Abstract
The Pelagonian stratigraphy of the Internal Hellenides consists of a Permo-Triassic basement and an Upper Triassic and Jurassic carbonate platform formation that has been overthrust by the Eohellenic ophiolite sheet during the Early Cretaceous. Intensive erosion, during the Cretaceous, removed most of the ophiolite and parts of the Jurassic formation. It is hypothesised that uplift and erosion of eastern Pelagonia was triggered by the break-off of the subducted oceanic leading edge of the Pelagonian plate. An investigation of the rocks that succeed the erosional unconformity shows that they constitute a shear-zone that is tectonically overlain by Cretaceous platform carbonates. Geochemical analyses of the shear-zone rocks substantiate that they are of mid-oceanic ridge and island arc provenience. Eastern Pelagonia collided with a Cretaceous carbonate platform, probably the Paikon forearc basin, as the Almopias ocean crust subducted beneath that island-arc complex. The Cretaceous platform, together with a substrate of sheared-off ocean floor mélange, overthrust eastern Pelagonia as subduction continued, and the substrate was dynamically metamorphosed into cataclastic rocks, mylonite, phyllonite and interpreted pseudotachylite. This complex of Cretaceous platform rocks and a brittle-ductile shear-zone-substrate constitute the here named Paikon-Palouki nappe, which was emplaced during Early Palaeocene. The Paikon-Palouki nappe did not reach Evvoia. Seismic tomographic models of the Aegean region apparently depict images of two broken-off ocean-plate-slabs, interpreted as Almopias-lithosphere-slabs. It is concluded that the western Almopias slab began to sink during the Early Cretaceous, while the eastern Almopias slab broke off and sank after the Paikon-Palouki nappe was emplaced in the Early Palaeocene.
Highlights
The area described and analysed in this paper is in the easternmost part of the Pelagonian zone of the Internal Hellenides (Fig. 1a)
The Pelagonian stratigraphy of the Internal Hellenides consists of a Permo-Triassic basement and an Upper Triassic and Jurassic carbonate platform formation that has been overthrust by the Eohellenic ophiolite sheet during the Early Cretaceous
It has been maintained that the rock assemblage of the Glossa unit is identical to ‘Eohellenic outliers’ [9, 11] and affirmed with two arguments, each of which is disputed in this presentation: 1) According to the cited authors, the Glossa series is not of Permo-Triassic age because, as they claim, it is completely different from other Pelagonian pre-Mesozoic basements
Summary
The area described and analysed in this paper is in the easternmost part of the Pelagonian zone of the Internal Hellenides (Fig. 1a). The hitherto interpreted ‘flysch’ of Alonnisos and Skopelos (Fig. 3b) is not a sedimentary formation but is part of the brittle-ductile shear zone that occurs below the Cretaceous carbonate rocks. In the area south of Panormos Bay (Fig. 7), where Matarangas reported microfossils indicating Cenomanian age, the present authors can contribute findings of shallow reefal wackestones, containing fossils (Table 1D) which expand the age of the Cretaceous in the southern Panormos area from Cenomanian to Late Santonian to Maastrichtian/Early Palaeocene [42, 43] The stratigraphy of these limestones is tectonically disrupted, and the rocks are mingled into the shearzone formation. This sample has a basalt REE plot (Fig. 8a2)
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