Alternating marine and lacustrine sedimentation during late Quaternary in the Gulf of Corinth rift basin, central Greece

The Gulf of Corinth in central Greece has a maximum depth of about 900 m an d is separated from the open sea by the Rion Strait, with a sill depth of 6 2 m marked by an extensive submarine terrace. During eustatic sea-level low stands, the Gulf of Corinth was a lake. Under lacustrine conditions, strati fied sediments accumulated in the deep-water basins and turbid underflows f rom rivers eroded the basin slopes. As the sea level rose, marine waters fl ooded the Gulf and deltas prograded across the shelves. In shallow-water ar eas, two key reflectors termed Z and X are terrace surfaces, commonly erosi onal, which mark the base of the overlying deltaic sequences. In deep-water basins. Z and X mark the top of the acoustically stratified sediments inte rpreted as lacustrine turbidites; reflectors Y and W mark the base of these stratified intervals and overlie acoustically transparent sections similar to the Holocene section. The last lacustrine conditions in the Gulf (Z to Y) were during isotopic stage 2 and terminated about 12 000 yr ago. Age est imates based on sedimentation rates suggest that the X to W interval corres ponds to the stage 4 lowstand of sea level. In the western Gulf of Corinth, shoreline transgressive surfaces corresponding to minor transgressions in stage 5 and to major transgression at the end of stage 6 are recognised. Th is seismic stratigraphy permits a detailed interpretation of the history of the Gulf of Corinth in the past hundred thousand years. It also provides a general model for sedimentation in rift basins in which marine and lacustr ine sediments alternate. (C) 2000 Elsevier Science B.V. All rights reserved .