Assessment of Black Sea water-level fluctuations since the Last Glacial Maximum

Abstract

This paper presents geophysical and core data obtained from several marine geology surveys carried out in the western Black Sea. These data provide a solid record of water-level fl uctuation during the Last Glacial Maximum in the Black Sea. A Last Glacial Maximum lowstand wedge evidenced at the shelf edge in Romania, Bulgaria, and Turkey represents the starting point of this record. Then, a fi rst transgressive system is identifi ed as the Danube prodelta built under ~40 m of water depth. The related rise in water level is interpreted to have been caused by an Increase in water provided to the Black Sea by the melting of the ice after 18,000 yr B.P., drained by the largest European rivers (Danube, Dnieper, Dniester). Subsequently, the Black Sea lacustrine shelf deposits formed a signifi cant basinward-prograding wedge system,\ud interpreted as forced regression system tracts. On top of these prograding sequences, there is a set of sand dunes that delineates a wave-cut terrace-like feature around the isobath −100 m. The upper part of the last prograding sequence is incised by anastomosed channels that end in the Danube (Viteaz) canyon, which are also built on the lacustrine prograding wedge. Overlying this succession, there is a shelfwide unconformity visible in very high-resolution seismic-refl ection profi les and present all over the shelf. A uniform drape of marine sediment above the unconformity is present all over the continental shelf with practically the same thickness over nearby elevations and depressions. This mud drape represents the last stage of the Black Sea water-level fluctuation and is set after the reconnection of this basin with the Mediterranean Sea

Evolution of the Danube Deep-Sea Fan since the Last Glacial Maximum: new insights into Black Sea water-level fluctuations

“…28,000 cal a. BP, and levee growth of the Middle channel-levee system thereafter) suggests an efficient river-canyon connection, an expected result with regard to the palaeoenvironmental conditions. Indeed, the level of the Black Sea 'Lake' was probably about 150-100 m lower than present sea-level at that time (Ryan et al, 1997;Winguth et al, 2000;Aksu et al, 2002;Lericolais et al, 2009Lericolais et al, , 2011. At this time the sediment load of the western Black Sea rivers, including the Danube River, was higher than today ( Fig.…”

“…(B) Reconstruction of the Black Sea 'Lake' level fluctuations. Thick, black line after Soulet et al (2011a,b); thin, black line and blue diamonds (seismic sequences dated) after Lericolais et al (2011Lericolais et al ( , 2013; dashed red area, probability inferred from the data of the present study. Note that a water-level of −70 m (i.e., delta progradation of ca.…”

“…The contribution of the Danube River, through its connection with the Alpine ice-sheet, is expected to be much less than that of the Dnieper River but no quantification exists for that time. Following the Younger Dryas cold event (~12,650-11,700 cal a. BP), Lericolais et al (2007Lericolais et al ( , 2009Lericolais et al ( , 2010Lericolais et al ( , 2011 suggest a new significant lowering down to −100 m, based on the occurrence of aerial coastal dunes still visible on the Romanian shelf under the post-glacial marine mud drape. However, no evidence of such a lowstand interval is found in the southwestern Black Sea (Aksu et al, 2002) for example, making this assumption controversial (e.g., Giosan et al, 2009;Mudie et al, 2014;YankoHombach et al, 2014).…”

“…At that time, the water level was controlled by regional climate and varied independently from global sea level (Ross et al, 1970). Based on seismic stratigraphy (Ryan et al, 1997;Winguth et al, 2000;Aksu et al, 2002;Lericolais et al, 2009Lericolais et al, , 2010Lericolais et al, , 2011 and reservoir age reconstructions (Soulet et al, 2011a), it is suggested that the water level of the Black Sea 'Lake' oscillated from ca − 150/− 100 m (e.g., during the LGM) to ca. − 35/− 25 m, that corresponds to the depth of the Bosphorus sill.…”

Absolute chronology of fluvial events in the Upper Dnieper River system and its palaeogeographic implications

“…The glacial melt water output is regarded as an important governing factor for the post-LGM level changes of the Black Sea (Lericolais et al, 2011;Sidorchuk et al, 2011). Large pulses of glacial-melt waters delivered to the Black Sea have been interpreted from geochemical composition of bottom sediments in the north-western shelf and dated to 18-16 ka cal BP (Major et al, 2006).…”