The continental shelf of the microtidal Black Sea, with its 4125 km-long coastline, has an average width of c. 40 km and may be subdivided into seven regions, the largest of these being the NW Shelf and the SW Shelf. Palimpsest shelf environments and terrestrially derived siliciclastic sedimentation are dominant. The Marmara Gateway, bisecting the southwestern shelf, controls the influx of Mediterranean-sourced water into the semi-enclosed Black Sea, and has been episodically open during the Quaternary. The best evidence for the most recent marine transgression of the pre-existing and isolated lake is found on the mid- and outer NW Shelf. Radiocarbon dating of marine and non-marine bivalve molluscs and peat indicates the most recent re-connection of the Black Sea with the oceanic reservoir occurred between 8200 and 8600 ¹⁴C years BP. Water levels during the transgression in the enclosed lake rose from a level 107 m or more below present values, to above the Bosphorus Sill (−35 m) in about 400 ¹⁴C years. However, the transition from low-salinity (0–5‰) lacustrine conditions to near-modern values (18‰) took ≥1000 years, indicated by the progression from freshwater to brackish molluscs and gastropods, dominated by Dreissena, to Mediterranean-derived estuarine taxa (e.g. Mytilus), suited to nutrient-rich conditions.