Eustatic and tectonic controls upon Quaternary coastal sedimentation in the Corinth Basin, Greece

Abstract

The late Quaternary sedimentology and palaeogeography of the Corinth Isthmus in central Greece is re-interpreted. A series of beach-to-shoreface sub-sequences are seen, each characteristically having an overall fining-up character. These occur within a coastal facies belt which has prograded to the west. Computer modelling illustrates the interaction of tectonic displacements and eustatic sea-level variation as controls of facies patterns. Late Pleistocene-Holocene facies geometries are predicted on the basis of published sea-level data over that time interval. On coastlines undergoing tectonic uplift, such as the Isthmus of Corinth, depositional patterns may be characterized by transgressive wedges. These sub-sequences merge basinwards below sea-level minima. Each transgression relates to a major eustatic sea-level peak. Such first order models are modified by variations in the rate of tectonic deformation, the second control on relative sea-level position. Modelled facies patterns are tested on the basis of new 230 Th/ 234 U dates obtained from sclerac-tinian corals of the Corinth canal area. Dated sub-sequence sediments correspond in age to late Pleistocene eustatic highs and observed facies patterns correlate with the major late Pleistocene-Holocene eustatic transgressions of c . 100 ka periodicity. Episodes of intrabasinal normal faulting are isolated from a structural history otherwise dominated by uplift across the Isthmus. Quantification of post-depositional vertical tectonic displacements is achieved, constraining the eustatic base-level at the time of deposition of a dated horizon by reference to the global late Quaternary sea-level curve. The original depositional level is then subtracted from the present outcrop level. Using available 230 Th/ 234 U dates to establish syn-depositional base-levels, minimum uplift rates of the order of 0.3 m ka −1 are calculated across the area, averaged through the late Pleistocene and Holocene.