The tephra record from the Sea of Marmara for the last ca. 70 ka and its palaeoceanographic implications

We report the results of tephrochronological studies on marine cores from the eastern and western part of the Sea of Marmara extending back to early MIS-4. Glass shard compositions using electron probe microanalyses (EPMA) and stratigraphic analysis assigned three distinct tephra layers to the eruption of Aydin (Somma-Vesuvius/Italy, 3.9 ka), Cape Riva (Thera/Santorini, 22 ka) and the Campanian Ignimbrite (Phlegrean Fields/Italy, 393 ka), respectively. Tephra layers are important chronostratigraphic markers for the refining of age-depth models of cores and thus for the reconstruction of the palaeoceanographic evolution of the Sea of Marmara. Accordingly, a continuous sedimentary record for the last ca. 67 ka in core MD01-2430, located at -580 m on the Western High, shows only one lacustrine-marine transition at 12.55 +/- 0.35 cal ka BP, which indicates that the Sea of Marmara was under lacustrine conditions disconnected from the Mediterranean Sea from early MIS-4 to early MIS-1. High lake levels and oxic bottom water conditions prevailed especially during the MIS-3 stadials. This implies that the sill depth of the canakkale Strait (Dardanelles) was probably higher during MIS-3 time than the present sill depth of -65 m. Alternatively, strong fresh water discharges from the Black Sea during the interstadials might have kept the Sea of Marmara stratified with a relatively thick layer of fresh waters above a weak Mediterranean inflow filling only deeper parts of the basins. Based on the radiocarbon and tephra-integrated age model the marine transgression at 12.55 +/- 0.35 cal ka BP was followed by the deposition of the main lower Holocene sapropel between ca. 12.3 and 5.7 cal ka BP, and in the shallow shelf areas (<-100 m depth) such as the Gemlik Gulf, by the formation of the upper Holocene sapropel between ca. 5.4 and 2.7 cal ka BP. (C) 2015 Elsevier B.V. All rights reserved.