Abstract We investigate the ability of a submarine landslide to generate the tsunami waves observed on the Bulgarian coast of Black Sea on 7 May 2007. In our simulations, a landslide is presented as a quasi-deformable body moving along a curvilinear slope under action of the forces of gravity, buoyancy, water resistance and bottom friction. We employ the fully non-linear weakly dispersive model for tsunami wave simulations. The computations show that the initial landslide position on the real slope is extremely important for its dynamics and the wave generation process. We constructed some model landslides which generated similar waves to those observed. Moreover, these landslides stopped in the same region. Finally, we evaluated the significance of the frequency dispersion effects in the simulations.

Abstract The exploration for petroleum in the Black Sea is still in its infancy. Notwithstanding the technical challenges in drilling in its deep-water regions, several geological risks require better understanding. These challenges include reservoir presence and quality (partly related to sediment provenance), and the timing and migration of hydrocarbons from source rocks relative to trap formation. In turn, these risks can only be better understood by an appreciation of the geological history of the Black Sea basins and the surrounding orogens. This history is not without ongoing controversy. The timing of basin formation, uplift of the margins and facies distribution remain issues for robust debate. This Special Publication presents the results of 15 studies that relate to the tectonostratigraphy and petroleum geology of the Black Sea. The methodologies of these studies encompass crustal structure, geodynamic evolution, stratigraphy and its regional correlation, petroleum systems, source to sink, hydrocarbon habitat and play concepts, and reviews of past exploration. They provide insight into the many ongoing controversies regarding the geological history of the Black Sea region and provide a better understanding of the geological risks that must be considered for future hydrocarbon exploration. The Black Sea remains one of the largest underexplored rift basins in the world. Although significant biogenic gas discoveries have been made within the last decade, thermogenic petroleum systems must be proven through the systematic exploration of a wide variety of play concepts.

Abstract Before the Late Cretaceous opening of the Black Sea, the Central Pontides constituted part of the southern margin of Laurasia. Two features that distinguish the Central Pontides from the neighbouring Pontide regions are the presence of an extensive Lower Cretaceous submarine turbidite fan (the Çağlayan Formation) in the north, and a huge area of Jurassic–Cretaceous subduction–accretion complexes in the south. The Central Pontides comprise two terranes, the Istanbul Zone in the west and the Sakarya Zone in the east, which were amalgamated before the Late Jurassic (Kimmeridgian), most probably during the Triassic. The basement in the western Central Pontides (the Istanbul Zone) is made up of a Palaeozoic sedimentary sequence, which ends with Carboniferous coal measures and Permo-Triassic red beds. In the eastern Central Pontides, the basement consists of Permo-Carboniferous granites and an Upper Triassic forearc sequence of siliciclastic turbidites with tectonic slivers of pre-Jurassic ophiolite (the Küre Complex). The Küre Complex is intruded by Middle Jurassic granites and porphyries, which constitute the western termination of a major magmatic arc. Upper Jurassic–Lower Cretaceous shallow-marine limestones (the İnaltı Formation) lie unconformably over both the Istanbul and Sakarya sequences in the Central Pontides. Two new measured stratigraphic sections from the İnaltı Formation constrain the age of the İnaltı Formation as Kimmeridgian–Berriasian. After a period of uplift and erosion during the Valanginian and Hauterivian, the İnaltı Formation is unconformably overlain by an over 2 km-thick sequence of Barremian–Aptian turbidites. Palaeocurrent measurements and detrital zircons indicate that the major part of the turbidites was derived from the East European Platform, implying that the Black Sea was not open before the Aptian. The Çağlayan turbidites pass northwards to a coeval carbonate–clastic shelf exposed along the present Black Sea coast. In the southern part of the Central Pontides, the Lower Cretaceous turbidites were deformed and metamorphosed in the Albian. Albian times also witnessed accretion of Tethyan oceanic crustal and mantle sequences to the southern margin of Laurasia, represented by Albian eclogites and blueschists in the Central Pontides. A new depositional cycle started in the Late Cretaceous with Coniacian–Santonian red pelagic limestones, which lie unconformably over the older units. The limestones pass up into thick sequences of Santonian–Campanian arc volcanic rocks. The volcanism ceased in the middle Campanian, and the interval between late Campanian and middle Eocene is represented by a thick sequence of siliciclastic and calciclastic turbidites in the northern part of the Central Pontides. Coeval sequences in the south are shallow marine and are separated by unconformities. The marine deposition in the Central Pontides ended in the Middle Eocene as a consequence of collision of the Pontides with the Kırşehir Massif. Supplementary material: The palaeontological data (foraminifera, nannofossil and pollen) are available at: https://doi.org/10.6084/m9.figshare.c.3842359

Abstract The Western Pontide Magmatic Belt consists of two different magmatic series corresponding to two distinct periods of intense volcanism, separated by a pelagic limestone marker horizon resting on a regional unconformity. The first stage of magmatism and associated extensional tectonic regime prevailed in the region between the Middle Turonian and Early Santonian. During the first stage, magmas were derived from a depleted mantle source containing a clear subduction signature. The extrusives intercalated with marine clastic sediments and pelagic carbonates associated with thick debris-flow horizons and olistoliths. Based on geochemistry and depositional features, the first stage is interpreted as an extensional ensialic arc setting developed in response to northwards subduction of the Tethys Ocean beneath the southern margin of Laurasia. During the Late Santonian, the volcanism stopped and the whole region suddenly subsided with the deposition of a thin, but laterally continuous, pelagic limestone horizon. This subsidence may imply the break-up of the Laurasian continental lithosphere and the beginning of oceanic spreading in the Western Black Sea Basin. The intensified extension is interpreted to be linked to the southwards rollback of the subducting slab. During the second stage in the Campanian, magmas were derived from two contrasting mantle sources: (1) a depleted lithospheric mantle enriched by a subduction component; and (2) an enriched asthenospheric mantle which is similar to that of the ocean island basalts (OIB). The depleted lithospheric source may be linked to the subcontinental lithospheric mantle of Laurasia, which was metasomatized by the previous Tethyan subduction event rather than by an active arc magmatism. Lavas derived from the depleted source are abundant throughout the stratigraphic column, whereas those from the enriched source dominate the end of the second stage. The presence of the alkaline lavas may indicate thinning of the lithosphere and upwelling of the asthenospheric mantle in the matured stages of rifting. We argue that the main cause of both rifting and temporal change in magma generation was the steepening and rollback of the northwards subducting slab of the Tethys Ocean. The aforementioned rollback also caused the Istanbul Zone to be moved to the south, and colliding with the Sakarya Zone in the south during the Maastrichtian. Based on geochemical, stratigraphic, palaeontological and sedimentary data, we suggest that the oceanic Western Black Sea Basin opened as an intra-arc basin during Turonian–Santonian time. Supplementary material : The full geochemical dataset in MS Excel workbook format is available at https://doi.org/10.6084/m9.figshare.c.3841255

Abstract It is generally believed that the western part of the Black Sea opened during the Early Cretaceous. However, recent data and interpretation from the Turkish margin suggest rifting continued into the Coniacian or Santonian. In this review, the evidence related to the Black Sea rifting on the conjugate Romanian margin is reassessed. Our integrated interpretation of this region, supported by outcrop observations, core and detrital zircon data, suggests that rifting started during the Aptian and continued intermittently until the mid-Turonian in two distinct stages. These stages are bounded by significant unconformities and reflect the progressive widening of the rift system. The first synrift stage started in the Aptian with the deposition of fluvial and lacustrine clastic successions, and locally marine carbonates in semi-isolated depocentres. These sinks began to coalesce during the latest Aptian–Albian with shallow-marine transgression from the east, and deposition of coastal swamp, deltaic and littoral facies. The second phase of rifting during the Cenomanian was marked by transgressive shallow-marine deposits overstepping the earlier Albian depocentres. Continental break-up followed in the mid-Turonian associated with regional uplift and erosion of the basin margin and the local deposition of fluvial conglomerates.

Abstract Oligocene and Lower Miocene deposits in the Paratethys are important source rocks, but reveal major stratigraphic and regional differences. As a consequence of the first Paratethys isolation, source rocks with very good oil potential accumulated during Early Oligocene time in the Central Paratethys. Coeval source rocks in the Eastern Paratethys are characterized by a lower source potential. With the exception of the Carpathian Basin and the eastern Kura Basin, the source potential of Upper Oligocene and Lower Miocene units is low. In general, this is also valid for rocks formed during the second (Kozakhurian) isolation of the Eastern Paratethys. However, upwelling along a shelf-break canyon caused deposition of prolific diatomaceous source rocks in the western Black Sea. Overall, Oligocene–Lower Miocene sediments in the Carpathian Basin (Menilite Formation) can generate up to 10 t HC m −2 . Its high petroleum potential is a consequence of the interplay of very high productivity of siliceous organisms and excellent preservation in a deep silled basin. In contrast, the petroleum potential of Oligocene–Lower Miocene (Maikopian) sediments in the Eastern Paratethys is surprisingly low (often <2 t HC m −2 ). It is, therefore, questionable whether these sediments are the only source rocks in the Eastern Paratethys.

Abstract 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.

Abstract This study comprises the source rock evaluation of 122 Late Middle Eocene–Early Miocene mudstones from the NE margin of the Black Sea. Samples are immature to early mature. The majority of samples have moderate to very good organic richness, poor to moderate source potential and a hydrogen-deficient to gas-prone source rock quality. However, a significant proportion of the samples have good to excellent organic richness and source potential, and an oil- and gas-prone quality derived from amorphous-rich kerogens. These samples would generate significant amounts of oil and associated gas where buried to peak maturity. They come from the lowermost (Rupelian) part of the Maykop Series and the late Bartonian–early Priabonian Kuma Suite or its stratigraphic equivalents. The Rupelian source-rock interval(s) in west Georgia is at least 60 m thick and potentially as much as 200 m thick. It has a source potential index (SPI) of 0.7–2.5 t HC m −2 . The thickness of the Kuma Suite-equivalent source rock interval south of the western Greater Caucasus is unconstrained. Maykop Series source rocks occur in the Black Sea Basin. Prospective Kuma Suite-equivalent samples on both the northern and southern margins of the Black Sea imply that similar sediments may also be present in the basin. Supplementary material: Additional information on the geographical location and age determination of the samples discussed in this paper are available at https://doi.org/10.6084/m9.figshare.c.3841399

Abstract The Rioni Basin is an underexplored petroliferous basin located at the Georgian margin of the Black Sea flanked by two folded belts (the Greater Caucasus and the Achara–Trialet Belt). Whereas the stratigraphy of the northern onshore Rioni Basin has elements which are common with that of the offshore Shatsky Ridge, the southern onshore Rioni Basin segment is both stratigraphically and structurally akin to the offshore Gurian folded belt in the eastern Black Sea. In the northern basin segment, the existing oil fields (East and West Chaladidi) and an undeveloped oil discovery (Okumi) are related to either post-salt or pre-salt antiformal traps in detachment folds or in poorly understood stratigraphic pinchouts beneath a regional Upper Jurassic evaporite sequence. In the southern Rioni Basin, the oil in existing fields has either anticlinal four-way closures (Supsa) or a subthrust trap (Shromisubani) related to the leading edge of the north-vergent Achara–Trialet folded belt. Despite the long history of petroleum exploration in the Rioni Basin, these proven plays are not fully understood and systematically explored using modern technology. The existence of an Upper Jurassic regional evaporite seal highlights the possibility of pre-salt plays in the northern part of the basin.