Geology
The area now occupied by the Carpathians was once occupied by smaller ocean basins. The Carpathian mountains were formed during the Alpine orogeny in the Mesozoic and Tertiary by moving the ALCAPA, Tisza and Dacia plates over subducting oceanic crust (see maps). The mountains take the form of a fold and thrust belt with generally north vergence in the western segment, northeast to east vergence in the eastern portion and southeast vergence in the southern portion.
The external, generally northern, portion of the orogenic belt is a Tertiary accretionary prism of a so-called Flysch belt created by rocks scraped off the sea bottom and thrust over the North-European plate. The Carpathian accretionary wedge is made of several thin skinned nappes composed of Cretaceous to Paleogene turbidites. Thrusting of the Flysch nappes over the Carpathian foreland caused the formation of the Carpathian foreland basin. The boundary between the Flysch belt and internal zones of the orogenic belt in the western segment of the mountain range is marked by the Pieniny Klippen Belt, a narrow complicated zone of polyphase compressional deformation, later involved in a supposed strike-slip zone. Internal zones in western and eastern segments contain older Variscan igneous massifs reworked in Mesozoic thick and thin-skinned nappes. During the Middle Miocene this zone was affected by intensive calc-alkaline arc volcanism that developed over the subduction zone of the flysch basins. At the same time, the internal zones of the orogenic belt were affected by large extensional structure of the back-arc Pannonian Basin.
Iron, gold and silver were found in great quantities in the Western Carpathians. After the Roman emperor Trajan's conquest of Dacia, he brought back to Rome over 165 tons of gold and 330 tons of silver.
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