[en] Straits are crucial in terms of oceanic circulation between basins. Many modern straits are dominated by tidal currents that flow differently than in the connected basins. These tidal currents are shaping the seafloor into complex geometries, alongside (in addition to) sediment sources, tectonic activities and inherited lowstand features. The proposed common tidal strait depositional model comprises a strait centre zone in erosion bounded on both sides by depositional areas with 2D and 3D tidal dunes (known as dune-bedded strait zones). This model does not consider another type of hydrodynamic forcing that can be generated in strait, internal tidal waves. The aim of this study is to evidence the combined effect of tidal currents and internal tides on the morphosedimentary features of the strait seafloor.
We focused here on the Rion-Antirion strait in Greece, which connects the Corinth Gulf with the Ionian Sea. This strait of 2 km wide and 70 m deep is strongly impacted by the tidal currents even in this microtidal Mediterranean context. Using the high-resolution multibeam bathymetry (MBES) acquired over a 21 km² area, morphological structures of the seafloor are evidenced using the bathymetry swath profiles extraction. These profiles are coupled with chirp sub-bottom and sparker reflection profiles imaging the internal sedimentary structures and with currents data (ADCP) and CTD profiles for the oceanographic measurement. To get an overview of all the oceanographic parameters that are coming into play, satellite data and ROMS modelling were used.
The complex bathymetry features displayed in the Rion strait show a lack of tidal dunes. At the location of the expected tidal dunes, only erosive area with pool and crest morphology are observed. These observations complete the tidal strait depositional model where the strait is swept by an internal tide and strong tidal currents as evidenced by the numerical modelling of the area.
