Abstract The Black Sea is a 423,000-km 2 (163,000-mi 2 )-large Cretaceous-Tertiary basin surrounded by Alpine fold belts. It consists mainly of two large subbasins separated by the northwest-southeast-trending mid-Black Sea ridge (Figure 1 ). The west Black Sea basin is floored by oceanic crust overlain by more than 3-km (1.8-mi)-thick flat-lying sediments probably of Cretaceous and younger age ( Letouzey et al., 1977 ; Finetti et al., 1988 ; Okay et al., 1994 ; Robinson, 1996 ). Thenorthwest-trending east Black Sea basin has a thinned continental or oceanic crust overlain by less than 10-km (6-mi)-thick sediments, which are intersected by a large number of faults. It is generally accepted that the Black Sea opened during the Mesozoic as a back-arc basin above the northward-subducting Tethyan oceanic lithosphere (e.g., Bocceletti et al., 1974 ; Şengör and Yilmaz, 1981 ). A kinematic model for the opening of the Black Sea, based largely on data from onshore areas, was suggested in 1994 by Okay et al. The model involved separate mechanisms for the origin of the west and east Black Sea basins. The west Black Sea basin was believed to have opened by orthogonal rifting of a continental fragment from the odessa shelf starting in the Albanian-Cenomonian ( Okay et al., 1994 ). This continental fragment, called the Istanbul zone (Figure 1 ), drifted south, bounded by two major strike-slip faults, opening the oceanic west Black Sea basin in the north and closing the Tethyan Ocean in the south (Figure 2 ). During the early Eocene, the Istanbul zone collided with the Sakarya zone in the south, thereby causing a change-over from extension to compression in the Black Sea. Okay et al. (1994) suggested that the eastern half of the Black Sea, including the east Black Sea basin, mid-Black Sea ridge, and the easternmost part of the west Black Sea basin (Figure 1 ), opened through the anticlockwise rotation of a large continental block around a pole situated in Crimea (Figure 2 ). Such a mode of opening explained the Tertiary compression in the Caucasus, which diminishes northwestward toward the pole of rotation, as well as the segmented southern boundary of the eastern Black Sea. The rotation was believed to have been contemporaneous with the rifting in the west Black Sea basin (Figure 2 ).

Abstract The Neogene marginal succession of the Eastern Paratethys (EP) crops out along the southern Black Sea coast and in the Marmara region of Turkey, and provides important clues to the tectono-sedimentary and palaeoceanographic conditions. In the Tarkhanian stage, the southern margin of the EP basin was largely a carbonate platform covered by warm, marine waters. From the end of the Tarkhanian to the Early Chokrakian there was an overall emergence throughout the basin, which is indicated by an influx of siliciclastic sediments. The fossil assemblage indicates that normal marine conditions persisted during most of this period, except for a salinity reduction towards the end due to an eustatic isolation of the basin, which in turn led to anoxic bottom water conditions. The Late Chokrakian isolation became even more severe during the Karaganian as indicated by the endemic fossil assemblage indicating brackish-marine conditions. Carbonate platform conditions prevailed in the northern Pontides during this time. In the Early Konkian, the basin was reconnected briefly with the world ocean by a transgression from the Indo-Pacific Ocean. In the Late Konkian there was a return to brackish-marine conditions. Lower Sarmatian sediments are absent in the southern margin of the EP, but elsewhere in the basin this stage is characterized by a widespread marine transgression. In the Middle-Late Sarmatian, the EP basin was partially isolated with freshening and anoxic bottom-water conditions. During this time there was a brief marine transgression from the Mediterranean into the Marmara region, but it did not reach the Paratethyan basin. The Pontian is characterized by an extensive transgression from the EP that inundated the Marmara and northeastern Aegean regions. The connection with the Marmara Basin was cut off during the Kimmerian and re-established during the Late Akchagylian, when the EP basin was inundated by the Mediterranean waters via the Sea of Marmara as a result of increased North Anatolian Fault activity and a short-term global sea level rise.

Abstract The Western Black Sea Basin began opening as a back-arc basin by the rift-ing of a juvenile continental margin magmatic arc during the Aptian. Its southern continental margin succession is well exposed in the Western Pontides, Northwest Turkey. This succession consists predominantly of vol- canogenic coarse clastic rocks, shales, and carbonates with a deepening- upward character. The volcanogenic clastic rocks are mostly turbidites and mass-flow deposits in places with huge exotic blocks. The volume and nature of this clastic material were controlled by both relief of nearby sediment sources and arc volcanism, whereas the carbonates depended on ocean circulation and surface organic productivity. The Aptian to lower Cenomanian part of the succession formed during the synrift stage, whereas the rest accumulated during the postrift stage. The synbreakup stage is marked by the upper Cenomanian to Campanian sedimentary facies. The synrift sediments commence locally with Aptian lagoonal black shales, rich in organic matter. They pass laterally and upward into an Albian unit, comprising marginal marine glauconitic sandstones succeeded by siliciclastic turbidites, marls, sandy limestones, and blue to black shales with abundant glauconite. This unit includes several levels of mass-flow deposits, comprising mostly conglomerates and olistoliths of various sizes, ranging from a few centimeters to hundreds of meters in diameter. The synrift sedi-ments end with a Cenomanian succession of blue to black shales and clayey limestones, in part with exotic blocks derived from the underlying rocks. The postrift sediments at the base of upper Cenomanian to Campanian consist of pelagic red micrites and marls followed by mainly volcanogenic (both andesitic and basaltic) terrigeneous and carbonate turbidites and deep- water sediments, ranging from Turonian to lower Eocene. The basal pelagic carbonates rest with a slightly angular unconformity on the synrift deposits and represent the breakup facies. Facies analyses of the rift succession indicate that the Western Black Sea Basin was isolated during its synrift stage from free interchange with the Intra-Pontide Ocean to the south, and therefore was euxinic. During the rift- drift transition in the late Cenomanian, the euxinic conditions largely disap-peared, and the water column above the arc margin of this basin became well mixed. The volcanic activity in the arc also increased in intensity soon after this transition, and largely controlled the postrift sedimentation.

Abstract The southern continental margin of the Black Sea back-arc basin is represented predominantly by a thick clastic sequence of Aptian to Recent age. Potential source, reservoir, and cap rocks are common in various Stratigraphic levels of this sequence. The most prospective source and reservoir rocks appear to have been deposited in the synrift stage of the basin. During this stage, the rift trough was probably relatively shallow and restricted from free interchange with the Neotethys Ocean in the south. During the postrift stage, a thick sequence of volcaniclastic turbidites and subordinate pelagic limestones, with limited source and reservoir potential, accumulated. This accumulation was interrupted at the end of the early Eocene by compressional tectonics, which resulted from the closure of the Neotethys. The postrift sedimentation probably carried the earlier source rocks into the hydrocarbon generation window, while the Eocene compressional tectonics generated the main prospective traps.

Abstract Strike slip on various scales and on faults of diverse orientations is one of the most prominent modes of deformation in continental convergence zones. Extreme heterogeneity and low shear strength of continental rocks are responsible for creating complex “escape routes” from nodes of constriction along irregular collision fronts toward free faces formed by subduction zones. The origin of this process is poorly understood. The two main models ascribe tectonic escape to buoyancy forces resulting from differences in crustal thickness generated by collision and to forces applied to the boundaries of the escaping wedges. Escape tectonics also creates a complicated geological signature, whose recognition in fossil examples may be difficult. In this paper we examine the Neogene to present tectonic escape-dominated evolution of Turkey both to test the models devised to account for tectonic escape and to develop criteria by which fossil escape systems may be recognized. Since the late Serravallian (—12 Ma), the tectonics of Turkey has been dominated by the westward escape of an Anatolian block (“schölle”) from the east Anatolian convergent zone onto the oceanic lithosphère of the Eastern Mediterranean Sea, mainly along the North and East Anatolian strike-slip faults. This tectonic regime generated four distinct neotectonic provinces: (1) The East Anatolian contractional province, located mainly east of where the North and East Anatolian faults meet, and characterized by roughly north-south shortening; (2) the weakly active North Turkish province situated north of the North Anatolian fault, and characterized by limited east-west shortening; (3) the West Anatolian extensional province characterized by north-south extension; and (4) the Central Anatolian “ova” province characterized by northeast-southwest shortening and northwest-southeast extension. Large, roughly equant, complex basins ( “ovas” ) form peculiar structural elements of the Central Anatolian province. The two latter provinces are located within the westerly-moving Anatolian schölle. A number of pull-apart and fault-wedge basins have formed along the North and East Anatolian fault zones in addition to several other “incompatibility basins,” arising from space problems where these faults interfere with each other and with other large-scale structures. Incompatibility basins seem to have the most complicated structural history. The pull-apart basins are located on either primary or secondary releasing bends along the North and East Anatolian faults. The secondary type is related to the intersection of east-trending zones of high convergent strain with the North and East Anatolian fault zones. The tectonic escape regime in and around Turkey was not caused by buoyancy forces resulting from crustal thickness differences, but such forces may have been maintaining it. A knowledge of the geology of escape-related basins is critical both for our understanding of the nature of tectonic escape, and for its recognition in the geological record. We believe that the present tectonic scheme of Turkey constitutes an excellent guide for understanding the causes and consequences of escape, and for the recognition of its fossil representatives.