Marine geoarchaeological survey in the Vathy bay of Astypalea island, south Aegean sea
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Date
2024
Authors
Νότη, Αλεξάνδρα
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Abstract
Coastal restricted basins serve as invaluable repositories of information concerning global sea level changes and regional climate shifts, offering crucial insights into paleogeographic, paleoenvironmental and paleoclimatic conditions. This study employs a multi-faceted approach, integrating geophysical, visual, sedimentological, and geochemical data, to meticulously reconstruct the paleogeography, paleoenvironment, and paleoclimate of Vathy bay, in the South Aegean Sea. Examining a submerged archaeological site near cape Elliniko, the study utilizes dense radiocarbon analyses, providing accurate dating of ancient constructions and human activities.
The research delineates three major environmental stages during the Holocene, identified as seismic facies (SF1-3) and lithological units (LU I-III). These stages highlight the basin's gradual transition from isolated to shallow marine conditions over the last 9.1 thousand years. Notably, the study pinpoints the onset of marine influence around 7.3 thousand years ago, coinciding with a global mean sea level of approximately -8 meters. Analysis further reveals arid periods between 7.3–6 and 4.1 thousand years ago, leading to Sr-rich carbonate precipitation in the basin and a general trend of aridification. Conversely, wetter conditions prevailed during the intervals of 9.1–7.3 and 6–5.4 thousand years ago.
Additionally, geochemical proxies, particularly ASTC1 records, provide high-resolution climate reconstructions for the last 8.7 thousand years, aligning with aridity cycles identified in various Northern Hemisphere records. These findings demonstrate a correlation between mid-Holocene aridity events and the southern migration of the Intertropical Convergence Zone (ITCZ), followed by a retreat of monsoonal rains by the end of the African Humid Period (AHP). Short-term fluctuations in Ti/Al and Zr/Si ratios indicate transient cycles of enhanced terrigenous supply, correlating with Holocene "Rapid Climate Change" events (RCCs). Importantly, the study's spectral analysis identifies cyclical patterns of dry/cold climatic conditions with periodicities at 2500, 1200, and 525 years, corresponding with Hallstatt and Bond cycles, reflecting drier conditions and heightened dust input.
The marine geoarchaeological research unveils submerged ancient structures, including linear constructions, conical rubble structures, and submerged walls, indicating potential harbor installations and navigational landmarks. These findings underline the intricate relationship between sea level changes, climate variability, sedimentation, and human activities, emphasizing the interconnectedness of climate systems across different regions and time scales. This study not only sheds light on the complex Holocene climate dynamics in the Eastern Mediterranean but also elucidates early human interactions with the coastal environment, providing crucial historical context for the region.
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Keywords
Marine geoarchaeology, Μarine remote sensing, Μarine sediments, Holocene, Climate changes