Evidence for the existence of a paleosubduction zone beneath the Rhodopean massif (Central Balkans)

Shanov, Stefan; Spassov, Edelvays; Georgiev, Ts. B.

doi:10.1016/0040-1951(92)90382-g

Cited by 22 publications

(11 citation statements)

References 4 publications

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“…The crust of this area is poorly known and only a few studies have been carried out in the region. Several authors (Dachev & Volvovsky 1985; Babus̆ka & Plomerová 1987; Shanov et al 1992) suggest a quite complex crustal structure, with a deep Moho in the south, possibly related to a paleosubduction (Shanov et al 1992) and crustal thinning in the northern‐central part related to graben formation and a shallow asthenosphere. The zone of thin crust we imaged in Bulgaria is more elongated in the N–S direction compared with the studies mentioned above.…”

Section: Resultsmentioning

confidence: 99%

Joint inversion of local, regional and teleseismic data for crustal thickness in the Eurasia-Africa plate boundary region

Marone

Meijde

Lee

et al. 2003

Geophysical Journal International

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SUMMARY A new map for the Moho discontinuity (EAM02) in the Eurasia–Africa plate boundary region is presented. Reliable results have also been obtained for the southern and eastern Mediterranean Basin, the northern African coasts and the eastern Atlantic Ocean, regions only occasionally considered in studies on the Mediterranean region. The Moho topography model is derived from two independent sets of constraints. Information contained in the fundamental and higher‐mode Rayleigh waves obtained from waveform modelling is used to constrain the Moho depth between estimates of crustal thickness taken from published reflection and refraction surveys, gravity studies and receiver function analysis. Strong lateral variations in the Moho topography have been observed in the Mediterranean Sea, confirming the complex evolution of this plate boundary region. In the west, the Moho discontinuity has been found at 15–20 km depth, suggesting extended and, at least in some locations, oceanic crust, while in the east the crust is on average 25–30 km thick. There it is interpreted either as Mesozoic oceanic or thinned Precambrian continental crust covered by thick sedimentary deposits. Standard continental crust (30–35 km) is observed along the eastern part of the northern African coast, while to the west a rapid change from a relatively deep Moho (down to 42 km) below the Atlas Mountain Range to the thin crust of the southwestern Mediterranean Sea has been found. The crust beneath the eastern North Atlantic Ocean can be up to 5 km thicker compared with standard oceanic crust (6 km). The crust has been interpreted to be heterogeneous as a consequence of irregular magma supply at the Mid‐Atlantic ridge. In addition, serpentinization of the sub‐Moho mantle could contribute to the imaging of apparently anomalous thick oceanic crust. In Europe, the presence of crustal roots (>45 km) beneath the major mountain belts has been confirmed, while thin crust (<25 km) has been found beneath extensional basins. Comparing the obtained Moho topography and Moho depth computed assuming isostatic compensation at 60 km depth shows that most of the Mediterranean and eastern Atlantic region appears to be in isostatic equilibrium. The large positive residuals observed for the eastern Mediterranean are likely to be due to overestimating crustal thickness, owing to the thick sediment deposits present.

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Section: Resultsmentioning

confidence: 99%

Joint inversion of local, regional and teleseismic data for crustal thickness in the Eurasia-Africa plate boundary region

Marone

Meijde

Lee

et al. 2003

Geophysical Journal International

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“…Along the considered traverse, the process ruled the Cenozoic formation of the Hellenic chain [141], and is now traced back to the Late Jurassic. Consistently, the large volume of subducted lithosphere, which is still depicted in the asthenosphere as far north as Bulgaria [142,143], attests for a long-lived subduction or, more precisely, a long shift-governed succession of subduction planes.…”

Section: Conclusioñmentioning

confidence: 98%

Rhodope and Vardar: the metamorphic and the olistostromic paired belts related to the Cretaceous subduction under Europe

Ricou¹,

Burg²,

Godfriaux³

et al. 1998

Geodinamica Acta

159

111

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The Rhodope massif of Bulgaria and Greece is a complex of Mesozoic synmetamorphic nappes stacked in an Alpine active margin environment. A new analysis of the Triassic to Eocene history of the Vardar suture zone in Greece discloses its Cretaceous setting as a subduction trench. We present a geological traverse that takes into account these new observations and runs from the Hellenides to the Balkans, Le. from the African to the Eurasian sides of the Tethys ocean, respectively. The present review first defines the revisited limits of the Rhodope metamorphic complex. In particular, the lower part of the SerboMacedonian massif is an extension of the Rhodope units to the west of the Struma river. Its upper part is separated as the Frolosh greenschist unit, which underlies tectonic slivers of CarpathicBalkanic type. Several greenschist units, which locally yield Mesozoic fossils, follow the outer limits of the Rhodope. Their former attribution to a stratigraphic cover of the Rhodope has been proven false. They are divided into roof greenschists, which partly represent an extension of the Strandza Jurassic black shales basin, and western greenschists, which mostly derive from the Vardar Cretaceous olistostromic assemblage. The Rhodope complex of synmetamorphic nappes includes Continental Units and Mixed Units. The Continental Units comprise quartzo-feldspathic gneisses in addition to thick marble layers. The Mixed Units comprise meta-ophiolites as large bodies or small knockers. They are imbricated, forming an open dome whose lower, Continental Unit constitutes the Drama window. The uppermost Mixed Unit is overlain by remnants of the European plate. The presentday structure results from combined large-scale thrust and exhumation tectonics. Regional inversions of synmetamorphic senseof-shear indicate that intermediate parts of the wedge moved upward and forward with respect to both the lower and upper plates. A kinematic model is based on buoyancy-driven decoupiing at depth between subducted continental crust and the subducting lithosphere. Continuing convergence allows coeval underthrusting of continental crust at the footwall, decoupling at depth, and upward-forward expulsion of a low-density metamorphic wedge above. The continental crust input and its upward return may have lasted for at least the whole of the Early Cretaceous, as indicated by isotopic ages and the deformation history of the upper plate. A Late Eocene marine transgression divides the. ensuing structural and thermal evolution into a follow-up uphft stage and a renewed uplift stage. Revision of the limits of the Vardar belt in Greece first resulted in separating the Paikon mountain as a tectonic window below the Vardar nappes. It belongs to the western, Hellenic foreland into which a system of thrust developed downward between 60 and 40 Ma. The eastern limit is a dextral strike-slip fault zone that developed greenschist facies foliations locally dated at 50-40 Ma. Revision of the lithological components discloses the preponderance of Cretaceous volcano...

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“…17). This implies the retreat of the southward-migrating subduction boundary, and also possible slab break-off of the subducting slab, as shown by seismic studies indicating the remnant of subducted fragments under the Rhodope (Shanov et al 1992). Mantle seismic tomography has also documented the primary role of slab roll-back in the tectonic evolution of the Aegean since the Oligocene (Wortel & Spatman 2000).…”

Section: Geodynamic Contextmentioning

confidence: 99%

From syn- to post-orogenic Tertiary extension in the north Aegean region: constraints on the kinematics in the eastern Rhodope–Thrace, Bulgaria–Greece and the Biga Peninsula, NW Turkey

Bonev

Beccaletto

2007

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The Aegean region experienced back-are extension related to the Hellenic subduction system at least from the latest Oligocene to the present. We document Tertiary extension-related kinematics in the north Aegean, in the eastern Rhodope-Thrace of Bulgaria-Greece and the Biga Peninsula of NW Turkey. A regionally consistent NNE-SSW-to NE-SW-oriented kinematic direction, delineated in both areas by stretching lineations and associated ductile-brittle shear fabrics in exhumed metamorphic domes beneath detachments, suggests that they were kinematically coupled during the Tertiary extension. This kinematic framework, combined with regional geochronological data and the stratigraphic record in hanging-wall supradetachment basins, defines an extensional history that includes syn-and post-orogenic episodes from Paleocene to Miocene times. Paleocene-early Eocene synorogenic extension in the Kemer micaschists of the northern Biga Peninsula and in the Kesebir-Kardamos dome in Rhodope-Thrace accommodated gravitationally induced hinterland-directed exhumation of the orogenic stack, coeval with the closure of the Vardar Ocean. Then, following collision within the region, it was succeeded by latest Oligocene-Early Miocene extension as recorded in the Kazdaǧ Massif in the southern Biga Peninsula, which overlaps the Aegean back-arc post-orogenic extension, widely recognized in the central Aegean and southern Greek Rhodope. The protracted record of extension is interpreted to reflect progressive exhumation of the orogenic wedge along the Eurasian plate margin. Southward migration of extension and magmatism across the study areas accounts for sequential shift and roll-back of the subduction boundary at that margin, from the latest Cretaceous in the Rhodope to its present position at the Hellenic trench. The results allow recognition of the investigated areas as an important extensional domain in the north Aegean region, which underwent Tertiary syn-and post-orogenic extension.

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Evidence for the existence of a paleosubduction zone beneath the Rhodopean massif (Central Balkans)

Cited by 22 publications

References 4 publications

Joint inversion of local, regional and teleseismic data for crustal thickness in the Eurasia-Africa plate boundary region

Joint inversion of local, regional and teleseismic data for crustal thickness in the Eurasia-Africa plate boundary region

Rhodope and Vardar: the metamorphic and the olistostromic paired belts related to the Cretaceous subduction under Europe

From syn- to post-orogenic Tertiary extension in the north Aegean region: constraints on the kinematics in the eastern Rhodope–Thrace, Bulgaria–Greece and the Biga Peninsula, NW Turkey

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