The paleoenvironmental reconstruction of the Sarandopotamos river valley (Amarynthos, Evia Island, Greece): studying long term human- environment interactions.

The Swiss School of Archaeology in Greece is aiming to reconstruct the human occupation of the Sarandopotamos watershed (Euboea, Greece) through a prospection campaign (André et al., 2023). This region has been occupied almost without interruption since the Neolithic and was an extremely important religious centre during antiquity (Ducrey et al., 2007, Fachard et al., 2017). With such a rich historical context understanding human/environment interactions is crucial and a central goal is understanding when and how the environment has changed in the study area. The most sacred sites are located close to the land-sea interface such that they may have experienced the effects of both catchment-scale changes in runoff and sediment supply and rapid sea level rise during the Holocene. Thus, a primary goal of this study has been to quantify the rates and origins of sediment delivered to the coastal plain in the Sarandopotamos watershed at the scale of the Holocene.

In order to investigate these topics, one core drilled in the Amarynthos floodplain was extensively studied. We performed granulometry, X-ray diffraction, XRF, RockEval and CHNS analysis, in addition C14 dating was performed on six charcoals. The results allowed determination of deposition rates. A period with a very high deposition rate is identified between 7 kyrs BP and 4.8 kyrs BP, resulting in the accumulation of approximately six meters of sediments. After that the deposition rate dropped markedly, with only three meters deposited from 4.8 kyrs BP to the present day. The geochemical data allowed the core to be divided into distinct units, suggesting time-varying sediment sources as well as a link between the composition of the sediments and the deposition rate. Initial interpretations suggest that periods of enhanced sediment supply tend to have particular geochemical origins and may reflect different local sensitivities of the catchment to Holocene climate change; although an association between human land use changes and sediment erosion cannot be excluded.