Like the Alps and Western Carpathians, the Apuseni Mountains represent a fragment of the Variscan orogen involved in the Alpine crustal shortenings. Thus the more extensive Alpine tectonic unit in the Apuseni Mountains, the Bihor Autochthonous Unit is overlain by several nappe systems. During the Variscan orogeny, the Bihor Unit was a part of the Somes terrane involved as the upper plate in subduction, continental collision and finally in the orogen

he Sebeş–Lotru terrane in the South Carpathians mountain range comprises a lower, Neoproterozoic metamorphic unit (Lotru) and an upper, Ordovician metamorphic unit (Cumpãna) that were juxtaposed during the Variscan orogeny. Two orthogneisses from the Lotru metamorphic unit yield U/Pb LA-ICP-MS zircon crystallization ages of 549.3 ± 3.8 Ma and 587.5 ± 3 Ma, respectively. Two orthogneisses from the Cumpãna metamorphic unit yield zircon crystallization

The basement of the Romanian Carpathians is comprised of pre-Variscan metasedimentary and metaigneous units. Age patterns from corresponding detrital zircons show similarities to those from the eastern Mediterranean region. Consistently, these patterns suggest a northern Gondwanan origin for the Carpathian terranes with the most common detrital sources representing fragments of the Pan-African Orogen, Arabian-Nubian Shield, Kibaran Orogen, and West