The evolution of the Triassic-Jurassic Maliac oceanic lithosphere: insights from the supra-ophiolitic series of Othris (continental Greece)

Abstract

Major ophiolitic thrust sheets are widespread within the internal Hellenides, particularly in the Pelagonian domain (Greece and Albania). The ophiolitic sheets are notably well exposed in western Othris mountains of continental Greece. In that area, the structural stacking of oceanic nappes obducted in the Jurassic is particularly well constrained. New sedimentological and structural data from recently studied outcrops, together with new micro-paleontological data, allow to reconsider the architecture of the ophiolitic nappes and their evolution in the Othris mountains. Our new data set includes notably the description of a Mid-Late Jurassic sedimentary succession, from basal litharenites and radiolarites to syn-obduction mélange, on top of the uppermost Mega Isoma ophiolitic Unit. These results are crucial in the perspective of constraining the Jurassic contractional evolution of the Maliac Ocean from the beginning of the subduction and intra-oceanic obduction to the final obduction on the Pelagonian continental crust. Another major result concerns the dating of primary conformable series of Middle and Late Triassic age on top of the pillow-lavas of the Fourka unit. Since this lava unit, with MORB affinities, is one of the syn-obduction Jurassic nappes, we propose that this very large Fourka nappe represents the major reference unit of the initial (Triassic) Maliac oceanic crust.

From obduction to continental collision: new data from Central Greece

“…1) the transition from the Pelagonian Platform to the more distal eastern marginal series (West Maliac Margin Units) and up to the oceanic crust is well documented. The onset of oceanization in the Maliac–Vardar basin is testified to by the oldest radiolarites (Anisian) deposited on top of MOR basalts (Bortolotti et al 2006; Bortolotti et al 2013; Ferrière et al 2015). By contrast, since Early Jurassic time the Pindos and Ionian geotectonic zones are interpreted as pelagic intracontinental basins separated by an intervening carbonate platform represented by the Gavrovo Unit (Fig.…”

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

“…Many new biostratigraphic data on Triassic and Jurassic radiolarites in mélange areas have recently been obtained in the Dinarides, Albanides and Hellenides (e.g., Gawlick et al 2008Gawlick et al , 2016Vishnevskaya et al 2009;Djerić et al 2010Djerić et al , 2012Chiari et al 2011Chiari et al , 2013Ozsvárt et al 2012;Bragin et al 2014;Ferrière et al 2015Ferrière et al , 2016Gawlick & Missoni 2015), but still a lot of questions remain open. Detailed microfacies investigations and biostratigraphic data allow detailed information about the depositional history for both the carbonate (e.g., Flügel 2004) and the radiolarite sequences.…”

The Main Pelagonian Detachment (MPD): extensional reactivation of the frontal thrust of the Internal Zones of the Hellenides (Greece)

“…The major collisional phase started by the Eocene but the involved rifted continental margins were affected by earlier compressional events. Indeed, during the Middle-Late Jurassic, the distal parts of the Adria-Africa continental margin (Pelagonia) underwent an obduction event implying ophiolitic nappes emplacement from the Maliac (Vardar) oceanic seaway [e.g., Ferrière et al, 2012Ferrière et al, , 2015Ferrière et al, , 2016. The Internal Zones (IZ) correspond to the areas that were covered by the ophiolitic nappes during the Jurassic obduction [Brunn, 1956], while the External Zones (EZ) were deformed only during Tertiary times (Figure 2B).…”

“…34 to 28 km-thick), gradually thinning further east towards the Aegean Sea where the crust reaches 22 to 18 km-thick approximately [Makris et al, 2001[Makris et al, , 2013. These IZ have a much more complex structural pattern as they underwent polyphase development since late Jurassic times, including crustal thickening with obduction of the Maliac Ocean and underthrusting of EZ such as the Gavrovo and Pindos zones [Ferrière et al, 2012[Ferrière et al, , 2015[Ferrière et al, , 2016. The existence of underthrust units from the EZ below the Pelagonian crust is clearly demonstrated by their occurrence at exposure in the Olympus and Ossa windows (see Figure 8B).…”