Thermomechanical Modeling of Black Sea Basin Formation, Subsidence, and Sedimentation
Giacomo Spadini, Andrew G. Robinson, S.A.P.L. Cloetingh, 1997. "Thermomechanical Modeling of Black Sea Basin Formation, Subsidence, and Sedimentation", Regional and Petroleum Geology of the Black Sea and Surrounding Region, A. G. Robinson
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We demonstrate the key role of prerift rheology on the kinematics of basin formation and subsidence history in the Western and Eastern Black Sea basins. Constraints on modeling results are provided by a large data set based on >50,000 km of multichannel seismic data, offshore and onshore wells, regional gravity and magnetic surveys, refraction seismic data, and field studies. The western and eastern parts of the Black Sea appear to be two distinct basins, characterized by different evolutionary paths determined by different prerift conditions. The model supports the presence of important differences in the thickness and in the thermal state of the lithosphere, which rifted to form the Western (middle Barremian) and the Eastern (middle Paleocene) Black Sea subbasins. A 200-km thick and an 80-km thick prerift lithosphere appears to have driven the deformation in the Western and in the Eastern Black Sea, respectively. Differences in the geometry and in the mechanical properties of the prerift lithosphere have a strong control on the depth of necking and, thus, on the basin morphology. The model sheds light on paleotectonic and paleogeographic reconstructions, duration of rifting events, location of subsiding areas, and erosional surfaces.
Stratigraphie modeling provides new constraints on the paleowater depth evolution of the basin and associated basement subsidence. The model reproduces and provides explanations for several features of the stratigraphy of the Black Sea: the apparent near absence of synrift strata (other than in the Western Pontides), thin to condensed early postrift sequences in both basins, a thick upper Eocene in the Eastern Black Sea, a relatively thin Oligocene to Miocene and a very thick Quaternary. It also predicts the geometry and depth of the lake that developed in the center of the Black Sea when sea level fell by 1500 m during the late Miocene.
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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