more evident for the Base Oligocene unconformity where parallel reflectors are
onlapping on a paleo-relief surface.
Similar to the previous line the Oligocene – Quaternary sequences have the same
wedge shapes and thicken in a NE-ward direction. The largest variations are
observed in the case of the Oligocene deposits with increased thickness in the
local depocenters (e.g. Kamchya and Histria Depressions), and in the case of the
Middle Miocene- Middle Pontian which are thinning and disappear towards the
Bulgarian shelf (Fig. 6.5). The internal geometry of Oligocene sequences is changing upwards from draping parallel sub-parallel reflectors to a more parallel continuous configuration. In the case of the other sequences we can notice large variations
from parallel, sub-parallel to chaotic seismic facies. Like in the previous lines some
divergent facies can also be observed in the Pliocene-Quaternary sequences.
The first dip oriented line BS04 (Fig. 6.6) on the present day shelf crosses the
deeper part of the WBS basin from the Romanian slope in the NW to Turkey deep
water parts (Fig. 6.1). From a tectonic point of view the line connects the northern
and southern continental margins separated by the oceanic domain (Fig. 6.1). The
presence of the first two interpreted sequences with reduced thickness is limited to
the central part of the section which corresponds to the oceanic domain and locally
to the stretch-continental crust (Fig. 6.6). Starting with the Oligocene the sequences
have relatively constant thickness and extend on the entire section with a lens shape
thinning at both edges.
The internal architecture of the sequences is given by the parallel to sub-parallel
reflectors moderate to high continuity, except the youngest two sequences that in
the NW part are defined by chaotic facies or divergent wedge shape. Noticeable the
Oligocene and Lower Miocene deposits exibit clear onlap terminations.
We have included the last present OGS line, BS03 (Fig. 6.7) in a composite line,
in order to have a better constrain on the age calibration and general architecture of
the basin margin. The southern part have been completed with the seismic line
publish by Menlikli et al. (2009).
The line goes parallel to the BS04 but it is located in a more southern position
(Fig. 6.1). Both lines are showing similar features of the sequences development
with the noticeable difference in the thickness which is reduced.
Almost all the sequences are gradual thinning and disappearing towards the
Southern Turkish margin. The only exception is the Lower Miocene which has an
increased thickness south of the uplifted structure defining a prograding wedge
shape geometry. The uplifted structure separates two sub-basins with different
basin infill, Eocene vs. Eocene-Oligocene in age. Above this structural high the
shallow sequences are affected by the normal faults which terminates in the Upper
Miocene deposits and are reaching the sea bottom.
The two lines offshore Romania have been integrated in this study for the
calibration of the age of WBS basin sedimentary cover (Figs. 6.8 and 6.9). The
composite line in Fig. 6.8 shows the architecture of the NW basin continental
margin with the overall basin-ward prograding and growing of the WBS basin
sedimentary cover starting with Eocene deposits which define a clear prograding
wedge. Another interesting observation is the presence of the normal gravitational
6 New Insights into the Black Sea Basin, in the Light of the Reprocessing of. . .
109
onlapping on a paleo-relief surface.
Similar to the previous line the Oligocene – Quaternary sequences have the same
wedge shapes and thicken in a NE-ward direction. The largest variations are
observed in the case of the Oligocene deposits with increased thickness in the
local depocenters (e.g. Kamchya and Histria Depressions), and in the case of the
Middle Miocene- Middle Pontian which are thinning and disappear towards the
Bulgarian shelf (Fig. 6.5). The internal geometry of Oligocene sequences is changing upwards from draping parallel sub-parallel reflectors to a more parallel continuous configuration. In the case of the other sequences we can notice large variations
from parallel, sub-parallel to chaotic seismic facies. Like in the previous lines some
divergent facies can also be observed in the Pliocene-Quaternary sequences.
The first dip oriented line BS04 (Fig. 6.6) on the present day shelf crosses the
deeper part of the WBS basin from the Romanian slope in the NW to Turkey deep
water parts (Fig. 6.1). From a tectonic point of view the line connects the northern
and southern continental margins separated by the oceanic domain (Fig. 6.1). The
presence of the first two interpreted sequences with reduced thickness is limited to
the central part of the section which corresponds to the oceanic domain and locally
to the stretch-continental crust (Fig. 6.6). Starting with the Oligocene the sequences
have relatively constant thickness and extend on the entire section with a lens shape
thinning at both edges.
The internal architecture of the sequences is given by the parallel to sub-parallel
reflectors moderate to high continuity, except the youngest two sequences that in
the NW part are defined by chaotic facies or divergent wedge shape. Noticeable the
Oligocene and Lower Miocene deposits exibit clear onlap terminations.
We have included the last present OGS line, BS03 (Fig. 6.7) in a composite line,
in order to have a better constrain on the age calibration and general architecture of
the basin margin. The southern part have been completed with the seismic line
publish by Menlikli et al. (2009).
The line goes parallel to the BS04 but it is located in a more southern position
(Fig. 6.1). Both lines are showing similar features of the sequences development
with the noticeable difference in the thickness which is reduced.
Almost all the sequences are gradual thinning and disappearing towards the
Southern Turkish margin. The only exception is the Lower Miocene which has an
increased thickness south of the uplifted structure defining a prograding wedge
shape geometry. The uplifted structure separates two sub-basins with different
basin infill, Eocene vs. Eocene-Oligocene in age. Above this structural high the
shallow sequences are affected by the normal faults which terminates in the Upper
Miocene deposits and are reaching the sea bottom.
The two lines offshore Romania have been integrated in this study for the
calibration of the age of WBS basin sedimentary cover (Figs. 6.8 and 6.9). The
composite line in Fig. 6.8 shows the architecture of the NW basin continental
margin with the overall basin-ward prograding and growing of the WBS basin
sedimentary cover starting with Eocene deposits which define a clear prograding
wedge. Another interesting observation is the presence of the normal gravitational
6 New Insights into the Black Sea Basin, in the Light of the Reprocessing of. . .
109