Structural Control on the Routing of Axial and Transverse Subaqueous Channels in the Gulf of Corinth, Corinth Rift, Greece. An AUV High-Resolution Survey

The interaction between active extensional structures and the development of axial and transverse subaqueous canyons is analysed from high-resolution (submeter) bathymetry, sub-bottom profiles and synthetic aperture sonar data (HISAS) recently acquired in the Gulf of Corinth, Greece, using an AUV Hugin 1000. The surveys focused on the slope canyons offshore of the Selinous, Kerinitis and Vouraikos rivers in the western part of the gulf. These three mountainous rivers form partially coalesced coarse-grained deltas in the hanging wall of the Eastern and Western Helike faults, with a submerged shelf (-60 to -80 m) that extends for ~1.5 km basinwards of the river mouths. At shelf edge, slopes steepen to between 12° to 22°. The slope canyons trend north to north-east and are 200 to 600 m wide and ~100 m deep. Canyon floors sloping 9° to 3° until water depths of ~550–650 m, where they are blocked by a WNW–ESE-striking normal fault. This normal fault redirects the slope canyons into an axial trunk channel that slopes between 1.5° and 0.5° and runs eastward, in the immediate hanging wall of the fault at water depths between ~450–750 m. Large scours, 250 by 450 m in map-view and up to 12 m deep, are found on the base of the axial channel at the confluences with the slope canyons. Variations in the axial channel orientation and the location where it loses confinement coincide with a major shift in the dominant tilting direction of the main fault blocks in the area.