Oceanography and sedimentation in the semi-enclosed, deep-water Gulf of Corinth (Greece)

Sedimentological and oceanographic characteristics in the Gulf of Corinth are examined, to define modern sedimentation processes over its central part; this is a restricted deep water body (depths >900 m), with a sill depth of 65 m. CTD data collected in May 1983 indicate the presence of a thermocline layer (0-60 m) associated with a rapid temperature decrease. This layer is separated from an almost uniform bottom water mass (>100 m) by a transitional zone (60-100 m), in which temperature decreases gradually with depth. The salinity remains almost constant (38.5+/-0.1 psu) throughout the whole of the water column. Dissolved oxygen levels vary from 1.9 to 2.6 ml/1; in water depths >600 m, these indicate the absence of anoxic conditions. Near-bed currents are <8 cm/s, which are not capable of resuspending bottom sediments. These currents relate to atmospheric pressure changes. The modern sedimentary cover of the Gulf is mainly terrigenous in origin. Generally, coarser-grained (gravely muddy sand) material is present along the narrow and steep southern continental shelf and slope. Mud deposits dominate the deeper parts of the Gulf, whilst a bauxitic red-mud slurry (discharged by an aluminium processing factory) is accumulating over the gently-sloping northern shelf (Antikyra Bay). Some of this artificially-induced fine-grained material reaches the abyssal plain, up to 18 km from its depocentre. Depositional processes are dominated by gravity-driven mass hows (i.e. turbidites, debris flows, and slides), for which the main triggering mechanism appears to be earthquake activity. In some cases, slope steeping through structural control and flood events associated with high sediment inputs (from ephemeral rivers and streams) contribute to the process.