Vardar Ocean Research Articles

Tithonian limestone as a marker of early contraction of NeoTethyan Vardar Ocean: structural constraints on the latest Jurassic–earliest Cretaceous “docking” (Dobroljupci, Kuršumlija, Jastrebac Mt., Serbia)

Tithonian limestone as a marker of early contraction of NeoTethyan Vardar Ocean: structural constraints on the latest Jurassic–earliest Cretaceous “docking” (Dobroljupci, Kuršumlija, Jastrebac Mt., Serbia)

Did the Western and the Eastern Vardar ophiolites originate through a single intra-oceanic subduction? Insight from numerical modelling

The ophiolites of the Balkan Peninsula are distinguished into the Western and the Eastern Vardar ophiolites and it is generally accepted that both of them resulted from the latest Jurassic/earliest Cretaceous closure of the Vardar branch of the Tethys Ocean (Vardar Tethys). This study is aimed at testing the possibility that the origin and emplacement of these two ophiolite belts can be explained in terms of a single NE-dipping intra-oceanic subduction, which commences in mid Jurassic and lasts until the lowermost Cretaceous, and then transitions into collision between the African and the European plate. The subduction is accompanied by creation of a new oceanic lithosphere in the back-arc. In order to test this hypothesis, we use 2D numerical thermomechanical modeling for investigating the nucleation of the East Vardar Ocean in the back-arc and intra-arc region. Our numerical results suggest that a single intra-oceanic subduction can indeed be simultaneously responsible for both the westward obduction of the Western Vardar ophiolites and for complex active margin processes along the western rim of the European plate. The simulations show that the single intra-oceanic subduction zone is able to produce a pronounced extension and oceanic spreading along the European margin, which can be associated with the formation of the Eastern Vardar ophiolites in this subduction related setting (SSZ and BAB). The comparison of the numerical modeling results with available natural data suggests that our models are capable to approximate the regional geodynamic evolution during and immediately after the closure of Vardar Tethys.

Missing link on the western Paleotethys configuration: Stratigraphic constraints on the truncated Triassic “Gornjak” sequence (eastern Serbia, Balkan/Carpathian hinterland)

There is a major overlap of the two lithospheric-scale early Alpine (post-Variscan) extensional geodynamic drivers which contributed to the crustal thinning of the north Mediterranean margin/south European foreland/ Dinaride-Hellenide-Carpathian/Balkan/Rhodope continental amalgamation. A widespread late Permian-Triassic Alpine extension interacted with the coeval Paleotethyan rollback, producing a number of intraplate and marginal basins, later coalesced to form the Neotethys Vardar Ocean. However, some of these externally-positioned, north-south striking elongated basins (eastern Serbia), were abruptly interrupted by an unreported Triassic event. This event truncated the latest Permian to Lower – Middle Triassic sequence of the Getic unit, best exposed near the Gornjak area (Balkan-Carpathian hinterland, “Carpatho-Balkanides”, western Moesian foreland). At Carpathian-Balkan scale, this rather undocumented geodynamic episode is consistent with the “early Cimmerian” “docking” event (recorded within the Moesian platform, and the North Dobrogea Orogen). Based on the surface/ subsurface geological and available scarce literature data, the truncated Lower- and Middle Triassic sedimentary successions of the “Gornjak basin” (eastern Serbia), provide new constraints on the timing of the Triassic western Paleotethyan closure. The study emphasizes a far-field effect of the Upper Triassic Paleotethyan demise and Cimmerian “docking”, largely obscured by the late Alpine shortening and the formation of the Carpathian/Balkan fold-and-thrust belt.

The role of the pre-Alpine polycrystalline basement in the paleogeographic configuration of multiple Neotethyan oceanic basins

AbstractThe study provides a deeper understanding of the early Mesozoic paleogeogeographic spatial-temporal relationship by studying the two Adria-Europe intervening basement blocks. The Drina-Ivanjica and Pelagonian crustal fragments play important role in the internal early Alpine oceanic constitution further controlling the late Jurassic emplacement of Tethyan Dinaric-Hellenic ophiolites. The proposed paleogeographic reassessment is driven by the new paleocontinental inheritance data associated with the Variscan – pre-Variscan basement terranes. The recently published data suggest an Avalonian-type inheritance of the Pelagonian basement block which indicates a different pre-Variscan plate-tectonic journey, including separate spatial arrangement during Variscan amalgamation. In turn, Cadomian-type basement inheritance has been documented within the sliced Adria microplate. Thus, the Avalonian inheritance place the Pelagonian block away from the Apulia/Adria (Dinarides). In the investigated context of Paleozoic-Mesozoic paleogeographic transition, the Pelagonian block may represent a segment of the Cimmerian ribbon continent or southernmost segment of the Variscan Europe. With regards the nearby Adria microplate, a Triassic-Jurassic oceanic opening led to the decoupling (spreading away from the main Adria microplate) of the Drina-Ivanjica block. The rifting is in line with the simultaneous yet opposite or westward-directed drift of the Pelagonides. The breakup of south European Variscan configuration eventually result in the spatial alignment of the two basement fragments referred to as the “Drina–Pelagonide continental splinter”. By linking the paleogeographic pre-Jurassic–Jurassic relationship between these continental units, the two landlocked Neotethyan Vardar s.l. basins are extrapolated, “Dinaric Tethys” / Inner Dinaric-(Mirdita-Pindos) and the main Vardar Ocean (Western Vardar Zone).

Tectonomagmatic considerations about the Cimmerian metamorphism and magmatism in Bulgaria

Problems of the Cimmerian igneous activity are briefly discussed at the background of the plate tectonics of the Balkan Peninsula. We mostly comment on the relations of the tectonometamorphic evolution of the Bulgarian territory with the Vardar Ocean and its subduction beneath the European continent. A number of problems still remain open especially in regard to the Jurassic evolution of the Rhodope massif.

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.

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.

The role of the 'Zvornik suture' for assessing the number of Neotethyan oceans: Surface - subsurface constraints on the fossil plate margin (Vardar Zone vs. Inner Dinarides)

The balancing exercise of the ?single-ocean model? and reexa - mination of Jurassic paleogeographic conditions and tectonic interaction allowed the reconstruction of the mosaic of independent microplate margins and sutured northwestern Tethyan realm (Vardar Ocean). The overprinted Mesozoic convergent margin referred to as the ?Zvornik suture? was of special interest in the reconstruction of the displaced ophiolite belts of Dinarides and Vardar Zone. The surface?subsurface constraints of these mixed crustal units, in particular the polyphase strike-slip character of the ?Zvornik suture? yields the presence of at least two of Neotethyan basins extrapolated in the vicinity of the northwestern segment of this paleosuture - related fault system. The restoration and synopsis shows a limited capability for obduction-related emplacement of the Vardar oceanic lithosphere (West Vardar Zone) accounting the polyphased strike-slip tectonics. The balancing and the proposed tectonic/paleogeographic recon struction does not exclude obduction, but it shows a limited capability with much shorter across-strike width of the highlydeformed West Vardar ophio lite. The presence of the two distinct autochthonous Tethyan oceans divided by this important dextral strike-slip fault zone is suggested: The Inner Dina ric?(Mirdita?Pindos) Ocean or Dinaric Tethys (identified by the Inner Dinaric Ophiolite Belt) and the Vardar Ocean (identified by the West Vardar Zone). The West Vardar Zone remains to be a subzone of the principal composite Neotethyan suture referred to as the Vardar Zone s.s., whereas the Dinaric Tethys have been (re)incorporated to the area of Dinarides (Adria microplate). The northern segments of these two landlocked basins were on both sides of the Inner Dinaridic continental ridge (referred to as the Drina-Ivanjica block), divided by the protracted strike-slip activity of the ?Zvornik suture?.

A few remarks on the Triassic paleogeography and geodynamic link between the Dinarides an the Serbo-Macedonian unit

A recently recycled tectonic hypothesis in which the Serbo-Macedonian Unit rifted off during Ladinian from the Dinarides is tested. The Triassic rifting, according to this concept, led to the opening and the formation of a northwestern branch of Neotethys (=Vardar Ocean). Similar concept explains the developments within the Inner Hellenide allochoton (Serbo-Macedonian Unit and Pelagonides). The testing of early Alpine configuration in Serbia shows, however, that the two crystalline basement units have significant paleogeographic variances. The study moreover includes the differences in Paleozoic metamorphic grades between two inliers, their exhumation times, etc. The investigated pre-Triassic paleogeographic and geodynamic variances unambiguously contradict any connection before and during Triassic (Ladinian). In this regard, by using the available field data, and the juxtaposed Late Paleozoic Variscan tectonometamorphic differences, the paper underscores the large differences in the (pre)Triassic plate configurations and paleogeography. The synthesis displays the two separate positions of these microplates situated along with the length of this segment of the Triassic Eurasian continental margin.

The inception of the Maliac Ocean: Regional geological constraints on the western Circum-Rhodope belt (northern Greece)

Abstract Considerable debate surrounds the early-Alpine paleogeographic significance of the Circum-Rhodope belt (CRB, Greece), in particular, whether it was a rifted section of the southern Euroasian foreland, or of the late Mesozoic back-arc system of the Vardar Ocean or of both. In the attempt to clarify the complex nature of the CRB, nine new lithostratigraphic formations (with its members) in consideration of the spatiotemporal and regional geological context are constrained by tracing the changes in regional plate interactions and linked magmato-sedimentary record. The analysis of the stratigraphic data in combination with the highly complex, yet poorly constrained regional geology is employed to reconstruct the late Permian, Triassic, and latest Jurassic developments of this part of the southern European foreland. A continuum between the rifting and Triassic opening of the Maliac Ocean, the Carnian Eo-Cimmerian docking, is supported by the consolidated new data embedded into a collection of the nine distinct lithostratigraphic formations. The terminal Vardar plate approach during the latest Jurassic - earliest Cretaceous and the convergence with the investigated portion positioned to the south of the Balkan-Hellenic foreland thrust belt configured this regional Neotethyan flysch trough, whereas the Paleocene - Eocene east-west shortening and nappe stacking ejected the incoherent early Alpine system referred to as the CRB. The ejected Permo-Triassic, including the early Jurassic ophiolite-bearing formations of the CRB, are matched to be in line with those of the regional Southeast European importance. In fact, the results place the western CRB or eastern Maliac Ocean to lie at the distal southern margin (promontory) of the Eurasian craton aligned with the early- and late Paleozoic crystalline terranes: Paleozoic to Lower Triassic Variscan basement (segment of the Pelagonian Unit), “Veles Series” and Lower Complex of the Serbo-Macedonian Unit (Vertiskos Unit).

Cretaceous‐Paleogene Tectonics of the Pelagonian Zone: Inferences From Skopelos Island (Greece)

AbstractWe have investigated subduction‐exhumation processes in the Pelagonian zone, exposed on the Northern Sporades islands (Aegean Sea) related to successive episodes of ocean continent and continent‐continent convergence through integrating multiscale structural analysis, metamorphic petrology, and white mica 40Ar/39Ar dating. Two major progressive phases of ductile deformation are documented, which are related to distinct episodes of tectonic burial and exhumation of the Pelagonian continental margin, which was facing the Neotethys/Vardar ocean. Review of existing data sets from neighboring regions shows that both deformation phases can be correlated along strike up to the Dinarides. The first phase of tectonic burial and exhumation (D1) is characterized by NW‐SE tectonic transport, greenschist facies metamorphism, and Early Cretaceous (~105‐135Ma) 40Ar/39 Ar white mica single fusion ages. D1 is correlated with the initial closure of the Vardar ocean by top‐to‐the‐W to NW ophiolite obduction and the underthrusting of the Pelagonian margin below the oceanic upper plate. Underthrusting was followed by exhumation and the deposition of Late Cretaceous‐Paleogene sediments. The second phase of burial and exhumation (D2) is characterized by NE‐SW tectonic transport, greenschist to blueschist facies metamorphism, and latest Cretaceous‐Early Eocene 40Ar/39 Ar white mica ages of S2 fabrics. Top‐to‐the‐SW shearing is correlated with the tectonic burial of the Pelagonian zone below the Eurasian continent (Rhodopia), while top‐to‐the‐NE shearing is attributed to subsequent extensional exhumation. D2 fabrics record low‐grade P‐T conditions suggesting that the decoupled cover formations exposed on Skopelos were incorporated in an accretionary wedge that formed above the subducting Pelagonian basement during Paleogene times.

Structural and geochronological constraints from the Drina-Ivanjica thrust sheet (Western Serbia): implications for the Cretaceous\u2013Paleogene tectonics of the Internal Dinarides

We have investigated successive episodes of ocean-continent and continent–continent convergence in Western Serbia (Drina-Ivanjica thrust sheet). The coupled application of structural and petrological analyses with Illite Crystallinity measurements and K/Ar dating has revealed the timing and structural characteristics of multiple regional deformation phases, and allowed us to revise the origin of the different Triassic units outcropping in the study area. D1 tectonic burial was characterized by anchizonal metamorphism, dominantly WNW-verging isoclinal folding (F1), and related axial planar cleavage (S1) formation in the Paleozoic basement and the stratigraphic cover of the Drina-Ivanjica thrust sheet exposed along the northern rim of this thrust sheet. The timing of D1 deformation is constrained by K/Ar ages suggesting 135–150 Ma tectonic burial for the Drina-Ivanjica thrust sheet. D1 deformation and metamorphism is correlated with the closure of the Vardar ocean by top-W to NW ophiolite obduction and the underthrusting of the Adriatic distal passive margin below the oceanic upper plate. Since D1 structures are lacking in the southern occurrences of Triassic rocks within the study area it is proposed that this Triassic is may not be the original sedimentary cover of the Drina-Ivanjica Paleozoic basement. We propose that this southern Triassic originated from a more external Dinaridic thrust sheet and was transported to its present-day position by a top-NE backthrust presumably during late Early Cretaceous–Paleogene times. Map-scale, NW–SE striking D2 thrust faults and abundant NW–SE trending F2 folds observed in all units correspond to the general trend of the Dinaridic orogen and are attributed to the latest Cretaceous–Paleogene collision between Adria and Europe. Regional Latest Cretaceous–Paleogene shortening was followed by strike-slip tectonics (N–S shortening and perpendicular extension) and subsequent Miocene normal faulting in both orogen-parallel and orogen-perpendicular directions driven by slab rollback processes of the Carpathian-Dinaridic realm.

Boninite volcanic rocks from the mélange of NW Dinaric-Vardar ophiolite zone (Mt. Medvednica, Croatia) – record of Middle to Late Jurassic arc-forearc system in the Tethyan subduction factory

In the Late Jurassic to Early Cretaceous ophiolite melange from the Mt. Medvednica (Vardar Ocean) blocks of boninite rocks have been documented. They emerge as massive lavas made of augite, spinel, albite and secondary hydrous silicates (e.g., chlorite, epidote, prehnite, and pumpellyite). An established crystallization sequence (spinel→clinopyroxene→plagioclase±Fe-Ti oxides) was found to be typical for the boninite series from the suprasubduction zones (SSZ). Augite crystallization temperatures and low pressures of ~1048 to 1260 °C and ~0.24 to 0.77 GPa, respectively, delineated the SSZ mantle wedge as a plausible source of boninite parental lavas. Their whole-rock geochemistry is characterised by low Ti, P2O5, Zr, Y, high-silica, and high Mg# and Cr# values. Low and U-shaped REE profiles are consistent with the negative Nb-Ta, P and Ti anomalies indicative for SSZ. Thorium and LILE enrichment, and very low initial Nd-isotopic values (eNd(T = 150 Ma) + 0.49 to +1.27) act as vestiges of mantle-wedge metasomatism. The mantle source was likely depleted by the MORB and IAT melt extraction and was contemporaneously affected by subduction fluids, prior to the large-scale adiabatic melting of the mantle hanging wall. This eventually gave rise to boninite lavas and an ultra-refractory harzburgite residiuum. The genesis of boninites is related to the Tithonian mature forearc setting that evolved from an intra-oceanic, Callovian to Oxfordian, island-arc environment. The Mt. Medvednica boninite rocks stand for the youngest SSZ-related Jurassic oceanic crust from the NW segment of the Dinaric-Vardar Tethys that are nowadays obducted onto the passive margins of Adria. Taking into account the existence of similar rocks in the ophiolite zones of Serbia, Albania and Greece, the boninites of Mt. Medvednica strongly favours the single Tethyan oceanic basin that existed in this part of Europe during the Late Jurassic.

Stratigraphic correlation and structural position of Lower Cretaceous flysch-type deposits in the eastern Southern Alps (NW Slovenia)

Lower Cretaceous syn-orogenic sediments derived from the obducted ophiolites of the Meliata–Maliac–Vardar (Neotethys) Ocean are typically found in the Dinarides and the Austroalpine units. Correlative flysch-type deposits linking both regions through the Southern Alps had been reported from the Bohinj area (NW Slovenia), but their stratigraphic and structural framework remained poorly known. Our research focused on stratigraphic and structural field studies in a 50 km2 area between Lake Bled and Lake Bohinj in the Julian Alps. The mixed carbonate–siliciclastic sediments, informally named the Studor formation, range in age from the Valanginian (possibly late Berriasian) to the Aptian. They occur on top of two different stratigraphic successions, which we assign to two separate nappes. The first succession consists of deep-water Middle Triassic to Lower Cretaceous deposits of the Bled Basin and belongs to the Pokljuka Nappe, which is the uppermost nappe of the Julian nappe stack. The second succession consists of Upper Triassic to Lower Jurassic platform carbonates and a thin Jurassic–Cretaceous deep-water sequence. This succession was deposited in the marginal area of the Julian Carbonate Platform/Julian High and now belongs to the underlying Krn Nappe. The original (Dinaric) thrust contacts between the Pokljuka and Krn nappes are obliterated by younger deformations. The present-day boundaries between these two nappes are steep NE–SW and younger NW–SE trending faults. The post-nappe deformation sequence characterizing the Alps–Dinarides transition zone has been recognized: (1) Oligocene–Early Miocene NW–SE contraction; (2) Early–Middle Miocene extension; and (3) Late Miocene to recent inversion and transpression.

Subduction Evolution of the Dinarides and the Cretaceous Orogeny in the Eastern Alps: Hints From a New Paleotectonic Interpretation

AbstractThe geological evolution of the Dinarides and Eastern Alps is reconsidered taking into account the constraints from a new paleotectonic interpretation for the central Mediterranean. The geological record of the Dinarides suggests that more than one ocean existed between Africa and Europe in Late Triassic‐Late Jurassic. Besides the large Vardar ocean, it is inferred that the basin located to the west of the Pelagonian domain is floored by oceanic‐like lithosphere. Following the Late Jurassic‐Early Cretaceous westward obduction of the Vardar ophiolite onto Pelagonia, subduction resumed close to the European margin and continued until early Paleogene, when the Vardar oceanic basin was consumed. Subsequently, the substrate of the narrow Pindos ocean‐like basin was subducted to the east, accommodating a few hundreds of kilometers of Adria‐Eurasia convergence. Plate kinematics indicate that N‐S convergence between Africa and Europe initiated only after the Cenomanian, well after ophiolite obduction occurred in the Dinarides‐Hellenides. In the Eastern Alps, however, an early Late Cretaceous orogeny has been recorded, separated from the tectonic evolution of the Alps sensu strictu. This Cretaceous orogeny of the Eastern Alps has not been fully understood. The new reconstructions suggest that the Pindos and Vardar oceans merged north of Pelagonia and were confined by a transform fault bounding to the south the Austroalpine domain. Within this frame, where the occurrence of wider oceanic domains is considered, the Cretaceous orogeny of the Eastern Alps can be linked to different episodes of ophiolite obduction and a subsequent shift of tectonic activity that has been recorded in the Dinarides.

Eastern Mediterranean Tectonics

extended to many other colleagues working in the Eastern Mediterranean. The papers of the present issue were written by structural geologists, sedimentologists, petrologists, geochemists, geophysics and seismologists, thus covering a wide range of disciplines. All these contributions are aiming to reveal the tectonic evolution and paleogeography of the Eastern Mediterranean. A first collection sequence of papers is dealing with the pre-Alpine tectonic evolution and paleogeography. A second collection is addressing problems related to the Eoand the Meso-Alpine orogenic phases occurring from Late Jurassic to Oligocene. Finally, there are papers dealing with the Late Miocene to Holocene evolution of the south Aegean and west Anatolian domains. Specifically, the issue starts with two papers (Chatzaras et al., and Zulauf et al.), which are mainly based on detrital zircon U–Pb ages to track the margin of northern Gondwana and the Paleotethys suture in the southern and southwestern part of the External Hellenides. Detrital zircon U– Pb ages are also used by Hinskens et al. to constrain Late Cretaceous maximum sedimentation ages and a Triassic to Neoproterozoic provenance for the metasedimentary rocks of the Cycladic blueschists of Tinos. The following two papers by Ferriere et al. and Michail et al. describe the evolution of the Vardar Ocean and suggest west-directed obduction of the ophiolitic complex to the Pelagonian zone during the Eo-Hellenic orogenic phase. Based on structural and geochronological data, Georgiev et al. suggest Jurassic to Paleogene nappe stacking in the Rhodope metamorphic complex and Middle Eocene extensional overprinting. Okay and Altiner present new constraints on the Cretaceous development of the southern part of the Pontides close to the Izmir–Ankara suture (Haymana and Ankara regions) using mainly biostratigraphical data. The Late Cretaceous to Eocene evolution of the Asterousia Most rocks exposed in the Eastern Mediterranean show evidence for a long-standing and complex tectonic history. Besides the active Hellenic subduction system, this history includes at least four major orogenic episodes, namely the Cadomian, the Variscan, the Cimmerian, and the Alpine Orogeny, accompanied by the destruction and/or formation of large oceans such as the Paleotethys and the Neotethys. Therefore, with the term “Eastern Mediterranean Tectonics” we refer to all tectonic processes that occurred from the Neoproterozoic to present and contributed to the formation of the present geological edifice of the Eastern Mediterranean. This topical issue of the International Journal of Earth Science sheds some more light on the tectonic history of the Eastern Mediterranean presenting a collection of fifteen papers, which cover processes that took place in Aegean and Anatolian domains from the Neoproterozoic to the present (Fig. 1). The idea for this issue was born during the GeoFrankfurt2014 conference, where we convened a session entitled “The Evolution of the Alpine Orogenic System in the Eastern Mediterranean.” Apart from the participants of this session, the invitation to submit papers was

Tectonic evolution of Western Tethys from Jurassic to present day: coupling geological and geophysical data with seismic tomography models

ABSTRACTThe geodynamic evolution of the Western Tethys is characterized by multiple phases of rifting, seafloor spreading, subduction, and collisional events. Regional reconstructions are highly dependent on the kinematic history of the major plates bounding the Atlantic and Tethyan tectonic domains, as well as small micro-plates resulted from the fragmentation of northern Gondwanaland. The complexity of tectonic events in this area leads to major discrepancies between competing models about the timing, location, and polarity of subduction zones, for both the Cenozoic evolution and earlier phases. We focus on unravelling the Mesozoic evolution of the Western Tethys. We first reassessed kinematic models for the Early Jurassic–Late Cretaceous opening of the central, north central, and north Atlantic and used these as boundary conditions on the kinematic reconstructions of the Tethyan realm. We combined reconstructions of rifting and early seafloor spreading in northern Pangea that incorporate quantitative estimates of continental extension, and suggest a transtensional motion of Iberia relative to Europe in Early Cretaceous time to fit within the refined plate configuration of Central North Atlantic. We combined this regional framework with a recently published model for the motion of smaller blocks within the Western Tethys; from this model, we created synthetic isochrons for extinct oceanic basins and built evolving topological plate boundaries based on the new rigid plate model to derive a self-consistent and time-dependant model for the last 200 million years. We then examined the consistency of subduction history implied by the kinematic reconstructions, by comparing reconstructed plate boundary configurations to mantle velocity structure imaged by a range of seismic tomography models. Our results show that a satisfactory match can be made between Cenozoic subduction events in the Western Tethys region and observed shallow tomographic high-velocity material. However, the match is less clear for older subducted material. Correlations between surface reconstructions and deep Earth structure suggest that mid-deep mantle seismic features under present day Northeast-Central and Northwest Africa-Arabia may correspond with the Mesozoic subduction systems in the Vardar Ocean, Alpine Tethys, and Western Neotethys, respectively. These correlations support a model with intra-oceanic subduction of the Vardar Ocean from Middle Jurassic to Early Cretaceous, and mid-Early Cretaceous initiation of oceanic subduction in the Ligurian-Piemont Ocean. The results from the plate-tomography comparison suggest the existence of oceanic subduction in the Alpine Tethys Oceans in late early Cretaceous time. We investigated the uncertainties in the tectonic model in terms of absolute and relative plate motion and surface velocities and showed that choice of absolute reference frame can partially account for the lateral offset between the Vardar subduction zone and associated slab material in deep mantle; additional mismatches may be attributable to the limitations of our methodology, such as the assumption that slabs sink vertically.

Provenance of Tertiary volcanoclastic sediment in NW Thrace (Bulgaria): Evidence from detrital amphibole and pyroxene geochemistry

Detrital heavy mineral and bulk rock geochemistry and a review of sandstone petrographic data have been used to investigate the post-collisional effusive magmatism that followed the closure of the Vardar Ocean and the generation of volcanic sediments in a complex and compositionally variable volcanic region. Available petrographic data gives evidence of contributions from three key source areas corresponding to the three main tectonic units: the structurally lower Gneiss–Migmatite Complex (Byala Reka-Kechros and Kesebir-Kardamos domes) and the upper Variegated (Kimi) Complex, both fringed by the low-to-medium-grade Mesozoic rocks of the Circum-Rhodope Belt. Besides the deposition of siliciclastic material, volcanic contributions from both, intermediate and acid products represent an important source of sediment in the area. Despite dominant intermediate to acid volcanic products, volcanic lithic fragments in sandstones (microlithic, lathwork and brown vitric textures) indicate main inputs from intermediate and basic-intermediate products generating questions on the interpretation of volcanic detritus in reconstruction of provenance. Detrital amphibole and pyroxene chemistry is used to characterise the supply of volcanic material as well as the dispersal mechanisms and understand the role played by each of the volcanic centers present in the area in the infill of the north-western Thrace basin. Amphibole chemistry reveals high compositional heterogeneity according to both compositional variability of the numerous volcanic centres active at the time of deposition and presence of metamorphic amphibole. 4Al and AlT apfu values indicate that most of the amphiboles from the NERZ are not of volcanic origin and their presence can only be attributed to the numerous amphibolite facies metamorphic rocks abundantly documented in the area. Detrital amphibole compositions from the ZKVS indicate major contributions from the Iran Tepe and Zvedzel volcanoes. Analysed detrital clinopyroxenes from the NERZ are mostly diopside–augite, with no hedenbergite or Fe–augite detected. The 4Al/6Al ratio is comparable with compositions of volcanic pyroxenes from the Momchilgrad–Arda (ZKVS) region and products from the pre-caldera phase of the Borovitza.

Late Cretaceous UHP metamorphism recorded in kyanite–garnet schists from the Central Rhodope Mountains, Bulgaria

In this study, we report the first discovery of microdiamond inclusions in kyanite–garnet schists from the Central Rhodope Mountains in Bulgaria. These inclusions occur in garnets from metapelites that are part of a meta-igneous and meta-sedimentary mélange hosted by Variscan (Hercynian) orthogneiss. Ultra-high-pressure (UHP) conditions are further supported by the presence of exsolved needles of quartz and rutile in the garnet and by geothermobarometry estimates that suggest peak metamorphic temperatures of 750–800°C and pressures in excess of 4GPa. The discovery of UHP conditions in the Central Rhodopes of Bulgaria compliments the well-documented evidence for such conditions in the southernmost (Greek) part of the Rhodope Massif. Dating of garnets from these UHP metapelites (Chepelare Shear Zone) using Sm–Nd geochronology indicates a Late Cretaceous age (70.5–92.7Ma) for the UHP metamorphic event. This is significantly younger than previously reported ages and suggests that the UHP conditions are associated with the Late Mesozoic subduction of the Vardar Ocean northward beneath the Moesian platform (Europe). The present-day structure of the RM is the result of a series of subduction–exhumation events that span the Cenozoic, alongside subsequent post-orogenic extension and metamorphic core complex formation.

Erratum to: Stratigraphy and tectonics of a time-transgressive ophiolite obduction onto the eastern margin of the Pelagonian platform from Late Bathonian until Valanginian time, exemplified in northern Evvoia, Greece

The obduction of an ophiolite sheet onto the eastern Pelagonian carbonate platform complex of the Hellenides began during the Late Bathonian and ended with the final emplacement of the ophiolite during Valanginian time. The early stages of obduction caused subaerial exposure of the platform, recorded by an unconformity of Callovian age, which is marked by laterites overlying folded and faulted, karstic substrates. The laterites have distinct ophiolitic geochemical signatures, indicating that emergent ophiolite had been undergoing lateritic weathering. This unconformity coincides with widespread western Tethyan, Callovian gaps, indicating that the obduction in the Hellenides was probably related to far-reaching plate tectonic processes. Resumed gravitational pull and rollback of the subducted, oceanic leading edge of the temporarily exposed ophiolite. Platform drowning continued into Tithonian–Valanginian time, documented initially by reefal carbonates and then by below-CCD, carbonate-free radiolarian cherts and shales. Subsequently, siliciclastic turbidites, which apparently originated from uplifted Variscan basement, were deposited together with and over the radiolarite as the ophiolite nappe sheet advanced. The nappe substrate underwent tectonic deformations of varying intensity, while polymictic melange and syntectonic sedimentary debris accreted beneath the ophiolite and at the nappe front. The provenience of the ophiolite nappe complexes of northern Evvoia most probably has to be looked for in the Vardar ocean.

Paleolatitudes of Late Triassic radiolarian cherts from Argolis, Greece: Insights on the paleogeography of the western Tethys

The Hellenides fold-and-thrust range comprises two subparallel ophiolite belts of Triassic to Jurassic age – the external ophiolite belt (e.g., Mirdita, Pindos, Argolis) in the west, and the internal ophiolite belt in the east – broadly separated by the continental crust units of the Korabi–Pelagonian Zone. It is still a matter of debate whether these ophiolites derived from a single ocean (Meliata–Maliac–Vardar) or mark the suture of two distinct oceanic seaways (Pindos and Meliata–Maliac–Vardar). We contribute to the resolution of this controversy by studying the Migdalitsa Ophiolitic Complex in Argolis (Greece), which contains Triassic oceanic basalts and pertains to the external (western) ophiolite belt. Three key areas were mapped and several sites were targeted for structural, biostratigraphic, and paleomagnetic analyses. Radiolarian cherts in primary or tectonic contact with oceanic basalts were dated to the Late Triassic (Carnian–Norian) using radiolarians, and provided paleomagnetic directions of primary origin carried by magnetite and hematite. The derived mean direction was corrected for sedimentary inclination shallowing and yielded a paleolatitude of ~22°N that was placed in a broader paleogeographic context by reconstructing Pangea at ~225±5Ma using a recent apparent polar wander path corrected for sedimentary inclination shallowing. The Late Triassic paleogeography of the Tethys Ocean was constrained using additional paleolatitude estimates from the literature, which we checked and corrected (when possible) for sedimentary inclination shallowing. According to our reconstruction, the Meliata–Maliac–Vardar Ocean between Adria – the promontory of Africa – and Europe represents the locus of origin of the Late Triassic Argolis ophiolitic rocks of the external ophiolite belt, presently resting in tectonic contact on the Pindos–Subpelagonian zones, which represent a deep-water trough with no substantial evidence of in situ oceanization in the Triassic.