New insights into the palaeoenvironmental evolution of Magdala ancient harbour (Sea of Galilee, Israel) from ostracod assemblages, geochemistry and sedimentology

Despite several studies have focused on the past bio-sedimentary response of the Mediterranean coastal areas to ancient seaport activities, only few geoarchaeological and palaeoecological data are available on strictly lacustrine harbours, to date. At the archaeological site of Magdala/Taricheae (Sea of Galilee, north Israel), an interdisciplinary study, combining ostracod fauna composition and shell chemistry with sedimentology, geochemistry of sediments and archaeological data, was undertaken on the sedimentary succession buried beneath the Roman harbour structures in correspondence of two key-sections. This approach provided detailed information about past environmental changes, otherwise not visible, into a high-resolution pottery-based chronological framework at the transition from a natural (pre-harbour) to anthropogenically influenced (harbour) lacustrine depositional setting.New bio-sedimentary and archaeological (pottery) data document that remarkable hydrodynamic and hydrochemical changes took place during the Hellenistic period (from the 3rd-2ndcentury BC to the first half of the 1stcentury AD), in response to the construction of the oldest Magdala harbour installations and, possibly, to the following Hasmonean structures. The high V-Cr concentrations observed in the harbour sediments, and the substantial increase of ostracod species (Pseudocandona albicans) preferring slow moving waters and fine-grained substrates point to the establishment of a semi-enclosed, shallow, and organic-rich setting. Coupled ostracod-geochemical analyses also testify to an alkali ions (Na+and K+) enrichment within whole-sediment samples, reasonably driven by increasing evaporation in response to the partial isolation of the lake margin. The increase in sodium and potassium concentrations is accompanied by the sudden appearance of Heterocypris salina, a brackish-tolerant species, and by the almost absolute dominance of noded valves of Cyprideis torosa, whose shells are enriched in Na, K and Cl. The positive covariance between Na2O+K2O values and the frequencies of noded C.torosa seems to confirm the relation between node development and changes in ionic concentration within hypohaline settings.