Sea-level changes and shelf break prograding sequences during the last 400 ka in the Aegean margins: Subsidence rates and palaeogeographic implications |
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| Authors: | V Lykousis |
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| Institution: | 1. UMR 5199 PACEA, Université de Bordeaux, bâtiment B18, Allée Geoffroy Saint-Hilaire, 33615 Pessac CEDEX, France;2. Service de Préhistoire, Université de Liège, Place du XX Août, 4000 Liège, Belgium;3. SARL Paléotime, 6173 Rue Jean Séraphin Achard Picard, 38350 Villard-de-Lans, France;4. 21 rue du Général Ferrié, 38100 Grenoble, France;5. UMR 5140 Archéologie des sociétés méditerranéennes, Université de Montpellier 3, Route de Mende, 34199 Montpellier, France;6. UMR 6042 GEOLAB, Université Clermont Auvergne, Université Blaise Pascal, 4 Rue Ledru, 63052 Clermont-Ferrand cedex 1, France;7. Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany;1. Department of Anthropology, University of Manitoba, 15 Chancellor Circle, Winnipeg, MB R3T 2N2, Canada;2. Center for Earth Observation Science, University of Manitoba, 125 Dysart Road, Winnipeg, MB R3T 2N2, Canada;3. Department of Geological Sciences, University of Manitoba, 125 Dysart Road, Winnipeg, MB R3T 2N2, Canada;4. Department of Anthropology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada;5. Archaeological Services, Heritage Branch, Department of Tourism, Heritage and Culture, Government of New Brunswick, 225 King Street, Fredericton, NB E3B 5H1, Canada |
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| Abstract: | The subsidence rates of the Aegean margins during the Middle-Upper Pleistocene were evaluated based on new and historical seismic profiling data. High-resolution seismic profiling (AirGun, Sparker and 3.5 kHz) have shown that (at least) four major oblique prograding sequences can be traced below the Aegean marginal slopes at increasing subbottom depths. These palaeo-shelf break glacial delta sediments have been developed during successive low sea-level stands (LST prograding sequences), suggesting continuous and gradual subsidence of the Aegean margins during the last 400 ka. Subsidence rates of the Aegean margins were calculated from the vertical displacement of successive topset-to-foreset transitions (palaeo-shelf break) of the LST prograding sediment sequences.The estimated subsidence rates that were calculated in the active boundaries of the Aegean microplate (North Aegean margins, Gulfs of Patras and Corinth) are high and range from 0.7 to 1.88 m ka?1, while the lowest values (0.34–0.60 m ka?1) are related to the low tectonic and seismic activity margins like the margin of Cyclades plateau. Lower subsidence rates (0.34–0.90 m ka?1) were estimated for the period 146–18 ka BP (oxygen isotopic stages 6–2) and higher (1.46–1.88 m ka?1) for the period from 425 to 250 ka BP (oxygen isotopic stages 12/10–8). A decrease of about 50% of the subduction rates in the Aegean margins was observed during the last 400 ka.During the isotopic stages 8, 10, 11 and 12, almost the 50–60% of the present Aegean Sea was land with extensive drainage systems and delta plains and large lakes in the central and North Aegean. Marine transgression in the North Aegean was rather occurred during the isotopic 9 interglacial period. The estimated palaeomorphology should imply fan delta development and sediment failures in the steep escarpments of the North Aegean margins and high sedimentation rates and turbidite sediment accumulation in the basins. It is deduced that the Black Sea was isolated from the Mediterranean during the Pleistocene prior oxygen isotopic stage 5. |
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