Fish tanks of eastern Crete (Greece) as indicators of the Roman sea level

摘要

The ancient fish tanks and fish traps of Crete are relics of the Roman domination of the island; they were usually constructed near the major urban centers of that period. The direct relationship of their various functional characteristics with past sea levels and the relatively accurate determination of their construction dates establish them as sensitive indicators of sea level change through space and time.The fish tanks presented in detail in this study, namely those of Matala, Chersonissos, Mochlos and Sitia and the fish trap in the gulf of Zakros, have all been reported, recorded and/or interpreted in regard to their operation by previous researchers. In the absence of a comprehensive interdisciplinary approach to the issue, uneven methodologies, inaccurate data and wrong measurements have led to erroneous conclusions about sea level during their operation and about the size and direction of vertical tectonic movements in eastern Crete during the Upper Holocene.The present study is based on a new underwater survey, in the course of which the architectural and functional features of the ancient constructions were reexamined precisely; their depth from modern sea level was measured and their relationship with coastal landforms, indicative of a past sea levels, was investigated.A review of their manner of operation and their modern submerged position allowed the definition of a Roman mean sea level 1.24 m ± 0.09 m below the present one. The submersion of the central and eastern parts of Crete - included in the same tectonic block with a total length of at least 150 km - at an average tectonic rate of 0.65 mm/year during the last 1900 ± 100 years occurred, as is shown by historical evidence, during a paroxysmal tectonic event, probably related to the strong earthquake of 1604.