High frequency sea level fluctuations recorded in the Black Sea since the LGM

Abstract

This paper presents a 3D geometric interpretation of very high resolution seismic Chirp profiles acquired on the Romanian shelf during ASSEMBLAGE European Project. The results provide a solid record of the Black Sea Last Glacial Maximum (LGM) water level fluctuations. This pseudo-3D seismic interpretation shows that the Black Sea lacustrine shelf deposits form a significant basinward-prograding wedge system. On top of these prograding sequences is a set of sand dunes that delineates a wave cut-terrace like feature around the isobath −100 m. Landward of this dune field are small depressions containing barkhan-like bodies. The upper part of the last prograding sequence is incised by anastomosed channels which end in the Danube (Viteaz) canyon which are also built on the lacustrine prograding wedge. Ten stratigraphic units were distinguished and correlated with analyses of cores retrieved from this area. The results demonstrate that the first eight sequences represent lacustrine prograding wedges, the ninth sequence is the dune system itself and the tenth is a marine mud drape which covers the entire continental shelf. The lacustrine prograding wedges represent a lowstand deposit characterised by forced regression-like reflectors mapped from the pseudo-3D seismic data. Their hinge point corresponds to the wave erosion surface mapped around −100 m isobath on the multibeam mosaic. Dated cores give age control on this lowstand period, which lasted from 11 to 8.5 kyr 14 C BP as implied by: (1) the continuously dry climatic conditions in the region inferred by high percentages of herbs and steppe elements determined from ASSEMBLAGE cores and, (2) the formation of dunes between 10 and 8.5 kyr 14 C BP on the desiccated north-western Black Sea shelf at −100 m and (3) all of these covered by a marine mud drape confirming that the dune system is no longer active. The buried, anastomosed fluvial channels that suddenly disappear below 90 m depth, and a unique wave-cut terrace between 95 and 100 mbsl on the outer shelf are also consistent with a major lowstand base-level at around −100 m water depth. Preservation of sand dunes and the occurrence of small, buried incised valleys mark a rapid transgression within less than a century during which ravinement processes related to the water level rise had no time to significantly erode the seafloor.

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

“…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.…”

Kinematics of back‐arc inversion of the Western Black Sea Basin

“…The initial exposure of the shelf margin triggered instability and failure of the outer shelf and slope, generating gravitational gliding and mass transport of sediments toward the deep-sea part of the basin [Dinu et al, 2005;Ţambrea, 2007]. Rapid sea level changes are also inferred for the Pliocene-Quaternary endemic evolution of the Western Black Sea [Winguth et al, 2000;Lericolais et al, 2009], when sea level drops triggered the transport of important volumes of sediments toward the deep-sea part of the basin. Consequently, thick successions of mass-transport and turbiditic deposits are observed along a number of deep-sea fans in front of modern rivers discharging into the Black Sea [e.g., Popescu et al, 2001].…”

Landscape change and archaeological settlements in the lower Danube valley and delta from early Neolithic to Chalcolithic time: A review

“…Both are compatible with the archaeological data discussed in this paper. However, data from Lericolais et al (2009) strengthen the hypothesis of a Black Sea flooding around 7400 bce.…”

“…In the case of the Black Sea, the hypothesis of a rapid flooding around w7400 bce is still a controversial topic (Ryan et al, 1997;Görür et al, 2001;Hiscott et al, 2007;Yanko-Hombach, 2007 and review within; Lericolais et al, 2009). Scenarios proposed by Major (2006) and Lericolais et al (2009) rest on imprecise radiocarbon dating related to the hardwater effect discussed by Fontugne et al (2009).…”

“…Scenarios proposed by Major (2006) and Lericolais et al (2009) rest on imprecise radiocarbon dating related to the hardwater effect discussed by Fontugne et al (2009). They diverge, however, on the timing of the final Black Sea water flooding.…”