Stratigraphic and Structural Development of the Gulf of Odessa, Ukrainian Black Sea: Implications for Petroleum Exploration
Andrew G. Robinson, Edward Kerusov, 1997. "Stratigraphic and Structural Development of the Gulf of Odessa, Ukrainian Black Sea: Implications for Petroleum Exploration", Regional and Petroleum Geology of the Black Sea and Surrounding Region, A. G. Robinson
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The Gulf of Odessa forms the northern rift and passive margin of the extensional Western Black Sea. The prerift comprises the Scythian Proterozoic to Triassic platform in the north (which dips gently southward) and, in the south, a Triassic-Early Jurassic back-arc basin that closed during the Middle Jurassic (Tavric-Kiire Series). Both of these units were covered by a Late Jurassic carbonate platform prior to the Aptian-Albian doming and rifting that preceded the opening of the Western Black Sea (Cenomanian). During the late Eocene to Oligocene, Aptian-Albian half-grabens suffered limited inversion related to closure of the Tethyan Ocean in Central Anatolia. The main play in the Gulf of Odessa has involved Lower Paleocene chalk in inversion-related anticlines formed during the late Eocene to Oligocene. The chalks are not significantly fractured, and permeabilities are of the order of a few millidarcys. The source rock for the wet gas has not been positively iden-tified, but may be Paleozoic, possibly Devonian, or Albian in age. Extensional structures that formed prior to inversion may still contain the early oil charge from such a source. Adjacent to the deep Black Sea Basin, there is an east- west-trending extensional high (Kalamit Ridge) that extends into Romania and includes the Lebada oil field. The Lebada play, transgressional Albian sandstones draped over partly inverted extensional fault blocks and charged by a Tertiary (Upper Eocene?) source rock in the deep Black Sea Basin, extends into Ukrainian waters.
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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