Holocene palaeogeographies of the central Acheloos River delta (NW Greece) in the vicinity of the ancient seaport Oiniadai

Abstract

The shipsheds of the ancient seaport Oiniadai (5th-3rd cent. BC), today located in the central Acheloos River delta on top of the Trikardo hills 9 km inland, document considerable coastal changes. This paper deals with the reconstruction of coastal palaeogeographies in that area since the mid-Holocene. Sediments encountered in 51 vibracores were used to detect the distribution pattern of facies. Facies discrimination was based on sedimentological and micro- and macrofaunal analyses. Palaeobotanical, micromorphological and geophysical studies were accomplished to rebuild palaeoenvironmental settings. A geochronology was set up by means of 50 14C-AMS-dates which also helped to establish a relative sea level curve. At 6000 cal BC, delta progradation started from the north and, by 4500 cal BC, closed off a large lagoon north of Trikardo. At 5400-3100 cal BC, a southern delta arm approached and, by 1350-1000 cal BC, surrounded Trikardo by two distributaries. At 600-200 cal BC, a river channel flowed into the Lagoon of Oiniadai. Thereafter, at 200 cal BC, the delta front switched to the southeast. Delta progradation in today's direction started during Byzantine times. Essential geoarchaeological results are that (i) an Early Helladic harbour, unknown until now, existed southeast of Trikardo on a lagoonal shore and that (ii) Oiniadai's shipsheds were, in Classical Hellenistic times, accessible from the sea via a lagoon.