Holocene sea level changes and palaeogeographic reconstruction of the Ayia Irini prehistoric settlement (Keos Island, Cyclades archipelago, Greece)

The history of the Ayia Irini promontory is closely linked to seismic activity and the successive changes in Relative Sea Level from the Late Neolithic to the Hellenistic period. After an occupation period of approximately 500 years, it was suddenly abandoned in 2000 BC, when the RSL rose from -5.0 ± 0.10 m to -3.60 ± 0.30 m. Following an undetermined interval, the promontory was resettled and the town grew in size and prosperity. The first landward fortification was constructed in the early 19th century BC and destroyed in the early 18th century BC. A larger fortification followed in the 16th century BC, which was reconstructed after the 16th century BC earthquakes probably related to the eruption of the Thera volcano. The coastal part of the Great Fortification was founded on an extended artificial rock fill that surrounds the promontory, thus expanding the area of the town to the seashore. In the mid-15th century BC a major earthquake caused widespread destruction, signalling the end of the settlement. The settlement was re-established and then completely abandoned following a severe earthquake in the mid-14th century BC. In the mid-2nd century BC, the RSL rose to -2.35 ± 0.15 m, a stand that probably lasted until ca. 1200 AD. A new sea level of -1.40 ± 0.10 m was maintained throughout the Venetian occupation period of Cyclades and after ca. 1570 the RSL rose to -0.85 ± 0.15 m. During the last 400 years, the RSL rose to its current position, completely submerging the coastal rock fill and the overlying fortifications