Late Pleistocene, Holocene, and Recent Ostracodes from the Gulf of Argos, Greece

The objective of this study is to outline the Late Quaternary history of a submarine depositional environment and the evolution of its ostracod fauna. Samples from the beach and the bottom of the Gulf of Argos provided recent ostracod populations, which are used here as ecological indicators and compared with fossil assemblages taken from core samples of buried marine Holocene and Pleistocene deposits. The Late Quaternary depositional environment of the Gulf of Argos is characterized by sediment accumulation and eustatic sea-level changes which have produced a succession of transgressive and regressive sequences. Each transgressive sequence begins with an assemblage of those organisms which first populated the newly formed euryhaline environment, in which the near-shore fauna as a whole can be characterised as a little diversified Xestoleberis/Loxoconcha assemblage. Rising sea-levels during the Holocene and Pleistocene interglacials are indicated by more diversified assemblages occurring at deeper biotopes. In such deposits the Xestoleberis and Loxoconcha species are associated increasingly, and alternately, with those of Basslerites, Pontocythere, Pontocypris, Leptocythere, Hiltermannicythere, Aurila, Cytheridea, Cytherella, Cytherelloidea, Cytheretta, Callistocythere, Semicytherura, Urocythereis, Pterygocythereis, Tenedocythere, Carinocythereis, Caudites, Costa, Buntonia, Acamhocythereis and Henryhowella. In regressive sequences, the pure marine populations change upwards into monotonous Cyprideis assemblages indicating a change from marine to brackish conditions and recording the withdrawal of the coastline. Same samples near the present surface are rich in freshwater taxa such as Candina, Cypris and Ilyocypris.