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

Marcelle Boudagher-Fadel,Rudolph Scherreiks

doi:10.14324/111.444/ucloe.000024

Marcelle Boudagher-Fadel, Rudolph Scherreiks

Open Access

https://doi.org/10.14324/111.444/ucloe.000024

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Abstract

Seismic tomographic images of the mantle below the Hellenides indicate that the Vardar Ocean probably had a composite width of over 3000 km. From surface geology we know that this ocean was initially located between two passive margins: Pelagonian Adria in the west and Serbo-Macedonian-Eurasia in the east. Pelagonia was covered by a carbonate platform that accumulated, during Late Triassic to Early Cretaceous time, where highly diversified carbonate sedimentary environments evolved and reacted to the adjacent, converging Vardar Ocean plate. We conceive that on the east side of the Vardar Ocean, a Cretaceous carbonate platform evolved from the Aptian to the Maastrichtian time in the forearc basin of the Vardar supra-subduction volcanic arc complex. The closure of the Vardar Ocean occurred in one episode of ophiolite obduction and in two episodes of intra-oceanic subduction. 1. During the Middle Jurassic time a 1200-km slab of west Vardar lithosphere subducted beneath the supra-subduction, 'Eohellenic', arc, while a 200-km-wide slab obducted onto Pelagonia between the Callovian and Valanginian times. 2. During the Late Jurassic through to the Cretaceous time a 1700-km-wide slab subducted beneath the evolving east Vardar-zone arc-complex. Pelagonia, the trailing edge of the subducting east-Vardar Ocean slab, crashed and underthrust the Vardar arc complex during the Paleocene time and ultimately crashed with Serbo-Macedonia. Since the late Early Jurassic time, the Hellenides have moved about 3000 km toward the northeast while the Atlantic Ocean spread.

Highlights

Relicts of oceanic lithosphere can be traced from the Dinarides through the Hellenides and Taurides
This surface geology is aligned with seismic tomographic images that depict two perturbations in the mantle below the central Hellenides, that we interpret as two slabs of Vardar Ocean lithosphere, which sank into the mantle during two episodes of subduction
The demise of the once over 3000-km wide Vardar Ocean has been reconstructed from field investigations of its remnants in its onetime peripheries, and from seismic tomographic images of its remnants in the mantle below the Central Hellenides

Summary

Introduction

Relicts of oceanic lithosphere can be traced from the Dinarides through the Hellenides and Taurides. Closure of the Vardar Ocean from the early Middle Jurassic to the Paleocene time of the Pelagonian zone which is covered by disrupted ophiolite followed by schistose pyroclastic units interleaved with slices of radiolarian cherts, volcaniclastic and chloritic marble layers This tectonic transition between Pelagonia and the western edge of the Vardar zone is shown by Sharp and Robertson [6] in the Arnissa area (Fig. 6): a ∼500-m-thick succession of imbricated ophiolite mélange. Near Nisi and Karydia (Fig. 6) these cataclasites (Plate 2a,b) occur below Campanian limestone (Table 1b 4) (Plate 1) At its base, this succession contains olistolith marbles of Triassic–Jurassic age Closure of the Vardar Ocean from the early Middle Jurassic to the Paleocene time and overlie white micaceous Triassic marbles in suggested transgressional contact [55]. The analyses of the basalts from the Eohellenic ophiolite of Evvoia and those of the Elias complex are incorporated in the REE and atomic force microscopy (AFM) diagrams (Fig. 7a and c) (Table 2b) and they indicate MORB and IAB affinities

Discussion and conclusions

Summary