Geology and Tectonic Evolution of the Pontides
Yücel Yilmaz, Okan Tüysüz, Erdinç Yiğitbaş, Ş. Can Genç, A. M. C. Şengor, 1997. "Geology and Tectonic Evolution of the Pontides", Regional and Petroleum Geology of the Black Sea and Surrounding Region, A. G. Robinson
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This chapter describes the internal divisions and the orogenic evolution of the Pontides, the northernmost tectonic division of Turkey.
The Pontides are an east-west-trending orogenic belt, representing an amalgamated tectonic entity in which three tectonostratigraphically different sectors can be distinguished: the Western Pontides, the Central Pontides, and the Eastern Pontides. The Western Pontides consist of the Istranca Massif, the istanbul-Zonguldak Zone, the Armutlu-Almacik Zone, and the Sakarya continent. The Eastern Pontides are represented by the following east- west-trending tectonic zones: a magmatic belt, a fore-arc basin fill, a belt of metamorphic massif, an ophiolitic suture zone, and a remnant basin fill. The Central Pontides represent a tectonic knot where the eastern Pontide units and the western Pontide units have been tectonically juxtaposed.
The Pontides represent segments of the Tethyside system that carry the record of Cimmeride and Alpide orogenic events. The Cimmeride orogeny resulted from the elimination of Paleotethys and her dependencies such as the Karakaya marginal basin, which existed during the Triassic. The Paleotethyan Ocean was located to the north of the Cimmerian continent, parts of which form the basement of the Pontides. During the closure of the Paleotethys, an Andean-type magmatic belt was developed on the Cimmerian continent due to the southward subduction of the Paleotethyan Ocean floor. During this period, the Neotethys began to open, possibly as a back-arc basin, behind the Cimmerian continent. In the Dogger assemblage, while the collision between the Scythian platform of Laurasia and Cimmerian continent took place in the north and eliminated most of the Paleotethys Ocean floor, the Neotethys continued to grow in the south.
The late Cretaceous witnessed the elimination of the Neotethys due to its northward subduction under the Pontides. This created a new active conti-nental margin arc. The closure of the Neotethys resulted in the collision between the Pontides arc and the Tauride-Anatolide Platform. Its effects con-tinued until the middle Eocene. The present mountain regions began to elevate as a giant horst block 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