Mirdita Zone ophiolites and associated sediments in Albania reveal Neotethys Ocean origin

Abstract

The Mirdita Ophiolite Zone in Albania is associated with widespread mélanges containing components of up to nappe-size. We dated matrix and components of the mélange by radiolarians, conodonts, and other taxa. The components consist of radiolarites, pelagic limestones and shallow-water limestones, all of Triassic age, as well as ophiolites. Triassic radiolarite as a primary cover of ophiolite material proves Middle Triassic onset of Mirdita ocean-floor formation. The mélange contains a turbiditic radiolarite-rich matrix (''radiolaritic flysch''), dated as Late Bajocian to Early Oxfordian. It formed as a synorogenic sediment during west-directed thrusting of ophiolite and sediment-cover nappes representing ocean floor and underplated fragments of the western continental margin. The tectonic structures formed during these orogenic events (''Younger Kimmeridian or Eohellenic Orogeny'') are sealed by Late Jurassic platform carbonates. The geological history conforms with that of the Inner Dinarides and adjoining areas; we therefore correlate the Mirdita-Pindos Ophiolite Zone with the Vardar Zone and explain its present position by far-distance west-directed thrusting.

Age and microfacies of oceanic Upper Triassic radiolarite components from the Middle Jurassic ophiolitic mélange in the Zlatibor Mountains (Inner Dinarides, Serbia) and their provenance

“…This is valid for the late Middle and Late Triassic except the Julian stage. Accordingly, radiolarites of this age can only be expected in more distal oceanic areas (Gawlick et al 2008;Krische et al 2014).…”

“…In addition, synorogenic sedimentary basin fills or mass transport deposits in trench-like basins in front of a propagating nappe stack, are commonly overprinted by multiple deformational events or reworked by tectonics, showing the typical features of a mélange. To distinguish a tectonic from a sedimentary mélange (Hsü 1968(Hsü , 1974Gawlick & Frisch 2003;Gawlick et al 2008Gawlick et al , 2012bGawlick et al , 2016Festa et al 2010 a, b;Plašienka 2012) is especially complicated in cases, in which the synorogenic basin fills were incorporated into the nappe stack becoming sheared forming olisto stromal carpets (Festa et al 2016).…”

“…One classical approach is provenance analysis, the reconstruction of the source area from the clast spectrum of the re-sedimented rocks (Blatt 1967;Zuffa 1980Zuffa , 1985Lewis 1984). Whereas the detailed provenance analyses of siliciclastic material is common, provenance analyses of carbonate or radiolarite clasts in conglomerates or breccias remain rare (Gawlick et al 2008(Gawlick et al , 2009(Gawlick et al a, 2015(Gawlick et al , 2016Krische et al 2014). For reliable results, a macroscopic description of the incorporated clasts has to be combined with microfacies analyses (Flügel 2004) and age dating.…”

“…At present it is commonly believed that ophiolite obduction on the Adria margin started in the Late (latest) Jurassic and that the ophiolite nappes including their underlying mélange were emplaced in the area of the Dinaridic Ophiolite Belt around the Jurassic/Cretaceous-boundary or the Early Cretaceous (Djerić et al 2007;Schmid et al 2008). However, Gawlick et al (2009Gawlick et al ( b, 2016 proved that the onset of obduction onto the Adria continental margin of the Inner Dinarides was Middle Jurassic, and therefore contemporaneous with the onset of obduction in the Albanides (Gawlick et al 2008) or Hellenides (Baumgartner 1985;Ozsvárt et al 2012;Ferriére et al 2016). Gawlick et al (2016 b) speculated therefore that ophiolite obduction started in the middle Middle Jurassic, affecting at that time the most distal parts of the Adria margin, and continued until the early Late Jurassic reaching at that time the area of the Drina-Ivanjica unit.…”

“…On basis of the commonly accepted reconstruction of the Triassic to Early Jurassic shelf (passive continental margin) (compare Gawlick et al 1999Gawlick et al , 2008Haas et al 2011;Kovács et al 2011) and the reconstruction of the westward propagating nappe stack during Middle to early Late Jurassic times (Gawlick et al 2008(Gawlick et al , 2012Schmid et al 2008) we present here new data which clearly indicate, that 1) the deposition of the ophiolitic mass transport deposits on top of a carbonateclastic trench-like basin fill with material from the back-reef to fore-reef facies belt of the destroyed Triassic-Jurassic passive margin of Adria took place in late Middle to early Late Jurassic times in 2) an area east of or on top of the Drina-Ivanjica unit.…”