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Oligo-Miocene (‘Maikopian’) deposits are considered the main source rocks in the Black Sea area, although only a few source-rock data are available. Geochemical logs from nine wells are used together with age constraints provided by calcareous nannoplankton, well and seismic data to determine vertical and lateral changes of the source potential. Oligocene rocks overlie Eocene deposits with a major unconformity on the western Black Sea shelf in Bulgaria. A west–east-trending erosional structure (the Kaliakra canyon) developed during Lower Oligocene time and was filled with Oligo-Miocene deposits. Potential source rocks are present in different stratigraphic units, but the most prolific intervals accumulated during time intervals when the isolation of the Paratethys resulted in oxygen-depleted, brackish environments with high bioproductivity. These include Lower Solenovian rocks related to blooms of calcareous nannoplankton, which form an extensive layer outside the Kaliakra canyon. This unit hosts a good potential to generate oil and gas. Diatom-rich, very good oil-prone source rocks accumulated during a second isolation event in the Kozakhurian. Thick sections of these diatom-rich rocks occur within the canyon and are present in thin layers outside of it. High productivity of siliceous organisms is attributed to upwelling within the canyon. All studied units are thermally immature on the shelf.

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An unconformity has been observed along the Black Sea shelf on seismic reflection profiles and wells which is broadly similar to the one associated with that formed during the Messinian salinity crisis (MSC) in the Mediterranean. Therefore, this intra- (or Middle) Pontian unconformity has been traditionally interpreted as the manifestation of the MSC in the Black Sea Basin. However, the magnitude of the sea-level fall associated with this erosive surface does not appear to be nearly as significant as was assumed previously. Also, the inferred MSC surface itself cannot be easily followed into the palaeo-deep-water basin as a regional unconformity in the same manner as in the Mediterranean. Moreover, around the Black Sea, there is no evidence of major river incisions during the MSC, unlike the well-documented cases in the Mediterranean region. If the MSC evaporites in the Mediterranean indeed deposited in a subaerial setting at the basin floor, the lack of a major drawdown in the Black Sea explains why there are no Messinian evaporites in the Black Sea. Owing to the approximately 500 m MSC sea-level drop the Black Sea basin system, this basin did not even get close to the conditions required for the formation of evaporites in the basin centre. As the magnitude of the sea-level drop and the overall impact of the MSC in the Black Sea is interpreted to be less significant than in the Mediterranean, the risk of breaching pre-existing hydrocarbon traps during the MSC is less than has been suggested before.

The Levant Basin is a deep-water basin in the eastern Mediterranean region. A large part of the basin contains a characteristic set of closely spaced normal faults, informally called the “piano key faults.” These normal faults trending NW-SE have a fairly high-frequency map-view spacing of approximately 3–4 km on average and tens to hundreds of meters of interpreted throw. A large part of the pre-Messinian sedimentary strata is faulted, including the entire Miocene-to-Oligocene sequence. At depth, all the faults consistently die out at the same intra-Eocene detachment level. This stratigraphic level is interpreted to have a regionally developed shale sequence acting as the basal detachment surface for the piano key faults. The amount of throw on the individual faults appears to decrease toward the basin margin and the faults do not extend into the adjacent basins of the broader eastern Mediterranean area.