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

摘要

The Gulf of Corinth in central Greece has a maximum depth of about 900 m and is separated from the open sea by the Rion Strait, with a sill depth of 62 m marked by an extensive submarine terrace. During eustatic sea-level lowstands, the Gulf of Corinth was a lake. Under lacustrine conditions, stratified sediments accumulated in the deep-water basins and turbid under-flows from rivers eroded the basin slopes. As the sea level rose, marine waters flooded the Gulf and deltas prograded across the shelves. In shallow-water areas, two key reflectors termed Z and X are terrace surfaces, commonly erosional, which mark the base of the overlying deltaic sequences. In deep-water basins, Z and X mark the top of the acoustically stratified sediments interpreted 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 estimates based on sedimentation rates suggest that the X to W interval corresponds 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. This 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 rifi basins in which marine and lacustrine sediments alternate.