Introduction a l'évolution tectoniqueet paléogéographique de la Bulgarie au cours du Jurassique

Abstract

During the Jurassic the northern parts of the territory of Bulgaria represented parts of the southern margin of Eurasia-Moesian platform. In south of Moesia existed a fragment—the Thracian plate, which in east prolonged in the exotic ridge of Zlatarski and the hypothetic land of Euxinia (South of Crimea in the Black Sea). In NW direction the Thracian plate passed into the Geticum. These two big blocks with continental crust were separated one from other by the Perimoesian zone. During the Early and Middle Jurassic in this suture, in eastern Stara Planina Mountains, was formed the flysch trough of the Matorides, connected with the turbidity basin of Nalbant (north Dobrogea), southern Crimea, and the Greater Caucasus. On Bulgarian territory this trough was closed at the end of Bathonian. Later, displaced little to North, in this suture took place the Nis-Trojan flysch trough (Callovian-Valanginian). In East it was connected with the turbidity basin of southern Crimea, and in NW direction-with Severin-Sinaia trough. The existed in southern Bulgaria allochtonous jurassic sediments-black shales with Radiolaria, was deposited in the Perithracian zone, which separated the Thracian plate from the Serbo-Macedonian massif-Moravicum-Suprageticum. In SW Bulgaria, by obduction, it was closed during the Kimmeridgian. During the Early and the Middle Jurassic on the Moesian platform took place a progressiv transgression with epicontinental terrigenous and terrigenous-carbonate sedimentation. The principal area alimented the sedimentation was the Thracian plate. In the Late Jurassic took place a change in the sedimentation on the Moesian platform, when two carbonate platforms were formed, separated by the central Moesian basin with pelagic carbonate and “ammonitico rosso” type sedimentation. This palaeogeodinamic and palaeogeographic situation in Bulgaria persisted to the end of the Early Cretaceous when it was changed by the Austrian tectogenesis. During this tectogenesis the Nalbant zone, the Crimea, etc. were displaced few hundred kilometers to the North, along a strike-slipe fault.