A gradual drowning of the southwestern Black Sea shelf: Evidence for a progressive rather than abrupt Holocene reconnection with the eastern Mediterranean Sea through the Marmara Sea Gateway

Core M02-45 recovered 9.5 m of a [not, vert, similar]12 m-thick transgressive succession on the SW Black Sea shelf. The underlying transgressive unconformity, alpha , deepens toward the shelf edge, so that the coresite was never isolated from the open Black Sea. Fourteen radiocarbon dates indicate sedimentation from [not, vert, similar]9.3 ka to the present, with only one hiatus at [not, vert, similar]270 cm depth spanning [not, vert, similar]4.5-2.5 ka. Three units are present in the core: Unit A (0-270 cm)=burrowed mud with laminated silt beds and mollusc shells of Mediterranean affinity (accumulation rate [not, vert, similar]125 cm/ky); Unit B (270-525 cm)=silty mud with shelly interbeds containing Truncatella subcylindrica, Mytilus galloprovincialis, Parvicardium exiguum, Rissoa spp. and Modiolula phaseolina (rate [not, vert, similar]85 cm/ky); Unit C (525-950 cm)=burrowed silty mud with graded beds of silt and fine sand, and shells of T. subcylindrica, P. exiguum and Dreissena polymorpha (rate [not, vert, similar]360 cm/ky). Unit C developed below storm wave base at a time when proponents of a catastrophic flood in the Black Sea claim that the shelf was subaerially exposed. Clearly it was not. Ostracoda of Caspian affinity indicate [not, vert, similar]5ppt salinity until [not, vert, similar]7.5 ka. Dinocysts and foraminifera confirm a low but rising salinity after [not, vert, similar]8.6 ka. An increase of delta super(34)S from [not, vert, similar]5-30ppt through 8.4-7.6 ka is attributed to a first pulse of sulfate-rich Aegean water into an already high Black Sea, after which this sulfate was quantitatively precipitated as sulfide. delta super(34)S then dropped at [not, vert, similar]8 ka to [not, vert, similar]-20ppt as dysoxia and water-column stratification were established because of the initiation of two-way flow through the Bosphorus. Earlier water exchange with the Mediterranean was likely impeded by strong Black Sea outflow which prevented easy access of the Aegean water mass.