**5. Discussion**

Due to the high resolution of the data, it was possible to indicate incised valleys, which are rarely seen on seismic sections. Their existence proves that we provided the correct definition of the sequence boundaries. Incised valleys have very high hydrocarbon potential (both for conventional and unconventional plays), here verified by the results of the sweetness attribute and spectral decomposition. However, despite being small in size in the presented case, their existence shows the applicability of the proposed methodology. Moreover, erosional truncations that are associated with the sub-aerial erosion and diverse relief of the onshore part of the highstand delta (HST) could have been indicated by chronostratigraphic interpretation.

It should be noted that there is an ongoing discussion regarding the methodology of sequence boundary interpretation and the specialistic nomenclature [46,51,54,55]. Nevertheless, in the presented study, we decided to divide sequence boundaries into two types, type I and type II [56], even though type II discontinuities were recently considered to be an integral part of the failing stage system tract (FSST; a shift in the shoreline basinward during one sequence with a fall in the relative sea level).

The high-resolution seismic image enabled the identification of di fferences in the failing stage system tracts between type I and type II depositional sequences. The interpretation of a Wheeler diagram made it possible to define and di fferentiate between FSST type II from lower-lying highstand deposits (HST).

The heterogeneous sequence under analysis exhibits significant thickness changes and the rebuilding of architecture. This is a result of continuous fluctuations in sediment flux, the rate of subsidence and eustatic sea level. Depositional architecture is also controlled by intensive tectonics; its influence is prominent in the non-according contacts between chronostratigraphic horizons and

in the erosional cutting of older deposits by younger sediments [47,55]. Depositional sequences are characterized by a geometry that ensures that the lack of a link between the shelf and basin deposits can be proposed. After each erosional episode, signatures that prove the rebuilding of the sedimentary basin can be defined; a shift in the basin axis toward the NE direction can also be indicated. The increase in the transportation rate brings fluvial erosion to a halt and shifts the shelf margin towards a higher subsidence area. This is proved by the increasing thicknesses of the sediments and the development of basin elements (slope fans, basin floor fans). After stabilization, the sediment flux rate is lower than the subsidence rate and the deposits exhibit retrogradational character until the next tectonic episode.
