Abstract The Black Sea is traditionally thought to be a back-arc basin with active rifting beginning in the middle Cretaceous. As to the magmatic arc associated with the southern margin of the0 basin, however, there are many open-ended questions regarding the nature, age of the arc, and even the polarity of subduction associated with the arc. Also, many models attempt to explain the formation of the Black Sea Basin in terms of geodynamic models of modern back-arc basin formation, in which extension is driven by slab roll-back. The age of rifting in the Western Black Sea (WBS) basin is still an unresolved issue. Whereas some suggested an Early to middle Cretaceous age ( i.e. , Barremian to Cenomanian) for the opening, others prefer a younger, Late Cretaceous age for the rifting, such as Turonian to Santonian, or Cenomanian to Santonian. Yet others recently described an unusually long rifting phase from the Barremian to the Santonian. The stratigraphic record of rifting on the conjugate margins of the WBS basin is markedly different. On the Turkish side, in the Pontides, a significant part of the synrift strata is missing either by erosion or by nondeposition. This is attributed to either uplift/erosion on a rift-shoulder, or to uplift/erosion due to collision to the south of the Central Pontides during Cenomanian–Coniacian times. On the conjugate Bulgarian, Romanian, and Ukrainian margin, the stratigraphic record of the Black Sea rifting is much more complete, indicating separate extensional periods for the Aptian–Albian, Cenomanian–Coniacian, and the Santonian–Campanian. The opening of the WBS Basin can be explained by asymmetric rifting at the southern margin of the European plate without invoking back-arc extension, at least for the first, wide-rift style phase of rifting during the Aptian–Albian. The subsequent Turonian–Coniacian narrow-rift style phase of rifting of the WBS basin may have been driven by subduction roll-back associated with the Pontides. Therefore only the extensional phase during the Cenomanian/Turonian to Coniacian(?) could be considered as a synrift opening period for a truly back-arc basin. The subsequent prolonged postrift subsidence is punctuated by arc volcanism along the southern margin of the WBS basin during the Campanian.

Abstract Despite having at least one major river, the Danube, supplying sediment to the Black Sea, the presence of significant deep-water clastic reservoirs has always been viewed as the major exploration risk. Source to sink concepts have been used examine this risk. Reconstruction of plausible paleodrainage scenarios combined with knowledge of the paleogeography, climate and hinterland geology have been used to estimate paleosediment budgets and provide an assessment of reservoir quality in the basin. Analysis of the basin fill, interpreted from extensive seismic coverage calibrated by wells, allows further refinement of the rates of sediment supply. A forward model of the basin fill has been created that successfully produces a postulated fill matching the observed geometry of the fill of the basin. Our analysis shows that fluvial drainage into the Black Sea from the Oligocene through to the Pleistocene has been dominated by small, local, mountainous hinterland drainage, formed in the many surrounding orogens and volcanic arcs. The resulting sediment supplied is predicted to be of low quality. Likely routes for large long-lived fluvial systems draining the continental shields to the north and west, include many updip sediment-trapping basins on the way to the Black Sea, suggests that sediment entered the basin in volume only in the latest Pleistocene. Therefore the risk of finding large volumes of sandstone in the form of large pre-Pleistocene deep-water fan complexes is high. However, smaller volume locallysourced fan-aprons may be common throughout the pre-Pleistocene succession around the margins of the basin.

Analyses of marine sediment lithology, paleorelief, and depositional environments on the northwestern Black Sea shelf were used for paleogeographic reconstructions reflecting the time periods of 30–25 ka, 15.5–15 ka, 11–10 ka, 9 ka, and 4 ka. The landscape of 25 ka, when sea level was 87 m below present, consisted of three geomorphic elements: (1) a denudation plain incised by numerous rivers and uniformly dipping southward, (2) a late Pleistocene alluvial terrace plain, within which the valleys of the Dnieper, Dniester, and Danube formed a common alluvial plain, and (3) a low coastal delta plain. The subsequent sea-level rise of the Neoeuxinian sea-lake to −55 m (15.5–15 ka) and −37 m (11–10 ka) resulted in the flooding of deltaic lowlands and a large portion of the alluvial terrace plain containing the deeply embayed Dniester and Dnieper limans. After the Drevnechernomorian transgressive phase at 9 ka, the sea flooded almost the entire late Pleistocene alluvial terrace plain, and the Dniester and Dnieper limans were converted to open marine embayments. Through Kalamitian time (4 ka), the entire Chilia section of the Danube delta was flooded. A large tract of land existed in the region of the Tendra Spit and Odessa bank. Around 25 ka, forest landscapes were common for the highlands and valley slopes of rivers and gullies. A steppe zone occupied the alluvial plain, which dominated the landscape to the south. This study demonstrates that paleogeographic reconstructions may serve as a basis for (1) locating submerged ancient settlements and (2) constraining possible migration routes.

An accurate chronology for the exchange of aquatic species between water basins is important for paleoenvironmental reconstruction on both regional and continental scales. During the early Holocene, the range of zebra mussels, Dreissena polymorpha , was limited to the Black, Azov, Caspian, and Aral Seas, as well as the estuaries and lower and middle reaches of the Pontic-Caspian rivers. We present new findings that challenge the currently held view that this species migrated into the Baltic Sea watershed during the early 1800s through the canals joining the tributaries of rivers that drain into the Black and Baltic Sea basins. Geological investigations along the southeast Baltic Sea coast (Curonian and Vistula spits and lagoons) have uncovered shells of D. polymorpha that yielded radiocarbon ages older than 1000 radiocarbon yr B.P. We propose two scenarios to explain the new radiocarbon dates for D. polymorpha . The first scenario involves an anomalously large reservoir effect—as large as 600–800 yr—however, several lines of evidence cast doubt upon the validity of such a large reservoir correction. The second scenario that might explain the old zebra mussel ages is the earlier arrival of Dreissena polymorpha into the Baltic region. Natural exchange may have been facilitated by the proximity of the tributaries draining the Pontic and Baltic watersheds. Human-mediated transport is also considered in association with Viking voyages from the Baltic to the Black and Caspian Seas between A.D. 800 and 1000, and the riverine trade exchange during the Lithuanian expansion into the Pontic steppe in subsequent centuries. It is likely that both scenarios played a role, with implications for late Holocene biogeography and paleoecology of the Pontic-Caspian and Baltic basins.