faults which affects the upper part of the sedimentary pile and are connected basin
wards with toe of thrusts defining a shelf collapse system.
The line in Fig. 6.9 together with the previous lines details the internal architecture of the sedimentary cover of the WBS basis, with particular insights into the
Pliocene-Quaternary sequence that have been described elsewhere on the previous
sections (Figs. 6.4–6.7). Looking in details one can see the typical deep sea features
like: mass transport complexes (MTC) characterized by chaotic facies; basin floor
fans (BFF) marked by parallel high amplitude continuous reflectors; channel leveed
system (LC) with their characteristic divergent wedge reflectors pattern and transparent facies and the channel fill (CF) marked by the chaotic high amplitude
reflectors.
6.4 Discussions and Conclusions
The first order feature that characterizes all the seismic lines is the increased
thickness towards the basin centre, this is clearly related with the basin subsidence
history. Based on this we can split the basin evolution into four main stages. During
the first one, before the Oligocene, the sedimentary sequences Upper Cretaceous?Eocene are thinning towards the basin centre. This might have at least two main
reasons: one is that the extension that started in the Lower Cretaceous continued
until Eocene with the formation of the oceanic crust since uppermost Cretaceous
(see also Munteanu et al. 2013); the second one might be related with the sediments
supply, with the sediments being trapped in continental normal faults (tilted blocks)
related sub-basins with limited amount of sediments reaching the basin centre
which was starving.
The second stage starts with the Oligocene deposition and marks the beginning
of deep water WBS basin, as a consequence of the thermal subsidence of the
oceanic domain. This steady and gradual subsidence is also evident by the uniform
Oligocene-Lower Miocene architecture and facies and their spatial distribution.
The observed differences in the Oligocene thickness could be related to the
deposition and filling over an inherited paleo topography relief that was tectonically
controlled and created the sub-basins. The structural grain is related with the
inherited geometry from extensional history of the basin and in part with the
inverted structures during the Upper Eocene-Miocene times that affected the
basin margins.
The third stage marks the transition from a tectonically controlled basin to
mainly sea-level driven mechanism. This stage is defined by the general reduced
thickness of the Middle Miocene to Upper Miocene sequences and numerous local
unconformities.
The last stage starts after the major sea-level drop at the Miocene-Pliocene
boundary, which created a large unconformity (MSC unconformity) with shelf
collapse and formation of gravitationally related structures that affected the previous deposits including the Oligocene. Some of these faults can be active in the
110
I. Munteanu et al.
wards with toe of thrusts defining a shelf collapse system.
The line in Fig. 6.9 together with the previous lines details the internal architecture of the sedimentary cover of the WBS basis, with particular insights into the
Pliocene-Quaternary sequence that have been described elsewhere on the previous
sections (Figs. 6.4–6.7). Looking in details one can see the typical deep sea features
like: mass transport complexes (MTC) characterized by chaotic facies; basin floor
fans (BFF) marked by parallel high amplitude continuous reflectors; channel leveed
system (LC) with their characteristic divergent wedge reflectors pattern and transparent facies and the channel fill (CF) marked by the chaotic high amplitude
reflectors.
6.4 Discussions and Conclusions
The first order feature that characterizes all the seismic lines is the increased
thickness towards the basin centre, this is clearly related with the basin subsidence
history. Based on this we can split the basin evolution into four main stages. During
the first one, before the Oligocene, the sedimentary sequences Upper Cretaceous?Eocene are thinning towards the basin centre. This might have at least two main
reasons: one is that the extension that started in the Lower Cretaceous continued
until Eocene with the formation of the oceanic crust since uppermost Cretaceous
(see also Munteanu et al. 2013); the second one might be related with the sediments
supply, with the sediments being trapped in continental normal faults (tilted blocks)
related sub-basins with limited amount of sediments reaching the basin centre
which was starving.
The second stage starts with the Oligocene deposition and marks the beginning
of deep water WBS basin, as a consequence of the thermal subsidence of the
oceanic domain. This steady and gradual subsidence is also evident by the uniform
Oligocene-Lower Miocene architecture and facies and their spatial distribution.
The observed differences in the Oligocene thickness could be related to the
deposition and filling over an inherited paleo topography relief that was tectonically
controlled and created the sub-basins. The structural grain is related with the
inherited geometry from extensional history of the basin and in part with the
inverted structures during the Upper Eocene-Miocene times that affected the
basin margins.
The third stage marks the transition from a tectonically controlled basin to
mainly sea-level driven mechanism. This stage is defined by the general reduced
thickness of the Middle Miocene to Upper Miocene sequences and numerous local
unconformities.
The last stage starts after the major sea-level drop at the Miocene-Pliocene
boundary, which created a large unconformity (MSC unconformity) with shelf
collapse and formation of gravitationally related structures that affected the previous deposits including the Oligocene. Some of these faults can be active in the
110
I. Munteanu et al.