Plate-tectonic geodynamics of the Tisza–Dacia terrain, Ukrainian Carpathians

Abstract

In the work, the knowledge about the geological structure and evolution of the Marmarosh Massif (part of the Dacia terrane or the larger Tisza–Dacia terrane) of the Ukrainian Carpathians is supplemented and summarized. The geodynamic conditions of the formation of the Marmarosh massif are reconstructed in the context of the general evolution of the folded border of the East European craton on the basis of the author's geological observations and with taking into account previous data. Detailed geological mapping was carried out to identify some areas, the results of which are partially published on the State Geological Map of Ukraine. The Marmarosh massif of the Central Eastern Carpathians is represented by a crystalline basement, which includes pre-Hercynian and Hercynian metamorphosed complexes, and a late Paleozoic – Cenozoic cover of unmetamorphosed or weakly metamorphosed sediments. The Precambrian basement Bilyi Potik and Dilove formations are metamorphosed up to amphibolite (possibly to granulite?) facies. Vendian – Early Paleozoic volcanogenic-terrigenous and carbonate weakly metamorphosed Berlebash and Megura formations are correlated with the Tulghes Formation (Romania), that compared with the remains of an ancient accretionary prism and volcanic arc. This prism/arc could belong to the Avalonia microcontinent, which collided with Baltica in the Early Paleozoic. The collision caused the formation of the pre-Alpine Caledonian thrust structure of the Marmarosh massif basement. Paleozoic volcanogenic-sedimentary, carbonate, and terrigenous complexes (Kuzya Formation in Ukraine, and Rusaia, Repedea and Cimpoiasa formations in Romania) were accumulated in a rift basin, the closure of which caused the Hercynian tectogenesis. Late Paleozoic coal-bearing Kvasnyi Formation and red-colored Krasnyi Pleso Formation are belonged to epi-Hercynian molasse and to the cover of the Marmarosh crystalline massif. Jurassic rifting and spreading led to the separation of the Dacia microcontinent and the formation of a (sub)oceanic basin between Dacia microcontinent and Eurasia. This basin is now marked by the Fore-Marmarosh suture zone. The dipping of the Dacia into the subduction zone, which was inclined to the west, could have caused the formation of the Marmarosh basement nappes and their thrust eastward towards the Fore-Marmarosh basin (future Carpathian flysch basin). An accretionary flysch prism grew in front of the Marmarsh nappes, a significant part of the prism sank under the Marmarosh nappes (=crystalline massif) where it could generate hydrocarbons, which allows us to support the assumption about the prospects of the under Marmarosh nappes flysch autochthon.