Relative Sea Level Variations at Alexandria (Nile Delta, Egypt) over the Last Millennia: Archaeological Implications for the Ancient Harbour

• Autores: Jean-Philippe Goiran, Cécile Vittori, Brice Noirot, Magdy Torab
• Localización: Ägypten und Levante: Internationale Zeitschrift für ägyptische archäologie und deren nachbargebeite, ISSN 1015-5104, Nº. 28, 2018, págs. 219-234
• Idioma: inglés
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• Resumen

  • During the 19th Century, remains of an ancient harbour were found underwater at a depth of 5 to 6 metres in the eastern port of Alexandria. A research program was undertaken to determine when the harbour of Alexandria submerged underwater. Data were collected throught underwater surveys by scuba diving and by campaigns of corings on land. Geomorphological (i.e. notches and pebble beaches), archaeological (harbour structures), and biological (i.e. marine macrofauna, bioconstructions, and biodepositions) sea level indicators were correlated to understand changes in relative sea level during the last 6 milennia. For each proxy, the altitudinal (vertical) and chronological ranges of imprecision were discussed. The results indicate that the rate of the relative sea level rise is ~80 mm per century between the middle of the 6th millennium and the 5th-6th century AD. An abrupt relative sea level rise (3.5 m + 1.5 m) ocurred during the mid 8th century to the end of 9th century AD. In the 8th century AD, a similar phenomenon was observed for Heracleion (25 km east of Alexandria). Thus, a wide movement of sinking affected in a synchronous manner the western coastal margin of the Nile delta. Since this 8th-9th century AD. event, the subsidence has increased around 2m. The role of abrupt sinking events and subsidence remain determining in the deltaic context to anticipate future coastal adaptations and the risk of submersion.