Speaker
Description
Deep marine basin sediments serve as repositories of information on physicochemical processes and the transport behavior of tracers in aquatic environments. The vertical profiles of radionuclides in the water column combined with radiochronological models in the seabed cores can provide new information in terms of geological and radiological processes. The activity concentration data of four sediment cores from different sites in the Aegean Sea were utilized to evaluate sedimentation rates and dating using the $^{210} Pb$ (CF:CS, CIC, CRS/PF) and $^{137} Cs$ models for the sediment cores sampled at the Lemnos, North Skyros, Athos and Cretan basins. The use of multiple dating approaches enables a more comprehensive reconstruction of sediment accumulation history, as well as a better understanding of the use of the models according to each marine ecosystem. The activity distributions of radionuclides provide baseline information on system stability and potential disturbances. In the sediment cores from the Skyros, Athos and Cretan basin, discrepancies in $^{210} Pb_{ex}$ are observed due to rapid changes of the activity concentration of natural radionuclides with the core depth. These are attributed to possible seismic or flooding events, or other episodic processes that resulted in the deposition of additional sediment material. Specifically, in the Athos and Cretan basins, the sediment accumulation rate (SAR), calculated using the CRS and PF models, increases at depths where higher activity concentrations are recorded. In contrast, the sediment cores from the Lemnos and Skyros basins indicate that the sedimentation and accumulation processes are characterized by relatively constant sediment deposition, taking into account the riverine and gravity-flow inputs from the North Aegean region. Consequently, the SAR is approximately two times higher compared to the CF:CS model during the last 20–30 years.
Keywords: $^{210} Pb$ dating models, deep basins, accumulation/sedimentation rate
Acknowledgements
This work was supported by the MARRE project through National Strategic Reference Framework (NSRF) 2014–2020 co-financed by Greece and the European Union (European Social Fund ESF). The authors would also want to acknowledge the crew of the research vessel R/V AEGEAO for the sampling using the box corer during the cruise in the frame of MARRE project. The HCMR group would like also to acknowledge IAEA (RER7015 project) due to know-how transfer in terms of reconstruction of environmental magnitudes as well as the EU Horizon project with the acronym CONTRAST supporting updated tools for interpreting signatures from anthropogenic and natural processes using sediment cores.