Sea floor features in Black Sea. Bacterial mats, encrustaceans and gas bubbles streaming upwards from vents. Images courtesy GHOSTDABS - Hamburg University.
Black Sea water level fluctuations since the LGM
The Black Sea semi-enclosed basin is one important part of the receiving basin collecting the Fennoscandian and part of the Alps melt waters. Actually, it is receiving the waters from main Eastern Europe rivers such as the Dniper, the Dinestr, the Don, and also the Danube which has recorded the melting of the Alps. For this, the Black Sea is a unique laboratory for paleo climatic studies as its water level fluctuations are directly linked to the climate variability without any hysteresis effect compared to the global ocean. The timing and processes which led to the last connection between the Black Sea and the Mediterranean Sea is still under keen debate. During the 3 year ASSEMBLAGE European Project (EVK3-CT-2002-00090 from 2003 to 2006) a seismic transect was shot from the Danube Delta down to the Deep Sea fan. Moreover, four long piston cores (longer than 30 m) were recovered on specific targets. The seismic transect was analysed in term of sequence stratigraphy and a succession of depositional sequences and eroded phases were evidenced and the stacking pattern was made down to the Last Glacial Maximum (LGM). The results obtained from the four core analyses allowed to complete and date the stratigraphic sequences evolution, from the Danube Delta down to the continental shelf edge.From this transect analysis it comes that since the LGM, the Black Sea evolution was induced by several important paleo environmental changes underlined by a succession of water level system tracts: (1) a lowstand system tract at -160 m with a first erosion surface on the shelf associated with a pro Delta extension formed during the LGM; (2) then a high-stand system tract at -40 m can be associated with the Bölling-Alleröd Black Sea high-stand; (3) a second low-stand system tract between -80 m and – 120 m associated to a second erosion surface on the shelf formed since the Younger Dryas and marqued by a second pro Delta. (4) the preservation of coastal barriers and paleo-river channels cutting across the continental shelf can be related to a rapid transgression. This results obtained at the Danube mouth North of the Viteaz canyon confirm previous results obtained from paleo coastal areas studied at the Southern part of the Viteaz Canyon where a wave cut terrace dated between Younger Dryas and Pre-Boreal was described.
Watch your (geological) language!
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Can’t cut and paste this - but I agree with the earthquake scenario...