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Visnovitz F.,Eötvös Loránd University | Bodnar T.,Eötvös Loránd University | Toth Z.,University of Bremen | Spiess V.,University of Bremen | And 4 more authors.
Near Surface Geophysics | Year: 2015

Lake Balaton, a large shallow lake in Central Europe (Hungary), has been the site of extensive ultrahigh- resolution acoustic and multichannel seismic profiling in the period of 1997-2013. These surveys showed the widespread occurrence of shallow gas in the lake sediments and their immediate substrata. We analyzed about 2000 km of two-dimensional profiles and mapped the different gas occurrences in the uppermost 20 m. The anomalies caused by free gas were identified, classified, and assigned to upper, middle and lower levels based on gas signatures and stratigraphic position. Monitoring of the uppermost gas front has revealed temporal variations between surveys from different years and seasons that manifested in the changes of free gas content in the upper two levels. Free gas in the lower part of the lake sediments and at around the base of the mud indicated greater stability. The different nature of the three free gas levels can be explained by vertical changes in quantity, production rate, and solubility of methane and carbon dioxide gases. We suggest that methane was derived from the microbial decomposition of organic matter in the mud and Pleistocene peat at the base of the mud, whereas CO2 is transported to the lower mud layers by upwelling fluids. © 2015 European Association of Geoscientists & Engineers.

Visnovitz F.,Eötvös Loránd University | Horvath F.,Eötvös Loránd University | Horvath F.,Geomega Ltd. | Fekete N.,University of Bremen | Spiess V.,University of Bremen
International Journal of Earth Sciences | Year: 2015

Strike-slip tectonics has been the dominant style of deformation during the neotectonic (Pliocene and Quaternary) evolution of the Pannonian basin. Main faults are exposed in the “island mountains” of the basin, but strike-slip tectonic features can be best studied in the basin fill by seismic data. Lake Balaton offers the opportunity to carry out high to ultra-high-resolution seismo-acoustic surveys to image stratigraphic and tectonic features in the central part of the Pannonian basin. Several campaigns in the lake using different acquisition techniques have resulted in more than 2000-km seismo-acoustic profiles with a range of resolutions and penetration depths. Interpretation of faults and folds shows a few kilometers wide shear zone below the lake in Late Miocene–Pliocene strata. This zone can be identified as the continuation of the Balatonfő line known onshore to the east of the lake. Mapping revealed a set of duplex structures and highlighted the importance of this shear zone in the formation of Lake Balaton. Comparison of our results to analogue clay models suggests that the observed shear zone is sinistral and the horizontal displacement is on the order of hundreds of meters. Looking at 3D industrial seismic data to the south of the lake, we suggest that the first-order Balaton line, which represents the continuation of Periadriatic line, is also sinistral and characterized by small horizontal displacement of about 1.0–1.5 km during Pliocene and Quaternary times. This indicates a 0.2–0.3 mm/year average slip rate, which is compatible with recent GPS measurements. © 2015 Springer-Verlag Berlin Heidelberg

Cserkesz-Nagy A.,Eötvös Loránd University | Thamo-Bozso E.,Geological Institute of Hungary | Toth T.,Geomega Ltd. | Sztano O.,Eötvös Loránd University
Geomorphology | Year: 2012

The upper 20-30m of the Pleistocene alluvial sequence on the Tisza River, Hungary is investigated by 200km of VHR single-channel seismic sections. Frequent internal configurations, such as (1) bundles of inclined reflections, (2) trough-shaped converging, and (3) horizontal, parallel reflections are interpreted, respectively, as lateral accretion of point bars, abandoned channel fills and floodplain deposits. The series of 5-8m-thick inclined strata sets occurring at the same depth throughout the area suggest the presence of a meandering river dated to about 43-47ka in the Late Pleistocene according to OSL data. Newly recorded quasi-3D seismic profiles reveal that each 1-3km-long inclined series correlates with an individual point bar continuously migrating in the same direction. Small deviations in the direction of migration are caused by natural wandering of the meander bend. Morphometric parameters of point bars are used to calculate ancient channel parameters (width and depth of 200-500m and 5-8m, respectively). Values imply a channel-forming discharge of Q=400-900m 3/s. These results imply a greater amount of runoff and supply in the basin during MIS3 compared to the present day. Long-lasting meandering indicates the role of local factors and a different fluvial environment compared to the commonly anastomosing systems in NW Europe. Our data support the thesis of the three-axis drainage system for the basin. New evidence is provided for the antecedent existence of a temporally active third trunk river in addition to the ancestors of Danube and Tisza Rivers, contrary to the present-day two-axis drainage pattern. © 2012 Elsevier B.V.

Horvath F.,Geomega Ltd. | Horvath F.,Eötvös Loránd University | Musitz B.,Geomega Ltd. | Balazs A.,Eötvös Loránd University | And 8 more authors.
Geothermics | Year: 2015

The Pannonian basin is an integral part of the convergence zone between the Eurasian and Nubian plates characterized by active subductions of oceanic and continental plates, and formation of backarc basins. The first part of this paper presents an overview of the evolution of the Alpine-Mediterranean region in order to understand the large scale crustal and upper mantle processes in and around the Pannonian basin, resulting a collage of terranes of Alpine and Adriatic origin. It will be followed by a summary of the history of sedimentation, volcanism and tectonic activity. As an illustration, three regional cross sections have been prepared on the base of seismic and borehole data. Reviewing current tectonic ideas and models, we come up with a speculative tectonic scenario depicting Alcapa and Tisza-Dacia as orogenic wedges detached from their mantle lithosphere in the Alpine and Adriatic/Dinaric collision zone during the Late Oligocene to Early Miocene. They suffered a dramatic thermal impact leading to crustal melting during extrusion, when these crustal flakes could have been directly superimposed on the asthenosphere in the Carpathian embayment. Since then, the large part of the Pannonian has been cooling and a new mantle lithosphere growing. Geothermal data show that the Pannonian basin with cessation of volcanic activity in the Late Miocene is still very hot and Miocene to Quaternary clastic basin fill, together with karstified Mesozoic carbonates form good geothermal reservoirs of regional extent. In addition to these gravity-driven aquifer systems, a strongly overpressured reservoir can be found below a regional pressure seal in synrift strata and fractured basement rocks. Eventually, we show maps of geothermal installations in the Pannonian basin and suggest that at the present level of knowledge and geophysical surveying it is easy to find additional resources, however proper water management is a critical issue to avoid harmful drawdown of the groundwater table. © 2014 Elsevier Ltd.

Balazs A.,Eötvös Loránd University | Balazs A.,University Utrecht | Matenco L.,University Utrecht | Magyar I.,MOL Hungarian Oil and Gas Plc. | And 4 more authors.
Tectonics | Year: 2016

The architecture of sedimentary basins reflects the relationship between accommodation space and sediment supply, their rates and localization being variable during basin evolution. The mechanisms driving the interplay between tectonics and sedimentation in extensional back-arc basins overlying rheological weak zones inherited from an earlier orogenic evolution are less understood. A typical example is the Pannonian back-arc basin of Central Europe. It is floored by continental lithosphere and was affected by large amounts of extension driven by the subduction rollback that took place in the Carpathians and/or Dinarides. A novel kinematic and seismic sequence stratigraphic interpretation calibrated by wells allows the quantification of the link between the formation of half grabens and coeval sedimentation in the Great Hungarian Plain part of the basin. While the lower order tectonic-induced cycles characterize the main phases of extension in various subbasins, the higher-order cyclicity and associated unconformities define individual moments of fault (re)activation. Our novel interpretation of a temporal and spatial migration of extension during Miocene times explains the contrasting present-day strike of various subbasins as a result of their gradual clockwise rotation. Incorporating the observed asymmetry, in particular the associated footwall exhumation, infers that the amount of extension is much larger than previously thought. The quantitative link between tectonics and sedimentation has allowed the definition of a novel model of sedimentation in asymmetric basins that can be ported to other natural scenarios of similarly hyperextended back-arc basins observed elsewhere. ©2016. American Geophysical Union. All Rights Reserved.

Pap N.,University of Pécs | Kitanics M.,University of Pécs | Gyenizse P.,University of Pécs | Hancz E.,University of Pécs | And 3 more authors.
Erde | Year: 2015

Exploration in search of the tomb of Sultan Suleiman I and the buildings around it in the vicinity of Szigetvár, Baranya county, southern Hungary, has been going on for some one hundred years and on a number of sites (on the banks of Almás stream, at St. Mary's Church in Turbék). On the basis of newly discovered documents and map representations, the authors have carried out a reinterpretation of earlier known sources and have abstracted from these information appropriate for a renewed geographical identification of the site of the tomb. The results have been construed in a reconstructed end-17th-century landscape using geoinformation methods. Identification of the Ottoman settlement at Turbék, which can be associated with the construction of the Sultan's türbe (tomb), was made possible through the collection of finds on the surface of the archaeological site at the Turbék vineyard, the increased intensity of finds and through geophysical examination. The little town was a unique settlement in occupied Hungary, standing between 1574 and 1692 as a symbol of the Islamic conquest of the region.

Cserkesz-Nagy A.,Eötvös Loránd University | Toth T.,Geomega Ltd | Vajk O.,Middle Tisza District Environment and Water Directorate | Sztano O.,Eötvös Loránd University
Proceedings of the Geologists' Association | Year: 2010

We present a case study on how riverbed morphology of the engineered and meandering Tisza River of the Pannonian Basin (Hungary) has changed during post-engineering times. The objectives were (1) mapping the location and morphology of scours and point bars, (2) reconstructing their changes in a 150 year time-scale in response to engineering work, (3) describing the differences of quasi-natural and engineered channels and (4) distinguishing of local and general causes, both natural and anthropogenic. Recent erosion and deposition have been traced on continuous ultrahigh resolution (UHR) seismic profiles. These results were matched up to channel cross-sections and to time-series planimetric and bathymetric maps. The topography of the riverbed is determined primarily by two factors: the plan view geometry of the channel and the lithology of the substratum. As well as naturally developing scours in the river bends, shallower and elongated, slightly refilled ones appear on straight reaches or in engineered channels. Elongated bed scours and extraordinary forms are related to local human effects. However, erosion is observed everywhere in the investigated 102. km long Middle-Tisza region. As a result of cut-offs the gradient increased and, as a consequence, the riverbed became incised. Sedimentation is reflected in accelerated point bar development, which resulted in intensive lateral migration and increasing sinuosity, which is enhanced in the vicinity of human interventions. Changes do not propagate far away. Channel adjustments happened in two phases: rapid incision was followed by a slower sinuosity increase in order to obtain a new dynamic equilibrium. © 2009 The Geologists' Association.

Sunkavalli S.,Geomega Inc. | Kidder J.,Geomega Inc. | Heatwole K.,Geomega Inc. | Shier D.,Geomega Inc. | Davis A.,Geomega Inc.
Minerals and Metallurgical Processing | Year: 2013

Acid rock drainage (ARD) is produced when sulfides are exposed to oxygen and water. Oxidation reactions typically result in a depression of pH and leaching of solutes and metals. Many oxidation models have been developed based on oxygen diffusion, but in environments with high permeability, other transport processes (i.e., convection and advection) can play an important role. Multiple sulfide mineral phases with differing oxidation rates should also be incorporated. WROC, a finite-difference model, was developed to account for these factors in predicting ARD. The program includes sulfide mineral oxidation using a shrinking core mechanism, heat transfer by conduction, heat of reaction and oxygen transport by diffusion and advection. The model was validated using data from the literature. After validation, the WROC model was used to simulate several different waste rock scenarios, including different forms of sulfide mineralization and the effect of implementing a waste rock cover. The results demonstrate that including specific sulfide mineral phases can have a significant effect on oxidation and that implementation of a cover can also aid in reducing waste rock oxidation. © SME.

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