Preliminary biostratigraphy and 3D geometry of the Vouraikos Gilbert-type fan delta, Gulf of Corinth, Greece
Résumé
Along the southern coast of the Gulf of Corinth, interactions between Pleistocene to Recent normal faults and a number of syn-rift Gilbert-type delta systems can be studied. These relationships are exemplified in the Vouraikos Gilbert delta, which has a complex internal sedimentary and structural geometry that was influenced by basin-forming and intra-deltaic planar and listric syn-sedimentary normal faults, as well as by later planar (second-order) extension faults. A thick alluvial succession, well exposed to the east of the Vouraikos delta, predates the delta system. Preliminary biostratigraphical (palynological) data indicate that the Vouraikos delta was deposited during the Early Pleistocene, and built out into a marine body of water, based on the presence of a newly observed shallow marine limestone, which is associated with distinctive coastal facies conglomerates and sandstones. Accommodation space for the >800 m thick Vouraikos delta was mainly created by up to 1000 m of vertical displacement on the north-dipping Pirgaki–Mamoussia Fault. The delta has a grossly concave-upward basal (diachronous) surface in transverse section, thought to be generated by the fixed location of the principal fluvial gravel input to the system. The largest foresets observed in the delta indicate building into a water-filled basin of 300–400 m depth, and a crudely radial form to the delta, shown by NW- and NE-inclined surfaces. The latest sediments of the delta are flat-lying topsets, which are overlain by thick, highly reddened soil sequences exposed in a number of plateaux. These predate the Late-Pleistocene marine terraces that incise the range front.