difficult to constrain since they are only indirectly calibrated and the age of the
oceanic crust, which might constrain their base, is still under debate, ranging from
Lower Cretaceous to Upper Cretaceous (Cloetingh et al. 2003; Galushkin et al.
2007; Nikishin et al. 2015b; Robinson et al. 1995) or even younger, possibly
Paleocene (Munteanu et al. 2013).
6.3.2 Geological Interpretation of the Seismic Lines
The first interpreted OGS line, BS01A (Fig. 6.4) goes from the Turkey margin
towards the Crimean margin crossing the deep sea part of the WBS (Fig. 6.1). The
line is directly calibrated with Limankoy-2 well, Limankoy-1 and Karadeniz-1
wells, through the BS014 seismic line and the line in Fig. 6.2 of Menlikli et al.
(2009). A more regional calibration can be done using the BS03 and BS04 (Figs. 6.6
and 6.7) and the ION-GXT lines published in Nikishin et al. 2015a, b (Fig. 6.1). In
the southern part of the line one can see the complex structures of the front part of
the Pontides Orogen, represented here by the thrusting and folding of OligocenePliocene with the thrust decollement at the base of Oligocene (Fig. 6.4).
The overall NE-ward orientated wedge shape geometry of the sedimentary cover
is clear in almost all the geological formations (Fig. 6.4). Differently, the oldest
sequences, Upper Cretaceous-Eocene wedge, are thinning NE-ward from the continent towards the oceanic deep sea basin (Fig. 6.4). The next sequences, Upper
Eocene-Lower Miocene in age, covering this unit have a more uniform thickness,
although small increases in thickness can be observed towards the edges (Fig. 6.4).
Starting with the Middle Miocene (e.g. Badenian-Sarmatian) all the sequences are
thinning out SW-ward resembling a NE-ward orientated wedge shape geometry.
The uppermost unit, Pliocene-Quaternary in age, has the most dramatic increase in
thickness (Fig. 6.4).
The overall internal geometry of the sequences is defined by the parallel to
sub-parallel continuous reflectors, with the exception of the Upper Meotian-Middle
Pontian which locally has a chaotic facies, and with the Pliocene-Quaternary one
that has a more complex geometry with chaotic to parallel and even divergent
reflectors.
The northernmost second interpreted line, BS09 (Fig. 6.5), parallel with the
previous one, crosses the present day shelf – slope to deep-water transition of the
Bulgarian-Romanian margin, overlapping with the transition from continental to
stretched-continental crust (Fig. 6.1). The oldest interpreted sequences which are of
Eocene age, are gradually thinning NE-ward, in contrast with the other sequences
that have the SW-ward trend (Fig. 6.1). Although not interpreted in the Northern
part of our section, the Upper Eocene could be locally present in depocenters such
as the one in Fig. 6.8.
Compared with the previous line the sequences boundaries have a clear unconformity character defined by their rough topography (Fig. 6.5). This character is
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I. Munteanu et al.
oceanic crust, which might constrain their base, is still under debate, ranging from
Lower Cretaceous to Upper Cretaceous (Cloetingh et al. 2003; Galushkin et al.
2007; Nikishin et al. 2015b; Robinson et al. 1995) or even younger, possibly
Paleocene (Munteanu et al. 2013).
6.3.2 Geological Interpretation of the Seismic Lines
The first interpreted OGS line, BS01A (Fig. 6.4) goes from the Turkey margin
towards the Crimean margin crossing the deep sea part of the WBS (Fig. 6.1). The
line is directly calibrated with Limankoy-2 well, Limankoy-1 and Karadeniz-1
wells, through the BS014 seismic line and the line in Fig. 6.2 of Menlikli et al.
(2009). A more regional calibration can be done using the BS03 and BS04 (Figs. 6.6
and 6.7) and the ION-GXT lines published in Nikishin et al. 2015a, b (Fig. 6.1). In
the southern part of the line one can see the complex structures of the front part of
the Pontides Orogen, represented here by the thrusting and folding of OligocenePliocene with the thrust decollement at the base of Oligocene (Fig. 6.4).
The overall NE-ward orientated wedge shape geometry of the sedimentary cover
is clear in almost all the geological formations (Fig. 6.4). Differently, the oldest
sequences, Upper Cretaceous-Eocene wedge, are thinning NE-ward from the continent towards the oceanic deep sea basin (Fig. 6.4). The next sequences, Upper
Eocene-Lower Miocene in age, covering this unit have a more uniform thickness,
although small increases in thickness can be observed towards the edges (Fig. 6.4).
Starting with the Middle Miocene (e.g. Badenian-Sarmatian) all the sequences are
thinning out SW-ward resembling a NE-ward orientated wedge shape geometry.
The uppermost unit, Pliocene-Quaternary in age, has the most dramatic increase in
thickness (Fig. 6.4).
The overall internal geometry of the sequences is defined by the parallel to
sub-parallel continuous reflectors, with the exception of the Upper Meotian-Middle
Pontian which locally has a chaotic facies, and with the Pliocene-Quaternary one
that has a more complex geometry with chaotic to parallel and even divergent
reflectors.
The northernmost second interpreted line, BS09 (Fig. 6.5), parallel with the
previous one, crosses the present day shelf – slope to deep-water transition of the
Bulgarian-Romanian margin, overlapping with the transition from continental to
stretched-continental crust (Fig. 6.1). The oldest interpreted sequences which are of
Eocene age, are gradually thinning NE-ward, in contrast with the other sequences
that have the SW-ward trend (Fig. 6.1). Although not interpreted in the Northern
part of our section, the Upper Eocene could be locally present in depocenters such
as the one in Fig. 6.8.
Compared with the previous line the sequences boundaries have a clear unconformity character defined by their rough topography (Fig. 6.5). This character is
108
I. Munteanu et al.