Morphosedimentary evolution of a sediment-starved coastal system in response to late pleistocene sea-level oscillations: structural and hydrodynamic controls (western Sardinian margin)

The evolution of a submerged coastal system shaped during the Late Pleistocene has been reconstructed through the integration of high-resolution seismic profiles (Chirp and Sparker), multibeam bathymetry, backscatter data, and sediment samples. The study area is located on the sediment-starved continental shelf of western Sardinia, where coastal dynamics were influenced by the interplay between scarce fluvial input, inherited structural and morphological features, and wave-driven sediment reworking via longshore currents. A previously unrecognized fault system defines a localized Pliocene basin, later incised by an erosive surface marking the base of the Quaternary. The uppermost tilted Pliocene deposits, preserved below this surface, acted as a morphological barrier that influenced the distribution of fluvial sediments, while the longshore currents contributed to sediment reworking and lateral confinement. Seismic stratigraphy reveals a set of four backstepping depositional terraces interpreted as the preserved record of the Younger Dryas, reflecting stages of relative sea-level stabilization, and two overstepping barriers, associated with rapid sea-level rise. Despite the presence of a fluvial source, the absence of a typical deltaic deposit is attributed to the combined effects of low sediment supply, longshore currents, and inherited paleo-topography. These findings highlight the dominant role of inherited paleo-topography and hydrodynamic controls in shaping transgressive coastal systems in starved settings, offering an alternative model to classical delta-dominated coastal evolution.