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Article Dans Une Revue Byzas Année : 2014

Geoarchaeology of Alexandria (Egypt): 8,000 Years of Coastal Evolution

Résumé

In this paper, we report the palaeoenvironmental evolution of Alexandria’s coastline during the past 8000 years based on 15 sedimentary cores. Seven morphogenetic phases have been identified. (1) Pharos was an island at the end of the 7th millennium B.C. following the Holocene marine transgression. (2) Up until the 7th millennium B.C., a ≈5 m thick tombolo accreted, made-up primarily of Cladocora, Serpulidae and marine shells. (3) Protected by this sandbank, the eastern bay of Alexandria was infilled with fine-grained sediments whereas sands characterize the more exposed western harbour. The eastern bay, which later became the Magnus Portus, comprised a natural coastal shelter from the 1st millennium B.C. onwards. (4) Between the end of the Classical period and the beginning of the Hellenistic period, the tombolo lay close to the water surface. This shallow sandbank greatly facilitated the construction of the Heptastadium, which was built upon a natural spit rather than human infill as has sometimes been speculated. (5) After its construction, the chronostratigraphy shows powerful coastal currents around the Heptastadium. Conversely, the harbour basins constructed around the eastern bay continued to accrete with sediments. (6) On the tombolo-Heptastadium, sandy sedimentation took place around the 4th century A.D.; sedimentation rates of 10 mm-1 are attested in the harbour basins. (7) During the 8th century A.D., a coarse deposit is observed in the stratigraphy, marking the end of fine-grained sedimentation in the harbour basins. This unit appears consistent with one or more high-energy events (e. g. storms or tsunamis). Our geoarchaeological research has yielded insights into the coastal landscapes of the city before and after its foundation by Alexander the Great.
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Dates et versions

halshs-01979104 , version 1 (12-01-2019)

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  • HAL Id : halshs-01979104 , version 1

Citer

Jean-Philippe Goiran, Nick Marriner, Christophe Morhange, Julien Cavero, Christine Oberlin, et al.. Geoarchaeology of Alexandria (Egypt): 8,000 Years of Coastal Evolution. Byzas, 2014, Harbors and Harbor Cities in the Eastern Mediterranean from Antiquity to the Byzantine Period: Recent Discoveries and Current Approaches, 19 (2), pp.727-741. ⟨halshs-01979104⟩
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