The northwest Pindos Mountains of Greece expose a sequence of Mesozoic and Tertiary thrust sheets, which include the Jurassic Pindos ophiolite, composed of ultramafic and mafic oceanic crust and mantle. Regional mapping has established the tectonic order of these units from top to base as follows: i) a mainly ultramafic ophiolitic thrust sheet (Dramala Complex of the Pindos Ophiolite Group) and basal metamorphic sole (Loumnitsa Unit of the Pindos Ophiolite Group); ii) Late Cretaceous platformal limestones (Orliakas Group); iii) dismembered intrusive and extrusive ophiolitic rocks (Aspropotamos Complex of the Pindos Ophilite Group); iv) tectonic melange and olistromes, dominated by Triassic-Jurassic volcanic and sedimentary rocks (Avdella Melange); v) coherent thrust sheets of Late Jurassic-Late Cretaceous deep-water sediments (Dio Dendra Group); vi) Early Tertiary flysch (Pindos Flysch). Immobile trace-element studies indicate that the Triassic and Jurassic extrusives of the volcanic-sedimentary melange, formed mainly at within-plate through to mid ocean ridge settings. By contrast, the structurally overlying ophiolitic extrusives include boninite series volcanic rocks and depleted island arc tholeiites, indicative of a supra-subduction zone origin. Initial displacement of the ophilite (ca 165 Ma) is recorded in the formation of a metamorphic sole, passing structurally downwards from a basal peridotite mylonite zone into amphibolite and greenschist facies rocks. The sole rocks in general have MORB and WPB trace-element chemical affinities, although a limited number of samples are more depleted in high field strength elements, and can be correlated with rocks of island arc origin, including boninites. Petrological and structural comparisons suggest the Pindos ophiolite is regionally continuous beneath the Meso-Hellenic trough with the Vourinos ophiolite to the east. This ophiolite, similarly has a supra-subduction zone chemical signature, and is also underlain by fragmentary metamorphic sole and melange units. In the favoured tectonic model, the Pindos ophiolite formed above a Early to Mid Jurassic westerly-dipping intra-oceanic subduction zone. Continuing subduction produced a thick accretionary complex, now represented by the Avdella melange that underlies the Pindos ophiolitic units. During the Late Jurassic, the supra-subduction zone ophiolite was emplaced as a relatively undeformed sheet, northeastwards onto the Pelagonian Zone, an assumed microcontinent. The 'fore-arc' crust situated immediately above the subduction zone was detached and overthrust by the remainder of the ophiolite sheet. Following this, the Pindos ocean remained partly open to the west as a remnant basin, undergoing deep-water and marginal carbonate deposition from the Late Jurassic to late Cretaceous. In Early Tertiary time (?Palaeocene-Eocene), this basin began to close; the Pindos ophiolite was sliced, and together with the Jurassic melange and younger deep-water sediments, was thrust westwards over a flexural foreland basin (Pindos Flysch), and then onto the Apulian continental margin as an inboard-propagating thrust stack. Inferred footwall structures (old palaeogeographic features?) or late stage folding were mainly responsible for the formation of large orthogonal (e.g. Armata-Milea corridor) and transverse (e.g. Perivoli corridor) culminations. Final thrusting was accompanied by extension behind the deformation front, leading to the formation and infilling of the Meso-Hellenic molasse basin.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:653151 |
| Date | January 1990 |
| Creators | Jones, Gregory |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12215 |
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