The Aegean and Ionian regions are known as tectonically and seismically very active areas and are characterized by frequent earthquakes and fault rupturing. In Central Greece particularly, the active neotectonic basins of the Gulf of Corinth and the North Evia Gulf undergo strong crust deformation under high strain rates during Pleistocene – Holocene, as indicated by vertical (uplift or subsidence) movements along their margins. The superposition of long-term vertical tectonics on the effect of the successive sea-level changes has produced a remarkable relief composed of uplifted marine terraces and submerged terrestrial landscapes.
Both the Gulf of Corinth and the North Evia Gulf are connected to the Ionian and Aegean Sea respectively through narrow and shallow straits. Maximum depth in the straits does not exceed 65-70m. Systematic high resolution seismic profiling, swath bathymetry and gravity piston coring have shown that both marine basins were isolated lakes when the sealevel was about 120-125m lower than the present one during the last glacial maximum(LGM). AMS radiochronology data have shown that sea water entered the lakes about 13-14kyrs before present, when sea-level rise drowned the shallow straits. The prehistoric landscapes which surrounded the LGM lakes became submerged and subject to tectonic movements and marine sedimentation.
The coastline of the LGM Corinth lake has been detected in seismic profiles from the northern margin of the Gulf at -90 m below present sea level. Geological data show that the northern margin of the Gulf subsides at 0.7-1.0 m/kyr while the southern margin emerges at 1.0-1.3 m/kyr. Consequently, the coastline of the LGM Corinth lake should have been initially at 77-80 m below present sea level. On the uplifting southern margin of the Gulf the coastline of the lake has not been detected yet but is expected to have emerged at about 65-70 m below present sea level since the incursion of sea water.
The water level of the LGM North Evia lake has been found in seismic profiles at about 90 m below present sea level. Vertical tectonic movements are evident around the Gulf but have not been quantified yet, so the initial lake level can not be determined precisely. Holocene sedimentation in the Gulf is mainly depended on the fertile clastic material supplied by rivers which drain the surrounding mountains. The submerged prehistoric landscape is covered be marine sediments, their thickness being up to 40 m off the outflow of rivers along the southern margin. Limited sedimentation areas or even relict landscapes have been mapped away from river mouths.
Thorough evaluation of the seismic data and sedimentological and laboratory analyses of the sediment cores are essential for the precise reconstruction of the submerged prehistoric landscapes around the Corinth and North Evia lakes during the last glacial maximum and early Holocene. Vertical tectonic movements and sedimentation rates need to be quantified and considered for the final paleo-morphological reconstruction.