This investigation focuses on sedimentological attributes and the litho- and chronostratigraphic framework of Holocene sediment core sections recovered in Alexandria's Eastern Harbor in Egypt, for many centuries the major port in the southeast Mediterranean. Holocene sediment trapped in the harbor, formed of marine calcareous sand, muddy sand, and mud, are examined to define major depositional patterns that developed before and after expansion of Alexandria in the 4th Century BC. Petrologic and radiocarbon data indicate that the harbor formed between two Pleistocene carbonate sandstone (kurkar) coastal ridges and was flooded by seawater during the transgression at about 8000 years before present (BP). Sediments accumulated at an average rate of 1–3 mm/y largely by wave- and wind-driven currents driving material from the Egyptian shelf into the high-energy basin. The association of distinct biological components, failed slump-like sediment strata, and important hiatuses (time gaps) record the episodic influence of powerful events, such as large storm surges, seismic tremors, and tsunamis. These events likely transported marine biota and sediment from the kurkar ridge and inner shelf north of the harbor and also eroded and displaced substantial amounts of older deposits laterally within the basin.
In addition to natural processes, the influence of human activity is detected in harbor sediments after ∼2400 years BP, following development of Alexandria by the Ptolomies and their successors, the Romans. Among important components in cores are artifacts and lithoclasts. The development of important mud-rich deposits from ∼2200 to 1800 years BP is attributed in part to construction of the Heptastadion, the large causeway and aquaduct system built to connect Alexandria with Pharos Island to the north. Structures such as breakwaters have modified sedimentation patterns but do not fully protect the quasi-closed harbor. Ongoing geoarcheological investigations hold promise to more precisely distinguish effects of natural processes from those of human-related activities.