Adria Microplate Research Articles

Surface sediment around the Jabuka Islet and the Jabuka Shoal: Evidence of Miocene tectonics in the Central Adriatic Sea

Abstract This paper is conceived as a contribution to understanding the tectonic setting in the Jabuka region in the Central Adriatic Sea, one of the seismically active regions within the Mediterranean. This seismicity is the result of the compressional tectonics within the Adria microplate, accompanied by halokinetic activity. The Jabuka Islet and the Jabuka Shoal appear to be Triassic igneous bodies extruded by diapir tectonics. Sedimentological, mineralogical and micropaleontological analyses of the surface sediments were done to provide insights into the depositional environment around these igneous outcrops. Coarse-grained gravelly sands surrounding the Jabuka Islet and the Jabuka Shoal are composed predominantly of biogenous detritus, containing small amounts of particles derived from igneous rocks. This highly carbonate sediment cover has been formed in the low-energy environment, below wave base and without terrigenous supply from remote areas. A peculiar finding of reworked Lower Miocene foraminiferal assemblage in the recent surface sediment accompanied with re-interpreted seismic profile was used to propose a conceptual geodynamic model for the Jabuka diapir protrusion. It suggested Miocene age for the earliest protrusion of the Jabuka diapir, followed by further Plio-Quaternary growth and shaping. Together with mostly Paleogene fossil calcareous nannoplankton, fossil foraminifera were presumed to have been weathered from the pierced and extruded overburden rocks and admixed to recent, slowly forming carbonate skeletal association, typical for cool-temperate depositional environments.

Mantle dynamics in the Mediterranean

The Mediterranean offers a unique opportunity to study the driving forces of tectonic deformation within a complex mobile belt. Lithospheric dynamics are affected by slab rollback and collision of two large, slowly moving plates, forcing fragments of continental and oceanic lithosphere to interact. This paper reviews the rich and growing set of constraints from geological reconstructions, geodetic data, and crustal and upper mantle heterogeneity imaged by structural seismology. We proceed to discuss a conceptual and quantitative framework for the causes of surface deformation. Exploring existing and newly developed tectonic and numerical geodynamic models, we illustrate the role of mantle convection on surface geology. A coherent picture emerges which can be outlined by two, almost symmetric, upper mantle convection cells. The downwellings are found in the center of the Mediterranean and are associated with the descent of the Tyrrhenian and the Hellenic slabs. During plate convergence, these slabs migrated backward with respect to the Eurasian upper plate, inducing a return flow of the asthenosphere from the backarc regions towards the subduction zones. This flow can be found at large distance from the subduction zones, and is at present expressed in two upwellings beneath Anatolia and eastern Iberia. This convection system provides an explanation for the general pattern of seismic anisotropy in the Mediterranean, first-order Anatolia and Adria microplate kinematics, and may contribute to the high elevation of scarcely deformed areas such as Anatolia and Eastern Iberia. More generally, the Mediterranean is an illustration of how upper mantle, small-scale convection leads to intraplate deformation and complex plate boundary reconfiguration at the westernmost terminus of the Tethyan collision.

Geochemistry of the Late Mesozoic - Early Cenozoic turbidites from the NE part of the Adria microplate

Cretaceous to Eocene sandstones from the Southeastern Alps and Outer Dinarides (Italy, Slovenia and Croatia) have been geochemically determined to detect their provenance. The first arenaceous strata of the Julian Basin are strongly chemically influenced by the disgregation of metamorphic and not-metamorphic rock types related to the ancient Vardar sea closure where Island Arc and MORB-like related rock types were generated. At about 56 Ma, one level testifies the strong involvement of continental upper crustal source rocks as a consequence of the rapid arising of the Dinarides. Such contribution is well evidenced also in the Claut basin strata. After this first stage, a new moment of upwelling involved the Julian sediments which contributed, with recycled materials, to the creation of Brkini (and Vipava) basins. Moreover, other protolith rock types, which will represent the main source of the Istrian Basin, begin to be significant.

Quaternary tectonic and depositional evolution of eastern Srem (northwest Serbia)

The area of eastern Srem is situated in the southern periphery of the Pannonian basin. Its depositional evolution during the Neogene and the Quaternary has been controlled by tectonic processes. Miocene extensional subsidence was followed by the Pliocene-Quaternary inversion of the basin. The latter was accomplished as the result of replacement of the tensile by the compressive stress field. Since the Late Neogene, the regional tectonic activity has been controlled by compressive stress produced by the northnortheastern propagation of the Adria microplate. In the compressive NE-SW-oriented stress field, the recent structural plan of the Pannonian basin and its wider environment, including its southern periphery, was reactivated. The youngest tectonic deformations are characterized by positive and negative vertical motions of large intrabasinal segments and basinal periphery, resulting in the final inversion of the basin. The effects of the basinal inversion can be recognized in genetic features of Quaternary sediments and geomorphological characteristics of the relief. Sources of data used for the interpretation of the Quaternary tectonic activity in the area of eastern Srem are of geological, geomorphological, thermochronological, and geophysical character. The positions of prominent fault structures have been ascertained by remote sensing, interpretations of available geophysical cross-sections, and using the field data.

An outer ramp to basin plain transect: Interacting pelagic and calciturbidite deposition in the Eocene–Oligocene of the Tuscan Domain, Adria Microplate (Italy)

The interaction of ramps, basin plains and turbidite systems on the scale of tens of km has been rarely observed in fossil examples. Deep marine Eocene–Oligocene beds are exposed in the axial zone of the Chianti Mountains, Italy, and compose a regionally continue stratigraphic succession known as the Scaglia Toscana Formation. The formation was deposited in the Tuscan Domain of the Adria Microplate. This research aims at depicting its depositional architecture and evolution in the type area. Stratigraphic and sedimentologic analyses were performed on a ca. 25km-long transect that includes depositional systems sectioned both in the down- and along-dip directions. Shaly-carbonate deposits compose a complex of interacting ramps, basin plains and turbidite floor fan systems. Ramp deposits accumulated above the lysocline and in oxic conditions. Basin plain beds were deposited below the lysocline and were subject to episodes of oxygen depletion. Turbidity flows fed elongate fan lobes characterized by poor channelisation. The basin palaeogeography hampered the development of slope apron turbidite systems.The Eocene–Oligocene geodynamic setting of the Tuscan Domain was characterized by the evolution of a peripheral bulge and by the early structuring of a foredeep basin. Syn-sedimentary tectonism acted a primary role in the basin-scale arrangement. However other mechanisms also contributed to the local facies distribution, including the disposition of sediment-source areas and intrabasinal confinement morphologies, as well as relative oscillations of the depositional surface with respect to the lysocline and oxycline.

Amphiboles and clinopyroxenes from Euganean (NE Italy) cumulus enclaves: evidence of subduction-related melts below Adria microplate

Euganean Hills are a magmatic district belonging to the Veneto Volcanic Province, whose magmatism developed during an extensional tectonic regime within the Alpine orogenesis in an intra-plate setting (the Adria microplate). Mafic and ultramafic cumulus enclaves occur within the Euganean trachytes. We estimated the trace element composition of liquids in equilibrium with cumulus minerals, employing a set of partition coefficients. Parental melts of cumulus clinopyroxenes are characterized by a marked enrichment in LILE, Th and U relative to N-MORB. Conversely, HREE and HFSE concentrations resemble N-MORB contents. These geochemical signatures are typical of subduction-related magmas, and also characterized the parental melts of Adamello cumulates. Conversely, Veneto Volcanic Province mafic lavas show geochemical patterns typical of anorogenic magmas. Therefore, those rocks are not cogenetic with Euganean cumulates, which are interpreted as crystallized from Alpine subduction-related basaltic magmas. These cumulates were subsequently dismembered and transported to shallower levels by ascending lavas related to the Veneto Volcanic Province magmatism. Therefore, magmatic products related to Alpine subduction are more widespread beneath the Adria microplate than previously known.

Geothermal and rheological regime in the Po plain sector of Adria (Northern Italy)

We present a thermo-rheological study of the Adriatic crust in the central Po plain (Northern Italy), which records the convergence of the Alpine and Apennine external fronts. The present thermal regime of the crust is inferred from geological and geophysical data from oil exploration. A set of temperature data from 37 deep boreholes (bottom hole, drill stem, and production test temperatures) is used to estimate undisturbed formation temperatures down to 6-7 km of depth. Best quality data are used to estimate upper crustal geotherms, which are subdivided into four groups taking into considerations the following factors: i) presence/absence of relevant fluid circulation; ii) conductive thermal refraction; iii) recent sedimentation, and iv) other disturbing tectonothermal processes (e.g., recent tectonics). Assuming average corrections for temperature data affected by recent sedimentation effects, geotherms fall within the same range and provide a homogeneous thermal signal. Temperature measurements in the upper ~7 km are used to constrain a 1-D thermal model at the crustal scale. The best fitting geotherm gives a thermal gradient of ~23 ± 5 mK m-1 (over 7 km of depth), a surface heat flow of ~46 ± 9 mW m-2, and an estimated Moho temperature of 620 ± 80 °C.Using the estimated crustal structure and composition and the best-fitting geotherm, a representative strength envelope is obtained.For hydrostatic and supra-hydrostatic pore pressures, the calculated total crustal strength of this sector of the Adria microplate (not including the upper mantle contribution) is in the 1.8-2.5 TN m-1 range. Considering also the lithospheric mantle contribution, the total lithospheric strength is estimated to be between 23 (wet peridotite)and 39 (dry peridotite) TN m-1.

Syn‐convergent extension observed using the RETREAT GPS network, northern Apennines, Italy

We present crustal deformation results from a geodetic experiment (Retreating‐Trench, Extension, and Accretion Tectonics (RETREAT)) focused on the northern Apennines orogen in Italy. The experiment centers on 33 benchmarks measured with GPS annually or more frequently between 2003 and 2007, supplemented by data from an additional older set of 6 campaign observations from stations in northern Croatia, and 187 continuous GPS stations within and around northern Italy. In an attempt to achieve the best possible estimates for rates and their uncertainties, we estimate and filter common mode signals and noise components using the continuous stations and apply these corrections to the entire data set, including the more temporally limited campaign time series. The filtered coordinate time series data are used to estimate site velocity. We also estimate spatially variable seasonal site motions for stations with sufficient data. The RMS scatter of residual time series are generally near 1 mm and 4 mm, horizontal and vertical, respectively, for continuous and most of the new campaign stations, but scatter is slightly higher for some of the older campaign data. Velocity uncertainties are below 1 mm/yr for all but one of the stations. Maximum rates of site motion within the orogen exceed 3 mm/yr (directed NE) relative to stable Eurasia. This motion is accommodated by extension within the southwestern and central portions of the orogen, and shortening across the foreland thrust belt to the northeast of the range. The data set is consistent with contemporaneous extension and shortening at nearly equal rates. The northern Apennines block moves northeast faster than the Northern Adria microplate. Convergence between the Northern Apennines block and the Northern Adria microplate is accommodated across a narrow zone that coincides with the northeastern Apennines range front. Extension occurs directly above an intact vertically dipping slab inferred by previous authors from seismic tomography. The observed crustal deformation is consistent with a buried dislocation model for crustal faulting, but associations between crustal motion and seismically imaged mantle structure may also provide new insights on mantle dynamics.

Seismic anisotropy and deformation patterns in upper mantle xenoliths from the central Carpathian–Pannonian region: Asthenospheric flow as a driving force for Cenozoic extension and extrusion?

We review deformation fabrics in mantle xenoliths from the central part of the Carpathian–Pannonian Region (CPR) and, in combination with seismic shear wave splitting data, attempt to define patterns of upper mantle anisotropy. Our interpretations from both lines of evidence support a model for east–west oriented asthenospheric flow, decoupled (at least in part) from the overlying lithosphere. Mantle flow fields resulting from Tertiary indentation of Europe by the Adria micro-plate and the resulting Alpine orogen may thus have been an important factor in driving the eastward extrusion of lithospheric blocks in the CPR accompanied by lithospheric extension, rapid ‘rollback’ of the Carpathian subduction system, and its diachronous collision with the European craton. According to this model, eastward asthenospheric flow would add significantly to the effects of slab rollback and gravitational instability. Thus, opening of the Pannonian Basin, rather than being exclusively driven by ‘slab pull’ and gravitational instability, could have been resulted, at least in part, from mantle flow associated with the Adria–European collision and ensuing Alpine orogeny. Such models have also been proposed for analogous geodynamic scenarios such as the western and eastern Mediterranean, and western and southwestern Pacific regions, offering a potential generic model for back-arc basin opening.

EPmantle: a 3-D transversely isotropic model of the upper mantle under the European Plate

SUMMARY We present a new 3-D transversely isotropic shear wave velocity model of the European and Mediterraneanuppermantleobtainedbyanalysisofsurfacewaves.Datausedarefundamentalmode Rayleigh and Love group velocity measurements in the period range 35–170 s, taken on seismograms recorded by European stations for regional earthquakes. The tomographic inversion to map the 3-D earth structure is split into two steps. First, we regionalize the group velocity dispersion measurements, obtaining distinct geographical group velocity maps at different periods; then, each local dispersion curve is inverted separately to find the shear wave velocity structure at depth. The inversion benefits from using ap rioriinformation from a 3-D global mantle model (S20RTS) and a new detailed European crustal model (EPcrust) to constrain the shallower layers. The inversion scheme follows a non-linear iterative algorithm by which Rayleigh and Love group slowness are inverted simultaneously for the best-fitting isotropic Voigt shear wave speed ( 2 vSV + 1 vSH) and radial anisotropy parameter (vSH − vSV). Final merging of the vS profiles results in a new higher resolution 3-D model of European upper mantle. We find that Western Europe and Mediterranean Sea are mainly characterized by relatively low velocities, strongly contrasting with the fast roots of the Eastern European Craton. Many regional scale structures are also evident in the model, thus providing insights into the complex geodynamic framework of the European continent. Most prominent are the low-velocity West Mediterranean spreading basins and European Cenozoic rift system, and seismically fast features connected to subduction of Adria microplate, Hellenic Arc and Calabrian Arc. Radial anisotropy does not vary very significantly with respect to the PREM profile, as available data only resolve lateral variations to a limited degree due to trade-off with velocity. EPmantle has the potential to provide a reliable seismological reference for the upper-mantle structure in the broad European region.

The crystalline basement of the Adria microplate in the eastern Alps: a review of the palaeostructural evolution from the Neoproterozoic to the Cenozoic

The frontal northern part of the continental Adriatic microplate is formed by a stack of Austroalpine nappes and by the Southalpine basement and cover units. Both basement portions are now side by side, separated by the Periadriatic (Insubric) fault system, but they became juxtaposed only during the Alpine orogeny. Permian HT-LP metamorphism is now recognised also within the Austroalpine basement of the eastern Alps, whilst it was known since long in the Southalpine basement. High thermal heat flow responsible for HT-LP metamorphism is related to the extensional tectonics and lithospheric thinning during the Permian and by concurrent magmatic underplating. During the Variscan orogeny, eclogite facies metamorphism is documented within the Ötztal and the Silvretta basements (350 Ma), as well as within the Nonsberg-Ulten unit (336 Ma). The HP events in the Ötztal and the Silvretta basements correlate temporarily with the closure of the Rheic Ocean between the Hanseatic and the Galatian terranes. Docking of the Galatian-Hanseatic composite terrane with Laurussia resulted in large-scale strike-slip tectonics and potentially in the formation of mega-folds (“Schlingen”) within the Austroalpine basement during the Visean. Palaeo-Tethys ridge subduction may be responsible for fast decompression and isobaric heating documented within the Ötztal basement. The Palaeozoic sedimentary sequences of the Austroalpine and the Southalpine phyllitic complexes testify that from Silurian to Devonian, both basement portions were in a passive margin position. During the Cambrian–Ordovician, the Austroalpine basement occupied a position along the leading edge of Gondwana facing the Proto-Tethys Ocean. The compositional variation of the intruded granitic suites confirm an evolution from a magmatic arc towards a collisional-type geodynamic setting related to the closure of the previously opened back-arc basins.

The bases for understanding of the NW Dinarides and Istria Peninsula tectonics

Thrust structure of the northeastern part of the External Dinarides is depended upon paleogeography of the Adriatic-Dinaric Mesozoic Carbonate Platform, which was in the southeast (in the recent position) composed of Dinaric and Adriatic segment with intermediate Budva Trough. In the northwest in the area of the present Slovenia, it represents uniform platform. In the northwestern continuation of the Budva Trough, shallow halftrough formed and more to the west, shallow Friuli Paleogene Basin came in to being, which separated so called Friuli Carbonate Platform from the central part of the carbonate platform. Area of Istria was separated from Adriatic segment with Kvarner Fault, originated already in the Mesozoic. External Dinaric Thrust Belt formed in the final phase of the Dinarides overthrusting. It originated from Dinaric segment of the Mesozoic Carbonate Platform at the end of the Eocene and was thrusted on the Adriatic segment of the Mesozoic Carbonate Platform. Whole process also triggered formation of the External Dinaric Imbricate Belt with Thrust Front of the External Dinarides against Adriatic-Apulian Foreland. Later also represents rigid indenter of the Adria Lithospheric Microplate ("Adria"), and External Dinaric Imbricate Belt represents its deformed margin, therefore we place it to the rigid indenter. Segmentation of the "Adria" occurred in the Miocene or later. It roughly disintegrated in the Padan and Adriatic part along Kvarner Fault. During rotation of the Padan part in the counter clockwise sense, the corner part, representing Istria Peninsula, rotated and underthrusted towards northeast under External Dinarides. As a result, Istria- Friuli Underthrust Zone formed, structurally conditioned with the position of the Friuli Paleogene Basin, and vast Istria Pushed Area between Southern Alps, Velebit Mts. and Želimlje Fault. This process is still active recently. During Istria underthrusting and pushing in the northwest direction, Raša Fault and Thrust Front of the External Dinaric Thrust Belt bended, and as a consequence, strike-slip movements along those planes were hindered. From the tip of the Kvarner Bay towards Idrija and Ravne Faults in the Upper Soča Valley, conditions for formation of the en echalon strike-slip belt were set up. The strike-slip belt is defined with segment of the Raša Fault southeast from Ilirska Bistrica, seismically active area between Ilirska Bistrica - Hruševje stretch, Vipava Fault, Predjama Fault and northwestern part of the Idrija and Ravne Fault. Therefore we postulate, that a segment of the External Dinaric Thrust Belt Front and shear boundary between the tip of Kvarner Bay and Upper Soča Valley, with extended branches of the Idrija and Ravne Faults, represents new attached block of the Adria Microplate rigid indenter edge.

Beauty and complexity of metamorphism: case studies from the frontal part of the Adria microplate

We review a selection of case studies that highlight the fascination and complexity of metamorphic processes and mechanisms, as revealed in rocks from the crystalline basement of the frontal part of the Adria microplate. The examples from the Austroalpine metamorphic rocks south of the Tauern Window, and from the crystalline basement lying more southwards underneath the Po plain, are presented for their petrologic importance and their relevance to other contexts worldwide. They mostly deal with important aspects of metamorphic processes such as kinetics of mineral reactions, thermobarometry in polymetamorphic rocks, fluid–rock interactions, and microstructures of contact metamorphism in previously metamorphosed rocks. Although they are reported primarily for their help in understanding nano-/micro-scale processes of metamorphism, these examples also have some implications for the geologic evolution of this sector of the Eastern Alps.

Tide gauge and GPS measurements of crustal motion and sea level rise along the eastern margin of Adria

We use observations from tide gauges and colocated continuous GPS (CGPS) stations to investigate crustal deformation and sea level changes along the eastern margin of the Adriatic Sea. We develop a new method to separate common‐mode relative sea level from spatially variable signals. Precise vertical crustal motions determined by CGPS allow us to further separate relative sea level into absolute sea level changes and crustal motions with respect to a local Central Mediterranean–fixed GPS‐defined reference frame. From the tide gauge data, we find fairly uniform relative sea level rise along the coast, with mean rate of 0.84 ± 0.04 mm/yr and weighted RMS variation about this mean of 0.2 mm/yr. This rate is a factor of 2–4 lower than estimates for global average sea level rise. In contrast, vertical motion of coastal rocks determined by CGPS vary appreciably from an average of −1.7 ± 0.4 mm/yr in southern Adria to 0.0 ± 0.4 mm/yr in northern Adria. This difference in crustal motion between the northern and southern regions is independent of our ability to separate sea level from crustal motion, and may be explained by crustal strain associated with an active thrust fault accommodating southern Adria microplate convergence with Eurasia. Enigmatically, the combination of tide gauge and CGPS measurements shows that absolute sea level relative to the GPS‐determined reference frame varies by as much as ∼1.8 mm/yr along the Croatian coast in such a way that the relative sea level remains roughly constant. There are several potential explanations for this result deriving from ocean, atmosphere, and solid Earth dynamics.

Present-day vertical isostatic readjustment of the Western Alps revealed by numerical modelling and geodetic and seismotectonic data

Abstract The active tectonics of the Western Alps reveals contrasting regimes: ongoing extension at the heart of the chain and transpression–compression at its external sectors. The active processes currently affecting this region are still a matter of debate. The classical models proposed in the literature invoke: Eurasia–Adria plate collision, counterclockwise motion of the Adria microplate, slab retreat of the subducted continental lithosphere and slab-detachment. More recently, several authors prefer the hypothesis of tectonics driven by isostasy–buoyancy forces. To better understand the influence of these processes on the velocity, strain and stress fields at the surface and in the crust, we developed 2D viscoelastic numerical models along a vertical cross-section perpendicular to the Western Alps. We run our models with different driving forces in order to investigate, one by one, the geodynamic processes proposed in the literature. Results are compared with available geodetic, geological and seismotectonic data. In order to bring into coincidence model predictions and observations, an important vertical isostatic readjustment must be included in the modelling, together with a slight horizontal compression (0.5 mm year −1 ), probably due to Africa–Eurasia convergence. We show that the subduction process in this Alpine region is likely to be dead and that buoyancy forces may be dominating the present-day tectonics.

Explosive evolution of an ancient group of Cyphophthalmi (Arachnida: Opiliones) in the Balkan Peninsula

AbstractAim To investigate the phylogeny of the genus Cyphophthalmus in the Balkan Peninsula and to test the current recognition of ‘phyletic lines’ and phylogenetic groups proposed in previous studies in order to elucidate the biogeographical history of the region.Location Europe, Balkan Peninsula, Adria microplate.Methods Two mitochondrial (cytochrome c oxidase subunit I and 16S rRNA) and two nuclear (28S rRNA and 18S rRNA) markers were used to infer the phylogenetic history of the group. Molecular dating with relaxed molecular clocks was used to elucidate the relative time of diversification within the genus Cyphophthalmus and its constituent lineages.Results Our analyses confirm the monophyly of the genus Cyphophthalmus, and that of the Aegean and gjorgjevici lineages, whereas the ‘Dinaric lineage’ appears paraphyletic.Main conclusions We show that the genus Cyphophthalmus is an old endemic from the Balkan biogeographical region, which gave origin to at least three main lineages. Those lineages have diversified within overlapping ranges. According to our molecular dating, they have also diversified within the same timeframe. The Dinaric Alps, although presenting a large number of species, cannot be inferred as the centre of origin of the group. Instead, the biogeographical evolution of the genus could be related to the palaeogeographic history of the Adria microplate.

GPS-derived motion of the Adriatic microplate from Istria Peninsula and Po Plain sites, and geodynamic implications

We studied the motion of the Adriatic microplate using Eurasian-referenced GPS-derived velocities from Istria Peninsula (Slovenia, Croatia) and Po Plain (Italy) sites and earthquake slip vectors around its edges from a Regional Centroid Moment Tensor catalogue. We explored kinematic parameters by inverting GPS velocities using a variety of site combinations and comparing results. Our best-fitting GPS Adria–Eurasia angular velocity vector (Euler pole) comes from 7 Istria Peninsula (Slovenia, Croatia) and 10 Po Plain (Italy) sites; it locates at 45.03°N, 6.52°E, with a 0.297 ± 0.116°/Myr counterclockwise rotation rate. This new GPS-derived pole locates and overlaps with our earthquake slip-vector-derived pole. An Adriatic microplate interpretation is at odds with Neogene geologic features that indicate recent convergence across the Apennines and Alps. The neotectonics–geology mismatch probably signals the recent birth of the Adria microplate upon termination of the Nubia–Eurasia Alpine collison and Adria slab break-off beneath the Apennines.

Surface kinematics in the Alpine–Carpathian–Dinaric and Balkan region inferred from a new multi-network GPS combination solution

The understanding of the intraplate tectonics of Central Europe requires a detailed picture of how stress is transferred from the interaction of the Eurasian, Nubian and Anatolian plates to the Alpine, Carpathian, Pannonian and Dinaric regions. Recent strain distribution is controlled by the Adria horizontal push, by the Vrancea vertical slab pull and associated horizontal displacements, and by the Aegean/Anatolia extension and slab-roll back. We present a horizontal velocity field for the Alpine-Carpathian-Pannonic-Dinaric and Balkan regions resulting from a new combination of seven different GPS networks formed from permanent and campaign stations. Dedicated velocity profiles in two specific regions are studied in detail. One is the Alpine Pannonian region, with a detailed picture of the NS indentation of the Adria microplate into the Southern Alps, in NE Italy, the deformation in the Tauern Window and the eastwards kinematics of a Pannonian plate fragment. The second study region includes Transylvania, the Southern Carpathians up to the Aegean sea and Albania, where a major right lateral shear deformation exists as a consequence of the NE convergence of the Apulia platform towards the Dinarids, and the SSW motion of Macedonia, Western Bulgaria and Rumania, related to the Hellenic arc dynamics in the Eastern Mediterranean. The profiles in the Alpine–Pannonian area indicate that a velocity drop of 2.5 +/− 0.4 mm/yr associated with the Adria indentation concentrates on a segment of some 50 km south of the Periadriatic fault. The deformation becomes extensional by a similar amount just north of the Periadriatic fault, in the Tauern Window, where the updoming of the Tauern Window implies vertical motion which could well be associated with surface extension. In the EW profile, we observe a sudden velocity change of 1.5 +/− 0.2 mm/yr in 20 km, corresponding to the right lateral Lavant fault, which seems to mark the border between dominant indentation kinematics to the West and dominant extrusion kinematics to the East. Three profiles are considered in Southern and Eastern Europe: one across the lower Adriatic sea from Apulia in Italy to the southern Dinarides, which enables it to constrain the velocity drop associated with the subduction of the Adria microplate into the Dinarides to 3.2 +/− 0.5 mm/yr in 140 km. The second profile is longitudinal and constrains the velocity inversion of 7.4 +/− 1.0 mm/yr in 350 km associated with right lateral shear faults in Albania. The third profile crosses the Transylvania region with a shortening of 2.3 +/− 1.0 mm/yr in 220 km, and the Wallachian–Moesian region up to the Chalcidic peninsula in N Greece. This lower part of the profile implies an extensional stretch of the upper crust of 3.2 +/− 0.9 mm/yr in 440 km, culminating in the Hellenic arc. Strain rate maps are presented in this regional scale, showing the excellent agreement between fault plane solutions of crustal earthquakes and the eigenvectors of the GPS derived two dimensional strain rate tensor. Three profiles are considered in the Balkan and SE Carpathians: one across the lower Adriatic sea from Apulia in Italy to the southern Dinarides, which enables to constrain the velocity drop associated to the subduction of the Adria microplate into the Dinarides to 3.2 +/− 0.5 mm/yr in 140 km. The second profile is longitudinal and constrains the velocity inversion of 7.4 +/− 1.0 mm/yr in 350 km associated to right lateral shear faults in Macedonia, a highly seismic region. The third profile crosses the Transylvania with a shortening2.3 +/− 1.0 mm/yr in 220 km, and the Wallachian–Moesian region up to the Chalcidic peninsula in N Greece. This lower part of the profile implies an extensional stretch of the upper crust of 3.2 +/− 0.9 mm/yr in 440 km, culminating in the Hellenic arc.

Geokinematics of Central Europe: New insights from the CERGOP-2/Environment Project

Abstract The Central European Geodynamics Project CERGOP-2, funded by the European Union from 2003 to 2006 under the 5th Framework Programme, benefited from repeated measurements of the coordinates of epoch and permanent GPS stations of the Central European GPS Reference Network (CEGRN), starting in 1994. Here we report on the results of the systematic processing of available data up to 2005. The analysis has yielded velocities for some 60 sites, covering a variety of Central European tectonic provinces, from the Adria Indenter to the Tauern Window, the Dinarides, the Pannonian Basin, the Vrancea Seismic Zone and the Carpathian Mountains. The estimated velocities define kinematical patterns which outline, with varying spatial resolution depending on the station density and history, the present-day surface kinematics in Central Europe. Horizontal velocities are analyzed after removal from the ITRF2000 estimated velocities of a rigid rotation accounting for the mean motion of Europe: a ∼2.3 mm/year north–south oriented convergence rate between Adria and the Southern Alps that can be considered to be the present-day velocity of the Adria Indenter relative to the European Foreland. An eastward extrusion zone initiates at the Tauern Window. The lateral eastward flow towards the Pannonian Basin exhibits a gentle gradient from 1 to 1.5 mm/year immediately east of the Tauern Window to zero in the Pannonian Basin. This kinematic continuity implies that the Pannonian plate fragment recently suggested by seismic data does not require a specific Eulerian pole. On the southeastern boundary of the Adria microplate, we report a velocity drop from 4 to 4.5 mm/year motion near Matera to ∼1 mm/year north of the Dinarides, in the southwestern part of the Pannonian Basin. A positive velocity gradient as one moves south from West Ukraine across Rumania and Bulgaria is estimated to be 2 mm/year on a scale of 600–800 km, as if the crust were dragged by the counterclockwise rotation along the North Anatolian Fault Zone. This regime apparently does not interfere with the Vrancea Seismic Zone: earthquakes there are sufficiently deep (>100 km) that the brittle deformation at depth can be considered as decoupled from the creep at the surface. We conclude that models of the Quaternary tectonics of Central and Eastern Europe should not neglect the long wavelength, nearly aseismic deformation affecting the upper crust in the Romanian and Bulgarian regions.

Late Cretaceous intraplate thrusting in central Europe: Effect of Africa-Iberia-Europe convergence, not Alpine collision

A well-established event of intraplate basin inversion and basement thrusting affected central Europe in Late Cretaceous time. It is widely accepted to have resulted from the collision of the Alpine orogen with Europe's margin. At that time an early Alpine orogen, located on the leading edge of the Adria microplate, still lay far southeast of its present-day position and had entered a phase of extension after a first orogenic event characterized by W- to NW-directed thrusting. This configuration is not likely to have induced SSW-NNE–directed thrusting and folding in the future European foreland that was still separated from the Alpine wedge by a strip of oceanic lithosphere. By contrast, the onset of intraplate contraction coincides with an important change in relative motion between the European and African plates. At ca. 90 Ma, Africa's SSE-directed sinistral transform motion relative to Europe changed to NE-directed convergence. This agrees well with the timing and kinematics of intraplate thrusting in central Europe. Structures of similar age and kinematics occurring in southern France, Spain, and North Africa suggest that the Late Cretaceous pulse of contraction was caused by pinching west-central Europe's thin lithosphere between Baltica and Africa. Only since the onset of N-directed thrusting in the Alps in Paleocene or Eocene time are the kinematics of the Alps and their European foreland compatible, indicating that mechanical coupling between Africa-Europe and the Adria microplate had been achieved.