Robinson, A.G., 1997, Introduction: tectonic elements of the Region, in A.G. Robinson, ed., Regional and petroleum geology of the Black Sea and surrounding region: AAPG Memoir 68, p. 1–6. Chapter 1

◆ Introduction: Tectonic Elements of the Black Sea Region

Andrew G. Robinson JKX Oil & Gas plc Guildford, United Kingdom

◆

INTRODUCTION apparently rifting during the mid-Cretaceous (Görür, 1988; Manetti et al., 1988). There was also the hint that In 1967 and 1969, two oceanographic cruises were the Black Sea had originated not as a single basin, but made in the Black Sea under the guidance of the as two—an eastern and a western Black Sea—that had Woods Hole Oceanographic Institute: The cruises coalesced during their postrift phases to form the sin- included scientists from many countries and disci- gle depocenter observed today. plines. Their aims were to determine the recent geo- The volumes referred to above did not reflect even a logical and geochemical evolution of the Black Sea, to small part of the total geological work carried out on map the shallow structure of the basin, and to study the Black Sea. Unfortunately, the vast volume of Soviet the interaction between the oxidized surface waters literature was inaccessible and, although often of good and the anoxic waters beneath them. The results were quality, was just as often difficult for a Western reader published 23 years ago, as AAPG Memoir 20 (Ross to understand. This was also largely true of the Turk- and Degens, 1974). During the 1969 cruise, the vessel ish literature, although research—mainly on the Pon- Atlantis II collected 40 piston cores, which formed the tides—by the group at I˙stanbul Technical University basis of most of the subsequent geological studies that was widely disseminated. None of the countries were restricted to very recent sedimentation. Specula- around the Black Sea made information obtained from tions concerning the origin of the basin and the rela- petroleum exploration programs available either to tionship of the geology offshore to that exposed each other or to the scientific community. It was even around the margins of the Black Sea were rooted in impossible to obtain geological maps from the sur- pre-plate tectonic concepts of basin formation and rounding onshore areas (other than old 1:500,000 geo- were in any case hampered by a lack of relevant data logical maps of northern Turkey). As much as any (Brinkmann, 1974). sedimentary basin, the Black Sea suffered from the In 1976, the Glomar Challenger visited the Black Sea cold war. on Leg 42B of the Deep Sea Drilling Project and drilled During the first few years of the 1990s, however, the and cored three deep-water sites (379, 380, and 381). profound political changes that took place in Eastern Well 381 north of the Bosporus encountered sediments Europe began to have an equally profound effect on as old as Miocene, including some apparently the quantity and quality of geological work carried out deposited in shallow water (Ross, 1978). in the Black Sea region. Romania, Bulgaria, , The next major volume in Western literature to deal Georgia, and Russia became independent sovereign with the Black Sea was published a decade later, col- states and, to a greater or lesser extent, opened their lecting papers presented two years earlier at a confer- offshore areas to exploration by Western oil compa- ence in Yalta. In this volume, a number of seismic nies (see Benton, this volume). In doing so, they made reflection lines—shot in 1975 by an Italian vessel— available a large amount of well and seismic data that were published and, for the first time, the scientific had until that time been regarded as state secrets. The community had a picture of the deeper structure of the new petroleum exploration programs led to the acqui- Black Sea (Finetti et al., 1988). The interpretation of the sition of new high-multiplicity marine reflection seis- seismic data, however, was still impeded by the small mic data and to the drilling of new exploration wells in number of wells drilled in the Black Sea to which the Bulgarian, Romanian, and Ukrainian offshore areas. lines could be tied, by the ambiguity of even these few At the same time, previously secret detailed geological ties, and by the presence of numerous multiples. By maps of excellent quality became available for all of this time, the Black Sea was nonetheless widely the former Soviet and Eastern European states regarded as a marginal basin developed to the north of (although, for the most part, these remain difficult to the northward-subducting Tethyan oceanic plate, obtain). It also became possible to visit these countries 1 2 Robinson more or less independently, to carry out field studies, This is a slightly odd map in that it tries to show a num- and to talk without hindrance to their scientists. Mean- ber of attributes, principally basin origin—age and while, in the southern part of the Black Sea, the early type—but also the latest deformation event. In many 1990s saw the licensing of much of the Turkish off- areas, the nature and exact positions of the boundaries shore sector to Western companies for petroleum of sedimentary basins are unclear; the origin of some is exploration. No new wells have been drilled in the disputed; and in some parts of the Black Sea, the map is licensed areas, but a large amount of reflection seismic based on scanty information. It is therefore a somewhat data has been acquired, interpreted, and in part pub- unsatisfactory hybrid and will be open to criticism from lished (Robinson et al., 1996). It is unfortunate that those who have detailed knowledge of particular areas. detailed geological maps of Turkey are still considered So, after many dark hours with blunted colored pencils secret and remain unpublished. during which I many times nearly consigned the map to As a result of this activity, a large amount of new the bin, I have ended up including it, having convinced high-quality geological work has been carried out on myself that it is better to have some map of this kind the Black Sea and surrounding areas. Much of this is covering the entire Black Sea region than it would be to published in this volume for the first time. The contri- have nothing at all. I encourage those who know where butions to the volume cover most of the major tectonic it is wrong or misleading to write and tell me. elements in and around the Black Sea. They do not do so evenly, and are biased principally toward those GENERAL SETTING OF areas that have received the most attention by oil com- panies, and toward northern Turkey, where Turkish THE BLACK SEA BASINS geologists have been active for many years. The chap- ters not only cover different areas but also encompass The present Black Sea morphology has been pro- very different types of study, based on different kinds duced by the coalescence of two basins during their of data. Thus, papers on the Pontides are essentially postrift phases (Robinson et al., 1996). Both formed as based on field mapping; those on the offshore shelf extensional basins north of a northward-subducting areas are based on seismic and well data. Perhaps not oceanic plate—the Tethys Ocean. The suture zone surprisingly, different workers using different data- where this ocean eventually closed is marked by an ophiolite belt and subduction-accretion complex run- bases sometimes come up with quite different and ˙ even opposing and incompatible conclusions. In edit- ning from Izmir on the Turkish Mediterranean coast, ing this volume, I have made no attempt to resolve through Ankara and Erzincan, and into the Sevan such differences or to sweep them under the carpet; I region of Armenia. The Western basin is widely wish to draw attention to them on the basis that the accepted as having rifted in the Aptian-Albian. There identification of a problem is the first step to its solu- is plenty of evidence of synrift deposits of this age tion. The volume begins with a series of chapters that onshore in Turkey, and of Aptian-Albian synrift deal with general aspects of the development of the geometries on offshore seismic data. The opening of Black Sea; subsequent chapters are organized in an the Eastern Black Sea is harder to date, partly because essentially counterclockwise fashion, beginning with synrift deposits appear to be absent, but a consensus Romania and ending in the Gulf of (Ukrainian seems to be emerging that it is younger than the West- offshore). There are notable gaps at Thrace (although ern Black Sea, within end-Cretaceous to Paleocene. the Thrace Basin is well documented in literature else- Spadini et al. (this volume) summarize the results of where; see later), the Greater Caucasus, the Russian their work modeling the subsidence and sedimenta- margin of the Eastern Black Sea, the Azov Sea, and tion history of the two basins. They show how West- onshore Crimea. ern and Eastern basins appear to have formed on quite To those not particularly familiar with the Black Sea different lithospheres with quite different thermal and area, the complexity of the geology and the volume of mechanical properties. They show how these differ- literature available (although often inaccessible) can ences influenced the subsequent development of the prove somewhat daunting. This chapter is therefore basins, and how they can explain the absence of synrift intended to serve not just as a background and intro- deposits in the Eastern basin and the variable thick- duction to the Memoir and the chapters in it, but also nesses of the early postrift stratigraphies. to the main tectonic elements in the Black Sea region. I These two most recent Black Sea basins are very hope that this will help the reader put the other chap- much the tip of a marginal-basin iceberg. Back- and ters into a regional context quickly. The complexity of intra-arc basins have been opening and closing near the area is such that it is impossible to write an uncon- troversial review, and this chapter inevitably reflects the southern margin of the East European continent my prejudices. Where others have very different prej- since at least the beginning of Mesozoic. Examples udices, I have tried to point this out. Indeed, a second include the Greater Caucasus basin (Early Jurassic rift) aim of this chapter is to indicate where there are major and the Küre-Tavric basin (Triassic), now split differences of interpretation. between the Central Pontides and Crimea by the Following, I give a brief description of the main tec- spreading of the Western Black Sea (indeed, the West- tonic elements in the Black Sea region, explaining how ern Black Sea rifted on the site of this older basin). these are covered in this Memoir. For detailed reference Reconstructing the original settings and geometries of lists, the reader should look in these chapters. I illustrate these older basins is not easy and is not helped by a the descriptions with reference to a map (Enclosure 1). complete lack of plausible paleomagnetic data. Banks Introduction: Tectonic Elements of the Black Sea Region 3 and Robinson (this volume) attempt an explanation view of petroleum exploration, as they form at least for the early Mesozoic basins in terms of strike-slip one oil reservoir—at the Tyulenovo oil field on the Bul- motion along major NW-SE faults such as the Pece- garian coast. The sedimentology of the carbonates is neaga-Camena fault in Romania. They envisage a set- described in detail by Harbury and Cohen (this vol- ting behind a zone of oblique subduction, rather like ume). They show a transition between shallow-marine the present-day Andaman Sea. carbonates in the north and deep-marine facies in the As the Tethys Ocean finally began to close during south, with the transition trending approximately east- the Paleogene, the elevation of the Pontides led to the west and passing through Varna in northern Bulgaria. development of a restricted basin system, partly iso- By the Hauterivian, a clastic wedge had developed on lated from the world’s oceans and known as the margin. Following a mid-Cretaceous hiatus, pre- Paratethys. At times, Paratethys stretched from the sumably reflecting the location of the area at the west- Pannonian basin in the west as far as the South ern margin of the Aptian Western Black Sea rift, Upper Caspian. Due to widespread provinciality of faunas Cretaceous facies are outer shelf to bathyal. At this and flora, the biostratigraphy of Paratethys is a subject time, the southern margin of the Moesian Platform in its own right. A digestible review of its stratigraphy (where the Balkanides are now) would have been is provided by Jones and Simmons (this volume), who linked to the Western Black Sea. The subsidence and attempt their explanation in a global sequence strati- structural history of the Balkanides are the subject of graphic framework. the chapter by Sinclair et al. (this volume). Using a combination of seismic, well, and outcrop data, they show how, at around the end of the Cretaceous, the WESTERN MARGIN OF THE WESTERN Jurassic extensional faults on the south-facing passive BLACK SEA: FROM THE SCYTHIAN margin were inverted as compression in the Balkanide PLATFORM TO RHODOPE region began. Most of the shortening is, however, thin- skinned and of early to middle Eocene age. Compres- The East European, Scythian, and Moesian plat- sion had ended by the beginning of the Miocene. forms appear to have had rather similar geological his- The Balkanides are also described by Banks (this tories and share a common general stratigraphy. The volume) in a chapter that attempts to integrate the Moesian Platform is described by Tari et al. (this vol- geological histories of all of the major tectonic units ume). They present a series of seismic lines and along a north-south transect from the delta to regional isopach maps that show that this area was Thrace. Banks describes how the early Mesozoic anything but platform-like during its pre-Late Jurassic stratigraphy of the Strandzha Zone (I˙stranca in Turk- history. The area was affected by a Hercynian (pre- ish) also restores to a south-facing passive margin, and Permian) deformation and, during the Middle Triassic, how the stratigraphy is similar to that exposed in the E-W trending rift basins developed in northern Bul- Balkanides. He suggests a Late Triassic age for the garia and southern Romania. Tari et al. describe these onset of compression (which is the same as that as failed arms of the Paleotethys Ocean. During the demonstrated by Tari et al. for the Moesian Platform Norian-Rhaetian, the area was again subjected to com- further north), but believes the main deformation to be pressional deformation. A foreland fold and thrust belt post-Middle Jurassic. Strandzha has also been affected developed in northern Bulgaria, with the effects of the by Tertiary compression. These relationships suggest compression dying out to the north in Romania. This that there is little extension associated with the thrust belt was presumably the external (northern) part Srednogorie Zone, which contains more than 3 km of of the Strandzha orogenic belt (Banks, this volume). Upper Cretaceous marine volcanics and volcaniclastic The disappearance of compressive structures of Late sediments. The chemistry of the volcanics suggests Triassic age to the north is interesting because north of that the zone principally represents a subduction- the Peceneaga-Camena fault and the North Dobrogean related volcanic arc. orogenic belt, on the southern edge of the Scythian Platform, there is another belt of thin-skinned compres- sive deformation beneath undeformed Upper Jurassic SOUTHERN MARGIN OF THE BLACK limestones that also appears to be of Triassic age (Odessmorgeologia, unpublished data; see map, Figure SEA BASINS: THE PONTIDES, ACHARA- 1). These two foldbelts—in north Bulgaria and south- TRIALET BELT, AND ASSOCIATED ern Ukraine—could be juxtaposed by 200–300 km of FORELAND BASINS sinistral strike-slip movement along the Peceneaga- Camena fault during or prior to the Late Jurassic. Such The Pontides are a complex belt of compressional movement is independently proposed by Banks and deformation that runs from Thrace in the west to Robinson (this volume) to explain the development of Georgia in the east, forming the northern coast of Late Triassic? extensional basins that closed prior to or Turkey and extending offshore to affect the postrift during the Middle Jurassic. fills of both Western and Eastern Black Sea basins. The During the Late Jurassic and Neocomian (and pos- northern deformation front mainly runs a few tens of sibly earlier), a south-facing passive margin devel- kilometers offshore. The Pontides are bounded to the oped, on which a carbonate ramp formed. The Upper south by a broad subduction-accretion complex with Jurassic carbonates are of interest from the point of ophiolites that was assembled through the Mesozoic 4 Robinson and early Tertiary as the Tethys Ocean closed. The linked to the Peceneaga-Camena fault in Romania. Pontides are in fact geologically quite diverse and Görür (this volume) links the southern and northern include at least three major terranes (and probably margins of the Western Black Sea in a different way, other smaller ones): the Western, Central, and Eastern joining the Western/Central Pontides boundary to a Pontides. Each of these has its own characteristic his- postulated West Crimean fault west of the Crimean tory of compressive, extensional, and strike-slip defor- Peninsula (see also Okay et al., 1994). mation, and each incorporates more than one basin The Eastern Pontides have been the subject of little type. An overview of the entire province is provided attention until recently. Their geological history is here by Yılmaz et al. (this volume), who summarize described by Okay and S¸ahintürk (this volume). The years of field studies by Turkish workers. Although pre-Jurassic deposits have a typically Laurasian charac- this chapter is long and presupposes at least some geo- ter, indicating that the boundary with Gondwana lay graphic familiarity with northern Turkey, it includes a further to the south. The usual south-facing carbonate- tremendous amount of detailed information that has dominated passive margin can be recognized for the for the most part been published only in Turkish. Late Jurassic to Barremian period and is located toward The Western Pontides are characterized by an the south of the Eastern Pontides. The Eastern Pontides unmetamorphosed Cambrian–Ordovician to Carbonif- are dominated at outcrop by two more or less coincident erous sedimentary sequence resting on Precambrian ensialic volcanic arcs of Late Cretaceous and Eocene metamorphic basement. On this is superimposed a Tri- (Lutetian) age. Okay and S¸ahintürk date the onset of assic rift to passive margin sequence followed by a Late subduction here as Cenomanian–Turonian and suggest Jurassic carbonate ramp. The similarity to the Moesian that the Eastern Black Sea extensional basin opened in Platform is clear. Indeed, it is now widely accepted that an intra-arc setting during the Maastrichtian, rather ear- the Western Pontides rifted from the Moesian Platform lier than the Late Paleocene suggested by Robinson et al. during the Aptian–Albian and moved south to their (1996). There appears to be a consensus emerging that present position during the Late Cretaceous, leaving the Eastern Black Sea is not just a separate basin, but is behind the Western Black Sea. In north Turkey, the significantly younger than the Western Black Sea. transition from shallow to deep-marine limestones in Further east, the deformation front jumps (or bends) the Upper Jurassic takes place close to the position of to the north, and the Eastern Pontides merge into the the North Anatolian fault zone. Prior to the Aptian, this Achara-Trialet Belt in Georgia. Banks et al. (this vol- area would therefore restore to a position immediately ume) describe a study of this fold belt and the related east of the present-day Balkanides. The onshore evi- Rioni and Kartli foreland basins, incorporating inter- dence for Aptian–Albian rifting and Late Cretaceous pretations of geological maps, fieldwork, and seismic postrift subsidence is summarized by Görür (this vol- and onshore well data. The Achara-Trialet Belt appears ume). The relevant stratigraphy has been exposed by to be a Paleogene extensional (back- or intra-arc) basin Tertiary inversion of the mid-Cretaceous extensional that began to close during the late Eocene or Oligocene. faults. Görür and Tüysüz (this volume) provide a sum- The stratigraphy is dominated by a very thick deep- mary of the petroleum potential of this part of northern marine Eocene sequence, including volcanics and vol- Turkey. Despite many years of onshore, as well as some canogenic turbidites in the Middle Eocene, the offshore, exploration, there has been no petroleum dis- equivalents of the Eastern Pontides Lutetian arc. This covery in the Pontides despite the presence of several sequence—in particular the very thick Eocene—is very oil and gas seeps (Derman and Iztan, this volume). My similar to the stratigraphy interpreted for the Eastern guess is that this is due to a timing problem: Source Black Sea by Spadini et al. (this volume). Indeed, Banks rocks in the Ordovician/Silurian and possibly the et al. consider that the Achara-Trialet Belt represents the Aptian were largely matured during or prior to rifting. closed eastern end of the Eastern Black Sea. The Rioni Most of the traps are compressional and of principally and Kartli basins developed mainly during Miocene, by Eocene age. flexure of the northern margin of the Eastern Black The Central Pontides are quite different from the Sea—Achara-Trialet Basin (the Shatsky Ridge) beneath Western Pontides. They have an ophiolitic basement the compressional fold belts to the north (Greater Cau- covered by Triassic–Lower Jurassic turbidites and casus) and the south. There has been oil exploration intruded by Mid-Jurassic postcollisional granites. The onshore in Georgia for around a century, mostly con- evolution of this area is covered by Ustaömer and centrating on the frontal folds of the Achara-Trialet Belt Robertson (this volume). They describe the presence of and the Rioni and Kartli basins. The petroleum geology a late Paleozoic oceanic arc and back-arc basin. The of this area is described by Robinson et al. (this volume). back-arc basin closed before Late Jurassic. What They provide further evidence for the regional develop- appears to be the same Triassic to Late Jurassic back- ment of an Upper Eocene oil-prone source rock (see also arc basin fill can be found in Crimea and in the off- Robinson et al., 1996). shore part of the Ukrainian Black Sea, the two areas having been separated by Late Cretaceous spreading in the Western Black Sea. Banks and Robinson (this NORTHERN MARGIN OF THE BLACK volume) accordingly believe that the eastern trans- SEA BASINS: GREATER CAUCASUS, form margin of the Western Black Sea runs between CRIMEA, AND GULF OF ODESSA the Eastern and Central Pontides, along the western edge of the Mid-Black Sea High, and that the bound- Regretfully, the northern margins of the Black Sea ary between the Western and Central Pontides can be are not well represented in this volume, or in any Introduction: Tectonic Elements of the Black Sea Region 5 accessible literature. The Russian coast is dominated Benton, J., this volume, Exploration history of the by the Greater Caucasus. This appears from geological Black Sea province, in A.G. Robinson, ed., Regional maps to represent an Early Jurassic extensional basin and petroleum geology of the Black Sea and sur- that accumulated a great thickness of Jurassic and Cre- rounding region: AAPG Memoir 68, p. 7–18. taceous deep-marine sediments before being closed Brinkmann, R., 1974, Geologic relations between the from the Late Eocene onward (Robinson et al., 1996). It Black Sea and Anatolia, in D.A. Ross and E.T. can perhaps thus be considered a forerunner of the Degens, eds., 1974, The Black Sea—geology, chem- Eastern Black Sea. The main foreland basin develop- istry, and biology: AAPG Memoir 20, p. 63–76. ment is to the north of the mountain belt (Indolo- Derman, A.S., and Y.H. Iztan, this volume, Results of Kuban Basin), but the Greater Caucasus had an effect geochemical analysis of seeps and potential source on the Kartli Basin (in Georgia) (Robinson et al., this rocks from Northern Turkey and the Turkish Black volume) and produced the small flexural Tuapse Sea, in A.G. Robinson, ed., Regional and petroleum Trough (offshore Russia). geology of the Black Sea and surrounding region: Toward the northeast, the Greater Caucasus seem AAPG Memoir 68, p. 313–330. to die out. It is tempting to link them with the Finetti, I., G. Bricchi, A. Del Ben, M. Pipan, and Z. Crimean fold belt, but the stratigraphy and style of Xuan, 1988, Geophysical study of the Black Sea area: deformation in the Crimea are quite different. Robin- Bolletino di Geofisica Teorica ed Applicata, v. 30, son and Kerusov (this volume) describe the seismic p. 197–324. stratigraphy of the offshore Gulf of Odessa (known Görür, N., 1988, Timing of opening of the Black Sea also locally as the North-West Shelf) and relate the basin: Tectonophysics, v. 147, p. 247–262. offshore to the exposed geology in Crimea. They Görür, N., this volume, Cretaceous syn- to postrift sedi- interpret offshore features and the Crimean Moun- mentation on the southern continental margin of the tains to represent Aptian–Albian half-grabens (devel- Western Black Sea Basin, in A.G. Robinson, ed., oped during Western Black Sea rifting) that were Regional and petroleum geology of the Black Sea and inverted from the middle Eocene onward. The degree surrounding region: AAPG Memoir 68, p. 227–240 of inversion is minor offshore, but very substantial in Görür, N., and O, Tüysüz, this volume, Petroleum Crimea. Gas-condensate fields offshore are found in geology of the southern continental margin of the inversion anticlines above Aptian–Albian extensional Black Sea, in A.G. Robinson, ed., Regional and faults and may have been sourced from the Paleozoic petroleum geology of the Black Sea and surround- of the Scythian Platform. ing region: AAPG Memoir 68, p. 241–254. Harbury, N., and M. Cohen, this volume, Sedimentary ACKNOWLEDGMENTS history of the Late Jurassic–Paleogene of Northeast Bulgaria and the Bulgarian Black Sea, in A.G. Robin- I would like to thank JKX Oil & Gas plc for sup- son, ed., Regional and petroleum geology of the porting the preparation of this Memoir, in particular Black Sea and surrounding region: AAPG Memoir Martin Miller. Many other people have been most 68, p. 129–168. helpful: I am grateful especially to Alexandru Maftei Jones, R.W., and M.D. Simmons, this volume, A (Enterprise Oil) and to David Roberts (BP Explo- review of the stratigraphy of Eastern Paratethys ration). I˙stanbul Technical University wins the award (Oligocene–Holocene), with particular emphasis on for preparing papers on time. Thanks to Petroconsul- the Black Sea, in A.G. Robinson, ed., Regional and tants for providing a Black Sea base map. petroleum geology of the Black Sea and surround- ing region: AAPG Memoir 68, p. 39–52. REFERENCES CITED Manetti, P., M. Boccaletti, and A. Peccerillo, 1988, The Black Sea: remnant of a marginal basin behind the Banks, C.J., this volume, Basins and thrust belts of the Srednogorie-Pontides island arc system during Upper Balkan Coast of the Black Sea, in A.G. Robinson, ed., Cretaceous–Eocene time: Bolletino di Geofisica Teor- Regional and petroleum geology of the Black Sea ica ed Applicata, v. 30, p. 39–51. and surrounding region: AAPG Memoir 68, Okay, A.I., and Ö. S¸ahintürk, this volume, Geology of p. 115-126 the Eastern Pontides, in A.G. Robinson, ed., Banks, C.J., and A.G. Robinson, this volume, Mesozoic Regional and petroleum geology of the Black Sea strike-slip back-arc basins of the Western Black Sea and surrounding region: AAPG Memoir 68, region, in A.G. Robinson, ed., Regional and p. 291–312. petroleum geology of the Black Sea and surround- Okay, A.I., A.M.C. S¸engör, and N. Görür, 1994, Kine- ing region: AAPG Memoir 68, p. 53–62 matic history of the opening of the Black Sea and its Banks, C.J., A.G. Robinson, and M.P. Williams, this effect on the surrounding regions: Geology, v. 22, volume, Structure and regional tectonics of the p. 267–270. Achara-Trialet Fold Belt and the Adjacent Rioni and Robinson, A.G., and E. Kerusov, this volume, Strati- Kartli Foreland Basins, Republic of Georgia, in A.G. graphic and structural development of the Gulf of Robinson, ed., Regional and petroleum geology of Odessa, Ukrainian Black Sea: implications for the Black Sea and surrounding region: AAPG Mem- petroleum exploration, in A.G. Robinson, ed., oir 68, p. 331–346. Regional and petroleum geology of the Black Sea 6 Robinson

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