Tectono-stratigraphic correlations between Northern Evvoia, Skopelos and Alonnisos, and the postulated collision of the Pelagonian carbonate platform with the Paikon forearc basin (Pelagonian–Vardar zones, Internal Hellenides, Greece)

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.

The closure of the Vardar ocean (the western domain of the northern Neotethys) from early Middle Jurassic to Paleocene time, based on surface geology of eastern Pelagonia and the Vardar zone, biostratigraphy, and seismic-tomographic images of the mantle below the Central Hellenides

“…An almost identical array of REE plots have been ascertained for the Northern Sporades where the present authors had drawn the conclusion that MORBs and IABs had been tectonically mixed in the mélanges of an extensive thrust-fault zone (Fig. 7) (Scherreiks and BouDagher-Fadel 2020a). As in the Northern Sporades, the REE-plots drafted for the Vardar zone indicate the side by side presence of both IAB and MORB (Fig.…”

“…Furthermore, the Cretaceous limestones of the Vardar zone are in tectonic contact with the subjacent ophiolite even where laterite is found at the contacts. The circumstances here are analogical to the Northern Sporades where a sedimentary contact of the Cretaceous Carbonates with its original substrate is nowhere to be found (Scherreiks and BouDagher-Fadel 2020a).…”

“…We have interpreted the perturbations beneath Hellenides as sunken Vardar ocean lithosphere and are of the opinion that the images verify two episodes of subduction (Scherreiks and BouDagher-Fadel 2020a) (Fig. 3c).…”

“…5). The eroded surface of Jurassic and Triassic platform carbonates is covered by a sheet of mélange composed of meta-basalt and radiolarian chert which is chaotically mixed with carbonate breccia and mylonitic phyllonites (Scherreiks and BouDagher-Fadel 2020a) (Fig. 4a and Fig.…”

The closure of the Vardar ocean (the western domain of the northern Neotethys) from early Middle Jurassic to Paleocene time, based on surface geology of eastern Pelagonia and the Vardar zone, biostratigraphy, and seismic-tomographic images of the mantle below the Central Hellenides

“…Quite the contrary, as will be shown, the "Vardar zone" is where the last slab of the Vardar ocean subducted BouDagher-Fadel 2020a and2020b) and probably corresponds to the "Sava suture zone" (Ustaszewski et al 2010;Schmid et al 2020).…”