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Thamo-Bozso E.,Geological Institute of Hungary | Csillag G.,Geological Institute of Hungary | Fodor L.I.,Geological Institute of Hungary | Muller P.M.,Geological Institute of Hungary | Nagy A.,Eotvos Lorand Geophysical Institute of Hungary
Quaternary Geochronology | Year: 2010

Fluvial, colluvial, and aeolian sediments were dated by optically stimulated luminescence (OSL) on quartz to improve the chronological framework for Quaternary sedimentation and landscape evolution in the forelands of the Vértes Hills (central Hungary). The separated quartz was suitable for age determination based on an OSL SAR protocol. Most samples have asymmetric equivalent dose distributions and OSL ages were calculated by the mean, central, and minimum De values. Considering geomorphology and earlier age data from the area, the central De values seem most appropriate for age calculation. A fan on the geomorphological level QV in the western foreland of the Vértes Hills was deposited 79-75 (±8) ka ago. In the south-eastern foreland an alluvial fan on level QIIb is at most 42 ± 4 ka old. Fluvial incision and aggradation occurred 16-10 (±1) ka ago on the geomorphic surface QIIa. Loess is 14 ± 1 ka old, and slope sedimentation was active 11-9 (±1) ka ago. Our OSL data demonstrate that in the north-western foreland of the Vértes Hills wind remained an important agent after the last glacial times, into the early Holocene (9-8 ± 1 ka) and was able to accumulate large aeolian dunes. © 2009 Elsevier Ltd. All rights reserved.

Palinkas V.,Research Institute of Geodesy | Lederer M.,Geodetic Control Section | Kostelecky J.,Research Institute of Geodesy | Simek J.,Research Institute of Geodesy | And 3 more authors.
Journal of Geodesy | Year: 2013

Since August 2001, the absolute gravimeter FG5#215 has been used for the modernization of the national gravity networks of the Czech Republic, Slovakia, and Hungary. Altogether 43 absolute stations were measured, some of them repeatedly. Absolute gravity at 29 stations had already been determined in 1990s by other absolute gravimeters (FG5 or JILAg). Differences of repeated measurements at most of the stations show an unexpected decrease of gravity (up to 22 μGal) over the whole region. An uncertainty assessment of absolute measurements with a special emphasis put on hydrological effects shows a statistical significance of the detected gravity variations at many stations. In this manuscript, three possible reasons of such findings are discussed: (1) a regional geodynamic activity, (2) systematic instrumental errors (offsets), (3) hydrological effects. The analysis and statistics of the gravity differences in context of international comparisons of absolute gravimeters show offsets up to 9μGal related to data of the JILAg-6 and FG5#107 gravimeters. Data collected in this study demonstrate that considering instrumental and hydrological effects on gravity are crucial for a correct interpretation of repeated absolute gravity measurements. © 2012 Springer-Verlag.

Marton E.,Eotvos Lorand Geophysical Institute of Hungary | Zampieri D.,University of Padua | Grandesso P.,University of Padua | Cosovic V.,University of Zagreb | Moro A.,University of Zagreb
Tectonophysics | Year: 2010

The central-western and the eastern Southern Alps are separated by the triangular shaped Adige embayment, which belongs to stable Adria and was the site of pelagic sedimentation from the Tithonian through Maastrichtian. The first part of this study presents paleomagnetic results from the Tithonian-Cenomanian Biancone and Turonian-Maastrichtian Scaglia Rossa formations sampled at 33 geographically distributed and biostratigraphically dated localities. The new and high quality paleomagnetic results from the Adige embayment are then combined with coeval paleomagnetic directions from autochthonous Istria (Márton et al., 2008), which also belongs to stable Adria. The combined data set (which for the Late Albian-Maastrichtian time period is constructed similarly to the synthetic African curve by Besse and Courtillot, 2002, 2003) reveals an important tectonic event (Late Aptian-Early Albian) characterized by 20° CCW rotation and sedimentary hiatus. Comparison between paleomagnetic declinations/inclinations expected in an African framework (i.e. with the assumption that Adria is still an African promontory) leads to the following conclusions. The time-distributed Tithonian and Berriasian (150-135 Ma) paleomagnetic directions exhibit the "African hairpin" with an inclination minimum and a sudden change from CW to CCW rotation at 145 Ma. Concerning the younger ages, the declinations for Adria continue to follow the African trend of CCW rotation till the end of Cretaceous. However, the Tithonian-Maastrichtian declination curve for stable Adria is displaced by 10° from the "African" curve as a result of two rotations. The first, an about 20° CW rotation of Adria with respect to Africa took place between the Maastrichtian and the mid-Eocene. During this time the orientation of Adria remained the same, while Africa continued its CCW rotation. The younger rotation (30°CCW) changed the orientation of Adria relative to Africa as well as to the present North. © 2009 Elsevier B.V. All rights reserved.

Oeberseder T.,Vienna University of Technology | Behm M.,Vienna University of Technology | Kovacs I.,Eotvos Lorand Geophysical Institute of Hungary | Falus G.,Eotvos Lorand Geophysical Institute of Hungary
Tectonophysics | Year: 2011

Seismic investigation of the lithosphere by means of active source experiments is mostly confined to the crust and the Moho. Structures in the upper mantle are more likely to be discovered by analyses of teleseismic data, although these methods are restricted in their resolution capabilities. The relatively rare evidence for upper mantle refractors or reflectors in active source data enables challenging and interesting studies of the lower and not so well known part of the lithosphere. We present such an example from the tectonically complex region between the Eastern Alps and the Western Carpathians. This area was covered by several extensive 3D wide-angle reflection/refraction experiments within the last decade, and their layout was designed to illuminate the crustal structure and in particular the Moho discontinuity. In some areas, reflections from below the Moho are also recorded. These reflections occur at recording offsets between 200 and 500. km, and they are particularly strong in cross line recordings. We derive a set of travel times from the data and perform a tomographic inversion for the depth and shape of the reflecting interface. The inversion makes use of an existing 3D crustal model which also includes the Moho topography. Since the upper mantle velocities are poorly constrained and the azimuthal distribution of the rays is biassed, several tests are applied to investigate the reliability of possible solutions. The results from the tomographic inversion indicate an overall horizontal and radially dipping reflector. The average depth of the reflector is 55. km, which is about 25. km below the crust-mantle transition, and amplitude modelling suggests that the reflecting interface represents a velocity increase. The investigated area is further characterised by deep sedimentary basins, high heat flow, high velocities in the lower crust, diffuse Moho signature and a strong positive Bouguer anomaly. Nearby xenolith outcrops exhibit a pronounced change in anisotropy and indicate the presence of two distinct layers in the lithospheric mantle, whereas the deeper layer is thought to present more juvenile lithosphere derived from thermal relaxation in the post-extension phase. Most likely the upper mantle reflector also represents this change in anisotropy, though other scenarios are also possible. We conclude that the entire lithosphere is significantly shaped by extensional processes which affect the area since the late Oligocene/early Miocene. © 2011 Elsevier B.V.

Marton E.,Eotvos Lorand Geophysical Institute of Hungary | Cosovic V.,University of Zagreb | Buckovic D.,University of Zagreb | Moro A.,University of Zagreb
Tectonophysics | Year: 2010

In the Northern Adriatic region, there is a clear boundary between the weakly deformed stable core of the Adriatic microplate and its tectonically complicated NE margin, the External Dinarides which are further subdivided on stratigraphic and structural grounds. Although most authors distinguish an Adriatic and a Dinaridic realm within the External Dinarides, the relationship and the present boundary between the realms are matters of discussion. The aim of this study was to obtain paleomagnetic directions from different parts of the Northern Adriatic segment of the External Dinarides and discuss their bearing on the different types of the tectonic models. For this purpose we carried out standard paleomagnetic measurements on biostratigraphically well-controlled samples from 28 localities from the Adriatic mainland and the Northern Adriatic islands and from one Middle Jurassic locality representing the stable core of the Adriatic microplate. In addition, six localities from the Northern Adriatic islands, earlier studied paleomagnetically, were biostratigraphically updated and thus included in the data set. For the Northern Adriatic islands an Albian (D/I=333°/48°, k=44, α95=9°) and a Cenomanian-Santonian (D/I=334°/46°, k=188, α95=5°) paleomagnetic direction was defined. They are in perfect agreement with coeval paleomagnetic directions from stable Adria. Thus, the paleomagnetic data clearly support the models which conceive the area as the imbricated margin of the Adriatic microplate. The Early (D/I=338°/49°, k=118, α95=11°), the Middle (D/I=342°/54°, k=112, α95=7°) and the Late (D/I=336°/42°, k=62, α95=16°) Jurassic paleomagnetic directions, all representing the tectonic units of the Adriatic mainland, suggest an about 30° CW rotation of this belt of the External Dinarides with respect to stable Adria. The difference can be interpreted as inherited from the differencial rotations of two independent carbonate platforms, an Adriatic and a Dinaric. Alternatively, thrusting of the more internal belt of the External Dinarides above the Adriaticum may be responsible for the difference. © 2010 Elsevier B.V.

Degi J.,Hungarian Academy of Sciences | Degi J.,Eötvös Loránd University | Abart R.,Free University of Berlin | Torok K.,Eötvös Loránd University | And 4 more authors.
Contributions to Mineralogy and Petrology | Year: 2010

The complex microstructure of kelyphitic rims around garnet in lower crustal garnet granulite xenoliths from the Bakony-Balaton Highland Volcanic Field, Central Pannonian Basin has been studied in order to identify controls on garnet breakdown. Symplectites comprised of a vermicular intergrowth of submicron sized anorthite, orthopyroxene and spinel replace garnet at a sharp reaction front. Based on element distribution maps the transformation of garnet to symplectite is isochemical. Phase diagram calculations indicate that this reaction was induced by a pressure decrease and/or a temperature increase. In site-specific TEM foils prepared by focused ion beam technique and oriented parallel and perpendicular to the reaction front 200 nm wide rods of anorthite and 20 nmwide rods of spinel are identified. The rods are oriented approximately perpendicular to the replacement front and are embedded in an orthopyroxene matrix. The regular spacing of the symplectite phases along the reaction front suggests that their growth is controlled by diffusion. The kinetics of symplectite formation has been modelled based on irreversible thermodynamics. During interaction of the xenolith with the host basalt the microstructure and chemistry of the An-Opx-Spl symplectite was significantly modified and it was partially replaced by an olivine bearing symplectite. In contrast to primary symplectite formation, these processes were metasomatic in nature including addition of sodium, titanium and some trace elements from the basaltic melt and can clearly be discerned from the garnet breakdown. Based on these observations it is inferred that symplectite formation took place within the deep crust during the extension of the Pannonian Basin between 15 and 30 km depth at high temperature (850-1,050°C) prior to the volcanic transport to the surface. © Springer-Verlag 2009.

Falus G.,Eotvos Lorand Geophysical Institute of Hungary | Falus G.,Montpellier University | Tommasi A.,Montpellier University | Soustelle V.,Montpellier University
Journal of Structural Geology | Year: 2011

Spinel peridotite xenoliths from Persani Mountains, Southeastern Carpathians, Romania, were submitted to deformation by dislocation creep accompanied by dynamic recrystallization under variable stress and temperature conditions. Predominance of low-angle boundaries parallel to (100) with well-defined [0vw] rotation axes in olivine indicates that subgrain rotation is the main recrystallization mechanism and that dislocation glide occurs mainly in [100]{0kl} systems. Analysis of olivine crystal preferred orientations highlights that recrystallization results in dispersion of the orientations of recrystallized grains relatively to the parent grains. This dispersion may be quantified by a dimensionless dispersion factor defined as the ratio of the random component of the [100] axis distributions between the recrystallized grains and porphyroclasts. This factor is largely independent from the overall fabric strength, the number of grains analyzed, and the recrystallized grain size. The olivine CPO strength and anisotropy at the rock scale, quantified by J-index, are largely controlled by the volume of recrystallized grains, which depends on finite strain. Comparison of olivine CPO in coarse- and fine-grained porphyroclastic peridotites shows that deviatoric stress and temperature conditions play nevertheless a role on the CPO evolution during recrystallization; selective grain growth, which is favored at high temperature and low stresses, does counteract the dispersion produced by the nucleation processes. © 2011 Elsevier Ltd.

Grabowski J.,Polish Geological Institute | Haas J.,Eötvös Loránd University | Marton E.,Eotvos Lorand Geophysical Institute of Hungary | Pszczolkowski A.,Polish Academy of Sciences
Studia Geophysica et Geodaetica | Year: 2010

Jurassic-Cretaceous sediments of Transdanubian Range in Northern Hungary mostly retain their primary magnetizations and are suitable for detailed bio- and magnetostratigraphic studies. The Lókút section, 13 m in thickness, is localized in the central part of the Transdanubian Range. It contains the Jurassic/Cretaceous boundary in pelagic carbonate facies. Although the colour of the rocks changes from reddish-pinkish in the bottom to almost white at the top of the section, magnetite was identified as a magnetic carrier without evidence of hematite. Integrated bio- and magnetostratigraphical investigations resulted in construction of chronostratigraphical scheme. The section, embraces magnetozones from M21r to M18r, of upper Lower Tithonian (Parastomiosphaera malmica Zone) to Lower Berriasian age (Calpionella alpina Subzone). Sedimentation rate of pelagic limestones increased from 1-3 m/My during Tithonian to 5-7 m/My during Berriasian. The sedimentation rate and its changes up the section are comparable to those from the Jurassic/Cretaceous boundary sections of Trento plateau (Southern Alps, Italy) - sedimentary environments of Trento plateau and central Transdanubian Range in that time might be similar. Sedimentation rate within Umbrian Apennine basins and Križna unit in the Western Tatra Mts. seems significantly higher. Analysis of rock magnetic parameters reveals that detrital input was much lower into the Lókút section than into Križna basin in the Tatra Mts. (Zliechov trough). Increase of sedimentation rate occurs in both sections in the Upper Tithonian - Lower Berriasian. It coincides with the onset of calpionellid limestone facies and is related to increased productivity of calcareous micro- and nannoplankton. Detailed correlation of both sections basing on rock magnetic parameters and susceptibility changes is, however, not possible. They are dependent mostly on the local sedimentary conditions (Bakony Mts. - deep water plateau; Križna unit - deep water trough) and correlation with any "global" paleoenvironmental (climatic, eustatic) trends is not straightforward. © Institute of Geophysics of the ASCR, v.v.i 2010.

Bechtel A.,University of Leoben | Hamor-Vido M.,Eotvos Lorand Geophysical Institute of Hungary | Gratzer R.,University of Leoben | Sachsenhofer R.F.,University of Leoben | Puttmann W.,Goethe University Frankfurt
Marine and Petroleum Geology | Year: 2012

Hydrocarbon source rocks (i.e. Tard Clay Formation), containing type-II organic matter, were deposited in the Hungarian Paleogene Basin during Lower Oligocene. A major contribution of aquatic organisms (green algae, dinoflagellates, Chrysophyte algae) and minor inputs from macrophytes and land plants to organic matter accumulation is indicated by n-alkane distribution patterns, composition of steroids, and δ 13C of hydrocarbon biomarkers. Microbial communities included heterotrophic bacteria, cyanobacteria, chemoautotrophic bacteria, as well as green sulphur bacteria. The presence of methanotrophic bacteria is indicated by 13C-depleted hop-17(21)-ene. Higher inputs of terrestrial organic matter occurred during deposition of the lower and uppermost units of the Tard Clay Formation. The terpenoid hydrocarbon composition argues for angiosperm-dominated vegetation in the area of the Hungarian Paleogene Basin. Diterpenoid hydrocarbons, derived from the resins of conifers, are about 2-3‰ enriched in 13C compared to the angiosperm biomarkers. Environmental conditions changed from marine to brackish, accompanied by oxygen-depletion in the lower parts of the water column. Organic carbon accumulation during this period was a consequence of stagnant bottom water conditions in the Hungarian Paleogene Basin due to salinity stratification. This is indicated by low pristane/phytane ratios (varying from 0.27 to 1.44), enhanced ratios of dimethylated versus trimethylated MTTCs (0.14-0.59), and the presence of aryl isoprenoids (from 0.4 to 14.1 μg/g TOC). A major marine incursion is evidenced by stable isotope ratios of organic matter and carbonates. In the uppermost member of the Tard Clay, a transition from brackish towards normal marine conditions is proposed. Up to 3 anoxic cycles are recognized in the drill core sections, separated by minima in pristane/phytane ratios and maxima in the depth trends of di-/tri-methylated MTTCs and aryl isoprenoid concentrations. In combination with the position of maxima of δ 13C of carbonate and organic matter and an abrupt decrease in perylene concentrations, the cycles can be used for intra-formational correlation of the Tard Clay. © 2012 Elsevier Ltd.

Rarely occurring clinopyroxene-plagioclase bearing, felsic granulite and skarn xenoliths were studied from the mantle and crustal xenolith-bearing alkaline basaltic and pyroclastic localities of the Bakony-Balaton Highland Volcanic Field (W-Hungary). Geobarometry and geothermometry of the xenoliths made it possible to categorise them in three groups according to their depth of formation. The first group formed in the lower crust together with mafic and metasedimentary granulites. The second group represents magmatic intrusions of the middle crust, and the third one comprises contact metamorphic rocks of relatively shallow origin. The calculated pressure difference from the core and rim compositions of plagioclase and clinopyroxene as well as garnet breakdown reactions in some xenoliths show evidence for pressure decrease due to crustal thinning both in lower crustal and middle crustal xenoliths during formation of the Pannonian Basin. Fluid inclusion studies reveal the dominance of the CO 2-rich fluids in the whole crustal section in contrast with fluids found in mafic garnet-bearing xenoliths. Crustal stratigraphy was constructed for the periods prior to the extension and after the extension on the basis of geobarometry and geophysical data. On the basis of mineral stabilities and geothermo-barometry, we estimated that the pre-extensional thickness of the lower and upper crust may have been 27-34 and 26-28 km, respectively. Comparison of pre-extensional and present-day thickness of the lower and upper crust indicate that thinning affected both the lower and the upper portion of the crust but on a different scale. The calculated thinning factors are between 2.25 and 3.4 for the lower crust and 1.3-1.56 for the upper crust. © 2012 Springer-Verlag.

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