinctive facies architectures and specific stratigraphic position of the shoreface-ravinement surface. Environmental conditions (rates of sea-level rise, sediment supply (±), barrier morphology) and kinematic modes both control stratal preservation. Transgressive roll-over, in particular, occurs on gently sloping shelves and involves erosion along the entire shoreface and landward sediment redeposition (by overwash and tidal inlet processes). Three different types of roll-over are possible depending on the conditions of sediment supply (Vs) to the coastal cell: neutral roll-over (Vs=0 m3), which produces no effect on the shelf; depositional roll-over (Vs >0) and erosional (Vs