Vertical land movements and sea level changes along the coast of Crete (Greece) since Late Holocene

Abstract

Geomorphological survey along the coasts of Crete revealed widespread evidence of uplifted and submerged tidal notches, different phases of beachrock formation, and many relics of ancient coastal constructions. About 1.6 ka BP, when the sea level was at −1.25 ± 0.05 m, the western tectonic block of the island uplifted by 9.15 ± 0.20 m in its westernmost extremity and by 2.00 m approximately in its eastern boundary and tilted southeastward. Repeated preceding episodes of subsidence submerged the western part of the island by 1.60 m in a period of 2300 years. Along the western coast, the younger phase of the submerged beachrocks was identified and measured at nineteen locations, together with the submerged tidal notches and archaeological remains. Land subsidence by 1.25 ± 0.05 m, subsequent to the uplift of the western part, occurred after the late Venetian occupation period (∼AD 1600), coincident with the submersion of the eastern part of the island.

In central and eastern Crete, the relative sea level change evidence from tidal notches and beachrocks revealed five distinct sea level stands at −6.55 ± 0.55 m, −3.95 ± 0.35 m, −2.70 ± 0.15 m, −1.25 ± 0.05 m and −0.55 ± 0.05 m. The lowest sea level stand can be identified with the oldest dated tidal notch of western Crete between 4200 ± 90 B P and 3930 ± 90 B P. Two subsequent sea levels can be linked with the Protopalatial (1900–1700 B C or 1600 B C) and Neopalatial period (1600–1450 B C) of the Minoan civilization, according to submerged prehistoric morphologies and inundated Minoan constructions. The change of sea level from −2.70 ± 0.15 m to −1.25 ± 0.05 m is placed between 1450 B C and the fourth century BC. The dating of −1.25 ± 0.05 m sea level stand was based on the measurement and interpretation of ancient coastal installations built along the coast of central and eastern Crete during Classical, Hellenistic, Roman, Byzantine and Venetian periods. Historical sources report a relative sea level rise by 0.70 m during the AD 1604 paroxysmal event. Over the last 400 years, the relative sea level rose by 0.55 m. The uplift of the coast of western Crete and the submersion in its central and eastern coast indicate that during the AD 365 paroxysmal event the island was split along a tectonic boundary identified with the neotectonic graben of Spili and its northern and southern prolongation.