31 research outputs found

    Dating of the Black Sea Basin: New nannoplankton ages from its inverted margin in the Central Pontides (Turkey)

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    International audienceThe Eocene uplift and inversion of a part of the Black Sea margin in the Central Pontides, allows to study the stratigraphic sequence of the Western Black Sea Basin. The revision of this sequence, with 164 nannoplankton ages, indicates that subsidence and rifting started in the Upper Barremian and accelerated during the Aptian. The rifting of the Western Black Sea Basin lasted about 40 Myr (from late Barremian to Coniacian). In the inner, inverted, Black Sea margin, the syn-rift sequence ends up with shallow marine sands. The uppermost Albian to Turonian was a period of erosion or non deposition. This regional mid-Cretaceous stratigraphical gap might result from rift flank uplift, as expected in the case of a thick and cold pre-rift lithosphere. However, coeval collision of the Kargi Block, along the North Tethyan subduction zone at the southern margin of the Pontides, might also have contributed to this uplift. A rapid thermal post-rift subsidence of the margin occurred during the Coniacian-Santonian. Collision of the Kirşehir continental block commenced in Early Eocene time (zone NP12) giving rise to compressional deformation and sedimentation in piggyback basins in the Central Pontides, whereas the eastern Black Sea was still opening

    Cross-sectional anatomy and geodynamic evolution of the Central Pontide orogenic belt (northern Turkey)

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    International audienceGeophysical data allowed the construction of a ~250-km-long lithospheric-scale balanced cross section of the southern Black Sea margin (Espurt et al. 2014). In this paper we combine structural field data, stratigraphic data, and fault kinematics analyses with the 70 km-long onshore part of the section to reconstruct the geodynamic evolution of the Central Pontide orogen. These data reveal new aspects of the structural evolution of the Pontides since the Early Cretaceous. The Central Pontides is a doubly vergent orogenic wedge that results from the inversion of normal faults. Extensional subsidence occurred with an ENE-trend from Aptian to Paleocene in a forearc setting. We infer that the Black Sea back-arc basin also opened during this period, which was also the period of subduction of the Tethys Ocean below the Pontides. As in the Western Pontides, the Cretaceous-Paleocene subsidence was interrupted from Latest Albian to Coniacian time by uplift and erosion that was probably related to a block collision and accretion in the subduction zone. The restoration of the section to its pre-shortening state (Paleocene) shows that fault-related subsidence locally reached 3600 m within the forearc basin. Structural inversion occurred from Early Eocene to Mid-Miocene as a result of collision and indentation of the Pontides by the Kırşehir continental block to the south, with 27.5 km (~28%) shortening along the section studied. The inversion was characterized by NNE-trending shortening that predated the Late Neogene dextral escape of Anatolia along the North Anatolian Fault and the modern stress field characterized by NW-trending compression within the Eocene Boyabat basin
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