RIFT-DRIFT, SEAFLOOR SPREADING, AND COLLISION TECTONICS OF THE ALBANIDES WITHIN THE MEDITERRANEAN ALPINE OROGEN

The Albanide segment of the Dinaride-Hellenide belt in the Alpine orogenic system records a complete history of rift-drift, seafloor spreading, and collision tectonics during the Mesozoic-Cenozoic evolution of Neo-Tethys near its western terminus. Main tectonic entities include, from west to east, the Apulian microplate (AP), Jurassic ophiolites, and Korabi-Pelagonian microcontinent (KP). Initial rifting of KP from AP in the early-Middle Triassic was accompanied by extensive MORB to WPB volcanism. Continued east-west rifting during the Liassic produced a narrow ocean basin (Pindos-Mirdita basin, PMB) adjoined by a subsiding passive continental margin pair. Passive margin sequences include U. Triassic neritic limestones overlain by pelagic Liassic-Dogger limestones, and U. Jurassic shale and radiolarian chert. These carbonate platforms were cut by basinward-dipping normal faults that created tilted fault blocks overlain by half-grabens filled with sedimentary rocks of rift-drift origin. Middle Jurassic rifting and initial seafloor spreading within PMB produced a Hess-type oceanic crust with a MORB affinity (Western-type ophiolites). With continued spreading and subduction zone influence, oceanic crust within PMB evolved into a Penrose-type, having an IAT-boninite affinity (Eastern-type ophiolites). These paired ophiolite belts reflect an eastward shift in space and time of the magmatic evolution of the oceanic lithosphere within PMB. Platform carbonates and the ophiolites are both overlain by Tithonian-Lower Cretaceous turbiditic-melange deposits, indicating the ongoing contractional phase in the evolution of PMB by the Late Jurassic. Trench-rollback associated with an intra-oceanic subduction zone in PMB caused the collision of KP passive margin with the trench and eastward emplacement of the ophiolites onto it in Tithonian-Berriasian time. Oblique continental convergence caused the terminal closure of the remnant PMB and westward displacement and stacking of all tectonostratigraphic units on the AP margin in the Oligo-Miocene. Small molasse basins started opening up in the Miocene as local depocenters within this broadly oblique convergent zone and have evolved during the Plio-Quaternary into a series of extensional sedimentary basins along the NW-SE trend of the Albanides.