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1 2008

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Evolution of the Mesozoic basins on the southwestern edge of the East European Craton (Poland, Ukraine, Moldova, Romania)

Świdrowska J., Hakenberg M., Poluhtovič B., Seghedi A., Višnâkov I.

Studia Geologica Polonica

2008

Vol. 130

3-130

The sedimentary cover of the SW margin of the East European Craton (EEC) records its Mesozoic evolution from Permian to Early Maastrichtian time. Structural units of the Mid-Polish Swell with bounding synclines, the Stryi Depression, the Moldavian Platform, the Pre-Dobrogea Depression (PDD) and the North Dobrogea (ND) are groupped along the Teisseyre-Tornquist Zone (TTZ), one of the most important lineaments of the European Plate. They developed above the Trans-European Suture Zone (TESZ), the contact zone of Precambrian and Palaeozoic domains of crustal consolidation. The investigated area forms a belt 1000 km long that strikes across four states down to the Black Sea. The stratigraphy and facies data based on the profiles from many hundreds of wells and outcrops are summarized on thickness and lithofacies maps covering 16 time-spans. They show palaeogeogra- phic history of sedimentary basins of the SE part of Mid-Polish Trough (MPT), the Stryi Depression and the Pre-Dobrogea Depression. Fragmentary record of epicontinental sediments in the ND could be interpreted referring to depositional history of the PDD. The facies-thickness maps were transfor- med to maps of accumulation rate reflecting subsidence rates. Sedimentary and structural evolution of the two outermost basins, MPT and PDD, give evidences for their genetic independence and the lack of their direct connections along direction of TTZ till the end of Jurassic time. The Triassic-Middle Jurassic evolution of the North Dobrogea suggests that it could lie farther to the SW in the Tethyan realm. Deep-water sequences of the ND did not display any relation to the epiplatform sediments in the PDD up to the Bathonian. Mid-Cimmerian transpressional docking of the ND block to the PDD gave the beginning of their common epicontinental Jurassic history with subsidence axis striking W-E. Geometric junction of both external basins (MPT and PDD) in NW-SE direction occurred during the Early Cretaceous as a result of origin of foredeep basin located to the north of the ND inverted block, together with the western part of the PDD. Inversion was a consequence of the Neo-Cimmerian collision in the Northern Tethys and docking of the Central Dobrogea to the ND. The evolution of the PDD was connected with the eastern Mediterranean realm from Albian time on. A multiphase (10 stages) tectonic history of the Mid-Polish Trough and the Stryi Depression was recognized. Clockwise rotation of the two principal stress axes in horizontal plane controlled basin opening. A change of the strike-slip component along the TTZ direction and over the TESZ occurred from sinistral (Early Jurassic), through the lack of horizontal displacements in Albian-Cenomanian time, to dextral component from the Turonian till the end of Cretaceous. During the inversion the s1 axis reached a NE-SW orientation.