THE STRUCTURAL ARCHITECTURE OF THE BOUNDARY BETWEEN THE EXTERNAL AND THE INTERNAL ALBANIDES-ALBANIA

The Albanides in the Balkan Peninsula are part of the Alpine orogenic belt and host one of the most significant oil fields in SE Europe. The late Mesozoic-Cenozoic evolution of the Albanides has been strongly controlled by the relative movements of Adria or Apulia, a microcontinent with a West Gondwana affinity with respect to Eurasia. In northeastern Albania, the Internal Albanides consist of Paleozoic – Jurassic basement rocks, which involved rift-drift, seafloor spreading, and subduction zone tectonics of the Pindos-Mirdita ocean basin. The External Albanides, on the other hand, represent a fold-and-thrust belt with deformation in a broad zone of oblique convergence. This tectonic domain is divided, from east to west, into five major structural zones: the Krasta-Cukali Zone, the Kruja Zone, the Peri-Adriatic Depression, the Ionian Zone, and the Sazani Zone. The structural architecture of the External Albanides is characterized by NW-SE-running and SW-verging thrust fault systems that involve a thick series of Mesozoic – Tertiary passive margin carbonates, unconformably overlain by Oligocene clastic units. The northern Ionian Zone has been prolific for oil and gas production, whereas the more intensely deformed southern Ionian Zone has been less explored. The Peri-Adriatic Depression west of the Sazani Zone has been recently identified as a major gas prospect. It is characterized by the Oligocene flysch and the Miocene-Pliocene molasses series. The External Albanides are dissected by the NE-SW-striking Vlora-Elbasan Transfer Zone, which extends eastwards into the Internal Albanides, affecting the structural architecture and the tectonic evolution of the entire mountain belt. This fault zone that has been tectonically active from the Triassic to recent has displayed diapiric structures along it.