6 Boreal Submerged Black Sea Landscapes
83
shelf-wide ravinement surface visible in high-very high resolution seismic reflection
profiles; (6) presence of a uniform drape of sediment beginning at the same time
above the unconformity with practically the same thickness over nearby elevations
and depressions and with no visible indication of coastal-directed onlap across the
outer and middle shelf.
As the Black Sea was in a very close vicinity to the Scandinavian-Russian ice
cap, the supply of the melting water from the glaciers into the Black Sea through the
major drainage system constituted by big European rivers (Danube, Dniepr, Dniestr
and Bug) was sufficient to raise the water level between − 40 m to − 20 m just after
the Melt Water Pulse 1A (MWP1A) at approximately 14,500 years BP. The − 40 m
upper limit is interpreted from records deduced from the Danube Pro-delta building
(Lericolais et al. 2009) which are not exhaustive, and the 20 m limit is certified by
(Yanko 1990).
Palynological studies conducted on BlaSON cores (Popescu 2004) show that
from the Bölling/Alleröd to the Younger Dryas a cool and drier climate prevailed.
North-eastern rivers converged to the North Sea and to the Baltic Ice Lake (Jensen
et al. 1999), giving reduced river input to the Black Sea are resulting in a receding
shoreline. The post Bölling/Alleröd climatic event had favoured the lowering of
the Black Sea water-level and the presence of the coastal sand dunes and wave-cut
terraces confirmed this lowstand. The anastomosed buried fluvial channels described
by (Lericolais et al. 2009; Popescu et al. 2004) that suddenly disappear below − 90 m
depth and a unique wave-cut terrace on the outer shelf, with an upper surface varying
between − 95 and − 100 m is therefore consistent with a major lowstand level situated
somewhere around − 100 m depth. Precedent studies have already proposed a depth
of − 105 m for this lowstand according to a regional erosional truncation recognised
on the southern coast of the Black Sea (Algan et al. 2007; Demirbag et al. 1999; Gorur
et al. 2001) but also based on a terrace on the northern shelf edge (Major et al. 2002).
On the Romanian shelf, preservation of the sand dunes and buried small incised
valleys is to be linked with a rapid transgression where the ravinement processes
related to the water level rise have no time to erode sufficiently the sea bottom
(Benan and Kocurek 2000). Around 8,500 years BP, the surface waters of the Black
Sea suddenly attained present-day conditions owing to a rapid flooding of the Black
Sea by Mediterranean waters, as shown by dinoflagellate cyst records (Marret et al.
2009; Popescu 2004; Wall and Dale 1974). This can also be related with the beginning
widespread and synchronous sapropel deposition across slope and basin floor. This
inflow of marine waters is confirmed by the abrupt replacement of fresh to brackish
species by marine species. Further more, the model developed by (Siddall and Kaplan
2008) shows that about 60,000 m
3 of water per second must have flowed into the
Black Sea basin after the sill broke and it would have taken 33 years to equalize
water levels in the Black Sea and the Sea of Marmara. Such a sudden flood would
have preserved lowstand marks on the Black Sea north-western shelf.
Besides the strong controversy about the conditions of the last reconnection of
the Black Sea, its salinity just prior to the last reconnection is also a matter of debate
(Burkhard et al. 1998). On one hand, a fresh Black Sea “Lake” (e.g. Ballard et al.
2000; Major et al. 2002; Ryan et al. 1997) would have allowed coastal farming
83
shelf-wide ravinement surface visible in high-very high resolution seismic reflection
profiles; (6) presence of a uniform drape of sediment beginning at the same time
above the unconformity with practically the same thickness over nearby elevations
and depressions and with no visible indication of coastal-directed onlap across the
outer and middle shelf.
As the Black Sea was in a very close vicinity to the Scandinavian-Russian ice
cap, the supply of the melting water from the glaciers into the Black Sea through the
major drainage system constituted by big European rivers (Danube, Dniepr, Dniestr
and Bug) was sufficient to raise the water level between − 40 m to − 20 m just after
the Melt Water Pulse 1A (MWP1A) at approximately 14,500 years BP. The − 40 m
upper limit is interpreted from records deduced from the Danube Pro-delta building
(Lericolais et al. 2009) which are not exhaustive, and the 20 m limit is certified by
(Yanko 1990).
Palynological studies conducted on BlaSON cores (Popescu 2004) show that
from the Bölling/Alleröd to the Younger Dryas a cool and drier climate prevailed.
North-eastern rivers converged to the North Sea and to the Baltic Ice Lake (Jensen
et al. 1999), giving reduced river input to the Black Sea are resulting in a receding
shoreline. The post Bölling/Alleröd climatic event had favoured the lowering of
the Black Sea water-level and the presence of the coastal sand dunes and wave-cut
terraces confirmed this lowstand. The anastomosed buried fluvial channels described
by (Lericolais et al. 2009; Popescu et al. 2004) that suddenly disappear below − 90 m
depth and a unique wave-cut terrace on the outer shelf, with an upper surface varying
between − 95 and − 100 m is therefore consistent with a major lowstand level situated
somewhere around − 100 m depth. Precedent studies have already proposed a depth
of − 105 m for this lowstand according to a regional erosional truncation recognised
on the southern coast of the Black Sea (Algan et al. 2007; Demirbag et al. 1999; Gorur
et al. 2001) but also based on a terrace on the northern shelf edge (Major et al. 2002).
On the Romanian shelf, preservation of the sand dunes and buried small incised
valleys is to be linked with a rapid transgression where the ravinement processes
related to the water level rise have no time to erode sufficiently the sea bottom
(Benan and Kocurek 2000). Around 8,500 years BP, the surface waters of the Black
Sea suddenly attained present-day conditions owing to a rapid flooding of the Black
Sea by Mediterranean waters, as shown by dinoflagellate cyst records (Marret et al.
2009; Popescu 2004; Wall and Dale 1974). This can also be related with the beginning
widespread and synchronous sapropel deposition across slope and basin floor. This
inflow of marine waters is confirmed by the abrupt replacement of fresh to brackish
species by marine species. Further more, the model developed by (Siddall and Kaplan
2008) shows that about 60,000 m
3 of water per second must have flowed into the
Black Sea basin after the sill broke and it would have taken 33 years to equalize
water levels in the Black Sea and the Sea of Marmara. Such a sudden flood would
have preserved lowstand marks on the Black Sea north-western shelf.
Besides the strong controversy about the conditions of the last reconnection of
the Black Sea, its salinity just prior to the last reconnection is also a matter of debate
(Burkhard et al. 1998). On one hand, a fresh Black Sea “Lake” (e.g. Ballard et al.
2000; Major et al. 2002; Ryan et al. 1997) would have allowed coastal farming