Benthic foraminiferal assemblages from Plio-Pleistocene open bay to lagoonal sediments of the Western Peloponnesus (Greece)

Abstract

A quantitative investigation has been carried out on benthic foraminiferal faunas from Plio-Pleistocene, open bay to lagoonal deposits of the Vounargon Formation of the western Peloponnesus, and a reconstruction has been made of the paleogeographic history of this area. After a period of denudation and deposition of lacustrine sediments in large areas of the Peloponnesus, a Late Pliocene transgression introduced an extensive shallow marine environment in the Pyrgos area, with numerous, probably East-West directed sand ridges. This depositional realm, which may have extended over large areas of the northern Peloponnesus, was probably connected with the open sea towards the North. To the South-East and South it was apparently bordered by a land mass, while a hypothetical ridge or shoal area, extending from the Gulf of Kyparissia towards Zakynthos may have formed the western boundary. The Gavrovo-Tripolitza flysch possibly was the main source for the material of the sand ridges. During the Pleistocene the area of maximum subsidence shifted to the northern part of the Pyrgos area, while large parts of the central Peloponnesus werd uplifted. In this episode the orientation of the sand ridges changed from East-West to North-South. Fifteen sections in the Vounargon Formation, which together are thought to present a characteristic picture of the open bay to lagoonal deposits, were studied in detail. A correlation could be established between the character of the benthic associations and environmental factors such as type of sediment, salinity, sub aquatic vegetation and depth. The relatively open marine basal parts of the Vounargon Formation appeared to contain a fauna of mud-dwellers with as its most important constituents Brizalina, Bulimina and Cassidulina. The faunas from environments associated with the sand ridges are generally characterized by high frequencies of species of Nonion, Elphidium and Ammonia. Sediments from environments with a strongly decreased salinity appeared to contain poor faunas made up almost entirely of Ammonia beccarii tepida.