Mesozoic–Tertiary tectonic evolution of Albania in its regional Eastern Mediterranean context

Abstract

Research carried out since the opening of Albania to the ‘western’ geological community in the 1990s allows the geology and tectonics of this small Balkan country to be integrated into an overall interpretation of Neotethys in the Eastern Mediterranean region, specifically Greece and the former Yugoslavia region. Albanian geology is most famous for the occurrence of contrasting ophiolites of Jurassic age. The country is sub-divided into three main geotectonic units. Those in the west (i.e. Sazani, Ionian, Kruja, Krasta–Cukali and the Albanian Alps) relate to the western margin of Apulia, effectively part of North Africa from Early Mesozoic time onwards. In the east is the Korabi zone, interpreted as a microcontinent located further northeast within Neotethys. Between the two is the Mirdita zone, dominated by two contrasting Jurassic ophiolites: the ‘Western-type’ ophiolite and the ‘Eastern-type’ ophiolite. Taking account of evidence from Greece and former Yugoslavia, the following tectonic evolution is proposed. From Early Mesozoic time onwards, Neotethys in Albania existed as a northward continuation of the Pindos oceanic basin in Greece (Pindos–Mirdita ocean). A Korabi microcontinent was rifted off Apulia in the Early–Mid Triassic, followed by passive margin subsidence until late Middle Jurassic time. A rifted, slow-spreading, MOR-type ophiolite formed within the western Pindos–Mirdita oceanic basin in Late Triassic?–early Late Jurassic time (using present co-ordinates). The Shkoder–Peje (Scutari–Peć) lineament in the north of Albania is interpreted as an important transform fault zone that influenced the regional tectonic evolution during the entire Mesozoic–Early Tertiary rift/drift/emplacement history of the Pindos–Mirdita ocean. Taking account of evidence from the Greek and former Yugoslavia ophiolites, the easterly Albanian ophiolites formed within the Pindos–Mirdita ocean above a westward-dipping intra-oceanic subduction zone in the early Late Jurassic. Metamorphic soles were formed during initial intra-oceanic displacement (ca. 162–174 m.y.), and underlying melanges originated as subduction–accretion complexes. The MOR, Western-type ophiolite evolved into the IAT–boninitic Eastern-type ophiolite after subduction began. During Tithonian–Berriasian time, trench–margin collision emplaced the ophiolites eastwards over the Korabi margin, coupled with redeposition of ophiolitic and continental margin material as exotic blocks, debris flow deposits and turbidites. These were emplaced onto the upper surface of the ophiolitic thrust sheet during the latest stages of emplacement onto the Korabi microcontinent. Following collision in the east, oceanic crust remained within a small, remnant Pindos–Mirdita oceanic basin. Passive conditions were restored in the Mid–Late Cretaceous, with shallow-water carbonate deposition on microcontinental units and both pelagic and redeposited carbonates in basinal settings. From the Maastrichtian onwards, Africa–Eurasia convergence resulted in large-scale westward thrusting, deforming the Apulian foreland in Oligo-Miocene time. The suture zone was re-activated in Oligo-Miocene time as the Albanie–Thassalie piggy-back-type basin in central and southern Albania. Albania as a whole was rotated 45° clockwise as part of the western Aegean arc in post-Eocene time. Coastal and offshore Albania experienced strong subsidence after Early Miocene time, forming the Periadriatic basin (including the Tirana depression), interpreted as a foredeep related to continuing regional convergence. Southern Albania experienced extensional tectonics in Plio-Quaternary time related to southward ‘roll-back’ of the Aegean active margin.