Three minor thrust belts are abruptly terminated at the Balkan coast of the Black Sea: the Strandzhides of Thrace and Bulgaria, the Balkanides of central Bulgaria, and the North Dobrogea belt of Romania.
The Strandzhides are the eastern external zones of the Rhodope Massif and were the site of a south-facing continental margin that started as a pas-sive margin in the Triassic, but soon became active. The major compression was in the Late Jurassic, and the belt is made up of at least four large thrust nappes, with large displacements. The foreland basin, if it exists at all, is now buried by a Late Cretaceous magmatic arc. The Balkanides are a narrow thrust belt involving Mesozoic-Paleogene stratigraphy that is remarkably different from south to north of the belt. The area was affected by extension, mainly in the late Triassic and early-mid Cretaceous (when the Western Black Sea opened). It was not seriously compressed until the Eocene, at which time a narrow foreland basin formed due to thrust loading of the otherwise stable Moesian Platform. North Dobrogea is an enigmatic zone separating Moesia from the Eastern European Platform. It was highly extended during the Triassic, and then compressed, probably transpressively, in the Late Jurassic.
The Mesozoic-Paleogene tectonic history of the Balkans was controlled by the northward subduction of the Vardar oceanic plate (a branch of Tethys) from the Mid-Late Triassic until its closure in the Eocene. It is suggested that North Dobrogea marks a major crustal boundary at the northern limit of back-arc deformation, where the Moesian Platform was displaced SE by a distance of several hundred kilometers during the Late Triassic to Early Jurassic. The Strandzhides and Balkanides constituted a mobile active margin of the overriding Moesian-European Plate, which was alternately extended (Triassic and Cretaceous) and compressed (Jurassic/Cimmeride and Paleogene/ Alpide), so that the area has become a mosaic of extensional and compressive structural elements.
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Regional and Petroleum Geology of the Black Sea and Surrounding Region
In 1967 and 1969, two oceanographic cruises were made in the Black Sea under the guidance of the Woods Hole Oceanographic Institute: The cruises included scientists from many countries and disciplines. Their aims were to determine the recent geological and geochemical evolution of the Black Sea, to map the shallow structure of the basin, and to study the interaction between the oxidized surface waters and the anoxic waters beneath them. The results were published 23 years ago, as AAPG Memoir 20 (Ross and Degens, 1974). During the 1969 cruise, the vessel Atlantis II collected 40 piston cores, which formed the basis of most of the subsequent geological studies that were restricted to very recent sedimentation. Speculations concerning the origin of the basin and the relationship of the geology offshore to that exposed around the margins of the Black Sea were rooted in pre-plate tectonic concepts of basin formation and were in any case hampered by a lack of relevant data (Brinkmann, 1974).
In 1976, the Glomar Challenger visited the Black Sea on Leg 42B of the Deep Sea Drilling Project and drilled and cored three deep-water sites (379, 380, and 381). Well 381 north of the Bosporus encountered sediments as old as Miocene, including some apparently deposited in shallow water (Ross, 1978).
The next major volume in Western literature to deal with the Black Sea was published a decade later, collecting papers presented two years earlier at a conference in Yalta. In this volume, a number of seismic reflection lines