A 6000-year geochemical record of human activities from Alexandria (Egypt)

Recent multidisciplinary investigations of sediment cores from the ancient marine bay of Alexandria (Egypt) have documented local human activities during the Iron Age (circa 900-1000 B.C.) prior to Alexander the Great's arrival in 331 B.C. (Goiran, 2001; Véron etal., 2006; Stanley etal., 2007, 2010), corroborating the existence of the so-called "Rakhotis" as evoked in previous archaeological literature (Jondet, 1916; Weill, 1919; Chauveau, 1999; Baines, 2003). Lead (Pb) Isotopic Analyses (LIA) from Alexandria Bay indicate a possible anthropogenic imprint as early as circa 2300-2650 (±200) B.C. and, to a lesser extent, 3500-3800 (±170) B.C. (Véron etal., 2006). Here we demonstrate that LIA in sediments from the nearby Maryut Lagoon display isotopic anomalies resulting from the release of contaminant Pb into the Lagoon during the Egyptian Early dynastic (at 2897±187 B.C) and Predynastic (at 3520±145 B.C.) periods that corroborate geochemical data from Alexandria Bay. Pb concentrations in Maryut sediments show enrichments that mirror isotopic findings. The absence of contaminant Pb imprints within the sediments from the nearby Nile Canopic branch confirms that isotopic anomalies found in Alexandria Bay and Maryut Lagoon sediments are local and do not originate from long-distance transport of contaminant Pb associated with Nile suspended material and/or wind-derived aerosols. LIA in Alexandria sediment cores correspond to commonly mined Pb and Cu (copper) ores from Turkey (Black Sea region), Cyprus, Crete and the Oman Gulf. LIA substantiate the use of copper-based relics in the Alexandria region during the Pre and Early dynastic periods, and provide insights into metal trading within the Eastern Mediterranean during the Chalcolithic-Early Bronze Age transition, 6000 years ago.