LATE QUATERNARY EVOLUTION OF THE GULF OF PATRAS, GREECE - TECTONISM, DELTAIC SEDIMENTATION AND SEA-LEVEL CHANGE

The Gulf of Patras is an actively subsiding late Cenozoic graben in western Greece that receives deltaic sediment from the large Acheloos and Evinos rivers. The late Quaternary sedimentation history of the gulf is interpreted from 3.5 kHz profiles, numerous short cores, and airgun seismic profiles. A widespread unconformity represents the isotopic stage 2 marine lowstand, when the gulf was subaerially exposed. Subsequent deltaic progradation and associated coastal transgression was greatest during the 13-10.5 ka slowdown in sea-level rise and the period of stable sea level since the mid-Holocene. Switching of delta distributaries can be related to the known evolution of the subaerial parts of the deltas. The stage 2 unconformity provides a datum for quantitative determination of rates of subsidence. The central graben is subsiding at rates of 3-5 mm/yr; rates in the northern part of the gulf average 1-2 mm/yr. This is consistent with a listric faulting model for the origin of the modern Patras graben.