ILP 2019 Abstracts

14th Workshop of the International Lithosphere Program Task Force Sedimentary Basins

conference dedicated to the memory of Frank Horváth

15-19 OCTOBER 2019 HÉVÍZ, HUNGARY Multi-method comparison of Quaternary river sediments – a case study from the Pannonian Basin Róbert Arató1, István Dunkl2, Gabriella Obbágy1, Sándor Józsa3, Keno Lünsdorf2, Hilmar von Eynatten2 and Zsolt Benkó1

1 Institute for Nuclear Research, Hungarian Academy of Sciences, 2 Department of Sedimentology and Environmental Geology, University of Göttingen 3 Department of Petrology and Geochemistry, Eötvös Loránd University, Budapest Corresponding author: [email protected]

The Pannonian Basin is one of the largest sedimentary reservoirs of Europe that presumably contains a great amount of Alpine detritus [1]. Further main sources of the basin fill include the Western and Eastern Carpathians as well as the Apuseni Mountains. The sedimentary material is delivered to the basin via numerous rivers from different source areas resulting in characteristic sedimentary signatures. Our long-term goal is to develop a robust multiparameter method to identify the characteristic features of these river sediments in the basin-fill deltas. Quaternary sediments of the Drava, Mur, Morava, Danube, Vah, Hron, Ipoly, Sajó, Hornád, Tisza, Somes, Crisul Repede and Mures rivers are compared. We simultaneously apply detrital thermochronology (AFT and ZFT), heavy mineral analysis (by optical microscopy and via automated Raman spectroscopy) and fine gravel petrography in order to obtain a multi-parameter dataset to characterize the major sources of sediments. On the first level of data evaluation, individual AFT and ZFT age components are defined with the help of BayesMix [2]. In the second step, composite low-T thermochronological – heavy mineral data sets are compared with the lithological composition and cooling age pattern of different catchment areas. This evaluation procedure is well feasible as the available petrographical and geochronological database is extremely large in the entire source area of the Danube river system, thus sediment provenance and yield can be well constrained. Moreover, using the detrital age distributions and cooling age maps compiled for the catchments, Quaternary erosion rates can be calculated for the source formations. Amongst detrital AFT ages Neogene, Paleogene and Cretaceous dates could be isolated in most rivers, which is in accordance with the cooling ages in the relevant source areas. Contrarily, ZFT ages show a broader scatter comprising Jurassic and Permian components as well, showing more significant dissimilarities between different rivers. In order to distinguish different source areas in a statistically rigorous manner, the combined comparison of AFT, ZFT, heavy mineral and fine gravel analysis data is carried out [3]. These results serve as a basis for tracing the origin of basin-fill

Hévíz, Hungary, 15-19 October, 2019 page 1 of 197 International Lithosphere Program sediments in future studies.

[1] Kuhlemann, Frisch, Dunkl, Székely (2001), Tectonophysics 330, 1-23. [2] Jasra et al., (2006) Mathematical Geology 38, 269-300. [3] Vermeesch (2019) Minerals 9(3), 193.

Hévíz, Hungary, 15-19 October, 2019 page 2 of 197 International Lithosphere Program Where do subduction zones initiate?

Antoine Auzemery1, Ernst Willingshofer1, Dimitrios Soukoutis2

1 Utrecht University, Department of Earth Sciences, Princetonlaan 4, 3584CB Utrecht, The Netherlands. 2 University of Oslo, Department of Geosciences, Oslo, Norway. Corresponding author: [email protected]

Subduction is the main driver of deformation on Earth. Yet it is still unclear where and how subduction initiates. It is widely accepted that it critically depends on the buoyancy and strength of oceanic lithosphere and can occur upon failure of the load-bearing crustal and mantle layers. However, when the lithosphere is too strong, high shear resistance in the lithospheric mantle do not permit failure, and subduction may occur by deforming the crust at ocean-continent transition. Therefore, this physical analogue and numerical modelling study aims at exploring favourable rheological and kinematic conditions that lead to the development of subduction zones. A selection of experiments, involving both oceanic and continental lithospheres in compression, is used to investigates the role of oceanic and continental lithosphere rheology for scenarios where convergence is orthogonal to the passive margin. Model results shows that strain localization is mainly controlled by the difference in strength between the continental and oceanic crust. On a second hand, under-thrusting depends mainly on the strength of lithospheric mantle. Analysis of deformation are used to define a boundary of rheological conditions enabling subduction either in oceanic domain or in continental domain. However, strain localization may change in response to weakening processes such as plumes or weak zones. Additionally, our Numerical simulations show the importance of thermal processes, such as shear heating, on the deformation of lithospheric mantle. This shows the importance of geological inheritance and thermo-mechanical feed-backs, which regard to the thickness of the oceanic lithosphere, may control the location of subduction.

Hévíz, Hungary, 15-19 October, 2019 page 3 of 197 International Lithosphere Program The rise and demise of forearc and backarc basins: inferences from 2D and 3D numerical modelling

Attila Balázs1, Kosuke Ueda2, Alexandre Boutoux1, Claudio Faccenna1, Francesca Funiciello1, Eric J.-P. Blanc3, Taras Gerya2,

1 Università Roma Tre, Department of Sciences, Rome, Italy 2 ETH Zurich, Institute of Geophysics, Zurich, Switzerland 3 Equinor, Oslo, Norway Corresponding author: [email protected]

We aim to contribute to the understanding of 3D surface topography and sedimentary basin evolution in the geodynamic context of oblique subduction systems. In this study we present a series of numerical experiments to analyze the evolution of oceanic and subsequent continental subduction prior to continental collision along an oblique continental margin. Numerical modelling is compared with analogue subduction experiments. We applied the thermo-mechanically coupled 3D finite-difference code I3ELVIS (Gerya, 2013). Simplified surface processes and phase changes are implemented in the simulations. Oceanic subduction is forced by an initial boundary velocity imposed on one model side for the first few million years. Subsequent subduction velocity varies in time as a function of the dynamics of the system, i.e. gradually increases during free-fall subduction and then starts to decrease at the onset of continental subduction. Oblique subduction (Figure 1) creates a specific mantle flow pattern. Orientation of the convective cell beneath the downgoing plate is parallel with the subduction velocity direction, while the poloidal return flow is near perpendicular to the trench. The obliquity between the two convective cells creates an overall asymmetrical mantle flow pattern leading to the along-strike variation of slab roll-back and upper- plate deformation. Furthermore, vertical axis rotation is recorded in the upper plate.

Figure 1. Phase composition and asthenospheric mantle flow pattern of the oblique subduction model shown at the onset of soft collision.

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Figure 2. Parameter test carried out by 2D models. We model the formation of the accretionary wedge behind a 4-6 km deep trench. 1-3 km accommodation space is created in the wedge-top forearc basin area recording repeated extensional and contractional deformation. A 2-3 km deep dynamic forearc sag basin forms at ca. 250 km distance behind the trench, during the main phase of slab steepening and roll-back. Furthermore, back-arc extensional deformation is distributed or localized at heterogeneities in the upper plate. Onset of continental subduction is diachronous due to the oblique margin geometry. The transition from oceanic to continental subduction is manifested in the gradual decrease of the accommodation space in the basins and the extensional stress regime changes to compression. Following a few million years of soft collision and continental subduction a high topography orogen is gradually built up during hard collision before subduction ultimately slows down. 3D simulatons were complemented by a series of 2D models analysing different rheological and kinematic parameters (Figure 2).

Hévíz, Hungary, 15-19 October, 2019 page 5 of 197 International Lithosphere Program On the tectonic evolution of the Pannonian Basin: inferences from numerical modelling and observations

Attila Balázs1, László Fodor2, Liviu Matenco3, Imre Magyar4,5, Taras Gerya6, Sierd Cloetingh3,

1 Università Roma Tre, Department of Sciences, Rome, Italy 2 MTA-ELTE Geological Geophysical and Space Science Research Group, Budapest, Hungary 3 Utrecht University, Department of Earth Sciences, Utrecht, The Netherlands 4 MTA-MTM-ELTE Research Group for Paleontology, Budapest, Hungary 5 MOL Hungarian Oil and Gas Plc., Budapest, Hungary 6 ETH Zurich, Institute of Geophysics, Zurich, Switzerland Corresponding author: [email protected]

The pioneering contributions of Ferenc ’Frank’ Horváth from the ‘70s paved the way to the understanding of the formation and deformation of sedimentary basins in the Mediterranean (Channel and Horváth 1976; Horváth et al. 1979). This region is a wide zone of convergence between the Eurasian and African plates. A noteworthy feature of this setting is the abundance of extensional basins overlying former orogenic structures. Their formation was coupled with oroclinal bending, block rotations and orogen-parallel displacement of tectonic units (Horváth and Berckhemer, 1982). The application of the plate tectonic concept in the Carpathian-Pannonian system well described the first order observations in the region, such as sedimentary basin subsidence patterns, intense Neogene-Quaternary volcanic activity, high heat flow, and the presence of an anomalous upper mantle and thinned crust (Horváth 1993). Building on the latest geophysical and geological constraints from the basin and surrounding orogens (e.g., Fodor et al., 1999; Wortel and Spakman, 2000), the proposed evolutionary models (Bada and Horváth 2001; Horváth et al., 2006; Horváth and Faccenna, 2011) highlighted the importance of prime geodynamic processes, such as slab roll-back, heterogeneous crustal and lithospheric thinning, elastic lithospheric response and asthenospheric mantle flow effects. In this presentation we give an overview on the state of the art geophysical and geological constraints and geodynamic numerical model results from the Pannonian basin system. A close relationship between lithospheric to crustal deformation and surface processes has been investigated and established in the Miocene to Quaternary formation and evolution of the Pannonian Basin. The major conclusion gained is that, despite some general evolution trend from initial rifting through post-rift thermal cooling to a final neotectonic inversion phase, all basin- forming process show temporal and spatial variations. Fault pattern and the timing and amplitudes of major deformation evens show differences in the sub-basins of the back-arc system.

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Figure 1. Comparison of numerical model results with the extension of the Pannonian Basin of Central Europe (Balázs et al. 2018). (a) Simplified tectonic outline of the Alpine-Carpathian-Dinaric- Hellenic region. The black and gray lines indicate the main sutures in the region. The dashed lines show the position of the orogenic fronts prior to back-arc extension. The red lines indicate the sutures that were reactivated during extension. SSZ, Sava suture zone. (b) Neogene basement depth map overlain by the main strike-slip fault zones in the Pannonian Basin system. Note the wide transcurrent Mid-Hungarian Fault Zone in the middle of the basin. GHP, Great Hungarian Plain. (c) Interpreted composite section through the southern parts of the basin. Upper crustal geometry is based on seismic interpretation. The Sava suture zone in mapped at the Dinaridic margin and inferred at depth toward the east. (d) Numerical modeling result shown by the strain rate after 6 Myr and phase configuration. Ucr, upper crust; Lcr, lower crust; LM, lithospheric mantle; As, asthenosphere.

Hévíz, Hungary, 15-19 October, 2019 page 7 of 197 International Lithosphere Program Specific crustal stress partitioning deformation across South-Eastern Carpathians of Romania and adjacent regions

A. Bălă1, M. Radulian1,2, D. Toma-Dănilă1, L. Maţenco3

1National Institute for Earth Physis, Magurele, Romania 2Academy of Romanian Scientists, Bucharest, Romania 3Universiteit Utrecht, Budapestlaan 6, 3584 CD Utrecht, The Netherlands

The main feature of the seismic activity in Romania is the strong concentration at the Carpathians Arc bend, at intermediate mantle depths (60-180 km) in the Vrancea region. Here, an isolated lithospheric slab downgoing in the mantle is permanently releasing seismic energy in an extreme narrow volume (40 x 70 km in section and from 60 to 180 km in depth). In average, three earthquakes with magnitude above 7 have been reported each century for a time span of six centuries. Seismicity in the crust is developed in particular in the foreland of the South-Eastern Carpathians, between the Intramoesian and (New) Trotus faults, and in the Banat region. The coupling between crustal structures and seismicity and the intermediate mantle mechanics is still far from a quantitative understanding. We aim to understand the crustal stress partitioning deformation across individual structures along the South-Eastern Carpathians of Romania and the adjacent Moesian platform and Transylanian basin. We start from an updated catalogue of fault plane solutions for earthquakes recorded between 1929 and 2012, where statistical features are outlied in correlation with the earthquake-prone areas and tectonics. To characterize the stress regime in the various study areas, we applied STRESSINVERSE code to obtain the principal compressional, tensional and intermediate stress directions. A stress inversion is carried out for clusters of events assuming that the stress is relative uniform in the region and for the structure where a cluster is located. The results of the stress regime are presented for ten clusters identified in the study area. Extensional stress regime characterizes the Southern Carpathians from the Carpathians Arc bend to the east to the Danube region to the west. One other extensional regime is observed in the Banat region as well. Compressional regime characterizes the north-eastern part of the Moesian platform which is adjacent to Vrancea region and Transylanian basin. Strike slip regime is obtained in the North Dobrogea orogen, along the northern segment of Peceneaga- Camena fault and its satellites. Results on stress regimes indicate that the stress is partitioned differently along various structures in the central and eastern parts of the Moesian platform. Our study outlines a complex stress regime in the Southern Carpathians and the contact with the neighbouring platforms. The diversity of Shmax orientations and the changes in the tectonic

Hévíz, Hungary, 15-19 October, 2019 page 8 of 197 International Lithosphere Program regime in the crust from one seismic zone to the other indicate that the local horizontal stress is differently partitioned along local faults or structures grouping multiple faults, which demonstrates a rather localized character of deformation. The regional stress does not have a notable influence upon the distribution of the horizontal stress in the crust.

Hévíz, Hungary, 15-19 October, 2019 page 9 of 197 International Lithosphere Program Variability of the Late Miocene lacustrine Depositional system at the junction zone of the Pannonian Basin and the Apuseni Mts.

István Róbert Bartha1, Dániel Botka2, Vivien Csoma2 Imre Magyar3,4, Orsolya Sztanó1

1 Department of Geology, ELTE 2 Department of Palaeontology, ELTE 3 MTA-MTM-ELTE Research Group for Paleontology; 4 MOL Plc. Corresponding author: [email protected]

Several large outcrops in the Șimleu Basin – in the junction zone of the Great Hungarian Plain (GHP) and the Apuseni Mts. – though represent only a small (less than 1.5 Ma) time window offer an insight into depositional environments from deep to shallow waters in the Late Miocene Lake Pannon. One of the key outcrops is Cehei, where the nonconformity between the basement and the lacustrine strata is exposed. Poorly sorted medium-grained sand, imbricated gravel, and boulder-sized clasts host a poorly preserved mollusc assemblage. Steeply dipping bed-sets downlap the unconformity and were deposited as a coarse-grained delta. It indicates flooding of local basement highs, the former source of clasts, during the Lymnocardium conjungens mollusc biochron (~11–9.6 Ma). Further flooding and deepening continued, thus lacustrine marls covered the crystalline basement, older Miocene strata, and the transgressive basal coarse clastics beds. These marls can be recognized above the deltaic topsets at the Cehei exposure and contained a Hungarocypris-dominated ostracod assemblage. Mud-prone sequences are also exposed in the Vârșolț quarry. Dark grey, bioturbated to laminated mudstones contained a low-abundance mollusc and ichnofossil assemblage, which reveals an open lacustrine environment with alternating dysoxic and aerated bottom conditions and suggests an age of ~11.45–9.6 Ma (Congeria banatica profundal mollusc biozone). The overlying heterolithic beds, i.e. thin intercalations of silty sands, are interpreted as turbidites. As their thickness and grain-size increase upwards, they may indicate the beginning of the long-term normal regression. Thick turbiditic sandstones crop out in the eastern part of the Șimleu Basin, near Zalău. Erosional scours draped by large rip-up mud-clasts and meter-thick amalgamated, structureless sandstones. Lateral facies changes are common, medium-bedded channel-fill sandstone interfingering with thin-bedded turbidites. This succession deposited near the toe of slope in a channel-levee system, where transport directions were from NE to SW. The youngest part of the succession can be studied in several outcrops near Nușfalău and Bocșa. It consists of fine-grained sand and silt. A few-meter-thick upward-coarsening parasequences and various current- and wave-induced sedimentary structures reveal deltaic

Hévíz, Hungary, 15-19 October, 2019 page 10 of 197 International Lithosphere Program environments, wave-dominated mouth bars, and distributary channels, prograding from NE to SW. A well preserved, high-abundance mollusc fauna of littoral origin supports the interpretation. The deltaic sediments were formed in the Lymnocardium conjungens biozone (~11–9.6 Ma), similarly to the oldest lacustrine sediments. Thus, the whole depositional sequence, from transgression to regression was formed during a relatively short period of 1.5 million years.

Fig.1. The junction of the Great Hungarian Plain and Apuseni Mts. provide an uncial place, where you can touch each key-element of the Pannonian depositional system.

During this short period, the several million year-long depositional history of Lake Pannon can be captured at this small portion of the Pannonian Basin. In addition, the exposed rocks are excellent analogues of the vast basin-fill at the subsurface, that is the target of hydrocarbon, geothermal or water prospecting.

This work was supported by the Papp Simon Foundation, the MOL Academic Aid Program, and the Hungarian National Research, Development and Innovation Office (NKFIH – 116618).

Hévíz, Hungary, 15-19 October, 2019 page 11 of 197 International Lithosphere Program Structural control on diagenesis: combined structural and isotope data on calcite cements of pre-rift clastic sediments in the Pannonian Basin

Barbara Beke1, László Fodor1, Emese Laczkó-Dobos1, Kinga Hips1

1MTA-ELTE Geological Geophysical and Space Science Research Group, H-1117 Budapest Pázmány sétány 1/C, Hungary Corresponding author: [email protected]

Deformation and post-depositional diagenesis are often parallel or concurrent processes during burial of siliciclastic-dominated sedimentary basins worldwide. The sum of all co-occurring structural and diagenetic alterations was defined as structural diagenesis by Laubach et al. (2010). Deformation in porous, granular rocks commonly starts with tabular fault-like strain localization structures―called as deformation bands (DB). From the sedimentation interface toward deep burial realm, the deformation mechanism tends to be progressed from granular flow to cataclasis accompanied with increasing porosity reduction. One possible scenario of decreased porosity is the end of DB evolution, and change to frictional slip along a discrete fault plane or developing mineral-filled veins. This change in mechanism is commonly attributed to physical properties, which gradually change with increasing depth in line with effective stress and pore pressure. During progressive burial, deposits are affected by diagenetic processes. Deeper burial related mesogenetic diagenetic alterations depend on many factors, such as tectonic settings, path of burial history and regional fluid flow. Such diagenetic processes may involve mechanical and chemical compaction, mineral alteration and precipitation of cement. All these processes affect the pore structure and porosity; thus, the capability for fluid flow. Consequently, the deformation mechanisms and associated diagenetic alterations are closely interconnected. In our study we exploit the mutuality of constraints gained from calcite cementation and deformation history of two coeval siliciclastic rock successions deposited just prior to the main rifting phase of the Pannonian Basin. We have investigated the carbonate cement phases of the host porous media and distinct type of deformation structures by combination of structural, petrographic and geochemical analysis. One hand, structural elements serves the temporal constraints on the fluid-flow history. On the other hand, O and C isotope values of calcite generations help determine the origin of parent fluid and temperature range of precipitation. The obtained constraints are integrated into subsidence history of study area in order to reveal paleo-fluid flow properties during stages of burial. The geochemical analysis show that stable carbon and oxygen isotope compositions of calcite 13 18 generations have δ CPDB values from 1.60 to -10.68‰, and δ OPDB ratio ranges from -1.30 to -15.20‰. The calcite associated to deformation structures and host rock preserved distinct isotopic records displaying a definite correlation within a wide range in most samples. The trend starts with marine values and tends 18 13 toward more negative δ OPDB accompanied by more depleted δ CPDB isotope values. The covariant trend in calcite generations is concordant with the progression of deformation elements and their relationship with the host rock cementation in time. Our hypothesis for this positive covariance is the variable rates of mixing between connate marine pore water of the host rock and downward circulating meteoric fluids. According to this theory, the temporally variable isotopic signatures were interpreted as increasing involvement of meteoric waters while temperature also increased. The obtained structural diagenetic records are correlated with potential depth range of diagenetic records in the simplified burial history (Beke et al. 2019). The calculated temperature range from isotope signatures of structural elements corresponds with burial, therefore we assume that calcite generations preserved various stages of diagenesis with the connected pore fluid composition. This combined data set

Hévíz, Hungary, 15-19 October, 2019 page 12 of 197 International Lithosphere Program helped constraint the timing, and formation depth of certain calcite generations.

Fig. 1: Isotope values in host rock and in deformation structures and their relationship with structural phases

The obtained evolutionary history suggests that the preserved records of fluid-flow mainly precipitated between D2-D6 deformation phases (23–12 Ma based on Petrik al. 2016). The evolution started with early and modified marine records during pre-rift phases (D2–D3, 23–18.2 Ma) while meteoric cements became more significant in the main syn-rift phases (D4–D6, 18.2–12 Ma). Lack of calcite associated with structural elements younger than D6 phase and the faulted cement in case of a D8 structure point that calcite cementation could have lasted to D6 phase in the studied sites. It may suggest that meteoric water was no longer capable to enter into this aquifer and cement small-scale fractures during deeper burial (phases).

Fig. 2: Deformation elements in simplified burial history with deformation phases

The research was supported by Hungarian scientific grants:NKFIH OTKA 113013.

Beke, B.; Fodor, L.; Millar, L., Petrik, A. 2019: Deformation band formation as a function of progressive burial: depth calibration and mechanism change in the Pannonian Basin (Hungary) – Marine and Petroleum Geology 105, 1-16. Laubach, S.E, Eichhubl, P., Hilgers, C., Lander, R.H., 2010: Structural diagenesis. — Journal of Structural Geology, 32 (12), 1866-1872. Petrik, A., Beke, B., Fodor, L., Lukács, R. 2016: Cenozoic structural evolution of the southwestern Bükk Mts. and the southern part of the Darnó Deformation Belt (NE Hungary) — Geologica Carpathica 67 (1), 83-104.

Hévíz, Hungary, 15-19 October, 2019 page 13 of 197 International Lithosphere Program An updated subsurface temperature model of the onshore Netherlands

Eszter Békési,1 Maartje Struijk2, Damien Bonté1, Hans Veldkamp2, Jon Limberger1,2, Peter A. Fokker1,2, Mark Vrijlandt2, and Jan-Diederik van Wees1,2

1 Department of Earth Sciences, Utrecht University, Utrecht 3584 CB, Netherlands 2 TNO Utrecht, Utrecht 3584 CB, Netherlands Corresponding author: [email protected]

Large-scale physics-based thermal models calibrated with temperature data are the key input to highlight potential areas for geothermal exploration. We present an updated high-resolution 3D thermal model of the onshore Netherlands. We constructed the model in 7 steps, starting from a lithospheric-scale, physics-based forward model and progressively detailing and updating it using temperature data. The model is built up from 14 sedimentary layers and layers for the upper crust, lower crust, and lithospheric mantle. We assigned a-priori thermal properties for each layer and updated them through an inversion procedure by the Ensemble Smoother with Multiple Data Assimilation (ES-MDA), using 1507 temperature measurements as observations. Misfits of the prior model are significantly reduced through the data assimilation procedure, demonstrating the effectiveness of ES-MDA as a tool for calibrating temperature models, supporting high-resolution external constraints. The resulting posterior model describes the thermal state in the uppermost 10 km of the Netherlands with a horizontal resolution of 1 km and a vertical resolution of 200 m. The thermal state of the deep subsurface is important for geothermal exploration that targets the deeply buried Devonian-Carboniferous carbonate formations in the Netherlands. These reservoirs are potentially suitable for industrial heating applications and electricity production. To this end, one of the main aspects of this study was to incorporate the thermal effect of hydrothermal convection within the Dinantian carbonate platforms, following the example found in the Luttelgeest-01 (LTG-01) well. Our model reveals areas in the Netherlands with potential for convection in these carbonate platforms, highlighting locations that can be suitable for deep geothermal development.

Hévíz, Hungary, 15-19 October, 2019 page 14 of 197 International Lithosphere Program The Geological Characteristics of the Pranjani Basin, Central Serbia

Bogdanovic Tamara1

1University of Belgrade, Faculty of Mining and Geology, Department of Regional Geology, g631- [email protected] Corresponding author: [email protected]

The Pranjani Basin (Figure 1) was part of the long-lived Miocene freshwater basins of the Dinaride Lake System. These lakes were controlled by numerous tectonic movements associated with the formation and development of the Pannonian Basin. The final stage of Pranjani Basin geodynamic history is represented with basin inversion caused by late Miocene-Quaternary transpressional regime. The characteristics of the “Oligo-Miocene” alluvial to lacustrine sediments and their biostratigraphical and paleoclimatogical importance will be presented.

Figure 1. Sketch of the Pranjani Basin and distribution of alluvial-lacustrine facies (Đurđević, 1992) Legend: 1-Bed of occasionally floated area; 2-Paraconglomerate; 3-Tuffite from Kamenica Analysis and interpretation of sedimentary infill was made of numerous data, relying both, on past research and own field observations and laboratory results. Those analyses include biostratigraphy of microfossils (ostracodes) and petrological thin section interpretation. Two sediment cycles could be divided in Pranjani Basin – Kamenica series of Oligocene Age and Čačak series of Lower Miocene Age (Figure 2).

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Figure 2. The Pranjani Basin depositional cycles (Anđelković M. et al., 1991).

The results of the study indicate that the sediments of the Pranjani Basin were deposited during peaceful conditions, with some rare stormy intervals. The flora fossil remnants suggested that paleoclimatic regimes at the time of deposition and diagenesis were warm, subtropic with the changes of humid and dry periods. Sediments that filled the basin are presented primarily as siliciclastic deposits - mostly sandstones, marlstones and mudstones, while also carbonate rocks and volcanoclastic sediments can be found within the basin as well. According to the Basic Geological Map (sheet Gornji Milanovac, Filipovic et al., 1971) those sediments are dated as Middle Miocene, but this study together with some other recent findings confirm the Oligocene and Lower-Miocene Age.

Anđelković, M., Eremija, M., Pavlović, M., Anđelković, J., and Mitrović-Petrović, J., 1991. Paleogeography of Serbia- Terciary. Faculty of Mining and Geology, University of Belgrade, Belgrade, p. 237 Đurđević, J., 1992. Sedimentological charasteristics of Neogene lacustrine basins; example of the Pranjani basin. MSci. Thesis, Faculty of Mining and Geology, University of Belgrade, p. 194 Filipović, I., Pavlović, Z., Marković, B., Rodin, V., Marković, O., Gagić, N., Atin, B. and Milićević, M., 1971. Basic geological map of Yugoslavia 1:100 000, Sheet Gornji Milanovac. Geoinstite, Belgrade, Serbia

Hévíz, Hungary, 15-19 October, 2019 page 16 of 197 International Lithosphere Program Structural differences around the Vrancea region (Romania) highlighted by the investigation of seismic data recorded by the stations placed around the epicentral region

Felix Borleanu1, Mircea Radulian1,2

1 National Institute for Earth Physics, Măgurele, România, [email protected] 2 Academy of Romanian Scientists, Bucharest, România, [email protected] Corresponding author: [email protected]

The Romanian seismic hazard is mostly caused by the intermediate-depth seismicity occurred at the South-Eastern Carpathians bending in a very confined area (Vrancea). This represents a complex and particular seismic source, located in a region of continental convergence of at least three major tectonic units. Here, three to five major earthquakes (MW > 7.0) are recorded per century generating a high seismic risk in densely populated areas of Europe. In the same area, the crustal deformation is accompanied by moderate size (Mw ≤ 5.6) crustal seismicity (h < 60 km). In front of the Vrancea region, previous studies (Tarapoanca et al., 2003) emphasized a Neogene foredeep sedimentary basin (Focsani basin) as thick as 13 km. In the inner side of the Carpathians, a post-collisional volcanism migrated from NW (11 Ma) to SE (10 Ka) (Seghedi et al., 2011). The last eruption took place just about 60 km NW from the Vrancea epicentral area. With the implementation of new stations in the volcanic area operated by the Romanian Seismic Network of National Institute of Earth Physics, we can estimate better the source parameters of the Vrancea earthquakes and reveal various characteristics concerning the wave propagation. The aim of the present study is performing a comprehensive analysis of the largest earthquakes occurred in Vrancea region within the last 5 years, re-computing the source parameters using spectral analysis and a full waveform inversion algorithm (Sokos and Zahradník, 2008), highlighting significant lateral variation in the seismic wave propagation to the front side versus to the back side of the Carpathians Arc bend. Of particular interest are the attenuation anomalies which are directly influencing the seismic hazard and shake map parameters.

Hévíz, Hungary, 15-19 October, 2019 page 17 of 197 International Lithosphere Program Polyphase tectonic evolution of the Gulf of Trieste (Northern Adriatic): from Mesozoic rifting to Cenozoic orogeny and active tectonics

Martina Busetti1, Marko Vrabec2, Michela Dal Cin1, Fabrizio Zgur1, Lorenzo Sormani1, Giuseppe Brancatelli1, Lorenzo Petronio1, Franco Pettenati1, Lorenzo Facchin1

1 Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Borgo Grotta Gigante 42/c, 34010 – Sgonico (Trieste), Italy 2 University of Ljubljana, Faculty of Natural Sciences and Engineering, Department of Geology, Aškerčeva 12, 1000 Ljubljana, Slovenia Corresponding author: [email protected]

The Gulf of Trieste in Northern Adriatic sits at the active collisional contact between the Adria microplate and Europe. We use 525 km of multichannel seismic reflection surveys, obtained in several campaigns in Italian and Slovenian waters of the Gulf (Figure 1), and structural observations from the perfectly exposed transect along the southeastern coast of the Gulf, to document and interpret the polyphase sedimentary and tectonic evolution of this region. Owing to its external position with respect to the collisional contact and its submarine setting, the Gulf presents a unique location to observe and investigate features that are not readily seen onland due to being either eroded or burried (Figure 2). We identify four major phases of tectonic deformation: 1) the Mesozoic (Jurassic-Cretaceous) synrift tectonics with normal and transtensional faulting and building of the Friuli Carbonate Platform; 2) the Cenozoic Dinaric orogeny, producing a foredeep filled by up to 1000 m of Eocene turbidites and a peripheral bulge in the western part of the Gulf, and associated with detachment thrusting along the carbonates/turbidites contact and imbricate thrusting in the hanging wall; 3) Late Cenozoic Southalpine shortening, with out-of-sequence thrusting and refolding of earlier Dinaric structures, and sedimentation of molasse-type sediments in the western part of the Gulf that were derived from the emerging South Alpine orogen; and 4) post-Messinian deformation, mainly represented by subvertical transpressional faults cutting the Messinian unconformity and the overlying Quaternary continental and marine sediments, but structural, geodetic and geomorphic indications also suggest ongoing deformation at the northeastern Gulf boundary on the Karst/Palmanova thrust.

Hévíz, Hungary, 15-19 October, 2019 page 18 of 197 International Lithosphere Program

Figure 1: Schematic geological map of the Gulf of Trieste and its hinterland, showing the grid of multichannel seismic reflection sections used in this study.

Figure 2: A combined SW-NE oriented seismic – structural section showing the principal tectonic features of the Gulf.

Hévíz, Hungary, 15-19 October, 2019 page 19 of 197 International Lithosphere Program From the Deep Earth to the surface: Frank Horvath as a source of inspiration

Sierd Cloetingh

Utrecht University, Department of Earth Sciences, The Netherlands

Sedimentary basins hold the key to connecting Deep Earth and surface processes through their record of the temporal evolution of the record of vertical motions. The thermo-mechanical structure of the lithosphere is paramount in the surface expression of the interaction of mantle and lithosphere interactions. These topics are in the heart of research efforts made in the International Lithosphere Task Force "Origin of Sedimentary Basins" and the TOPO-EUROPE Program in which Frank Horvath was a prominent participant. Frank has been through his out of the box thinking and pioneering research at the interface of geology and geophysics with a keen eye for impact in geo-energy and natural hazards as source of inspiration for co-workers and students. His research, characterized by a close linkage between data acquisition, multi-scale observational approaches and interpretation providing key constraints to quantitative modeling, has set the stage for future innovative research in integrated solid Earth science. In this presentation examples of current research on integrated modeling of tectonic processes are presented, inspired by Frank Horvath. In doing so, we focus on the role of lithosphere rheology in lithospheric folding and plume-lithosphere interactions and consequences for intraplate deformation and vertical motions.

Hévíz, Hungary, 15-19 October, 2019 page 20 of 197 International Lithosphere Program Investigations of the sedimentary structure along Transylvanian Basin

Alina Coman1,2, Elena Florinela Manea1, Carmen Ortanza Cioflan1, Mircea Radulian1

1 National Institute for Earth Physics, [email protected] 2 University of Bucharest, Faculty of Physics, [email protected] Corresponding author: [email protected]

Transylvanian Basin is located inside the Carpathian Arc and is affected mainly by crustal seismicity manifested in surrounding seismogenic areas (e.g. Fagaras-Campulung, Crisana- Maramures). The current seismicity is very low in the centre of Transylvania and no large events were recorded in the last decades. In the past, 7 events Mw>5 occurred between 1223 and 1880 (ROMPLUS catalogue, Oncescu et al., 1999) with observed epicentral intensities of VII and VIII MSK. In the absence of significant Mw>6 earthquake records (from crustal and intermediate-depth events as well), we have to rely on simulation of the seismic motion induced by future/possible/expected events using realistic models of source and path propagation media. Strong amplifications are expected to occur in sedimentary cover of basins, local studies are needed to evaluate the parameters responsible for these effects. The purpose of this study is to identify the sediment characteristics by mapping and interpretation of the fundamental frequency of resonance(f0) along the Transylvanian Basin using a non-invasive method applied on ambient vibration data. In order to evaluate local parameters as the spatial distribution of the fundamental frequency of S-waves resonance, a non - invasive Horizontal - to - Vertical Spectral Ratios (H/V, Nogoshi & Igarashi 1971; Nakamura, 1989) method was performed. Due to the low cost of performing ambient vibrations measurements, this method has become increasingly used to extract essential information of the geological structure below a specific area, in order to assess the local variability. The use of this type of data is the only way to analyze essential site parameters in regions where the seismic activity is mostly absent. In this study, the H/V ratio on ambient vibrations was performed in order to retrieve the f0 along the Transylvanian Basin. This ratio was computed for 20 seismic stations deployed during two international projects, SCP - South Carpathian Project (2009 – 2011, Ren et al., 2012),) and CALIXTO - Carpathian Arc Lithosphere X-Tomography (1999, Marin et al., 2005), and the ones operated by NIEP – National Institute for Earth Physics.

Hévíz, Hungary, 15-19 October, 2019 page 21 of 197 International Lithosphere Program

Figure 1. H/V spectral ratios of ambient vibrations at each station in the Transylvanian Basin

Figure 2. Variation of fundamental frequency of resonance (left side) and the first higher peak (right side) along the Transylvanian Basin.

The fundamental frequency of resonance along Transylvanian Basin varies from very low values (0.07 Hz) up to 11.2 Hz. In the light of geological layers, this peak is attributed to the geophysical bedrock and corresponds to the interface between the Badenian and Sarmatian layers. A second peak in the H/V ratios of ambient vibrations was observed, located between 0.35 and 4.9 Hz, and can be interpreted as the transition between consolidated sediments of Sarmatian age and subsequent Post-Sarmatian loose sediments. As this fundamental frequency of resonance is connected with the thickness and velocity structure of the sediments, future studies will be done on retrieving the geophysical bedrock depth based on the available geophysical/geological information.

Hévíz, Hungary, 15-19 October, 2019 page 22 of 197 International Lithosphere Program Natural CO2 occurrence in the Pannonian Basin: determination of geochemical parameters and stable isotope composition of CO2-bearing sandstones and their implications to the fluid system

Dóra Cseresznyés1, Csilla Király2, György Czuppon3, Csaba Szabó1, György Falus1,4

1 Lithosphere Fluid Research Lab, Eötvös University, [email protected] 2 Research Centre for Astronomy and Earth Sciences, HAS, [email protected] 3 Research Centre for Astronomy and Earth Sciences, HAS, [email protected] 4 Mining and Geological Survey of Hungary, [email protected] Corresponding author: [email protected]

The best-known natural CO2 occurrence in the Pannonian Basin is the Mihályi-Répcelak area, located in the Little Hungarian Plain. The area was filled up by sediments of a prograding delta system approximately 10-9 Ma ago forming a several km thick fluvial sedimentary sequence. Carbon dioxide inflow was related to a mafic intrusion in the Early Pliocene (7-4 million years ago) and the CO2 probably migrated along the Rába tectonic line westward towards the Mihályi-

Répcelak area, where the CO2 accumulated in the Pannonian sediments over millions of years. The

CO2 trapped in the turbidic sandstones, where its reactions in the host rock-porewater system can be observed.

The CO2 flooding in a geological reservoir causes physical and chemical changes in the water- rock system. Prior to CO2 flooding, the water is in dynamic equilibrium with the rock in the subsurface. When the CO2 floods in a geological reservoir, some of the CO2 is trapped and dissolved within the water phase, causing its pH to decrease. Therefore, some minerals (e.g. carbonates, alumosilicates) will dissolve and some will reprecipitate (carbonates, clay minerals), or new minerals, e.g. dawsonite, can form. The most sensitive minerals for the large CO2 inflow are the carbonates, but carbonate minerals could be also formed during diagenetic processes before the CO2 flooding. Therefore, they should be distinguished from the carbonate minerals that were formed by the CO2 flooding. The stable isotope analysis of the carbonate minerals can help to separate the different carbonate generations because their hydrogen, carbon and oxygen isotope ratios preserve information to their origins and the conditions in which they were formed. Thus, it is possible to distinguish which carbonates formed before and after the CO2 flooding. For these reasons, the C and O isotopic compositions of different carbonate minerals (dawsonite: NaAlCO3(OH)2 and siderite: FeCO3) were measured in sandstone samples. In addition, H isotopic composition of structural OH- in dawsonite was also determined. Using the obtained isotopic values and

Hévíz, Hungary, 15-19 October, 2019 page 23 of 197 International Lithosphere Program fractionation factor for calcite, as the determination of fractionation factor for dawsonite is in 13 18 progress, the δ C values of CO2 in equilibrium with dawsonite and the δ O values of water in 13 equilibrium with carbonate minerals were calculated. The δ C values of CO2 in equilibrium with siderite indicate that the dawsonite and siderite formed in different diagenetic processes. The CO2, which was present during the formation of dawsonite, had magmatic origin, whereas the porewater likely had a meteoric origin and the oxygen isotopic composition modified during the water-rock interaction.

Hévíz, Hungary, 15-19 October, 2019 page 24 of 197 International Lithosphere Program Identification and characterization of earthquake sources in South-Western Carpathian Bend Zone Raluca Dinescu1,3, Ioan Munteanu2, Corneliu Dinu3, Mihaela Popa1,4, Mircea Radulian1

1 National Institute for Earth Physics, [email protected] 2 Repsol S.A., Madrid, UK Exploration team 3 University of Bucharest, Faculty of Geology and Geophysics 4 Romanian Academy of Scientists Corresponding author: [email protected]

Crustal seismicity affects almost all the regions across the Romanian territory, from the north of Romania (Maramures region) to the southern Romania, Carpathian Orogen, and Eastern Romania Dobrogea and Black Sea offshore areas, with the bulk of crustal seismicity of Romania concentrated in the well know Vrancea region, at the Eastern Carpathians Bend zone. Our study focus on the other Carpathian bend zone, the South-Western Carpathians Bend Zone (SWCBZ) define by 90 degree turn and bend of South Carpathians at their connection with the Balkan Mountains. Geographically the area covers the triple junction of the Romania, Serbia and Bulgarian borders.

Figure 1. Geological map of the South-Western Carpathian Bend Zone (after Geological map of Romania Sandulescu et al., 1978). The seismic events (red dots) from ROMPLUS and SHEEC recorded between 1639 and 2018. Geologically (Figure 1) the South Carpathians are formed by a stack of basement and sedimentary nappes system, thrusted over the Moesian Platform, from the top units, Supragetic and Getic (Internal Dacides) and lower unit Danubian (Marginal Dacides, sensu Sandulescu, 1984).

Hévíz, Hungary, 15-19 October, 2019 page 25 of 197 International Lithosphere Program The sedimentary cover of the Internal Dacides starts with Upper Carboniferous and ends with Lower Cretaceous and is slightly younger in Marginal Dacides, from Permian to Upper Cretaceous. The current position of the SWCBZ study area is the result of tectonic transport during Paleogene- Neogene times (Matenco et al., 2007). The northward and subsequent right-lateral rotation of the orogen across platform (Moesian in this case) generated large scale wrench tectonics with the development of crustal scale strike-slip faults system (Timok-Cerna, Oravita Fault, etc) and associated pull-apart basins on top of the Getic and Supragetic tectonic units. The ongoing deformation process along the entire Carpathian arc is proved by large number of earthquakes, some of them very strong (Mw > 7.0) and at great depths (more than 100 km), such as the Eastern part of the Southern Carpathians (Vrancea Zone), where the slab continues its sink in the Upper Mantle. In contrast the SWCBZ is characterized mostly by shallow seismic activity of moderate magnitude. The seismicity is concentrated along the major tectonic elements such as: Cerna-Jiu Fault, Oravita Fault and in the bounding faults of the Neogene Intra-Carpathian Depression (including the basins Hateg, Caransebes-Mehadia and Petrosani) and it is characterized by sporadic events mixed with clusters of earthquakes Frequently the events from this region appear in clusters, such as the recorded earthquake sequences from 1889-1990, Moldova Noua, 2002 – Moldova-Noua, 2011 - Hateg, 2012 - Targu Jiu, 2013 in the Hateg Basin (HB) 2014, Caransebes- Mehadia Basin (CMB), 2016 - Cerna-Jiu, etc. The neotectonics is not restain to orogen core but extends southward along the northern rim of the Getic Depression into the Neogene fold and thrust belt and foreland of the Carpathians, as proven by the seismic cluster in the Targu-Jiu.

Figure 2. Yearly distribution of the events from the South-Western Carpathian Bend Zone between 1639 and 2018.

Hévíz, Hungary, 15-19 October, 2019 page 26 of 197 International Lithosphere Program The yearly distribution of the events in the South-Western Carpathian (Figure 2) could be separated in two different time intervals, 1639-2004 and 2005-2018. As we can see from the above graph, the number of events recorded in ROMPLUS catalogue during the 2005 - 2018 time interval is almost 20 times bigger than the number of events from the 1639-2004 time interval. The development of the Romanian Seismic Network (RSN) was followed by a substantially increase of the recorded events, some of them might be confused with quarry blasts from the anthropic activity from the region. The anthropic activity in this region, represented by clusters of events around quarries, is an important criterion in discrimination of the earthquake sources from quarry blasts sources. The cross-correlation method has been used for the discrimination between similar quarry blasts signals and tectonic events signals, the results shows that this method is very successful for the identification of anthropic events that can contaminate the tectonic signals. These sorted events will not be integrated in a new geological model for the understanding of SWCBZ neotectonics.

Hévíz, Hungary, 15-19 October, 2019 page 27 of 197 International Lithosphere Program Experimental modelling of diamond-to-graphite transformation: an implication for ultra- high pressure metasedimentary rocks

Larissa Dobrzhinetskaya1, Earl O’Bannon2, Feng Shi3

1Department of Earth and Planetary Sciences, Universityof California at Riverside, USA 2Lawrence Livermore National Laboratory, USA 3State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, China Corresponding author:[email protected]

Geological carbon is a ubiquitous material which occurs in many sedimentary basins in both organic and inorganic forms. The discovery of microdiamonds (crystallized from organic carbon) in metamorphic rocks (Kazakhstan, Norway, Germany, China and many others) became critical to the understanding of continental collisions, mantle dynamics, crust-mantle interactions through the processes of subduction and exhumation which are recorded in the rocks and minerals. These microdiamond formations show that buoyant continental crust can be subducted to a depth of > 150 km and then returned to the surface due to tectonic exhumation. In such a journey some microdiamonds may be completely replaced by graphite and, therefore, the sequences of the subduction-exhumation events may not be easily recognized due to the absence of high-pressure mineral-indicators. Therefore, an understanding of the diamond-to-graphite transformation mechanism is of great importance to the reconstruction of geological processes (eg. Korsakov et al., 2010; Dobrzhinetskaya, 2012).

Figure 1. Diamond inclusion in zircon: A - SEM image of diamond replaced by graphite (Dobrzhinetskaya et al., 2001). B – STEM image of FIB foil shows that fluid inclusions are situated at diamond-graphite interface.

The observation of diamond replaced by graphite in ultra-high pressure metasedimentary rocks of the Kokchetav massive, Kazakhstan showed that such transformations are always accompanied

Hévíz, Hungary, 15-19 October, 2019 page 28 of 197 International Lithosphere Program by fluids phases (Fig.1. A, B) containing hydrocarbon and other elements such as Cl, S, K, Fe (eg, Dobrzhinetskaya, 2012). Though diamond and graphite are chemically identical, their structures are very dissimilar: diamond has a cubic symmetry and characterized by sp-3 carbon bonding, and graphite has hexagonal symmetry with sp-2 carbon bonding. Since the reaction of diamond-to- graphite is sluggish due to an existing kinetic barrier, it requires an additional component(s) to trigger the diamond-to-graphite transformation. In a geological environment, such components can be fluid, gas, and/or melt which all circulate within subducting or exhuming slabs. Assuming a fluid is one of the more plausible components to trigger an sp3-sp2 transformation, we conducted anhydrous and hydrous experiments in a piston-cylinder apparatus at T=1300K and P=1 GPa, t=5hrs to transform synthetic diamond to graphite. Synthetic diamonds of 20-40 μm grain size from Amplex Superabrasives was used as a starting material. Powder of Mg(OH)2 (a chemical compound from Fisher Scientific) was added to the starting material as the H2O supply (1 wt. %) for the hydrous experiments. Run products were studied with SEM, STEM, FIB, and Raman spectroscopy combined with SEM in-situ. Anhydrous experiments showed that there is no direct transformation of diamond-to- graphite at 1300K, 1GPa and t=5hrs. Hydrous experiments conducted at the same PT,t conditions, showed the formation of amorphous carbon, “globular carbon” particles, and tiny flakes of graphite which were nucleated at the {100} and {111} diamond surfaces. We concluded that sp3-to-sp2 transformation was triggered by a fluid and accomplished through the following processes: (i) diamond reacts with a supercritical H2O fluid producing an intermediate 200-500 nm size “globular carbon” C2n-Hn formed on the {111} planes of diamond. This is a metastable phase of carbyne. (ii) Flakes of disordered graphite were crystallized during the decomposition of the metastable phase of carbyne due to re-organization of its linear sp-bonds into more stable sp2 bonds (graphite). The hydrous experiments illustrated the possibility for the synthesis of carbyne (hydrocarbyne), a metastable phase, during the diamond transformation to graphite. Experiments showed that an intermediate metastable phase of hydrocarbon (sp1 C-bonds) was required for transformation of sp3 C-bonds of diamond into sp2 C-bonds of graphite. This observation fits well to Ostwald’s Rule operating, which can be identified also in many other high- pressure geological environments.

Hévíz, Hungary, 15-19 October, 2019 page 29 of 197 International Lithosphere Program Dobrzhinetskaya, L.F., 2012. Microdiamonds — Frontier of ultrahigh-pressure metamorphism: A review. Gondwana Research, 21: 207-223. Korsakov, A. V., Perraki, M., Zedgenizov, D.A., Bindi, L., Vandenabeele, P., Suzuki, A., Kagi, H., 2010. Diamond–graphite relationships in ultrahigh-pressure metamorphic rocks from the Kokchetav massif, northern Kazakhstan. J. Petrology, 51: 763-783. Dobrzhinetskaya, L.F., Green, H.W., Mitchell, T.E., Dickerson R.M., 2001. Metamorphic diamonds: mechanism of growth and oxides inclusions. Geology. 29: 3:253-266.

Hévíz, Hungary, 15-19 October, 2019 page 30 of 197 International Lithosphere Program Energy dissipation along the subduction interface and its various controls on overriding plate deformation

Zoltán Erdős1, Ritske S. Huismans2, Claudio Faccenna3, Sebastian Wolf2

1Department of Geophysics and Space Science, Eötvös Loránd University, Budapest, Hungary 2Department of Earth Sciences, University of Bergen, Bergen, Norway 3Department of Science, University Roma Tre, Roma, Italy Corresponding author: [email protected]

While a wide range of studies were devoted to improving our understanding of divergent and convergent plate boundaries, the intricate nature of backarc extension, where subduction interacts with coeval extension is yet to be explored properly. The aim of this project is to study how the (1) rheological setup of the backarc, and (2) the presence of oceanic sediments affect the style of overriding plate deformation behind the subduction of a small oceanic domain. Using two- dimensional thermo-mechanical model experiments, we demonstrate, that the presence of a weak mantle-lithospheric block can result in backarc break-up even if the subducting oceanic domain is narrow such as the one postulated for the Carpathian embayment. Furthermore, the presence of a weak sedimentary layer on top of the oceanic lithosphere can reduce the energy dissipation along the subduction zone, increasing the pull exerted by the subducting slab on the overriding plate and promoting earlier extension. Our modeling results compare well to observations from the Carpathian-Pannon region.

Hévíz, Hungary, 15-19 October, 2019 page 31 of 197 International Lithosphere Program Geological and geomorphological remapping of the Miocene sedimentary-volcanic basin at the border area of the Mátra and Bükk Mountains (NE Hungary)

Péter Gál1, Péter Pecsmány2, Attila Petrik3, Réka Lukács3, László Fodor3,4, Szilvia Kövér4,5, Szabolcs Harangi1,3

1 Department of Petrology and Geochemistry, Eötvös Loránd University, Budapest, Hungary 2 Institute of Geography and Geoinformatics, University of Miskolc, Miskolc, Hungary 3 MTA-ELTE Volcanology Research Group, Budapest, Hungary 4 MTA-ELTE Geological, Geophysical and Space Science Research Group, Budapest, Hungary 5 Department of Physical and Applied Geology, Eötvös Loránd University, Budapest, Hungary Corresponding author: [email protected]

The border area of the Bükk and Mátra Mountains belongs to many physical geographical subdivisions (figure). This area has a varied geological setting, in the Southern Bükk Mountains and near to the Darnó Hill the Triassic-Jurassic basement is on the surface, while the other areas are covered by a thinner-thicker Neogene (mostly Miocene) sedimentary-volcanic succession. Many geological maps are available from the Bükk and Mátra Mts. and some part of their surroundings (e. g. Varga et al. 1975; Less et al. 2004, 2005) but the Western Bükk Foreland (Bükkalja) is poorly mapped (Schréter 1952). Some Miocene formations of the different maps from the Bükk and Mátra Mts. are not trackable in the Western Bükk Foreland area. Silica-rich volcanic pyroclastic deposits (mostly ignimbrites) occur in three or more levels in the entire area, however different formation names are used in the Mátra Mts. and in the Bükk-Bükk Foreland region, causing difficulties in separating/correlating them by using these maps. The aim of this work is to re-map the border area of the Bükk and Mátra Mts. (figure) in order to correlate the Miocene successions, particularly the silica- rich volcanic pyroclastic deposits and making a modern map from the geological conditions of the Miocene basin. We found significant differences between our field observations and the spread of the illustrated formations on the previous maps, particularly in the Western Bükk Foreland.

Hévíz, Hungary, 15-19 October, 2019 page 32 of 197 International Lithosphere Program Geotectonically the SSW-NNE striking Darnó Zone is crosscutting the mapping area which is a possibly Mesozoic structure, reactivated discontinuously in different stress field environments with variable fault types from the Oligocene to the present (Fodor et al. 2005). In the mapping area some parts of the Miocene succession are repeated at least three times in the Western Bükk Foreland due to the SW-NE striking strike-slip faults of the Darnó Zone active in the Late Miocene. In general, a tendency of formation youngening to the southwest is observable in the Miocene succession. Our mapped succession begins with Late Burgidalian formations. The biotite-quartz- rich ignimbrite of the Gyulakeszi Rhyolite Tuff (Ottnangian) is over lied by mostly offshore, shallow water (Garáb Schlier) or nearshore, shallow water deposited (Egyházasgerge Sandstone) sandstones-mudstones (Karpatian), covered by partly water-redeposited, cross-bedded pumice- scoria bearing andesite tuffs (Hasznos Andesite) occurs only in the northwestern part of the mapping area (Pelikán 2010), but we found these two latter formation far east than it was mapped before. The following four formations, that are most widespread represent the Langhian (Badenian). The ca. 14,8-15 million years old Demjén Ignimbrite (Lukács et al. 2018) contains riodacitic-dacitic non-welded and welded-silicified ignimbrites. It is possibly the Tar Dacite Tuff in the Eastern Mátra (Pelikán 2010) and the Felnémet Rhyolite Tuff in the Bükk Foreland (Less et al. 2005). This formation can be used as a controlling horizon, because it is well-exposured in typical erosional forms and has unique petrographical features (often visible with free eyes sized amphibole crystals, subordinated quartz content). The overlying with erosional discordancy water- redeposited andesite tuffs are very similar to the Hasznos Andesite. It is thought to be the lowest part of the Nagyhársas Andesite stratovolcanic succession in the Mátra Mts., covered by lava flows. However, we found these pyroclastics far east and out from the Mátra Mts. without lava cover. The Demjén Igrimbrite and the andesite tuffs seem to be underwater deposited in this area. The andesite and andesite tuffs are covered in the southern areas with partly redeposited, quartz- biotite-rich ash-fall tuffs of the 14,4 million years old Harsány Ignimbrite (Lukács et al. 2018). This is the footwall of Serravallian-Tortonian (Sarmatian-Pannonian) shallow marine sediments amongst the southern part of the mapping area. In the Mátra Mts. Sarmatian andesite dykes (Kékes Andesite) are common. In field we sampled the lithic clasts of the Demjén Ignimbrite. Their statistical, quantity and quality examination help us finding the source of the volcanic eruptions. To the geomorphological examinations we used digital elevation model (DEM) and its derivatives. The DEM was interpolated from digitized contour lines, point elevations and streams of topographic maps. In the field we

Hévíz, Hungary, 15-19 October, 2019 page 33 of 197 International Lithosphere Program observed many morphological levels (pediment or terrace) and landslides, especially near to bigger fault zones. Some fault can be detectable obviously in the DEM, but the most of them are signed by sudden changes of the succession. We investigated the river sinuosity which can be the indicator of recent active faults. We used the Global Mapper, ArcGIS, QGIS and MatLab softwares. We are making a geological and a geomorphological map with 1:25 000 resolution.

Fodor, L., Radócz, Gy., Sztanó, O., Koroknai, B., Csontos, L. and Harangi, Sz. 2005: Post-Conference Excursion: Tectonics, Sedimentation and Magmatism along the Darnó Zone. GeoLines 19, pp. 141-161 Less, Gy. and Mello, J. (eds.) 2004: Geological map of the Gemer-Bükk area 1: 100 000. Geol. Inst. Hungary, Budapest Less, Gy., Kovács, S., Pelikán, P., Pentelényi, L. and Sásdi, L. 2005: Geology of the Bükk Mountains. Explanatory Book of the Geological Map of the Bükk Mountains [1:50 000]. Geol. Inst. Hungary, Budapest, 251 p. Lukács, R., Harangi, Sz., Guillong, M., Bachmann, O., Fodor, L., Buret, Y., Dunkl, I., Sliwinski, J., von Quadt, A., Peytcheva I. and Zimmerer, M. 2018: Early to Mid-Miocene syn-extensional massive silicic volcanism in the Pannonian Basin (East-Central Europe): Eruption chronology, correlation potential and geodynamic implications. Earth-Science Reviews 179, pp. 1-19 Pelikán, P. 2010: The geology of the Matra and its surroundings. In Baráz, Cs. (ed.): The Mátra Landscape Park: On the border of Heves and Nógrád. In hung. Bükk National Park Directorate, Eger, pp. 17-26 Schréter, Z. 1952: The geological structure of the hill county northeast from the Mátra Mountains. In hung. Ann. Report Geol. Inst. Hungary, 1948, pp. 111-118 Varga, Gy., Csillagné Teplánszky, E., Félegyházi, Zs. 1975: Geology of the Mátra Mountains. In hung. Ann. Report Geol. Inst. Hungary, 1975, 575 p.

Hévíz, Hungary, 15-19 October, 2019 page 34 of 197 International Lithosphere Program Interaction of topography-, salinity- and temperature-driven groundwater flow in synthetic numerical models and along a hydrogeological section

Attila Galsa1, Márk Szijártó1,2, ÁdámTóth2,3, Tímea Havril2,3, Judit Mádl-Szőnyi2,3

1 Department of Geophysics and Space Science, Eötvös Loránd University, Hungary 2 József and Erzsébet Tóth Endowed Hydrogeology Chair, Hungary 3 Department of Physical and Applied Geology, Eötvös Loránd University, Hungary Corresponding author: [email protected]

In the most sedimentary basins, like in the Pannonian Basin the groundwater flow is primarily driven by the altitude differences of the water table, especially in the upper approx. 1 km thick part of the crust. Beyond that, the flow is also influenced by other processes, e.g. buoyancy force due to heterogeneous temperature and/or solute concentration. The elevated geothermal gradient in the Pannonian Basin is able to modify or even dominate the deep flow system in special geological situation, such as in thick, permeable layers with low anisotropy of hydraulic conductivity and moderate water table differences [Szijártó et al. 2019]. In confined karstified carbonate systems the presence of the free thermal convection is presumptive by both observed temperature anomalies [Mádl-Szőnyi 2019] and numerical model results [Havril et al. 2016]. The variation in groundwater salinity is another phenomenon which affects the coupled, topography-, salinity and temperature-driven groundwater flow system. Two-dimensional numerical calculations have been carried out in order to investigate how the salinity- and temperature-driven free convection modifies the flow pattern. The solute concentration and the temperature distribution was compared to the purely topography-driven forced convection. In the first synthetic model set the interaction of the salinity increasing with depth and the water table variation was studied. It was established, that the increase in density contrast between the lower saline and the upper fresh water zone reduces the Darcy flux, and therefore retards the decrease of the solute concentration. Beneath the recharge zone a dense, salt water zone evolves in which sluggish, inner convection forms with a Darcy flux lower by 1–2 orders of magnitude. The increase in the anisotropy coefficient of permeability (horizontal/vertical) stabilizes the deep, dense zone similarly. The mechanical dispersivity has minor effect on the regional flow. Increasing dispersivity enhances the transverse dispersive flux through the bottom boundary and slows down the flow slightly. In the second simulation suit the combined effect of the salinity- and temperature-driven free convection and the topography-driven forced convection was investigated. Initially, the solute concentration increased with depth linearly, while a constant bottom heat flux (90 mW/m2) was

Hévíz, Hungary, 15-19 October, 2019 page 35 of 197 International Lithosphere Program

Figure 1 Snapshots of (a) the concentration, (b) the Darcy flux and (c) the temperature in the synthetic numerical model with a depth of 5 km and length of 40 km. Water level is cosinusoidal with an amplitude of 50 m, relative density difference due to salinity is 15%, bottom heat flux is 90 mW/m2. (a) Concentration isocontour of c=0.5 is denoted by black line, (b) streamlines and flow direction are denoted by white lines and red arrows, respectively. prescribed at the bottom boundary. As the density difference due to salinity increased, the flow slowed down, the advective heat transport was suppressed, thus the thermal buoyancy increased and intensified the convection again. Figure 1 shows the quasi-stationary model solution when the density increase due to high salinity and the density decrease due to high temperature is dynamically balanced. The dynamic equilibrium between the two competitive effects results in intense inner convection within the salt water zone, while the topography-driven regional groundwater flow is constrained in the upper fresh water zone. Finally, a thermohaline convection model was applied along a 2D, west–east hydrogeological section crossing the Buda Thermal Karst [Fodor 2011]. Beneath the western, unconfined part of the karst system the intense topography-driven forced convection effectively reduces the salinity and the surface heat flux. On the other hand, within the eastern, confined karst system a vivid inner thermal convection evolves which preserves the high solute content of the groundwater. Beneath the River Danube, at the boundary of the confined and unconfined carbonates, the

Hévíz, Hungary, 15-19 October, 2019 page 36 of 197 International Lithosphere Program observed solute content and temperature anomaly can be elucidated by the mixing of the two types of groundwater. The project was supported by the János Bolyai Research Scholarship of the Hungarian Academy of Science, the ÚNKP-18-3 and ÚNKP-18-4 New National Excellence Program of the Ministry of Human Capacities. The project was also supported by the Hungarian Scientific Research Fund (K- 129279). This research is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 810980.

Fodor, L., 2011. A Budai-hegység felépítését szemléltető K–NY-i irányú szelvények [Geological sections across Budapest E–W]. In: Mindszenty A. (ed) (2013), Budapest: földtani értékek és az ember — városgeológiai tanulmányok [Budapest: geological values and man — urbangeological studies], Eötvös University Press, Budapest pp. 20. Havril, T., Molson, J.W., Mádl-Szőnyi, J., 2016. Evolution of fluid flow and heat distribution over geological time scales at the margin of unconfined and confined carbonate sequences – a numerical investigation based on the Buda Thermal Karst analogue, Mar. Pet. Geol., 78, 738–749. Mádl-Szőnyi J., 2019. Pattern of groundwater flow at the boundary of unconfined and confined carbonate systems on the example of Buda Thermal Karst and its surroundings, DSc thesis. p. 150. (in Hungarian). Szijártó, M., Galsa, A., Tóth, Á., Mádl-Szőnyi, J., 2019. Numerical investigation of the combined effect of forced and free thermal convection in synthetic groundwater basins, J. Hydrology, 572, 364–379.

Hévíz, Hungary, 15-19 October, 2019 page 37 of 197 International Lithosphere Program Understanding salt diapir dynamics at Praid (Transylvanian Basin): a petrographic approach

Orsolya Gelencsér1,2, György Falus1,3, Alexandru Szakács4,5, Ágnes Gál6, Eszter Szűcs4, István Bozsó4, István Horváth7, Viktor Wesztergom4, István János Kovács4, Csaba Szabó1,4

1 Lithosphere Fluid Research Lab, Institute of Geography and Earth Sciences, Eötvös University; H- 1117 Pázmány P. stny. 1/C, Budapest, Hungary, [email protected] 2 Isotope Climatology and Environmental Research Centre, Hungarian Academy of Sciences, H- 4001 Bem Sqr. 18/C Debrecen, Hungary 3 Mining and Geological Survey of Hungary, H-1145 Columbus street 17-23. Budapest, Hungary 4 Geodetic and Geophysical Institute, Research Centre for Astronomy and Earth Sciences Hungarian Academy of Sciences, H-9400 Csatkai E. st. 6-8. Sopron, Hungary 5 Institute of Geodynamics, Romanian Academy, Calea Victoriei st. 125. Bucharest, Romania 6 Babeș-Bolyai University, 400084 M. Kogălniceanu st. 1. Cluj-Napoca, Romania 7 Societatea Nationala a Sarii Bucuresti, S.A. Sucursala Salina Praid 537240 Harghita st. 44 Praid, Romania Corresponding author: [email protected]

In the Transylvanian Basin (TB), during the Middle Miocene Badenian Salinity Crisis event, few hundred meters thick halite deposited in marine environment. Recently, the salt body forms diapir alignments along both (western and eastern) margins of the TB. Some of the diapirs attain more than 2 000 meters height such as the Praid diapir situated at the eastern margin of the TB, which is a part of, or (at least) close to the geodynamically active Carpathian Bend area. Rock salt influences the basin evolution according to its specific characteristics including low porosity, permeability and density. The objective of this study is to associate micro-scale observations of the rock salt (by polarized and electron microscopy and microthermometry) with large-scale deformation mechanisms related to geodynamics of the TB. In Praid, mining operations carved a mine in the upper 400 m of the diapir where salt has been extracted for centuries. Samples were collected from the salt mine for petrographic and microstructural analyses. Two types of salt fabrics can be distinguished based on mineral composition, grainsize distribution and orientation of the salt grains: such as protomylonitic texture, and polygonal mosaic structure. Furthermore, several types of halite grain boundaries can be identified in the samples. Typically, grain boundaries have an irregular, lobate shape and filled two-phased (liquid and gas) fluid and gas inclusions. During the deformation events in salt, the role of the fluids is essential therefore fluid inclusion (FI) study, including petrography, microthermometry and Raman microspectrometry were carried out in order to distinguish primary and secondary features in the salt. The negative crystal shaped, liquid phase primary FIs are

Hévíz, Hungary, 15-19 October, 2019 page 38 of 197 International Lithosphere Program distributed along crystal growth zones of halite and originated from paleo seawater. The secondary FIs (Fig. 1.) shed light on late stage history of the salt body, because they formed during deformation events (diapirism, burial, or basin wide tension) after salt the salt deposition. The gas- rich secondary fluid inclusions may be originated from breakdown of organic matter, indicating that N-species and CH4-rich fluid migration events happened after the salt formation.

L

Figure 1. Distinct types of secondary fluid inclusions. A: Array of FIs and fluid film segments. Average inclusion size is ~ 1µm. B: Organic-rich FIs. C: Two phase FI showing various shapes. D: Gas FI occurring along healed microfractures. Om – organic matter, G – gas, L – liquid.

Besides petrography and FI studies, we applied Electron Backscatter Diffraction (EBSD) technique on saltrocks to measure subgrain size and preferred crystal lattice orientations, which refers to deformation mechanisms such as dislocation creep, pressure solution, grain boundary migration, fracturing and intergranular slip. Data of subgrain measurements refer to stress driving deformation. To sum up our work, we combined detailed microscopic observations to understand the dynamics of the salt dome of Praid. There is a clear correlation between the presence of primary

Hévíz, Hungary, 15-19 October, 2019 page 39 of 197 International Lithosphere Program fluid inclusions and subgrain content. The original grains, represent the formation environment of the halite, have more subgrains, than the grains which formed with recrystallization mechanism such as grain boundary migration. Detailed petrographic study allowed us to point out the mechanisms of salt movements at the mineral levels suggesting that the salt is still in a deformable state.

Hévíz, Hungary, 15-19 October, 2019 page 40 of 197 International Lithosphere Program Title: Lateral propagation of slab tear during retreating continental collision: numerical model and simple theory

Taras Gerya1, Dave Bercovici2, Claudio Faccenna3 1 Institute of Geophysics, ETH-Zurich, Switzerland, [email protected] 2 Department of Geology & Geophysics, Yale University, USA, [email protected] 3 Department of Geological Sciences, University of Texas at Austin, USA, [email protected] Corresponding author: [email protected]

Retreating oceanic plate subduction is common in nature and can terminate by collision of the retreating arc with an arbitrarily oriented passive continental margin. The collision is associated with rapid topographic changes and can result in partial or complete detachment of the oceanic slab by laterally propagating tear, which develops on the time scale of few Myr. Here we investigate this geodynamic transition by using 3D high-resolution thermomechanical models, in which a spontaneously retreating subduction zone limited by two STEP faults collides with a continental margin oriented at an angle to the retreating trench. Realistic visco-plastic plate rheology is used for the mantle and slab, which takes into account both brittle-plastic strain weakening and grain- size reduction assisted by Zenner pinning. Arc-margin collision results in the rapid growth of topography and trigger rotation of the retreating subduction arc toward the margin-parallel direction. Slab tear initiates at shallow depths at the part of the margin that collided earlier and rapidly propagates toward the other side of the forming arc-continent collision zone. The tearing process (Figure) is governed by a combination of plastic yielding and ductile strain localization caused by grain-size reduction. Based on the results of numerical experiments, we propose a simple theory that the lateral tear propagation rate Vt is mainly controlled by two parameters: (1) the slab retreat rate Vr and (2) the angle A of the passive margin obliquity relative to the retreating trench, such that Vt=Vr/sin(A). Slab tearing and subsequent detachment produces rapid uplift, which marks transition from compression to extension in the forming orogen. The detachment may also create a new subduction zone from one of the STEP faults that start to retreat along the passive margin being oriented orthogonal to it. Numerical experiments reproduce some essential aspects of the recent evolution of the Apennines related to the formation and enlargement of a slab window and subduction rearrangement in this region in the past 2 Myr.

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Figure. 3D numerical thermomechanical model of the lateral tear propagation

Hévíz, Hungary, 15-19 October, 2019 page 42 of 197 International Lithosphere Program The Neogene to Quaternary volcanism and its geodynamic relations in the Carpathian- Pannonian Region – evolution of ideas for the last 50 years

Szabolcs Harangi1,2, Réka Lukács1

1 MTA-ELTE Volcanology Research Group, Budapest, Hungary, [email protected] and [email protected] 2 Department of Petrology and Geochemistry, Eötvös Loránd University, Budapest, Hungary Corresponding author: [email protected]

The Neogene to Quaternary volcanism of the Carpathian-Pannonian Region has a strong connection to the geodynamic evolution of the area. Professor Frank Horváth’s remarkable work and his personal attitude inspired us to place the volcanic activity and the magma generation in a wider plate tectonic context. The plate tectonic concept helps to understand better the areal distribution of volcanoes and the chemical composition of the erupted magmas. Professor Horváth played a fundamental role in the acceptance of plate tectonic processes in Hungary and he continuously searched explanations about the origin and development and the geological and geophysical nature of the Pannonian Basin and the surrounding areas even until the sudden end of his life. The scientific results for the last 50 years highlight that the plate tectonic concept cannot be applied routinely and integration of various fields of geosciences are necessary to obtain a better knowledge how the Earth works. The magmatic and volcanic processes should be considered from the source up to the surface, i.e. from the evaluation of the magma generation processes, through the emplacement of magma in the crust, the processes and their timescale in the magma storage system, the reason of magma withdrawal up to the mechanisms of volcanic eruptions. The advance of new geochemical techniques enabled obtaining a massive geochemical and geochronological data base on the erupted products and eruption events. This extensive data set yields a strong base to interpret the reasons of volcanism. Although the petrogenetic models are getting to be refined considerably, the emerging new questions give a perspective for further studies. The Neogene to Quaternary volcanism of the Carpathian-Pannonian Region can be subdivided into four main groups: (1) eruption of silicic magmas; (2) calc-alkaline basalt-andesite-dacite- rhyolite volcanism; (3) alkaline basalt and trachyte volcanic activity and (4) eruption of potassic and ultrapotassic magmas. Extension and significant thinning of lithosphere and the continental crust played an important role in each of these volcanic activities. The onset of the rifting was coincided with eruption of andesitic to dacitic magmas at 19 to 20 Ma. This magmatism heated up the lithosphere allowing the subsequent emplacement of large volume of silicic magmas in the

Hévíz, Hungary, 15-19 October, 2019 page 43 of 197 International Lithosphere Program continental crust of the central part of the Pannonian Basin. The silicic volcanism between 17.5 and 14.4 Ma was the largest volcanic event in Europe for the last 20 Myr. The ignimbrite flare-up yielded more than 4000 km3 cumulative volume of volcanic material and several times larger amount of magma could have remained in the crust influencing strongly its thermomechanical properties. The new zircon U-Pb dates were used not only to determine the eruption ages, but also to constrain the time of two major block rotations (16.8-17.1 Ma and 15-16 Ma, respectively) and the lifetime of the magma storages. The extensive subvolcanic magmatic systems could exist for several 100’s kyr in the middle to upper crust. The volcanic ash deposits have a key-role providing a chronological framework and correlation tool in the Paratethys sedimentary sequences. The calc- alkaline volcanic rocks appear to follow principally the Carpathian orogenic belt. However, borehole data and seismic sections suggest that there are voluminous volcanic products and centres also in the interior of the Pannonian Basin. The northern segment of the volcanic belt along the Carpathians shows many differences compared to the eastern volcanic chain suggesting different origins. Volcanism at the northern segment occurred coeval with the major extension of the lithosphere. The primary magmas were formed by decompressional partial melting of the lithospheric mantle metasomatized by fluids during former (Paleogene or even earlier) subduction events. A marked change in the chemical composition of the erupted magmas can be observed around 13 Ma that indicates changes in the magma source regions. After ca. 13 Ma magma generation took place mostly in the upwelling asthenosphere leading subsequently to alkaline basaltic volcanism. On contrary, volcanism at the eastern segment occurred in a post-collisional setting, where tectonic processes appear to have controlled the magma generations and volcanic eruptions. Gradual migration of the transtensional tectonic processes led to younging of the volcanism towards south. The paroxysm of the alkaline basaltic volcanism was 5 to 2 Ma, well after the lithospheric extension. The temporal and areal distribution of the basalt volcanic fields as well as the petrogenetic modelling of bulk rock chemical composition imply derivation of the magmas by small volume melting of heterogeneous asthenospheric mantle. The triggering mechanism of the melting events could have been asthenospheric flow along the peripheral steep lithosphere- asthenosphere boundary due to the suction effect of the Pannonian Basin thin spot. The sporadic potassic to ultrapotassic magmas represent partial melts of lithospheric mantle with extreme enrichment of trace elements. Remobilization of such material occurred partly by decompressional melting during the main rifting period but the Quaternary potassic-ultrapotassic volcanism could be related to the heating by uprising asthenospheric material along the southern margin of the

Hévíz, Hungary, 15-19 October, 2019 page 44 of 197 International Lithosphere Program Pannonian Basin. The small volume magmas ascent along a marked west-east tectonic zone. The main period of the volcanic activity in the Carpathian-Pannonian region occurred from 17 Ma to 10 Ma, however, dozens of volcanic eruptions are known also during the Quaternary. Interpretation of the volcanic products of the last eruptions suggests that the asthenospheric mantle beneath our area is still capable to produce magma. Furthermore, the geodynamic environment still enables magma ascent and thus, there are still potential for further volcanic eruptions even though the seemingly long quiescence period since the last volcanic event. The new challenging scientific questions yield further perspective for researches to understand better the present geological and geophysical nature and the development of the Pannonian Basin involving the long-lasting volcanism carrying on Frank Horváth’s deep scientific and spiritual heritage.

Hévíz, Hungary, 15-19 October, 2019 page 45 of 197 International Lithosphere Program Paleohydrogeology and thermal history of marginal areas of confined and unconfined carbonate sequences - Implications of geological evolution on mass and heat transport processes

Timea Havril1, John W. Molson2, Judit Mádl-Szőnyi3 1 József and Erzsébet Tóth Endowed Hydrogeology Chair and Fundation, Department of Geology, Eötvös Loránd University, Hungary 2 Department of Geology and Geological Engineering, Laval University, Canada 3 József and Erzsébet Tóth Endowed Hydrogeology Chair and Fundation, Department of Geology, Eötvös Loránd University, Hungary Corresponding author: [email protected]

It has been recognised for decades, that groundwater flow systems are not static, i.e. flow mechanisms evolve continuously during the geological history of their host basins (Ingebritsen et al., 2006). Transient hydraulic and thermal conditions could therefore evolve, for example, in response to a variety of changes including those related to tectonic uplift and stress, sediment compaction, erosion, thermal conditions, geochemical reactions or climate (Deming, 2002). Due to re-oriented flow paths caused by changing geological conditions, the often-implied presumption that present-day hydrodynamics of a basin can be used to interpret past fluid migration events is likely to be false (Fowler and Grasby, 2006). Therefore, understanding the transient history of subsurface fluid flow systems could be essential and would help to explain the role of groundwater in a number of geologic processes. In the case of deep carbonate systems (>3000 m deep), the significance of changes in flow patterns and heat distribution over long time scales lies in its effects on the development of permeability and accumulation of heat, which e.g. can help to identify the geothermal and hydrocarbon resource potential of deep carbonate systems as well as prospective areas for carbon dioxide sequestration (Goldscheider et al., 2010). A particularly interesting flow pattern arises at the margin of confined and unconfined carbonate sequences. In such locations, regional fluid migration pathways are likely to have varied considerably throughout the geological evolution due to the topographical changes associated with vertical uplift and its consequences on gravity-driven groundwater flow, which might have also had implications on mass and heat transfer. In the current study, semi-synthetic snapshot models of coupled density-dependent flow and heat transport were used to gain insight into the paleohydrogeology and thermal history of marginal areas of confined and unconfined carbonate sequences. The main goal of the study was to answer the following questions: i) What are the main characteristics of the flow field and temperature distribution in these marginal carbonate systems with decreasing cover thickness at

Hévíz, Hungary, 15-19 October, 2019 page 46 of 197 International Lithosphere Program one ridge?, ii) What are the main effects of low-permeability confining formations with changing thickness overlying a permeable carbonate system?, and iii) What is the relative importance of gravity and buoyancy as main driving forces in the different geological evolutionary stages with different confining layer thicknesses? The numerical investigations of groundwater flow over geological time scales were placed into realistic geological evolutionary contexts through an example of the Buda Thermal Karst (Hungary) pilot area. Four scenarios were tested to represent characteristic snapshots of the fluid evolution of the studied system and to examine the effects of tectonic uplift and erosion of confining siliciclastic strata above the carbonates from the fully confined carbonate system to partially confined conditions. The semi-synthetic numerical simulations of fluid flow and heat transport highlight the effects of paleo-recharge and confining formations above the carbonate, as well as the role of an evolving hydrodynamic system on heat distribution and dissipation (Figure 1). Numerical investigations therefore have provided new insights into the processes controlling fluid flow and heat transport at the margin of unconfined and confined carbonates during their geological evolution. Effects of transient flow evolution on heat distribution, permeability, as well as groundwater geochemistry in such carbonate basins can then be interpreted in further studies based on these results and can provide a suitable background to clarify more detailed site-specific mass and heat transfer related questions.

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Figure 1 – Changes in the groundwater flow and temperature fields caused by uplift and decreased cover thickness along the western (W) part of the studied system. Red numbers represent maximum temperature; blue numbers represent temperatures at a distance of 10 km and 2 km deep, while orange numbers represent temperatures at 20 km and 1 km deep after a simulation time of 220 kyr. R1 and R2 show locations of recharge areas, D1, D2 and D3 show locations of discharge areas. Vertical Darcy flux at the boundary between the two sub-systems is indicated by qz. SP represents the location of the stagnation point.

Deming, D., 2002. Introduction to hydrogeology. McGraw-Hill College, New York. Fowler, M. and Grasby, S.E., 2006. Hydrocarbons and water in the Western Canada Sedimentary Basin—A tale of two fluids. Journal of geochemical exploration, 89(1): 112-114. Goldscheider, N., Mádl-Szőnyi, J., Erőss, A. and Schill, E., 2010. Review: thermal water resources in carbonate rock aquifers. Hydrogeology Journal, 18(6): 1303-1318. Ingebritsen, S.E., Sanford, W.E. and Neuzil, C.E., 2006. Groundwater in geologic processes. Cambridge University Press.

Hévíz, Hungary, 15-19 October, 2019 page 48 of 197 International Lithosphere Program A salient which lost its indenter – the curved Cretaceous thrust and fold belt of the southwestern and central Transdanubian Range (TR), West Hungary

Gábor Héja 1, Szilvia Kövér1, László Fodor1

1 MTA-ELTE Geological, Geophysical and Space Science Research Group of the Hungarian Academy of Sciences at Eötvös University

The Transdanubian Range, as the uppermost nappe of the Austroalpine nappe system, intensively folded during the middle Cretaceous. The related compressional structures form a curved thrust and fold belt (Transdanubian salient): in the central TR (Bakony) folds and thrusts are NE-SW trending, further southwest (in the Zala Basin) they become gradually N-S trending. Previous studies explain the formation of this salient as the result of two perpendicular phases of shortening. In this study we gave an alternative explanation for the origin of this salient. We took into consideration the Cretaceous “paleo-position” of the TR by the palinspastic restoration of the TR and the Southern Alps (Figure 1).

Figure 1. Supposed paleo-position of the TR based on Mesozoic facies transitions and movements along the Periadriatic fault

Hévíz, Hungary, 15-19 October, 2019 page 49 of 197 International Lithosphere Program Based on the Mesozoic facies transition, which are dissected by the Periadriatic fault, the TR should have situated significantly to the west in the northern neighbouring are of the Southern Alps, as it was pointed out by a number of previous works. Taking into consideration the Cretaceous paleoposition of the TR, the Transdanubian salient can be considered as an indenter controlled salient, where the indenter is represented by the rigid block of the eastern Southern Alps (Dolomites) (Figure 2). This model implies the Cretaceous presence of a transfer zone between the western and the eastern part of the Southern Alps (proto-Giudicarie fault), which made the proto-Periadriatic fault inclined. This indenter-salient system became dissected by the Cenozoic Periadriatic fault, which cut through the corner of the indenter. The sheared off pieces of the South Alpine indenter transported to the east, forming the present-day Mid-Hungarian shear zone.

Figure 2. 3D block cartoon showing suggested connections between the salient of the TR and the Dolomites as intenter.

Hévíz, Hungary, 15-19 October, 2019 page 50 of 197 International Lithosphere Program Orogeny: selected studies from Ludwig von Loczy to AlpArray

György Hetényi1

1 University of Lausanne, Switzerland, [email protected] Corresponding author: [email protected]

Within the broad domain of orogenic studies my selection is made by gathering topics discussed with or in company of Frank Horváth, and spans from Himalayan to Pannonian peaks. Ludwig von Loczy was not only an outstanding geoscientist of his time, working mostly on the Pannonian Basin, but also a pioneer of the Himalayas. In an expedition across Sikkim in 1878, he described the complete geographical-geological transect, reaching a high-altitude pass to Tibet. He recognized nappes and inverted metamorphism for the first time. Some consider he also first described the Trans-Himalayas – I will show why this, and a few other Loczy-related legends, are not (exactly) true. In the Pannonian Basin, structural seismology revealed a number of similarities to mountain belts. One of them is deep-lying: the mantle transition zone (MTZ). With the use of receiver functions we could map that not the entire MTZ has high seismic velocities as proposed based on tomography, but that the bottom of the MTZ is a slab graveyard, connected to the same feature beneath the Alps. At shallower depths, we confirm that the Alpine–Carpathian–Pannonian and Tisza–Dacia blocks thinned to the same crustal thickness, but show that beneath their shared boundary the crust-mantle transition is likely a broad vertical velocity gradient, as at a Tibetan terrain boundary. Another such zone is proposed for the root of the eastern side of the Tauern Window, based on the seismic images of the Eastern Alpine Seismic Experiment. A common feature of the Himalayas, the Pannonian Basin and the Alps is the spatially diffuse deformation pattern. But how well does the pattern of earthquakes match with that of faults? In a pilot study conducted in the Swiss Alps, we performed a quantitative comparison of seismicity and supposedly active faults known at the surface. While the two databases are inherently incomplete, there are consistent results on closeness and farness. This raises new questions for earthquake hazard and orogenic studies.

Hévíz, Hungary, 15-19 October, 2019 page 51 of 197 International Lithosphere Program Seismic Tomography Constrains the Evolution of the Pannonian-Carpathian Region.

Gregory Houseman School of Earth and Environment, University of Leeds, [email protected] Corresponding author: [email protected]

Frank Horváth has made huge contributions to our understanding of the Miocene extension of the Pannonian Basin. Over several decades he has led detailed structural, sedimentological and geophysical studies that have demonstrated the scale and scope of extension, orogeny and basin formation affecting the lithosphere of the Pannonian-Carpathian region. Regional seismic tomography of the upper mantle shows that this episode of lithospheric extension is just one aspect of a process that affected the entire upper mantle in this region, and might best be viewed as the surface manifestation of a localized overturn of the upper mantle. Seismic tomography shows us a distribution of materials that are characterised by different seismic velocity. Although the role of compositional variation is difficult to assess, temperature is probably the most significant factor influencing variation of velocity in the mantle, at a given pressure. It then follows that strong lateral variations of velocity imply buoyancy variations which drive flow now, and they are indicative of recent flow in which vertical movements have perturbed what otherwise might be a stable stratification. Even though tomographic images have limited spatial resolution, some important observations are readily apparent. A volume of relatively fast material occupies the transition zone (410 – 670 km deep) beneath the Pannonian Basin; its geographic extent closely mimics that of the basin above. The anomalous density of this fast material is indicated by the depression of the 670 km seismic discontinuity beneath it, yet there is no strong evidence that the dense material has yet started to sink into the lower mantle. It is generally assumed that this anomalous material represents subducted oceanic lithosphere that descended into the upper mantle beneath the northern and eastern arcs of the Carpathian Mountains as the Pannonian Basin extended over the retreating subduction zone. The available tomographic images, however, raise questions about this interpretation which need to be addressed, even if we accept the idea that this layer of anomalous material is derived from what was previously lithosphere. Although subduction has not been active at the Carpathians in the last 10 Myr or so, persistent mantle downwelling still occurs beneath the Eastern Alps and the southeast Carpathians. Beneath the Vrancea region of Romania a near-axisymmetric high velocity mass that extends to depths of about 400 km is connected to lithosphere of the Moesian block by a near-vertical conduit of

Hévíz, Hungary, 15-19 October, 2019 page 52 of 197 International Lithosphere Program material which is seismically active. The high level of seismic activity in this conduit implies that the great mass of fast material that constitutes the main body of the anomaly is moving down through the mantle at about 20 mm/yr. At present this downwelling material is probably still separate from the main body of anomalous material in the transition zone, although we can predict that it will begin to merge into the transition zone within a few Myr at most. The upper mantle elsewhere beneath the East Carpathians is seismically slow above the transition zone. Although the Vrancea structure has long been viewed as a remnant of an East Carpathian subducted slab, the rates of deformation implied by the seismic activity are more compatible with it having developed after the extension that formed the Pannonian Basin. In contrast the absence of any slab remnant elsewhere beneath the East Carpathians also implies that if a subducted slab were present at the time of the extension, it is now descended completely into the transition zone. Both observations imply a time-scale for descent through the upper mantle that is significantly less than 10 Myr.

Hévíz, Hungary, 15-19 October, 2019 page 53 of 197 International Lithosphere Program Kaolinite deposits trapped in karstic sinkholes of planation surface remnants used as paleotectonic, paleoclimate and provenance indicators, Transdanubian Range (Hungary), Pannonian Basin

Péter Kelemen1, Gábor Csillag2, 3, István Dunkl4, Andrea Mindszenty5, Ivett Kovács2, Hilmar von Eynatten4, Sándor Józsa1

1 Department of Petrology and Geochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117, Budapest, Hungary, [email protected], [email protected] 2 Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences (MTA), Budaörsi út 45, 1112, Budapest, Hungary, [email protected], [email protected] 3 MTA-ELTE Geological, Geophysical and Space Science Research, Pázmány Péter sétány 1/C, 1117, Budapest, Hungary 4 Geoscience Center, University of Göttingen, Goldschmidtstr. 3, Göttingen 37077, Germany, [email protected], [email protected] 5 Department of Physical and Applied Geology, Eötvös Loránd University, Pázmány Péter sétány 1/C, Budapest 1117, Hungary, [email protected] Corresponding author: [email protected]

In the southwestern part of Transdanubian Range (Keszthely Hills and South Bakony Mountains), there are karstic sinkholes on the planation surface of Triassic carbonates trapping grey clayey-silty kaolinite deposits. The depth of these sinkholes reaches up to 100 m in the South Bakony Mountains and up to 50 m in the Keszthely Hills. However, the latter is strongly eroded (Bohn, 1979). The composition and accumulation age of these terrestrial kaolinite deposits were determined by heavy mineral analysis and U-Pb zircon dating. Samples from the Southern Bakony Mountains showed a balanced zircon, rutile, tourmaline dominated heavy mineral spectrum. Their U-Pb data indicate an accumulation period between 20 to 16 Ma. Besides these young components, Archean to Mesozoic ages were also determined and implicating a mixed source. The Keszthely Hills sample consists almost no other heavy mineral species than 17.5 to 14 Ma euhedral zircons, reflecting a major contribution from the Carpathian-Pannonian Neogene volcanism. The shift in the Miocene age components can be explained by the landscape evolution and burial history of the planation surface remnants controlled by the local tectonic activity. The significant amount of 18 to 19 Ma zircons indicate that the kaolinite formation started earlier in the Southern Bakony Mountains and it is unclear whether they filled up newly formed or paleokarstic features. The absence of these older Miocene components in the Keszthely Hills, despite the high amount and representative measurements, suggests that the kaolinite deposits formed simultaneously with their hosting sinkholes in this area. The 50 m deep morphology and Paleogene nannoplankton content (Bohn 1979) combined with the new geochronological and

Hévíz, Hungary, 15-19 October, 2019 page 54 of 197 International Lithosphere Program heavy mineral data indicate that the Keszthely Hills sinkholes formed under the coinciding and preferable warm-humid climate conditions of the Miocene Climatic Optimum on a terrain affected by an active tectonism (Balla 1984, Csontos et al. 1998, Zachos et al. 2004, Schmid 2008, Balázs et al. 2016). The missing younger than 16 Ma components in the South Bakony Mountains indicate that around this time interval the kaolinite deposits were covered here, while in the Keszthely Hills they accumulated materials until 14 Ma.

The presented data are part of the Ph.D. project: ‘Provenance significance of residual sediments and associated siliciclastic deposits’ supported by the Eötvös Loránd University of Budapest; the Georg-August University of Göttingen; the Erasmus+ Internship programme and the Papp Simon foundations.

Balázs, A., Matenco, L., Magyar, I., Horváth, F., Cloetingh, S. A. P. L. (2016): The link between tectonics and sedimentation in back‐arc basins: New genetic constraints from the analysis of the Pannonian Basin. – Tectonics, 35(6), 1526–1559. Balla, Z. (1984): The Carpathian loop and Pannonian Basin: a kinematic analysis. – Geophysical Transactions 30, 313– 355. Bohn, P., 1979. A Keszthelyi-hegység regionális földtana (Geology of the Keszthely Hills, in Hungarian). Geologica Hungarica, Series Geologica, 19. Csontos, L., Nagymarosy, A. (1998): The Mid-Hungarian line: a zone of repeated tectonic inversions. Tectonophysics, 297(1-4), 51–71. Schmid, S. M., Bernoulli, D., Fügenschuh, B., Matenco, L., Schefer, S., Schuster, R., Tischler, M., Ustaszewski, K. (2008): The Alpine-Carpathian-Dinaridic orogenic system: correlation and evolution of tectonic units. Swiss Journal of Geosciences, 101(1), 139–183. Zachos, J., Pagani, M., Sloan, L., Thomas, E., Billups, K. (2001): Trends, rhythms, and aberrations in global climate 65 Ma to present. Science 292, 686-693.

Hévíz, Hungary, 15-19 October, 2019 page 55 of 197 International Lithosphere Program Dynamic interactions in the Central Mediterranean: insights from analog modeling

Ágnes Király1

1 Centre for Earth Evolution and Dynamics, University of Oslo Corresponding author: [email protected]

The recent tectonic evolution of the Central Mediterranean has started about 84 Ma with the convergence of Africa with respect to Europe and the consumption of the Tethys oceanic domains (Jolivet and Faccenna, 2000; Schmid et al., 2008; Handy et al., 2014). After the Alpine collision many continental and oceanic fragment remained between the African and the Eurasian plates. Their simultaneous subduction formed the tectonic evolution of the Mediterranean in the last 35- 30 Myr. These subductions were generally categorized by fast trench retreat with high angle to the convergence rate, which led to the opening of many back-arc basins (Faccenna et al., 2001, 2014; Horváth et al., 2006). According to most of the tectonic reconstructions, 30-35 Ma three subduction zones were active: in the West the Apennine slab was subducting with NW dipping, the eastern side of the Apulia-Adria plate has another NE dipping subduction zone, while the previous Alpine subduction has continued in the Carpathian embayment. The roll-back of the Carpathian slab has probably finished ~10 Ma, leaving behind a weak and hot back-arc area, the Pannonian Basin. On the other hand, subduction on the two sides (E and W) of Adria is still active along the Calabria and the Hellenic arcs. It has been proposed that the Mediterranean is a key area to observe and understand the role of slab-slab interactions (Király et al., 2016, 2018a, 2018b; Peral et al., 2018). In previous models, we found, that i) the fast retreat of the Apennine slab could aid the slab breakoff in the Western Alps as well as the Oligocene rotation of the Alps-Apennine junction area (Vignaroli et al., 2008; Király et al., 2016). The Apennine slab is also in close connection to the Dinarides-Hellenic slab, forming an outward dipping double-sided subduction system. Their interaction could induce some plate motion and more importantly a strong escape mantle flow from below the Adria plate towards the NE or SW (Király et al., 2018b). Here, I will present laboratory models, addressing the role of the mantle flux induced by the Adria plate’s double-subduction on the deformation of the strong Alpine and the weak Pannonian lithospheric plate segments. The models consist of a Newtonian upper mantle (glucose syrup) and silicon putty plates representing different segments of lithospheres in the Central Mediterranean. Deformation is driven by two subducting slabs (on the opposite sides of Adria) and the induced mantle flow. The escaping mantle flux from below the Adria plate can deform, and induce rotation in the weak Pannonian domain, while the strong

Hévíz, Hungary, 15-19 October, 2019 page 56 of 197 International Lithosphere Program Alpine domain might only experience solid block rotation (Figure 1a). Furthermore, owing to the vertical component of the escape flow, dynamic uplift is observed at the edges of both the Pannonian and Alpine domains (Figure 1b).

Figure 1: Simplified analog model of the Central Mediterranean, including the double-sided subduction of Adria and the laterally placed weak Pannonian and strong Alpine lithospheres. A) Model setup; B) Topography measurement; C) Mantle flow and plate deformation in three stages.

Faccenna, C. et al., 2014, Mantle dynamics in the Mediterranean: Reviews of Geophysics, v. 52, p. 283–332, doi:10.1002/2013RG000444.Received. Faccenna, C., Funiciello, F., Giardini, D., and Lucente, P., 2001, Episodic back-arc extension during restricted mantle convection in the Central Mediterranean: Earth and Planetary Science Letters, v. 187, p. 105–116, doi:10.1016/S0012-821X(01)00280-1. Handy, M.R., Ustaszewski, K., and Kissling, E., 2014, Reconstructing the Alps--Carpathians—Dinarides as a key to understanding switches in subduction polarity, slab gaps and surface motion: International Journal of Earth Sciences, v. 104, doi:10.1007/s00531-014-1060-3. Horváth, F., Bada, G., Szafián, P., Tari, G., Ádám, A., and Cloetingh, S., 2006, Formation and deformation of the Pannonian Basin: constraints from observational data: Geological Society London, Memoirs, v. 32, p. 191–206, doi:10.1144/GSL.MEM.2006.032.01.11. Jolivet, L., and Faccenna, C., 2000, Mediterranean extension and the Africa-Eurasia collision: Tectonics, v. 19, p. 1095– 1106, doi:10.1029/2000TC900018. Király, Á., Capitanio, F.A., Funiciello, F., and Faccenna, C., 2016, Subduction zone interaction: Controls on arcuate belts: Geology, v. 44, p. 715–718, doi:10.1130/G37912.1. Király, Á., Faccenna, C., and Funiciello, F., 2018a, Subduction zones interaction around the Adria microplate and the origin of the Apenninic arc: Tectonics, v. 37, doi:10.1029/2018TC005211. Király, Á., Holt, A.F., Funiciello, F., Faccenna, C., and Capitanio, F.A., 2018b, Modeling Slab-Slab Interactions: Dynamics of Outward Dipping Double-Sided Subduction Systems: Geochemistry, Geophysics, Geosystems, v. 19, p. 693–714,

Hévíz, Hungary, 15-19 October, 2019 page 57 of 197 International Lithosphere Program doi:10.1002/2017GC007199. Peral, M., Király, Á., Zlotnik, S., Funiciello, F., Fernàndez, M., Faccenna, C., and Vergés, J., 2018, Opposite subduction polarity in adjacent plate segments: Tectonics, p. 1–18, doi:10.1029/2017TC004896. Schmid, S.M., Bernoulli, D., Fügenschuh, B., Matenco, L., Schefer, S., Schuster, R., Tischler, M., and Ustaszewski, K., 2008, The Alpine-Carpathian-Dinaridic orogenic system: Correlation and evolution of tectonic units: Swiss Journal of Geosciences, v. 101, p. 139–183, doi:10.1007/s00015-008-1247-3. Vignaroli, G., Faccenna, C., Jolivet, L., Piromallo, C., and Rossetti, F., 2008, Subduction polarity reversal at the junction between the Western Alps and the Northern Apennines, Italy: Tectonophysics, v. 450, p. 34–50, doi:10.1016/j.tecto.2008.10.01.

Hévíz, Hungary, 15-19 October, 2019 page 58 of 197 International Lithosphere Program Subduction Zones Interaction Around the Adria Microplate and the Origin of the Apenninic Arc

Ágnes Király, Claudio Faccenna and Francesca Funiciello The study of slab-slab interactions has come to the front of geodynamics researches to explain geological and geophysical observations from tectonically complex areas. Here we aim to better understand the geodynamics of the Central Mediterranean, where the Adria plate subducts on its two opposite sides. Additionally, the slab below the Central South Apennines has been progressively breaking off during the last 3 Myr. The role of a slab window in a single slab or in an outward dipping double-sided subduction system is addressed by analog models at the scale of the upper mantle, realized using glucose syrup and silicone putty, to model the interaction between the Earth’s mantle and the lithosphere. Our results show that the presence of a slab window modifies the pattern of mantle circulation, as well as the trench geometry and kinematics. In particular, the opening of the slab window induces the formation of two arcs flanking the window, while the mantle flows through it and turns toward the arcs, creating a small-scale toroidal flow. The effect of a slab window is more pronounced on double subduction systems, as the outflow through the window is amplified, while internal deformation is induced in the plate by the opposite slab pull force. These experimental results suggest that the origin of the Apenninic and the Calabrian arcs is the result of the formation of a slab window, providing a new interpretation of the surface deformation and the SKS shear wave splitting pattern of the Adria microplate.

Hévíz, Hungary, 15-19 October, 2019 page 59 of 197 International Lithosphere Program 2D image analysis of sandstone samples from the Pannonian Basin

Csilla Király1, György Falus2,3, György Varga1, Zoltán Szalai1,3

1 Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Science, [email protected] 2 Mining and Geological Survey of Hungary 3 Eötvös University, Faculty of Science Corresponding author: [email protected]

The diagenetic processes may cause considerable changes in grain and pore morphology and size. The analysis of the complex geometry of the system is not straightforward. In this study 2D image analysis was used to determine the geometry of particles and pores in sandstones from thin sections. The studied samples originated from Szolnok Formation, which is a tubiditic sandstone assemblage in the Pannonian sediments. Thin sections were prepared from the samples, which were studied by scanning electron microscope and Morphologi G3 ID at Research Centre for Geographical Institute, Astronomy and Earth Sciences, Hungary. The applied analytical method (Morphologi G3 ID) is a polarized light microscope equipped with Raman spectroscope, which can perform 2D image analysis. The acquired data contain morphological parameters such as convexity, High Sensitivity (HS) circularity, aspect ratio, furthermore, contain different size parameters such as width, length, Circle Equivalent (CE) diameter. Raman spectrometer can help to identify the mineralogy of the analysed grains. The main aim of the study is to develop a method which could effectively characterize the grain and pore size and particle shape from thin sections. The studied sandstone samples were analysed from 1500 to 2250 m depth range from a single borehole (Za1). According to previous studies: characteristic detrital minerals of the Szolnok Formation are quartz, muscovite, dolomite, K-feldspar and plagioclase. The main diagenetic minerals are carbonates (calcite, Fe-dolomite, ankerite, siderite) and clay minerals (illite, kaolinite). The cement material can be ankerite, calcite, siderite and kaolinite. Moreover, in the studied samples the ankerite grew on the surface of the detrital dolomite grains as rims. The siderite is a fine grain material, which was found as replacement of detrital biotite with recognizable structure of the precursor mica. The results show that HS circularity is in relation with aspect ratio and with convexity. The results indicate that concerning particle shape, muscovite is a well separable group. Quartz and feldspar grains show high variability in shapes, because they are detrital minerals and sometimes

Hévíz, Hungary, 15-19 October, 2019 page 60 of 197 International Lithosphere Program arrived as lithic fragments. Other parts of these fragment could have been altered or even removed during diagenetic processes. The shape of carbonate minerals depends on the original pore size and shape, because these minerals are mainly diagenetic. 3 groups of pores can be divided, 1: resembling particle shape, 2: normal pores, 3: bounded pores.

Hévíz, Hungary, 15-19 October, 2019 page 61 of 197 International Lithosphere Program Numerical modelling of subduction initiation and tectonic nappe stacking in the Western Alps: thermo-mechanical insights on shear zone formation

Dániel Kiss1, Lorenzo G. Candioti1, Thibault Duretz1,2 and Stefan M. Schmalholz1

1 University of Lausanne, Institute of Earth Sciences, Lausanne, Switzerland 2 Univ. Rennes, CNRS, Géosciences Rennes - UMR 6118, F-35000 Rennes, France Corresponding author: [email protected]

The orogenic wedge model has been applied to explain the tectonic evolution of many orogens worldwide. Orogenic wedges are characterized by (1) a first-order shear zone, which thrusts the mantle lithosphere and the lower crust beneath the adjacent mantle lithosphere and (2) a sequence of second-order upper crustal shear zones which form tectonic nappes. Shear zone formation in the lithosphere is, however, incompletely understood, thus it is the focus of this study. We perform two dimensional numerical simulations of lithospheric and upper crustal shortening to study shear zone formation and the associated orogenic wedge and tectonic nappe formation. We consider visco-elasto-plastic deformation, heat transfer and thermo-mechanical coupling by shear heating and associated thermal softening due to temperature dependent rock viscosity. The initial setting of the lithospheric-scale simulations resembles a hyper-extended passive margin with exhumed sub-continental mantle. The simulations show subduction initiation for convergence velocities of 2 cm/yr, Moho temperatures between 525 and 550 oC and reasonable maximal deviatoric stresses around the Moho of ca 800 MPa. Subduction initiates in the region with thinned continental crust and is controlled by a thermally-activated ductile shear zone in the mantle lithosphere. The modelled forced subduction agrees with geological data and reconstructions of subduction during closure of the Piemont-Liguria basin. The initial setting of the upper-crustal-scale simulations resembles a passive margin, that is characterized by inherited mechanical heterogeneities. We consider tectonic inheritance with two initial mechanical heterogeneities: (1) lateral heterogeneity of the basement-cover interface due to half-grabens and horsts and (2) vertical heterogeneities due to layering of mechanically strong and weak sedimentary units. The model shows detachment and horizontal transport of a thrust nappe and stacking of this thrust nappe above a fold nappe. The detachment of the thrust sheet is triggered by stress concentrations around the sediment-basement contact and the resulting brittle- plastic shear band formation. The horizontal transport is facilitated by a basal shear zone just above the basement-cover contact, composed of thin, weak sediments. Fold nappe formation

Hévíz, Hungary, 15-19 October, 2019 page 62 of 197 International Lithosphere Program occurs by a dominantly ductile closure of a half-graben and the associated extrusion of the half- graben fill. We apply our model to the Helvetic nappe system in Western Switzerland, which is characterized by stacking of the Wildhorn thrust nappe above the Morcles fold nappe. The modelled structures and temperature field agree with data from the Helvetic nappe system.

Hévíz, Hungary, 15-19 October, 2019 page 63 of 197 International Lithosphere Program Fault pattern control of low-temperature hydrothermal Pb-Zn ore emplacement: Preliminary results from Lece mine (southern Serbia)

Vaso Kitanović1,2, Nemanja Krstekanić2,3

1 Koncern Farmakom MB, Lece Mine, Medvedja, Serbia 2 University of Belgrade, Faculty of Mining and Geology, Department of Regional Geology, Belgrade, Serbia 3 Utrecht University, Faculty of Geosciences, Department of Earth Sciences, Utrecht, the Netherlands Corresponding author: [email protected]

The Lece volcanic province is situated in southern Serbia, close to the suture zone between Adria-derived (i.e. the Dinarides) and Europe-derived units (i.e. the Serbian Carpathians of the Dacia mega-unit). It is comprised of various, mostly andesitic, sub-volcanic intrusions, lava flows and related volcaniclastics that intruded or otherwise overlie Serbo-Macedonian Unit and East Vardar ophiolites. This large volcanic province was formed in, at least, two closely-related magmatic episodes dated at ~33.5 Ma and ~32.6 Ma by Kostić et al. (2017), during the continental collision and gradual shift of deformation and magmatism from the Carpathians towards the foreland of the Dinarides (Andrić et al., 2018, and references therein). The Lece ore field is located on the eastern margin of the Lece volcanic province where low-temperature hydrothermal Pb-Zn ore deposits are highly controlled by post-magmatic faulting. However, the link between the local fault pattern and the hydrothermal activity is not fully understood. In this study we present preliminary results on the structural evolution and control of the Lece Pb-Zn ore emplacement. The main structure associated with the Lece volcanism and controlling the later metallic ore deposition is NW-SE oriented Tupale fault. Although it might have a Variscan precursor, post- volcanic activity along the Tupale fault during pre-ore, syn-ore and post-ore stages in Oligocene to Miocene times had a significant influence on the formation of ore bodies it the Lece ore field. Poly- phase tectonic activity along the Tupale fault from the beginning of volcanic activity and especially with the cessation of active volcanism influenced the formation of subsidiary structures of different kinematics and spatial orientations in this region. For most structures associated with major Tupale fault, ore-bearing low-temperature hydrothermal fluids were associated with multi-stage reactivation of these structures during overall brittle deformation of the Lece volcanic province.

Andrić, N., Vogt, K., Matenco, L., Cvetković, V., Cloetingh, S., Gerya, T. (2018). Variability of orogenic magmatism during Mediterranean-style continental collisions: A numerical modelling approach. Gondwana Research, 56, 119-134. Kostić, B., Šarić, K., Cvetković, V., Krstekanic, N., Pantelić, N., Bosić, D. (2017). A reinterpretation of the geological map of northwestern part of the Lece Volcanic Complex. 13th Workshop on Alpine Geological Studies – Émile Argand Conference (EGU Series) Abstract Volume, Zlatibor, Serbia, 7 –18 September 2017.

Hévíz, Hungary, 15-19 October, 2019 page 64 of 197 International Lithosphere Program Understanding a volcanic history of SW part of Lece Volcanic Complex from plagioclase composition, zircon geochemistry and U-Pb age

Bojan Kostić

Faculty of Mining and Geology, University of Belgrade Corresponding author: [email protected]

This study reports a petrography, new radiometric age, zircon trace element and microprobe analyses on plagioclase of the northwest part of Lece Volcanic Complex (LVC) in Southern Serbia. LVC is developed on the suture between the Vardar zone and Serbo-Macedonian Massif, and it is one of the major Oligocene volcanic regions in the Central Balkan Peninsula (figure 1a). Volcanism is clearly post-collisional, and the major driving force has been most probably the delamination of the metasomatized subcontinental mantle. Volcanic rocks occur as relics of large calderas, lava flows as subvolcanic intrusions and in different volcaniclastic facies of andesite. Radiometric data from U-Pb method revile two igneous events. The first event comes to 33.5 Ma (sample RU-09), while the second igneous event occurred at 32.6 Ma (sample BK-01) (figure 1b, c). Hornblende andesite is characterized as the first volcanic phase, while the second phase is dominantly presented with hornblende-pyroxene andesite. Zircon trace elements distribution pattern normalized to chondrite shows a smooth pattern typical for magmatic zircons. Pattern shows positive Ce and negative Eu anomalies. Yb/Gd vs. Th/U diagram show a normal trend of magma chamber fractionation (figure 1d). Elevated U/Yb with respect to increasing Hf concentrations that are indicative of derivation from a transitional type of environment with normal arc magmas contaminated with continental material (figure 1e). Different mineralogical composition in these two volcanic phases reviles that the younger phase has reverse plagioclase zoning with An48.5 in the centre, and An62.6 on the rim. All this evidence points probably to processes which suggest of reheating resident magma by overheated hot plumes which recharge reservoir or mixing two magmas with dramatically different compositions with a new portion of basaltic magma input.

Hévíz, Hungary, 15-19 October, 2019 page 65 of 197 International Lithosphere Program

Hévíz, Hungary, 15-19 October, 2019 page 66 of 197 International Lithosphere Program Messinian basin-fill architecture in the Drava Trough: stratigraphic forward modeling and field observations

Ádám Kovács1, Attila Balázs2, Marko Špelić3, Orsolya Sztanó1, Imre Magyar4

1 Department of Geology, Eötvös Loránd University, Budapest 2 Department of Sciences, Università degli Studi Roma Tre, Rome 3 Croatian Geological Survey, Faculty of Mining, Geology and Petroleum Engineering 4 MTA-MTM-ELTE Research Group for Paleontology Budapest Corresponding author: [email protected]

This study focuses on the appearance of two debated unconformities in the Drava Trough. In the Late Neogene lacustrine succession of the Pannonian Basin (PB) the so-called Pa-4 or “intra- Messinian” and the Miocene-Pliocene unconformities were recognized where gently folded lacustrine strata or steep portion of clinoforms are overlain by onlap surfaces. These two surfaces are often amalgamated which provides different interpretation possibilities. According to a group of researchers the Pa-4 unconformity can be correlated basin-wide and is inferred to be linked with the major lake-level drop connected to the Messinian Salinity Crisis (MSC) or its triggers. In contrary others argue, that in the eastern part of the PB this geometry is a result of local interplay between structural inversion and the superposition of two different sediment feeder systems, in addition these events are older than the MSC. There is still no consensus about the nature and age of this surface. In the Drava Trough the succession covers the time interval of the MSC. The Miocene-Pliocene unconformity is clearly present, the Pa-4, however is indiscernible. Instead features pointing to base-level rise are obvious. Our main goal is to analyze forcing factors controlling stratal geometries and to understand the rapid changes of the depositional environments. To this aim, 3D numerical simulations were performed by the DionisosFlow stratigraphic modeling software constrained by seismic and well data interpretation between the Mecsek mts (SW Hungary) and the Krndija mts (N Croatia). Water depth evolution and 3D facies distribution of the basin has been simulated as well as the evolution of the main sedimentary transport routes. Model results are compared and validated by field observations from the margin of the Krndija mts. A pronounced angular unconformity could be studied in details within the Late Miocene lacustrine succession, between profundal calcareous marls and shallow water deltaic clay and sand beds. The unconformity is a hardground, below an age of 10.2-9.6 Ma and above younger than 6 Ma is indicated by mollusk shell-beds. Our numerical simulation yields new insights in quantifying the tectonic and climatic controls

Hévíz, Hungary, 15-19 October, 2019 page 67 of 197 International Lithosphere Program onthe effects of the MSC in the Pannonian Basin. This presentation was supported by MOL Academic Aid Program, NKFIH 116618 and TÉT_16-1- 2016-0004.

Hévíz, Hungary, 15-19 October, 2019 page 68 of 197 International Lithosphere Program The Pannon LitH2Oscope project: developing the 'pargasosphere' concept

István Kovács 1,2, Gyöngyvér Szanyi 1,2, Zoltán Gráczer 1,2, Zoltán Wéber 1,2, Bálint Süle 1,2, Máté Timkó 1, Tibor Czifra 1,2, Nóra Liptai 1,2, Márta Berkesi 1,3, Thomas Lange 1,3, Attila Novák 1,2, Csaba Molnár 1,2, Eszter Szűcs 2, Csaba Szabó 3, and Viktor Wesztergom 2

1 MTA CSFK Lendület Pannon LitH2Oscope Research Group, Budapest-Sopron, Hungary 2 HAS, RCAES, Geodetic and Geophysical Institute, Sopron, Hungary, 3 Eötvös University, Lithosphere Fluid Research Lab, Budapest, Hungary Corresponding author: [email protected]

Earth is an exceptional planet and the exploration of its surface and near space has experienced significant advances, we know only little about its interior. ‘Water’ is a vital component of life, but also a decisive ‘ingredient’ for making Earth a geologically ‘active’ planet. Plate tectonics proposes that the Earth’ rigid outer layer, the lithosphere, ‘floats’ on the underlying less viscous asthenosphere. The reasons for their contrasting behaviours are still highly speculative. The everyday effects of plate tectonic activity (earthquakes, volcanism) obviously have great societal importance, however, the more precise definition of the lithosphere-asthenosphere boundary (LAB) remained an ultimate endeavour for Earth Sciences. The recently developed ‘pargasosphere’ theory may offer a new explanation how trace amount of ‘water’ and its speciation in the Earth interior influences the variations in physical and geochemical properties at the LAB under young continental extensional basins and oceanic plates (Green et al., 2010; Kovács et al., 2017). The Pannonian Basin, as such a young extensional basin, is excellent natural laboratory to test the predictions of this theory. The aim the Pannon LitH2Oscope Group is to implement a largescale multidisciplinary Earth Science experiment providing an unprecedentedly detailed insight into the Earth Interior with special respect to the LAB. The novel outcomes could significantly contribute to refine and develop global analogue and numerical plate tectonic models.

Green, D. H., Hibberson, W. O., Kovács, I., & Rosenthal, A. (2010). Nature, 467(7314), 448-451 Kovács, I., Lenkey, L., Green, D. H., Fancsik, T., Falus, G., Kiss, J., Orosz, L., Angyal, J. & Vikor, Z. (2017). Acta Geodaetica et Geophysica, 52(2), 183-204.

Hévíz, Hungary, 15-19 October, 2019 page 69 of 197 International Lithosphere Program On the arrival and evolution of the Danube River in the Dacian Basin

Krezsek1, C., Olariu2, C.

1 OMV Petrom, Bucharest, Romania 2 University of Texas at Austin, Texas, US

The Danube River is the largest continental scale river in Europe. It originates in the Alpine Molasse basin and flows across Vienna, the Pannonian and the Dacian basins and forms a large delta as it enters into the Black Sea. The timing of entry of the Danube in the Dacian Basin and then into the Black Sea are poorly understood (Magyar et al., 2019). Matoshko et al. (2019) recently proposed a Quaternary entry of the Danube into the Black Sea based on outcrops located at its presumed entry point, the Galati Seaway. In contrast, Olariu et al. (2017) suggested this entry 2 ma older (intra-Dacian) interpreting outcrops in the western part of the Dacian basin and correlated with biostratigraphy and seismic data from the Black Sea. Other authors, including Clauzon et al. (2005) and Munteanu et al. (2012), hypothesized a much earlier Danube entry into the Black Sea in relation to the intra-Pontian Messinian Salinity Crisis (MSC). In their view, the sea-level fall in the Black Sea may have triggered desiccation of the Dacian Basin and lake level fall in the Pannonian Basin. The proposed regional sea-level fall forced the Danube to spill over from the Pannonian Basin across the Iron Gates into the Dacian Basin and then rapidly cut through the Dacian Basin to develop a large lowstand systems tract in the Black Sea (Munteanu et al., 2012). This scenario has been debated by Stoica et al. (2013) which pointed out the magnitude of the MSC-related lake-level fall in the Dacian basin is less than a hundred meters, therefore desiccation of the basin is unlikely. In addition, the fan deltas at the Iron Gates used as evidence for the Paleo-Danube stepping into the Dacian basin are older, mid-Miocene in age, and therefore unrelated to the Danube (Jipa et al., 2011). In this study we complement existing outcrops and well data interpretations with basin-wide subsurface mapping using regional 3-D seismic datasets while searching for the Danube in the Dacian Basin. Our working hypothesis is that fluvial depositional architecture developed by such a large river system as the Danube is different from the small scale rivers akin to the ones flowing down from the present day Carpathians or Balkan Mts. Therefore, analysis of regional stratigraphy and sedimentary depocenters migration through time and space in addition to the character of the channel feeder systems could shed light on evidence for the Danube in the Dacian Basin. We will argue the Miocene fill of the Dacian Basin is not related to the Danube. The stratigraphy rather reflects evolution of fluvial systems controlled by the mid-Miocene uplift of the Carpathians.

Hévíz, Hungary, 15-19 October, 2019 page 70 of 197 International Lithosphere Program Earliest evidence for the Danube could be the Dacian deltaic deposits from the western part of the basin (Olariu et al., 2017). Then, in the Romanian, the Danube could be traced as a large river system flowing to the east along the Carpathians foredeep. Upper Romanian uplift of the Carpathians changed the pathway location and pushed the Danube River 100-200 km to the south, in the present day position.

Clauzon, G., Suc, J.-P., Popescu, S.M., Marinteanu, M., Rubino, J.-L., Marinescu, F., Melinte, M.C. 2005. Influence of the Mediterranean sea-level changes on the Dacic Basin (Eastern Paratethys) during the late Neogene: the Mediterranean Lago Mare facies deciphered. Basin Research 17/3, 437-462. Jipa, D.C., Stoica, M., Andreescu, I., Floroiu, A., Maximov, G. 2011. Zanclean Gilbert-type fan deltas in the Turnu Severin area (Dacian basin, Romania): a critical analysis. Geo-Eco-Marina 17, 1-12. Magyar, I., Krezsek, C., Tari, G. 2019, preprint. Clinoforms as paleogeographic tools: Development of the Danube catchment above the deep Paratethyan basins in Central and Southeast Europe. Basin Research. Matoshko, A., Matoshko, A., de Leeuw, A . 2019. The Plio-Pleistocene demise of the East Carpathian foreland fluvial system and arrival of the paleo-Danube to the Black Sea. Geologica Carpathica 70/2, 91–112. Munteanu, I., Maţenco, L., Dinu, C., Cloetingh, S. 2012. Effects of large sea-level variations in connected basins: the Dacian – Black Sea system of the Eastern Paratethys. Basin Research 24/5, 583-597. Olariu, C., Krezsek, C., Jipa, D. 2017. The Danube River inception: Evidence for a 4 Ma continental-scale river born from segmented Paratethys basins. Terra Nova 30/1. Stoica, M., Lazăr, I., Krijgsman, W., Vasiliev, I., Jipa, D., Floroiu, A., 2013. Paleoenvironmental evolution of the East Carpathian foredeep during the late Miocene–early Pliocene (Dacian Basin; Romania). Global and Planetary Change 103, 135–148

Hévíz, Hungary, 15-19 October, 2019 page 71 of 197 International Lithosphere Program Curved strike-slip fault evolution and associated deformation during oroclinal bending: Preliminary results from analogue modelling

Nemanja Krstekanić1,2, Ernst Willingshofer1, Liviu Matenco1, Marinko Toljić2, Uros Stojadinovic2

1 Utrecht University, Faculty of Geosciences, Department of Earth Sciences, Utrecht, the Netherlands 2 University of Belgrade, Faculty of Mining and Geology, Department of Regional Geology, Belgrade, Serbia Corresponding author: [email protected]

Many large-scale continental strike-slip faults, such as San Andreas fault, Alpine fault, North Anatolian fault or Dead Sea fault show distributed deformation and strain partitioning associated with transpressive and transtensive segments that result in formation of positive and negative flower structures, transpressional orogens and transtensive basins of various geometries. One such complex intra-continental strike-slip system is Cerna-Timok curved dextral fault system of the South and Serbian Carpathians. This strike-slip system accommodates up to 100 km of dextral offset during Oligocene – early middle Miocene. When compared with other large continental strike-slip faults, one rather unique feature of the Cerna-Timok fault system is its formation during the oroclinal bending of the Dacia mega-unit around the stable Moesian promontory, connecting the deformations in the Balkanides with those in the South Carpathians. In order to understand the kinematic evolution and geometry of strike-slip faulting of the Cerna- Timok faults system during rotation around the stable Moesian continental unit, we have performed a series of crustal scale analogue experiments. The modelling setup consists of two regions, one fixed, representing the stable Moesia, that is surrounded by a mobile part, representing deformable Dacia mega-unit. The mobile part of the model is initially only translated parallel to the margin of the stable segment, which is followed by translation and clockwise rotation around a fixed pole located in the corner of the stable region. Total amount of dextral offset along the velocity discontinuity between the stable and mobile regions of the model is same in all experiments, but that offset can be achieved by either translation or rotation or by combining their effects. We performed both brittle and brittle/ductile experiments where the total offset is achieved by varying the amount of rotation relative to translation, starting with pure translation in initial experiments and changing to small and high amount of rotation during the overall movement of the mobile segment of the model in later experiments. During the initial translation, a strike-slip fault formed parallel to the velocity discontinuity at

Hévíz, Hungary, 15-19 October, 2019 page 72 of 197 International Lithosphere Program the side of the stable region, while the strike-slip deformation is transferred into thrusting in front of the stable part forming a compressional wedge. In experiments with pure translation, strike-slip fault propagates in the direction of the wedge during deformation and cuts through it by creating an apparent decrease in offset in the same direction. In experiments with rotation, a transtensional triangular basin is opened along the velocity discontinuity at the side of stable segment, while the initial compressional wedge is gradually transferred around the corner into a strike- slip/transtensive corridor. Generally, the map view geometry of the basin is triangular, narrowing towards the pole of rotation, and is asymmetric in cross-sections with the largest amount of subsidence towards the stable region. The position and the geometry of the transtensional basin is controlled by the amount of total rotation, presence of the ductile crust and the width of the pre- rotational wedge that needs to be removed by normal faulting. All these analogue modelling observations show a good correlation with the actual geometry of Cerna-Timok fault system and associated Timok-Knjaževac basin. Dextral Timok fault demonstrates decrease in offset from ~65 km in its northern segment to ~2.5 km in the south while deformation is transferred into top to N thrusting in the Balkanides. In the same time, NW-SE oriented transpressive segment of the Timok fault south of the Timok-Knjaževac basin is linked with its N-S oriented segment along which triangular Timok-Knjaževac basin is formed. Such geometry shows best correlation with experiments in which small amount of rotation is achieved during total deformation.

Hévíz, Hungary, 15-19 October, 2019 page 73 of 197 International Lithosphere Program A study on the physical properties of the lithospheric mantle based on on upper mantle xenolith from the Perșani Mountains: the role of quantitative Fourier transform infrared spectroscopy

Thomas P. Lange1,2, Nóra Liptai2,3, Levente Patkó1,2,4, László E. Aradi1, Márta Berkesi1,2, Csaba Szabó1,3, István J. Kovács2,3

1 Lithosphere Fluid Research Lab, Institute of Geography and Earth Sciences, Eötvös University, 2 MTA CSFK Lendület Pannon LitH2Oscope Research Group, MTA CSFK 3 Geodetic and Geophysical Institute, CSFK, MTA, 4 Isotope Climatology and Environmental Research Centre, Institute for Nuclear Research, MTA, Debrecen, Hungary Corresponding author: [email protected]

Heterogeneity of the lithospheric mantle (rock and fluid/melt and distribution) results in different chemical (elemental and isotopic) and physical properties (e.g. seismic velocity, conductivity and effective viscosity) of a studied mantle portion. This heterogeneity is mostly constrained by indirect geophysical methods (e.g. seismic tomography, magnetotellurics). Data given by these indirect methods (with respect to their resolution) mostly define an average property of the studied mantle. A direct method to study the lithospheric mantle is to work on mantle xenoliths that are brought up to the surface by mostly basaltic volcanism. Numerous examines of mantle xenoliths conclude that the solid phases of the Earth lithospheric mantle consist basically of nominally anhydrous minerals (NAMs; e.g. olivin, pyroxene) and small amount of H2O-bearing minerals (e.g. amphibole, mica). Besides solid phases, fluid/melt phases and their proportion with respect to solid constituent changes with tectonic settings (e.g. rift settings or subduction) can be also identified. For mantle xenoliths petrography there is a strong tool to understand rock texture, to calculate rock modal compositions and solid/fluid ratios. Based on chemical composition of minerals, the depth and temperature of origin of the studied mantle xenoliths can be determined. Hydrogen is one of the key elements, which incorporates into NAMs, changing the melting temperature, rheology and specific electrical conductivity. The mode of H+ incorporation strongly depends on the composition of the host mineral (e.g. Ti content) and the oxygen, H2O and SiO2 activity. For identification of the H+ incorporation types and concentration in NAMs micro-FTIR (Fourier transform infrared) spectroscopy is a widely used analytical technique. Recent studies (e.g. James et al. 2014; Fullea 2017) highlighted that variation in rock texture, solid/fluid ratio and mineral composition of a mantle portion has a massive effect on geophysical

Hévíz, Hungary, 15-19 October, 2019 page 74 of 197 International Lithosphere Program properties. For example, solid/(fluid+melt) ratio has a huge effect on seismic wave velocities as increase in fluid/melt decreases Vs wave velocity significantly. Structural hydroxyl content weakens mineral structure resulting in rheological weakening. NAMs with high structural hydroxyl content react faster to stress than minerals close to ‘perfect’ crystal structure. Specific electrical conductivity is highly affected by the structural hydroxyl concentration of NAMs and fluid/melt content in the rock showing a positive correlation. Mentioned physical properties can be calculated knowing mineral composition and specific physical chemical parameters. Comparing the geophysical data (e.g. seismic tomography) to the calculated data from xenoliths can only be applied to young volcanic areas (younger than 10 Ma) making the Carpathian- Pannonian region (CPR) an excellent place to study the geophysical properties of the lithospheric mantle. Within the CPR, we focus on the lithospheric mantle beneath the Perșani Mountains Volcanic Field and use the gained knowledge to constrain the physical conditions. Comparing the results to other young monogenetic fields (Styrian Basin and Nógrád-Gömör) in the CPR we aim to have a about a refined image about the evolution of the CPR.

Fullea (2017): Surv Geophys, 38:963–1004. James et al. (2004): Geochem Geophy Geosy, 5.

Hévíz, Hungary, 15-19 October, 2019 page 75 of 197 International Lithosphere Program Modelling of thermal convection in the Fábiánsebestyén geothermal reservoir

László Lenkey1, Gergő Hutka1, Attila Balázs2

1 Department of Geophysics and Space Science, Eötvös Loránd University, [email protected], [email protected] 2 Department of Geological Science, Universita Roma Tre, [email protected] Corresponding author: [email protected]

In Hungary only low enthalpy thermal waters are utilized for central heating, green house heating, and bathing. However, in the SE part of the country some high enthalpy geothermal reservoirs exist in the basement of Neogene sediments. The most famous one was discovered by chance by the hydrocarbon exploration well Fábiánsebestyén-4. Mixture of hot water and steam (T = 170 °C, Q = 5000-8000 m3/d) has been blowing out from the well for a month until the well was shut down. The reservoir is not utilized due to technical difficulties and high costs. The reservoir is located in great depth (3800 m), it is highly overpressured (30 Mpa), the water is highly saline (30 g/L NaCl) and tends to form scaling. Two other high enthalpy reservoirs are proven by wells, but there might be more. The most probable candidates are the fractured and/or karstified carbonates like the Fábiánsebestyén reservoir, which is hosted by Triassic dolomite breccia. It has high permeability (2-5 Darcy), which may lead to the evolution of free thermal convection of the water in the reservoir. We calculated the temperature field resulting from the thermal convection in order to see how large is the thermal anomaly caused by the convection. Our purpose was to know whether temperature data from shallower depth can be applied to predict thermal convection in the basement and thus, help the exploration of geothermal reservoirs in large depth. Based on seismic and magnetotelluric sections we constructed the geometry of the Fábiánsebestyén reservoir and we calculated the temperature field using the finite element modelling software Feflow. The temperature anomaly dissipates in 500 – 1000 m distance from the top of the reservoir (see Figure). Therefore, only temperature data, preferably temperature logs, observed close to the basement are useful to predict thermal convection and thus geothermal reservoirs in the basement. We conclude that temperature data interpreted together with the results of 3D thermal modelling may help to work out perspective geothermal plays in large depth.

Hévíz, Hungary, 15-19 October, 2019 page 76 of 197 International Lithosphere Program Observed and modelled temperature in the Fábiánsebestyén-4 well

Hévíz, Hungary, 15-19 October, 2019 page 77 of 197 International Lithosphere Program The effect of ‘water’ on the rheology of the lithospheric mantle in the Carpathian-Pannonian region Nóra Liptai1,2, Thomas P. Lange1,3, Levente Patkó1,3,4, Zsófia Pálos2,3, Márta Berkesi1,3, László E. Aradi3, Csaba Szabó1,3, István J. Kovács1,2

1 MTA CSFK Lendület Pannon LitH2Oscope Research Group 2 Geodetic and Geophysical Institute, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences 3 Lithosphere Fluid Research Lab, Eötvös Loránd University 4 Isotope Climatology and Environmental Research Centre, Institute for Nuclear Research, Hungarian Academy of Sciences Corresponding author: [email protected]

‘Water’ can be present in the lithospheric mantle in different forms, either as H2O in fluid or melt inclusions, or within mineral structures as structurally bound hydroxyl. In the latter case, the abundance can reach up to ~2 wt % in volatile bearing mantle minerals (most frequently pargasite), or tens to hundreds of ppm in nominally anhydrous minerals (NAMs; olivine and pyroxenes). Pargasite is generally stable up to 1050-1150°C in water-undersaturated conditions (0.02 – 0.4 wt %) characteristic for the upper mantle (e.g., Green et al., 2010). Outside of pargasite stability, the excess water can be incorporated in the NAMs or occur as aqueous phase (e.g., in fluid inclusions) or dissolved in incipient partial melt. In these cases, water can have a significant effect on the rheological properties of the lithospheric mantle, such as lowering the melting temperature, resistivity, seismic velocity and effective viscosity (e.g., Hirth and Kohlstedt, 1996). In the Carpathian-Pannonian region, upper mantle xenoliths can be found on the surface at five areas, which include localities both at marginal (Styrian Basin, Perşani Mountains) and central (Little Hungarian Plain, Bakony-Balaton Highland, Nógrád-Gömör) regions of the basin system. The NAMs of xenoliths from the central localities have significantly lower water contents compared to those from the marginal ones. This is explained by re-equilibration under lower water activity due to the Miocene extension and asthenospheric updoming in the Pannonian Basin (Patkó et al., 2019). Our study shows that as a consequence, the lithospheric mantle in the central part of the basin has higher resistivity and effective viscosity, i.e., it is rheologically ‘stronger’ than at the marginal areas.

Green, D. H., Hibberson, W. O., Kovács, I., & Rosenthal, A. (2010). Water and its influence on the lithosphere- asthenosphere boundary. Nature, 467(7314), 448-451. Hirth, G. & Kohlstedt, D. L. (1996). Water in the oceanic upper mantle: implications for rheology, melt extraction and the evolution of the lithosphere. Earth and Planetary Science Letters, 144, 93-108. Patkó, L., Liptai, N., Kovács, I. J., Aradi, L. E., Xia, Q.-K., Ingrin, J., Mihály, J., O’Reilly, S. Y., Griffin, W. L., Wesztergom, V. &

Hévíz, Hungary, 15-19 October, 2019 page 78 of 197 International Lithosphere Program Szabó, C. (2019). Extremely low structural hydroxyl contents in upper mantle xenoliths from the Nógrád-Gömör Volcanic Field (northern Pannonian Basin): Geodynamic implications and the role of post-eruptive re-equilibration. Chemical Geology, 507, 23-41.

Hévíz, Hungary, 15-19 October, 2019 page 79 of 197 International Lithosphere Program Subvolcanic magma storage revealed: a zircon perspective study combined with geophysics, petrology and thermal modelling at the Ciomadul Volcanic Dome Field (Eastern-Central Europe)

Réka Lukács1, Luca Caricchi,2, Axel K. Schmitt3, Ozge Karakas4, Olivier Bachmann4, Marcel Guillong4, Kata Molnár5,6, Ioan SeghediI.7, Szabolcs Harangi1,6

1 MTA-ELTE Volcanology Research Group, Budapest, Hungary, [email protected] 2 Université de Genève, Genève, Switzerland, [email protected] 3 Ruprecht-Karls University, Heidelberg, Germany, [email protected] 4 ETH Zürich, Zürich, Switzerland, [email protected], [email protected], [email protected] 5 Isotope Climatology and Environmental Research Centre, Institute for Nuclear Research, Hungarian Academy of Sciences, Debrecen, Hungary 6 Department of Petrology and Geochemistry, Eötvös Loránd University, Budapest, Hungary, [email protected] 7 Institute of Geodynamics, Romanian Academy, Bucharest, Romania, [email protected] Corresponding author: [email protected]

Magma reservoirs beneath volcanoes are considered to exist dominantly in a form of crystal mush, i.e. in a high crystallinity with various but limited melt content and they could survive over 10’s to 100’s thousands of years. Within these crystal mush magma bodies, melt-dominated (>50% melt) regions, i.e. magma chambers can develop and feed volcanic activity. The presence and distribution of melt in the magma storage control the reactivation potential of a magma body. Therefore, detection of melt-bearing magma reservoir, estimation of the relative amount of melt fraction and the lifetime of magma storage is crucial to assess the level of potential volcanic hazards. However, there are still difficulties in detecting such partially molten bodies at depth. Interpretation of geophysical anomalies (e.g., low seismic velocity and/or low resistivity zones at depths) with petrologic observations, thermal modelling and zircon geochronology could offer a new methodology to characterize the nature and lifetime of the subvolcanic magmatic plumbing system. The Ciomadul volcanic dome field represents the youngest volcanism of the Carpathian- Pannonian Region. It was active between 1 Ma and 30 ka with 100-200 kyr and 10-40 kyr quiescence periods in the Old and Young Ciomadul eruptive periods, respectively. The cumulative volume of volcanic material (pyroclastic and lava rocks) is about 10 km3. Although the volcano is apparently inactive, there are many lines of evidences that reactivation cannot be unambiguously excluded. A geophysical anomaly was detected beneath it that was interpreted as a melt-bearing magma storage. A combined experimental, petrologic and thermal modelling study showed that the melt fraction could be significant with up to 50-55% in certain parts. The volcano is located

Hévíz, Hungary, 15-19 October, 2019 page 80 of 197 International Lithosphere Program close to the Vrancea zone, a geodynamically active area, where considerable seismic strain has been accumulated and deep earthquakes are common. This could be due to a descending lithospheric slab. Although the connection between the slab sinking and volcanism at Ciomadul is still unclear, it is assumed that local lithospheric ruptures could be caused by this process. Whatever is this relationship, the apparently inactive Ciomadul should be considered as a representative of a PAMS volcano, i.e. a long-dormant volcano with potentially active magma storage and therefore, it is crucial to have a better understanding how it works. Zircon is a common accessory mineral in silicic volcanic products that can easily be dated by U- Pb or U-Th geochronology and its compositional features reflect that of the equilibrated melt. These dates indicate the crystallization ages, whereas (U-Th)/He dating or other geochronological method can be used to constrain the time of eruption. Crystallization of zircons inferred from U-Pb and U-Th dates obviously precedes eruption and variation of such data provides information about the timespan of magma storage existence. We used high spatial resolution zircon geochronology (SIMS and LA-ICP-MS) and trace element analysis to reveal the lifetime and chemical evolution of this mid-upper crustal magma reservoir beneath Ciomadul. Zircons do not show significant compositional variation and crystallized mainly at 720-670°C based on Zr saturation and Ti-in- zircon thermometry. This is consistent with amphibole-plagioclase thermometry used for low-Al hornblendes and plagioclase with 30-40 mol% An content as well as Zr-in titanite thermometry results. In addition, U-Pb and U-Th dates of single eruption products show a long time interval, usually exceeding 300 kyr. These data are consistent with a protracted existence of a magmatic system in crystal mush state just above the solidus.

Hévíz, Hungary, 15-19 October, 2019 page 81 of 197 International Lithosphere Program

Zircon U-Th and U-Pb dates (i.e. inferred crystallization time) for the youngest eruptive epoch

Considering the entire zircon age data set, we can conclude that development of the magmatic system started ca. 1.5 Ma, well before the onset (1 Ma) of volcanic eruptions and was apparently continuous during the two eruptive periods and even during episodes of eruptive quiescence. Zircon crystallization model calculations adapted to the Ciomadul case suggest the existence of an upper crustal crystal mush with about 300 km3 volume and with a recharge flux of 1.5-2.3*10-4 km3/yr. This is consistent with thermal modelling results assuming emplacement of dikes and sills of basaltic composition in the lower crust for about 2 Myr followed by building up a magmatic system in the upper crust (7-15 km depth) by dacitic magmas for another 2 Myr. Our results provide further evidences that the geophysical anomaly beneath Ciomadul can

Hévíz, Hungary, 15-19 October, 2019 page 82 of 197 International Lithosphere Program indeed be interpreted as mushy magma storage at about 700-750 oC. The key element for this long-standing magma storage is the long-term magma flux even though with a low recharge value and the wet calc-alkaline compositional character of the magmatic body in the upper crust. An important point is that such magma body even with significant melt fraction can reside also beneath apparently inactive volcanoes characterized by long quiescence time and therefore it calls attention for potential reactivation even in case of such long-dormant volcanic systems. Further integrated studies involving geophysics, petrology, geochemistry, geochronology and thermal modelling could refine how such magmatic systems work and what is the triggering mechanism of the intermittent reactivation and eruption.

Hévíz, Hungary, 15-19 October, 2019 page 83 of 197 International Lithosphere Program Videologging and georeferencing of slope instabilities alog the road network using dbvl 5 (appliance)

Arjol Lule1, Shkëlqim Daja2, Shaqir Nazaj3, Eduart Murati4 (underline presenting author)

1 Faculty of Geology and Mining, [email protected] 2 Faculty of Geology and Mining, [email protected] 3 Faculty of Geology and Mining, [email protected] 4 Albanian Development Fund, [email protected] Corresponding author: [email protected]

The national road network in Albania is about 4,000 km length. Maintenance investments in road infrastructure are recently carried out. About 1350 km of national road network is subject of RRMSP-“Results-based Road Maintenance and Safety Project”, financed by World Bank. The remaining part of the national road network is maintained by Albania Road Authority. Problems related to slope instabilities are mostly identified along the entire national road network. The identification and prevention of these phenomena, resulting as dangerous and of expensive remediation, constitutes a challenge for the Albanian authorities. The aim of this paper is to present the use of DBVL 5 (Database Video-Logging 5) in creating a hazard database related to slope instabilities along national road network in Albania. The DBVL 5 is a software, performing the process of Video-Logging and geo-referencing during a single round trip. It is developed as a software which perform the automatic data collection using a digital camera (Cannon Legria FS 2000), and an Outdoor Handheld GPS (Trimble Juno SB). A continuous movie is taken during a trip and the geographic location is taken every 10 m of displacement. The software consists in dividing this movie into single images, associating the (UTM) coordinates to each image and the information is then transmitted to a GIS system. A progressive code is associated to each image, containing the ID (road code) and progressive distance from the beginning. The georeferenced imagery database obtained, for the road network, regarding the slope instabilities like landslides, rockfalls, debris flow, etc., constitutes a useful information for a preliminary hazard assessment along the road network. This software was tested in the inventory of about 3500 km of the secondary and local road network in Albania.

Hévíz, Hungary, 15-19 October, 2019 page 84 of 197 International Lithosphere Program Structure and tectonic evolution of the Congo Basin from analysis of geophysical data and 3D numerical simulations

Francesca Maddaloni (1), Damien Delvaux (2), Jessica Munch (3), Magdala Tesauro (1,4), Taras Gerya (3), and Carla Braitenberg (1)

(1) University of Trieste, Departement of Mathematics and Geosciences, Trieste, Italy, (2) Royal Museum of Central Africa, Tervuren, Belgium, (3) Institute of Geophysics, ETH Zürich, Zurich, Switzerland (4) Dept. of Earth Sciences, Utrecht University, Utrecht, Netherlands

The Congo basin (CB) is an intracratonic basin that occupies a large part of the Congo Craton (1.2million km2) covering approximately 10% of the continent [1]. It contains up to 9 km of sedimentary rocks from Mesoproterozoic until Cenozoic age. The formation of the CB started with a rifting phase during the Paleo-Mesoproterozoic period, with the amalgamation of the Rodinia supercontinent (1.2 Gyr). Afterwards, the main episodes of subsidence occurred during the subsequent post-rift phases in the Neoproterozoic, which was followed by phases of compression at the end of the Permian and during the Early Jurassic age and other sedimentation episodes during the Upper cretaceous and the Cenozoic [2]. In this study, we initially interpreted the seismic reflection profiles and well logs data located inside the central area of the CB (Cuvette Centrale), to reconstruct the stratigraphy and tectonic evolution of the basin. We compared geological and geophysical information to estimate the velocity, density, and thickness of the sedimentary layers and the depth of the lithostratigraphic units. The results have been interpolated to obtain 3D maps of velocity, density thickness and depth of the rock basement and each sedimentary layers. In this way, it was possible to get clues on the composition and rheology of the uppermost part of the crust. Afterwards, the gravity disturbance and Bouguer anomalies have been estimated from GOCE satellite derived gravity models and Eigen gravity models and using terrestrial data. From Eigen 6c4 gravity disturbance two types of anomalies have been detected: one with a long wavelength (~50 mGal) that covers the entire area of the Congo basin and a second one with a short wavelength (~130 mGal) more localized, having a NW-SE trend, which corresponds to the main depocenters of sediments detected by the interpretation of seismic reflection profiles. These results have been used as input parameters for 3D numerical simulations to test the main mechanisms of formation and evolution of the CB. For this aim, we used the thermomechanical I3ELVIS code [3] to simulate the initial rift phases. The first tests have been conducted considering the Congo craton composed of four cratonic blocks of Archean age [2] and applying a velocity of 5 cm/yr in two orthogonal directions

Hévíz, Hungary, 15-19 October, 2019 page 85 of 197 International Lithosphere Program (N-S and E-W), to test the hypothesis of the formation of a multi extensional rift in a cratonic area. We made these numerical tests for different geometries, temperature and rheology of the cratonic blocks. The results of these first numerical experiments show a progressive weakening from the center to the corners of the area, in response to extensional stress inducing the uplift of the asthenosphere.

[1] Kadima, E., Delvaux, D., Sebagenzi, S.N., Tack, L., Kabeya, S.M., (2011), Structure and geological history of the Congo Basin: an integrated interpretation of gravity, magnetic and reflection seismic data, Basin Research, Vol 23, No 5, October 2011 pp. 499 – 527, 10.1111/j.1365-2117.2011.00500.x. [2] De Wit, M.J., Stankiewicz, Jacek, Reeves, C.V., (2008), 399, 412, Restoring Pan-African-Brasiliano connections: more Gondwana control, less Trans-Atlantic corruption, 294, 10.1144/SP294.20, Geological Society, London, Special Publications. [3] Gerya, T., Introduction to numerical geodynamic modelling, Cambridge University PressT Gerya - 2009

Hévíz, Hungary, 15-19 October, 2019 page 86 of 197 International Lithosphere Program Single station analysis of microseismic noise in the Pannonian Basin

Elena Florinela Manea1, Erzsébet Győri2, Alina Coman1,3, Carmen Ortanza Cioflan1, Mircea Radulian1, István János Kovács2

1 National Institute for Earth Physics, [email protected] 2 Geodetic and Geophysical Institute, [email protected] 3 University of Bucharest, Faculty of Physics, [email protected] Corresponding author: [email protected]

The Pannonian Basin is located in the Eastern part of Central Europe and is one of the largest Neogene sedimentary basins in Europe. The seismicity along this area is moderate and large events don’t occur very often, a magnitude 6 earthquake is about once every 100 years, while a magnitude 5 event appears on average every 20 years (Tóth et al., 2008). In the context of rapid urban development of the region, recurrence of similar events would pose a high/significant seismic risk on the exposed communities. Although very strong (M>6) events are rare in this region, estimation of the impact of such events on buildings and life-line systems requires accurate evaluation of local seismic response. In this study, local site investigations were performed along the Pannonian Basin, in order to map and interpret local parameters as fundamental frequency of S-wave resonance by correlating and interpolating the results obtained from single station measurements with the available geological data. The horizontal-to-vertical Fourier spectral ratio (Nogoshi and Igarashi, 1971; Nakamura, 1989) was primarily applied to assess the variability of the fundamental frequency of resonance over the Pannonian Basin. These results were interpreted according to the available geophysical/geological information in order to extract essential information and to trace out the geometry of Pannonian Basin. Single station analysis was performed for 73 seismic stations, among these: 26 stations deployed during South Carpathian Project - SCP (2009-2011, Ren et al., 2012), 26 Carpathian Basin Project - CBP (2005-2007, Dando et al., 2011) and the rest of them belong to different countries seismic networks (2 - Slovenia, 2 - Serbia, 6 - Hungary, 1 - Croatia, 1 - Slovakia, 9 - Romania). The aspect of the computed H/V ratios over the entire area shows the existence of lateral variations within the subsoil of the Pannonian Basin and exhibit multiple peaks. The fundamental frequency of S-waves resonance varies between 0.1 and 6.2 Hz (Figure 1) and corresponds to the interface between the Miocene–Pliocene sediments (Horváth et al., 2006; Balázs et al., 2015). A second peak in the H/V ratios was observed, between 0.6 and 10 Hz (Figure 2), and its depth

Hévíz, Hungary, 15-19 October, 2019 page 87 of 197 International Lithosphere Program corresponds to Quaternary-Pliocene interface (Horváth et al., 1999). Hévíz, Hungary, 15-19 October, 2019 page 2 of 2 International Lithosphere Program

Figure 1. Distribution of fundamental frequencies of resonance over the entire area.

Figure 2. Distribution of first higher peak over the entire area.

Hévíz, Hungary, 15-19 October, 2019 page 88 of 197 International Lithosphere Program The information about these interfaces, will offer new and significant perspective on the quantification of its influence on the seismic site response on the Pannonian Basin and in this way to minimize their uncertainties in seismic hazard evaluation.

Hévíz, Hungary, 15-19 October, 2019 page 89 of 197 International Lithosphere Program The tectonic significance of the pre-salt wedge along the Angolan Passive Margin: implications on rifting style and tectonic processes.

Gyorgy Marton 1, Gabor Tari 2

1 Marton Geoconsulting / Pannon Imaging 2 OMV Corresponding author: Gyorgy Marton [email protected]

During the last two decades’ significant advancements have been made in area of continental margin studies. Because of their economic significance, salt basins, such as the Gulf of Mexico and the South Atlantic were given particular attention. Despite of the large amount of data gathered in the inboard portion of these basins, the details of rift evolution and rift-drift transition remain model driven and often speculative. Outboard, lack of direct well control and the masking effect of salt on the seismic makes it increasingly difficult to decipher the exact nature of the rocks and to understand the underlying tectonic processes. Observations made in the inboard rift domains, and the extrapolation of the findings to the outboard domain still remain critical to unravel the geological complexities of the whole system.

A previous research (Marton et. al, 2000), focused on the post-salt structural styles along the Angolan passive margin. The objective of the current paper is to document the major tectono- stratigraphic sequences in the pre-salt section and to put the early evolution of the margin in the context of an “asymmetric” rift. During the Neocomian rifting phase, inboard, a large amount of extension ( basement in the offshore Cabinda area reveals “domino style” faulting. Rift faults initiated at a standard 60 degrees, but as extension progressed, both strata and faults rotated to accommodate the increasing amount of extensional strain. At the end of the rifting, due to fault rotation, dips on the large normal faults decreased to about 20-30 degrees. The syn-rift sedimentary record includes

Hévíz, Hungary, 15-19 October, 2019 page 90 of 197 International Lithosphere Program the Lucula, Erva, and Lower Bucomazi Formations. Well drilled into basement in the Malongo area documents up to 40 degree NE dips in the early syn-rift Lucula Formation. This large dip is related to the rotation of the underlying basement blocks and the overlying sediments. Dip meter data changes from large NE dips to low W dips at about the Neocomian-Barremian boundary. This angular unconformity is interpreted as the “post-rift” unconformity in the Malongo sub-basin. Above the post-rift unconformity, the Barremian to Early Aptian age Mid to Upper Bucomazi, Toca and Chela formations were deposited in a thermally subsiding sag basin. These formations informally are lumped together and referred to as the “pre-salt wedge” in offshore Angola. It reaches up-to 3 km thickness in the central part of the basin. The pre-salt wedge is observed to thin both landward and seaward and interpreted to represent a sedimentary cycle prior to final break-up. Exact timing of the break-up is uncertain in this part of the South Atlantic but occurred no sooner than Aptian salt deposition. Indeed, restoration of transect “B” shows that both the pre-salt wedge and the Loeme salt were deposited in a sag basin and that salt pinches out against an “outer high” at the continent-ocean boundary. Latter relationship is well documented on available multi-channel seismic data. Thus, the Barremian to Aptian pre-salt wedge is observed to be an un-faulted tectonostratigraphic unit representing about ~10 My sedimentation in a thermally subsiding sag basin. In other words, the pre-salt wedge, including the Aptian salt, is a distinct tectonostratigraphic unit which deposited between the post-rift and break-up unconformities in offshore Angola. In the light of the above observations, the rift-drift evolution of the Angolan passive margin can be described by a three step extension process: During the Neocomian rifting, the large amount of upper crustal extension inboard was balanced by lower crustal to mantle lithospheric extension outboard. In response to the upper crustal extension and subsidence, inboard, the Neocomian syn-rift section was deposited. The end of the inboard rifting phase is documented by the early Barremian post-rift unconformity. Since inboard there was limited amount of mantle lithospheric extension, the ensuing thermal subsidence was also limited. Outboard, due to the increased amount of mantle lithospheric extension we expect uplift, non-deposition / erosion. During the Barremian to Aptian significant extension was localized outboard at the area of future break-up. There, due to the large amount of mantle lithospheric extension we expect continued uplift, erosion and non-deposition. During this time the pre-salt wedge and the salt was

Hévíz, Hungary, 15-19 October, 2019 page 91 of 197 International Lithosphere Program deposited in a 2-300 km wide thermally subsiding sag basin. The limit of deposition of this section is the rift shoulder to the east and the continent-ocean transition area to the west. The thickest pre-salt wedge (up-to 3 km thick) occurs roughly in the central portion of the examined transects (or about 200 km offshore). The pre-salt wedge sediments may have dual provenance, as clastic material can be derived from both the continental interior and from the emergent area at the proto Mid-Atlantic Ridge. The breakup occurred around the time of the Aptian salt deposition. When observed, the autochthonous salt pinches out against an “outer high”, which also coincides with the magnetically defined continent-ocean boundary. Ensuing thermal subsidence and gradual seaward tilt of the margin started in the Albian. The above analysis is based on the observations made along the Angolan margin only. Other studies, in an attempt to reconcile the tectonic setting with the conjugate passive margin on the Brazilian side use slightly different observation-based (Unternehr et. al, 2010) and modeling based approaches (Brune et. al, 2014). All these models, including ours, suffer from the uncertainties about the nature and exact configuration of the continent-ocean transition, which is often masked by the thick and inflated autochthonous and by the largely redistributed allochthonous salt. On the other hand, all these models agree that observed tectonic structures and the distribution of pre- salt stratigraphic sequences can’t be explained by the classical McKenzie model. Furthermore, all the modern models invoke “asymmetry” in the evolution of the Angolan margin. Asymmetry is proposed in the mode of extension, as lateral transfer of extension from the upper crust inboard to the lower crust/mantle outboard. Final breakup occurred at the area of maximum mantle lithospheric extension. The pre-salt wedge offshore Angola, on one hand, records the time delay between the abandonment of the inboard rifts and the actual continental breakup outboard. On the other hand, its presence points to unequal amount of stretching of the crust and lithospheric mantle along the rifted continental margin of Angola.

McKenzie, D., 1978, Some remarks on the development of sedimentary basins, Earth and Planetary Science Letters (Elsevier) 40: 25–32. Marton et. al, 2000, Evolution of the Angolan Passive Margin, West Africa, with Emphasis on Post-Salt Structural Styles, Atlantic Rifts and Continental Margins, Geophysical Monograph 115, p. 129-149. Unternehr et.al, 2010, Hyperextended crust in the South Atlantic: in search of a model, Pet. Geosci. 16, 207–215. Brune et. al, 2014, Rift migration explains continental margin asymmetry and crustal hyperextension. Nature Communications 5, Article number: 4014

Hévíz, Hungary, 15-19 October, 2019 page 92 of 197 International Lithosphere Program Multi-Scale Depositional Successions in Tectonic Settings

Liviu C. Matenco1 and Bilal U. Haq2,3

1 University of Utrecht, Department of Earth Sciences, The Netherlands, [email protected] 2 Sorbonne University, Institute of Earth Sciences, Paris, France, [email protected] 3 Smithsonian Institution, Department of Paleobiology, Washington, DC, USA Corresponding author: [email protected]

Observations in sedimentary basins affected by significant amount of deformation shows that the fault-induced depositional space, at various spatial and temporal scales, is closely linked to the basin kinematics. The tectonically-driven sediment infill reflects the history of deepening and shoaling facies controlled by the activation and changes in the fault’s offset rates. Simply stated, this translates as shifting sedimentary facies towards the basin center or towards the source area in response to increasing or decreasing depositional space. We propose a first-principle conceptual model for tectonic successions, controlled by the balance between the rates of creation of depositional space and sediment supply. These sediment bodies are bounded by succession boundaries and comprise basinward or sourceward shifting facies tracts that are separated at a point of reversal. Due to the relatively steep slopes associated with the evolution of faults, changes in sediment supply rates and mass-wasting is common phenomena in these systems and may complicate the normal rhythm of the shifting facies tracts. Once tectonic quiescence is achieved, and if the basin is connected to the open ocean, eurybatic or eustatic changes may take over and play a greater role in sediment deposition and cyclicity. The efficacy of the new concept is illustrated by examples from extensional, contractional and strike-slip basins. The basic tectonic succession model is applicable at all temporal and spatial scales and whether the tectonics cause subsidence or uplift, and in all types of tectonic settings that drive the evolution of sedimentary basins.

Hévíz, Hungary, 15-19 October, 2019 page 93 of 197 International Lithosphere Program Imaging of subducting Philippine Sea plate beneath the Tokai region, repeatedly megathrust earthquakes region.

Makoto Matsubara1, Hisatoshi Baba2, Hiroshi Sato3, Takahito Nishimiya4

1 National Researchi Institute for Earth Science and Disaster Resilience, [email protected] 2 Tokai University, [email protected] 3 Earthquake Research Institute, the University of Tokyo, [email protected] 4 Meteorological Research Institute, Japan Meteorological Agency, [email protected] Corresponding author: [email protected]

I. Introduction The Philippine Sea (PHS) Plate subducts to northwestward beneath the Eurasian (EUR) Plate from the Suruga Trough within the Suruga Bay. The Fujikawa-kako Fault Zone (FKFZ) continues to the north of the Suruga Trough. The megathrust earthquakes repeatedly occurred at this boundary and FKFZ may cause earthquake with the megathrust earthquake. The configuration of Tokai region is important to estimate the strong motion caused by the earthquake. Matsubara et al. (2017; 2019) analysed the seismic velocity structure beneath the whole Japanese Islands using the permanent seismic stations operated by National Research Institute for Earth Science and Disaster Resilience (NIED), Japan Meteorological Agency (JMA), national universities, and so on. In this study we analysed the seismic velocity structure beneath the Tokai megathrust earthquake region with the temporary Ocean Bottom Seismometer (OBS) date operated by Tokai University and Meteorological Research Institute (MRI) in addition to the data from the permanent seismic stations. 2. Data and methods The target region is 136°-139°E, 34-36°N, covering the Suruga Bay and Tokai region. We selected a earthquake having the largest number of picking data from each box with the size of 0.01°x0.01°x1 km. We used 3,025,189 P and S-wave arrival time data from 36,632 natural earthquakes, 92 arrival time data from four blasts, and 1,526 arrival time data from 181 earthquakes detected by OBS data. We used the seismic tomographic method (Zhao et al., 1992) with consideration of smoothing and station corrections (Matsubara et al. 2004; 2005).

Hévíz, Hungary, 15-19 October, 2019 page 94 of 197 International Lithosphere Program 3. Results and discussions Figure 1 shows cross section of P-wave velocity perturbation from Izu Peninsula to Tokai region across Suruga Bay and Suruga Trough. The shallow part at depths of 5-10 km beneath the Suruga Bay is also analysed owing to the OBS data.

Tokai region

Suruga Bay

(a ( ) b) P-wave velocity perturbation

Figure 1. Map views of P-wave velocity perturbation at depths of (a) 5 and (b) 10 km.

P-wave Velocity perturbati on

Figure 2. EW vertical cross section of (a) P-wave velocity perturbation with hypocentre and (b) P-wave velocity with low-angle thrust focal mechanism at a latitude of 34.9°. Subducting PHS plate is composed of low-velocity oceanic crust and high-velocity oceanic mantle. Seismic tomogram shows low velocity oceanic crust at the uppermost part of the PHS

Hévíz, Hungary, 15-19 October, 2019 page 95 of 197 International Lithosphere Program plate subducting from the Suruga Trough (Fig. 2). The earthquakes at the plate boundary of the PHS and EUR plates mostly have low-angle thrust type focal mechanism. We can estimate the configuration of the upper boundary of the PHS plate with consideration of hypocenters and low- angle thrust type earthquakes.

5. Conclusion The permanent seismic stations on land and temporal seismic stations beneath the Suruga Bay contribute to clarify the seismic velocity structure beneath the Tokai region where the megathrust earthquake is predicted to occur. Seismic tomogram shows the subducting PHS plate with low- velocity oceanic crust and high-velocity oceanic mantle. Seismic tomogram, hypocentre distribution of microseismicity, and low-angle thrust type earthquakes will contribute to construct the configuration of the PHS plate.

Hévíz, Hungary, 15-19 October, 2019 page 96 of 197 International Lithosphere Program In search of a fossil plate boundary of Baltica – the Teisseyre-Tornquist Zone revisited

Stanislaw Mazur1, Michał Malinowski2, Mateusz Mikołajczak1, Piotr Krzywiec1

1 Institute of Geological Sciences, Polish Academy of Sciences, [email protected] 2 Institute of Geophysics, Polish Academy of Sciences, [email protected] Corresponding author: [email protected]

The Teisseyre-Tornquist Zone (TTZ) is the longest European tectonic and geophysical lineament extending from the Baltic Sea in the NW to the Black Sea in the SE (Fig. 1). This transcontinental feature is clearly visible in seismic refraction data as a transition zone form the thick Precambrian crust of the East European Craton (EEC) to the thinner crust of the Palaeozoic Platform of Western Europe. The TTZ is evident from the seismic data as a perturbation of the Moho depth as well as from magnetic and gravity anomaly maps and heat flow distribution.

Figure 1. Simplified tectonic map of Central Europe showing the extent of the East European Craton and the main structural elements after Mikolajczak et al. (2019). Base map modified from several sources including Bogdanova et al. (2008). Mixed orange and pale pink stripes mean Baltica margin covered by the Variscan belt and its foreland basin. A-CDF – Alpine-Carpathian Deformation

Hévíz, Hungary, 15-19 October, 2019 page 97 of 197 International Lithosphere Program Front; CDF – Caledonian Deformation Front; GF – Grójec Fault; KLF – Kraków-Lubliniec Fault; PC – Pomeranian Caledonides (horizontal hatching); STZ – Sorgenfrei-Tornquist Zone; TTZ – Teisseyre- Tornquist Zone; VDF – Variscan Deformation Front.

For over a century, the TTZ has been considered a fossil plate boundary of the EEC corresponding to the limit of early Palaeozoic palaeocontinent Baltica. The nature of the TTZ has remained unresolved for a long time due to the lack of adequate data on its in-depth architecture. This situation has changed with the emergence of the first high-resolution reflective seismic profiles imaging the structure of the SW slope of the EEC. We present the results of quantitative interpretation of gravimetric and magnetic data, integrated with the interpretation of seismic reflection profiles from PolandSPAN™ survey to explain whether the TTZ is a tectonic boundary of the EEC.

Figure 2. Potential field anomaly maps for the territory of Poland. The coordinate system used is Poland 1992. (A) – Bouguer gravity anomaly map. The gravity data were derived from gravity ground stations and gridded at 2000 m interval. The Bouguer correction reduction density is 2.67 g/cm3. (B) – Magnetic anomaly reduced to the pole (RTP). The total magnetic intensity grid was compiled from ground and airborne surveys and gridded at 500 m interval and upward continued to 500 m mean terrain clearance. KL – Kuyavian Gravity Low, PL – Pomeranian Gravity Low, TTZ – Teisseyre-Tornquist Zone.

Our data indicate the continuation of the Precambrian basement of the EEC and its lower Palaeozoic cover toward the SW underneath the Palaeozoic Platform. Potential field modelling also suggests the occurrence of a crustal keel underneath the TTZ. These results imply the location of a Caledonian tectonic suture (Thor Suture), marking the site of the collision between Avalonia and

Hévíz, Hungary, 15-19 October, 2019 page 98 of 197 International Lithosphere Program Baltica, not along the TTZ, but farther SW, in NE Germany and SW Poland. Consequently, the extensive Permo-Mesozoic sedimentary basin of western Poland is established above the attenuated margin of the Baltica palaeocontinent. New geophysical evidence suggests which the TTZ was formed in the latest Precambrian as a crustal necking zone during Ediacaran rifting and break-up of the Tornquist Ocean. The study highlights the value and importance of regional deep reflection profiles, such as the PolandSPAN™ survey and the POLCRUST-01 line, since they revived the debate on the nature of the TTZ.

Bogdanova SV, Bingen B, Gorbatschev R, Kheraskova TN, Kozlov VI, Puchkov VN, Volozh YA (2008) The East European Craton (Baltica) before and during the assembly of Rodinia. Precambrian Research 160 (1): 23–45. Mikołajczak M., Mazur S. Gągała Ł (2019) Depth-to-basement for the East European Craton and Teisseyre-Tornquist Zone in Poland based on potential field data. International Journal of Earth Sciences 108(2): 547–567.

Hévíz, Hungary, 15-19 October, 2019 page 99 of 197 International Lithosphere Program The Apulia-Southern Apennines orogenic system during Pliocene-Quaternary times (Central Mediterranean)

Alfonsa Milia1, Pietro Iannace2, Maurizio M. Torrente3

1 ISMAR-CNR, [email protected] 2 free-lance geologist, [email protected] 3 DST-Università del Sannio, [email protected] Corresponding author: [email protected]

Since 30 Ma the convergence between Africa and Eurasia plates controlled the geodynamic evolution of Central Mediterranean and led to the formation of orogenic systems and back-arc basins (e.g. Gueguen et al. 1998; Faccenna et al., 2014). During the Plio-Quaternary the Southern Apennines thrust belt migrated toward the Apulia foreland simultaneously with the opening of the Tyrrhenian Sea back-arc basin (Patacca and Sandone, 2001; Sartori, 2003). Many studies concern the single geodynamic sectors, or the areas between two adjacent sectors, but a complete documentation of the relationship between the Apulia foreland, the accretionary prism and the back arc is still absent. The goal is to furnish a holistic view of the Central Mediterranean foreland- accretionary prism-backarc system and a Pleistocene change from an uncoupled to a coupled system during the postcollision stage. Our study area includes the offshore parts of the Southern Apennines chain and in particular the Taranto Gulf and Tyrrhenian Sea (Fig. 1). The interpretation of seismic reflection profiles, well data and the use of a dedicated GIS software permitted to reconstruct a detailed stratigraphic analysis, the structural pattern, and to create 2-D and 3D geological models of the primary geological surfaces from the foreland to backarc.

Hévíz, Hungary, 15-19 October, 2019 page 100 of 197 International Lithosphere Program

Fig. 1 Morpho-bathymetric and tectonic map of Italy and adjacent seas showing the study area and the transition between Ionian and Apulia crust (the physiographic map is from Brosolo et al., 2012).

Our geological analysis of the Central Mediterranean orogenic system (Milia et al., 2017a), combined with that of the Tyrrhenian Sea backarc (Milia and Torrente, 2015; Milia et al., 2017b, 2017c), and our Pliocene-Pleistocene paleogeographic maps led us to several findings. - The Apulia foreland features a complex fault pattern associated to two main tectonic stages: lower Pleistocene transtensional tectonics; middle-upper Pleistocene shortening/transpression. - The Southern Apennines accretionary prism, significantly developed during Pliocene-lower Pleistocene, is displaced by late lower-middle Pleistocene left-lateral faults parallel to the orogen (Monaco et al., 2001). - The Pliocene-Pleistocene evolution of this orogenic system was episodic and not continuum. The change from collision stages, featuring uncoupled plates, to postcollision stages occurred at 1.0 Ma,

Hévíz, Hungary, 15-19 October, 2019 page 101 of 197 International Lithosphere Program when the continental plates coupled and reorganized contemporaneously to activity of transcurrent faults. - The Pleistocene Central Mediterranean plates reorganization was likely due to the rupture of the Apulia/Ionian slab (Westaway, 1993; Wortel and Spakman, 2000; Milia et al., 2017c.), or to NNW-trending intraplate shortening transmitted from Africa (Bonini et al. 2011).

Bonini, M., F. Sani, G. Moratti, and M.G. Benvenuti (2011), Quaternary evolution of the Lucania Apennine thrust front area (southern Italy), and its relations with the kinematics of the Adria Plate boundaries, J. Geodyn., 51, 125–140. Brosolo, L., J. Mascle, and B. Loubrieu (2012), Morpho-bathymetry of the Mediterranean Sea, scale: 1:4000000, publication CGM/CGMW, UNESCO, Paris. Faccenna, C., et al. (2014), Mantle dynamics in the Mediterranean, Rev. Geophys., 52, doi:10.1002/2013RG000444. Gueguen, E., Doglioni, C., Fernandez, M., 1998. On the post-25 Ma geodynamic evo-lution of the western Mediterranean. Tectonophysics 298, 259–269. Milia, A., and M. M. Torrente (2015), Tectono-stratigraphic signature of a rapid multistage subsiding rift basin in the Tyrrhenian-Apennine hinge zone (Italy): A possible interaction of upper plate with subducting slab, J. Geodyn., 86, 42–60, doi:10.1016/j.jog.2015.02.005. Milia, A., M. M. Torrente, and P. Iannace (2017a), Pliocene-Quaternary orogenic systems in Central Mediterranean: The Apulia-Southern Apennines-Tyrrhenian Sea example, Tectonics, 36, 1614–1632, doi:10.1002/2017TC004571. Milia, A., P. Iannace, M. Tesauro, and M. M. Torrente (2017b), Upper plate deformation as marker for the Northern STEP fault of the Ionian slab (Tyrrhenian Sea, central Mediterranean), Tectonophysics, 710–711, 127–148, doi:10.1016/j.tecto.2016.08.017. Milia, A., M. M. Torrente, and M. Tesauro (2017c), From stretching to mantle exhumation in a triangular backarc basin (Vavilov basin, Tyrrhenian Sea, western Mediterranean), Tectonophysics, 710–711, 108–126 doi:10.1016/j.tecto.2016.10.017. Monaco, C., L. Tortorici, S. Catalano, W. Paltrinieri, and N. Steel (2001), The role of Pleistocene strike-slip tectonics in the Neogene-Quaternary evolution of the southern Apennine orogenic belt: Implications for oil trap development, J. Pet. Geol., 24, 339–359. Patacca, E., and P. Scandone (2001), Late thrust propagation and sedimentary response in the thrust belt-foredeep system of the Southern Apennines (Pliocene-Pleistocene), in Anatomy of a Mountain Belt: The Apennines and Adjacent Mediterranean Basins, edited by G. B. Vai and I. P. Martini, pp. 401–440, Kluwer Acad. Publ., Dordrecht. Sartori, R., (2003), The Tyrrhenian back-arc basin and subduction of the Ionian lithosphere. Episodes 26 (3), 217–221. Westaway, R. (1993), Quaternary uplift of southern Italy, J. Geophys. Res., 98(B12), 741–772, doi:10.1029/93JB01566. Wortel, M. J. R., and W. Spakman (2000), Subduction and slab detachment in the Mediterranean-Carpathian region, Science, 290, 1910–1917, doi:10.1126/science.290.5498.1910.

Hévíz, Hungary, 15-19 October, 2019 page 102 of 197 International Lithosphere Program Eruption chronology of the Ciomadul volcanic complex constrained by zircon geochronology

Kata Molnár1,2, Réka Lukács3, István Dunkl4, Axel K. Schmitt5, Ioan Seghedi6, Szabolcs Harangi1,3

1 Department of Petrology and Geochemistry, Eötvös Loránd University, Budapest, Hungary 2 Isotope Climatology and Environmental Research Centre, Institute for Nuclear Research, Hungarian Academy of Sciences, Debrecen, Hungary 3 MTA-ELTE Volcanology Research Group, Budapest, Hungary 4 Sedimentology and Environmental Geology, Geoscience Centre, Georg-August University, Göttingen, Germany 5 Institute of Earth Sciences, University of Heidelberg, Germany 6 Institute of Geodynamics, Romanian Academy, Bucharest, Romania Corresponding author: [email protected]

Combined zircon U-Th-Pb and (U-Th)/He dating was applied to refine the eruption chronology of the last 2 Myr for the andesitic and dacitic Pilişca volcano and Ciomadul volcanic dome field (CVDF), the youngest volcanic area of the Carpathian-Pannonian region, located in the southernmost segment of the Călimani-Gurghiu-Harghita volcanic chain (Eastern Carpathians, Romania). The proposed eruption ages, which are supported also by the youngest zircon crystallization ages, are much younger than the previously determined K/Ar ages. By dating every known eruption center in the CVDF, repose times between eruptive events were also accurately determined. Eruption of the andesite at Murgul Mare (1865 ± 87 ka) and dacite of the Pilişca volcanic complex (1640 ± 37 ka) terminated an earlier pulse of volcanic activity within the southernmost Harghita region, west of the Olt valley. This was followed by the onset of the volcanism in the CVDF, which occurred after several 100’s kyr of eruptive quiescence. Based on combined zircon U-Th and (U-Th)/He geochronology, volcanism of the Ciomadul volcanic dome field is divided into two main eruptive periods: Old Ciomadul (1 Ma – 300 ka; OCEP) and Young Ciomadul Eruptive Period (160-30 ka; YCEP). OCEP activity comprises three Eruptive Epochs which are characterized by small-volume lava dome formations and prolonged (ca. 100 to 200 kyr) quiescence periods. Eruptive Epoch 1 comprises the formation of four lava domes with distinct chemical compositions occurring in a restricted area, a few km’s from each another: the high-K–calc-alkaline, dacitic Baba-Laposa dome (942 ± 65 ka), the two shoshonitic Malnaş and Bixad domes (964 ± 46 ka and 907 ± 66 ka, respectively) and the high-K–calc-alkaline, andesitic Dealul Mare dome (842 ± 53 ka). The oldest, ca. 1 Ma lava domes of the Ciomadul volcanic dome field follow a NNE-SSW tectonic lineament along the Olt valley. After ca. 200 kyr of quiescence two other high-K–calc-alkaline dacitic lava domes extruded comprising the Eruptive Epoch 2 (Puturosul:

Hévíz, Hungary, 15-19 October, 2019 page 103 of 197 International Lithosphere Program 642 ± 44 ka and Balvanyos: 583 ± 30 ka). After another >100 kyr of repose time, the dacitic Apor lava flow erupted at 344 ± 33 ka. No other eruption event known at that time, although it cannot be excluded that such deposits are covered by subsequent lava domes of the Ciomadul. Thus, the Eruption Epoch 3 is composed of probably only one single eruption. Young Ciomadul Eruptive Period (YCEP) activity comprises Eruptive Epochs 4 and 5. The extrusion of most of the lava domes occurred between 160 and 90 ka (Eruptive Epoch 4) forming the main part of the Ciomadul volcanic complex. Eruptive Epoch 4 can be subdivided into three eruptive episodes at ca. 155, 135, and 95 ka (Eruptive Episodes 4/1, 4/2 and 4/3, respectively). The lava domes extruded along a NE-SW lineament, which is perpendicular to the regional NW-SE trend of the Călimani-Gurghiu-Harghita volcanic chain. Eruptive Epoch 5 occurred after a ca. 40 kyr of quiescence at ca. 55-30 ka, and is mainly characterized by explosive eruptions with a minor lava dome building activity. Most of the newly dated pyroclastic outcrops (KH, 226, DP, 205b), together with the Tf outcrop (Harangi et al., 2015a) and the lava dome of Piscul Pietros, belong to the older Eruptive Episode 5/1, with an eruption age of 55-45 ka. The two distal pyroclastic outcrops (201b, 202) together with the Bx and Vp outcrops comprise the Eruptive Episode 5/2 with an eruption age at ca. 34-30 ka. The eruption centers of Eruptive Epoch 5 are located at the junction of the conjugated NW-SE and NE-SW lineaments defined by the older eruptive centers. The whole-rock geochemistry of studied samples from the Ciomadul volcanic complex is fairly homogeneous (SiO2 = 63-69 wt%, K2O = 3-4 wt%). It also overlaps with the composition of the lava domes of the Old Ciomadul Eruptive Period, which implies for tapping a compositionally monotonous magma for the past 1 Myr. The eruption rates for the Ciomadul volcanism were determined based on the erupted lava dome volume calculations, supplemented with the eruption ages. The activity peaked during the Eruptive Epoch 4 (160-90 ka), having an eruption rate of 0.1 km3/kyr. In comparison, these values are 0.05 km3/kyr for the YCEP (160-30 ka) and 0.01 km3/kyr for the overall Ciomadul volcanism (1 Ma – 30 ka). Based on the geochemical characteristics, the quiescence periods and the lifetime of the complex, as well as the relatively small amount of erupted material, this volcanic system can be placed in a subduction-related post-collisional geodynamic setting, which shows strong chemical similarities to continental arc volcanism. The commonly observed long repose times between the active phases suggest that the nature of a volcano cannot be understood solely based on the elapsed time since the last eruption. Instead, comprehensive geochronology, coupled with the understanding of the magma storage behaviour could be a base of hazard assessment for volcanic fields, where the last eruptions occurred several

Hévíz, Hungary, 15-19 October, 2019 page 104 of 197 International Lithosphere Program 10’s of thousand years ago and therefore they are not considered as potentially active. This research on the Ciomadul volcano belongs to the scientific project supported by the NKFIH- OTKA (Hungarian National Research Fund) No. K116528.

Hévíz, Hungary, 15-19 October, 2019 page 105 of 197 International Lithosphere Program Integrated basin modelling (stratigraphic/thermal) for better understanding rocks and fluids evolution in sedimentary basins: Lessons learnt from Mediterranean and Middle East case studies

Fadi Henri Nader

IFP Energies nouvelles, Rueil-Malmaison – France, [email protected] Extraordinary Chair on Multi-Scale Fluid-Rock Interactions –Univeristy of Utrecht Corresponding author: [email protected]

Sedimentary basins host a large variety geo-resources and have often been the locations of major human settlements. Their sediments and fluids have recorded the influence of the principal extrinsic and intrinsic geodynamic and structural processes as well as climatic changes over geologic times. Hence, understanding quantitatively their genesis and deformation is a major challenge for sustainable development of related geo-resources, and for predicting the impacts of climatic changes and geohazards on societies. The genesis of sedimentary basins is inherently associated with subsidence which creates accommodation space for infilling sediments. Thereby, a variety of inter-related, multi-scale factors prevail, including deeper lithospheric processes (e.g. crustal stretching and rifting), shallower, localized tectono-sedimentary developments (e.g. extensional regimes, sediment transport and loading), and climatic conditions (e.g. arid/humid, latitudinal position). Moreover, sedimentary basins may be classified based on their locations within plate-tectonics context (e.g. inter- or intra- plate, type of plate boundaries). After the creation of such basins and their infill with sediments (including organic matter) and fluids, they may be deformed through inversion associated with compressional tectonic regimes and orogenesis. Such processes also have major effects on the rocks and fluids constituting the basin infill, resulting in economically viable geo-resources. Numerical modelling techniques have been developed and applied to solve specific problems related to the inter-related processes summarized above. For example, crustal modelling helps in constraining the depth of Moho and the Lithosphere-Asthenosphere Boundary (LAB) – both crucial for the subsidence mechanics and relative heating of the overlying sedimentary basins. Stratigraphic forward modelling is capable of quantifying the source-to-sink sediment infill (clastics and carbonates). This approach was used, for instance, to test different scenarios of sources of sediment influx feeding the Mesozoic-Cenozoic Levant Basin (East-Mediterranean region), following a source to sink, process-based approach. New developments also allowed the simulation of organic matter distribution throughout the basin. Thermal/burial modelling has been applied on the Permo-Triassic, Khuff carbonate reservoirs in the Middle East (UAE and Iran) in

Hévíz, Hungary, 15-19 October, 2019 page 106 of 197 International Lithosphere Program order to quantify the evolution of fluid-flow and fluid-rock interactions. Otherwise, thermal modelling is routinely used to assess the generation and accumulation of hydrocarbon as well as the applicability of geothermal energy projects. This numerical approach is based on “back- stripping” techniques, whereby the present-day structural architecture of the basin (used as input data), is sequentially restored to the past configurations. Other numerical tools were specifically developed to address this challenge, and were subsequently applied on complex fold and thrust belts. We will discuss a few examples from the Albanides and Dinarides orogens. Of course this approach can be coupled with forward sand-box modelling experiments, with the objective to deform the basinal layering sequentially from deposition until present-day configurations. Finally, all the listed numerical tools provide multi-realisations (i.e. a variety of solutions) rather than a unique solution. Therefore, uncertainty analysis becomes necessary to comprehend the whole amount of gained information. This contribution will present the integrated modelling workflow that was applied on the Levant Basin (Figure 1), in addition to some of the case-studies that are mentioned above. This workflow includes crustal modelling, source to sink stratigraphic forward simulations, thermal and burial evolutions and uncertainty analyses. The Levant Basin model covers a surface areas of some 200,000 sq. km, with horizontal cells grid resolution of 5 sq. km and less than 50m thick. The objective of this workflow is to produce reasonable multi-scenario simulations and probabilistic information that can help make sound decisions for less risky hydrocarbon exploration. Alternatively, the same approach can be applied to better understand sedimentary basins for developing hydrothermal energy resources and/or carbon and energy storage elsewhere.

Hévíz, Hungary, 15-19 October, 2019 page 107 of 197 International Lithosphere Program

Figure 1. Schematic illustration of the integrated basin (stratigraphic/thermal) modelling workflow that has been designed and applied on the Levant basin (Eastern-Mediterranean region).

An “integrated workflow” is not limited to the stacking of a variety of numerical tools, but it also involves a multi-disciplinary concept-thinking. To reach that end, a unique working environment has to be developed, securing the following steps: i) basic characterization/integration of all available geological, geophysical and geochemical data (leading to conceptual models); ii) sedimentary facies modelling (with stratigraphic forward numerical engines); iii) structural characterization and modelling (deformation, inversion and faults); iv) burial/thermal and petroleum systems modelling; and v) uncertainty analysis and modelling (risk management). Bridging the gap between geophysicists, sedimentologists, structural geologists, geochemists, petroleum geologists, and geo-modellers, is a must for achieving integrated concepts and thereafter numerical models.

Hévíz, Hungary, 15-19 October, 2019 page 108 of 197 International Lithosphere Program Tectonic modelling of Ionian zone and some considerations to its relationship with Sazani and Kruja tectonic zones

Msc Dhurata Ndreko1, Prof. Ass Agim Mësonjësi1, Prof. Dr Shaqir Nazaj1

1 Polytechnic University of Tirana, Geology and Mining Faculty, Tirana; Albania Corresponding author: [email protected]

This paper deals with some general considerations on the geological-tectonic modelling of the Ionian zone, especially of its central part, Patos-Verbas area (Figure 1). The Ionic Zone is represented by three sedimentary complexes: -Permo-Triassic evaporitic complex -Triassic-Eocene carbonate complex -Eocene-Quaternary terrigenous complex The deposits of the Ionian tectonic zone can be divided into two large megasequences: the lower one is represented by the deposits from Permo-Triassic to the Lower and Middle Liassic, which are considered as deposits of neritic facies and the upper megasequence which is represented by the post-rift deposits of Toarian to Paleocene in age. These post-rift deposits are interpreted as of pelagic facies within Ionian tectonic zone, while in Kruja and Sazani tectonic zones they belongs to neritic facies (Figure 2). The deposits both these megasequences belong to the passive edge of the Adria tectonic microplate. This passive edge has been like a very wide carbonate platform until the end of Lower and Middle Liassic time.After this time, as a result of rifting process, the tectonic model is represented by the presence of some half rotated horst and graben system of structures. The sedimentation of neritic facies continued on the horst structures, like in Sazani and Kruja tectonic zones, while the sedimentation of pelagic facies started within Ionian tectonic zone (“schists with Posidonia”, “Ammonitico rosso”), which are transgressively placed over the tops of the horst tectonic blocks. This kind of sedimentation of the pelagic facies continued until the end of Paleocene-Eocene time within Ionian tectonic zone. The big changes in thickness and facies variations, which are documented for the Triassic- Liassic deposits of Ionian zone, can be well explained with the presence of the big bended platformic carbonate or dolomitic blocks of the pre-rifting megasequence. These big bended platformic carbonate/dolomitic blocks resulted as consequence of the presence of tensile stress during the first stage of the rifting process. The Ionian zone in Albania can be divided into three major structural subzones from East to

Hévíz, Hungary, 15-19 October, 2019 page 109 of 197 International Lithosphere Program West: Berat structural subzone Kurvelesh structural subzone Cika structural subzone The structural units are overthrusted each other with horizontal amplitudes of several tens of kilometers. On the other hand, a combination of longitudinal and transverse tectonic faults is present giving to the region a kind of "independence" tectonic style passing from one sector to another one. As a result of this combination, moving from south (Otoni Islands in Greece) to the north, the Ionian tectonic zone passes to Sazani tectonic zone. Further to the north (Selenica area in Albania) the presence of another intersection between the western fault of Cika structural subzone and a transvers tectonic fault is proved by the data, which separate the southern structures from the South Adriatic basin to the north. The tectonic style of the Ionian tectonic zone show that there is a big change between the tectonic model to the south of Vlora-Elbasan transverse fault and the tectonic model to the north of this transverse fault. It is thought that evaporite deposits do not exist to the north of Vlora- Elbasan transverse fault.

Figure 1 –Ionian tectonic zone location in Albania and the main tectonic event T3-J1 (Lower&Middle Lias)/Middle-Upper Jurassic-Eocene.

Hévíz, Hungary, 15-19 October, 2019 page 110 of 197 International Lithosphere Program

Figure 2 –The tectonic modelling of Ionian tectonic zone in Albania (Modified from Roure F., & Nazaj Sh.; 2004: Thrust tectonics and hydrocarbon systems: AAPG Memoir 82, p.474-493).

Hévíz, Hungary, 15-19 October, 2019 page 111 of 197 International Lithosphere Program The brittle stage of the exhumation of a metamorphic core complex and supra-detachment basins: The Naxos and Paros supra-detachment basin, Greece and general remarks Franz Neubauer1, Shuyun Cao2

1 Dept. of Geography and Geology, Paris-Lodron-University of Salzburg, Austria, [email protected] 2 State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan, China; [email protected] Corresponding author: [email protected]

Structures of hangingwall units, mainly of supra-detachment basins (Leeder and Gawthorpe, 1987; Vetti and Fossen, 2012), of major detachment systems in extensional settings leading to metamorphic core complexes are equally important as the generally well-studied footwall rocks within the metamorphic core complex and the detachment faults above it. Here, we postulate a new type of supra-detachment basin, namely groove-syncline basins, which form parallel to the motion direction of the detachment and which are filled laterally by material derived from uprising and denudating metamorphic core complexes. The process is described on the example of hanging-wall structures of the North-Cycladic Detachment System on Naxos and Paros Islands of the Aegean Sea (Jolivet et al., 2010). There, we found that these structures and the sedimentary evolution consistently monitor the tectonic evolution of hanging blocks complementary to the footwall structures, vertical fluid flow as well as late-stage inversion of the whole extensional system. On Naxos and Paros, Upper Oligocene–Miocene and Pliocene sedimentary successions was deposited on the hangingwall unit, which is largely an ophiolite covered by uppermost Oligocene(?)–Miocene and Pliocene sedimentary successions. The sedimentary successions are separated by a hiatus arguing for a three-step tectonic evolution. The first step, Oligocene(?)– Miocene Lower Miocene marine marls with intercalated paraconglomerates, indicates moderate subsidence and some relief, and only denudation of the hangingwall unit. The Upper Miocene mostly terrestrial conglomerates and sandstones (ca. 11 to 6 Ma) indicate a sharply increasing relief and an over-steepened topography. Hydrothermal systems developed in the hangingwall rock succession (e.g. Miocene at Steladia) play an important role and resulted in large-scale silica precipitation and associated alteration similar as these found in subvolcanic epithermal systems (see also Siebenaller et al., 2016). This constrains a close link between shallow granodiorite intrusion in the footwall and near-surface processes (Bessiere et al., 2019). In the third step, the uppermost Miocene–Pliocene coarse boulder conglomerate includes the first appearance of abundant granite/granodiorite clasts and subsequent marble-rich debris on distant places like

Hévíz, Hungary, 15-19 October, 2019 page 112 of 197 International Lithosphere Program Palatia at Naxos town. The succession indicates sudden erosion and high-gradient relief resulting in catastrophic alluvial fans leading to erosion of the external sectors of the Naxos migmatite dome during uppermost Miocene and Pliocene. Within the sedimentary hangingwall successions on Naxos and Paros Islands, we can distinguish between three major tectonic events, which are in accordance with large-scale tectonic processes in the Aegean Sea: (a) ca. NNE–SSW extension in Early Miocene; (b) ca. E–W strike-slip compression during Late Miocene and which monitors, therefore, inversion and compression perpendicular to the previous extension direction; (c) N–S strike-slip compression (latest Miocene to Early Pliocene, and (d) again NNE-SSW extension (Late Pliocene to Recent). On a general level, our study allows for the following major conclusions: Structures of hangingwall units of major detachments above metamorphic core complexes are equally important compared to the generally well-studied footwall rocks. They allow date several tectonic events not necessarily found in footwall rocks. Here, we introduce a new subtype of supra- detachment basins and call this type groove-syncline basin. We define this sort of basin as forming in crustal-scale synforms between crustal-scale uplifting and exhuming metamorphic core complexes. On a smaller scale, such grooves parallel to the motion direction of detachment are well known (e.g., Pain 1985; Spencer, 2010) and we interpret that these crustal-scale grooves form in response of rheological contrasts between rheologically stiffer and weaker portions in the deeper crust and its interaction with buoyancy. The remnant of the basin on eastern Paros as well as the Neogene remnants within the Melanes syncline and those of the Moutsounas peninsula may represent such groove-syncline basins. The flat-lying marble conglomerates on Moutsounas peninsula and on small island to the east with similar sedimentary rocks and abundant travertine may be part of a syncline in the east as well as the sea between Paros and Naxos islands. Beside the lateral tectonic position within synclines between metamorphic core complexes, lateral sedimentary transport is another important feature of groove-syncline basins. Large-scale grooves in t abundant he detachment plane seem to be a regular feature of detachment systems over MCCs.

Bessiere, E., Rabillard, A., Précigout, J., Arbaret, L., Jolivet, L., Augier, R., Mansard, N., 2018. Strain localization within a syntectonic intrusion in a backarc extensional context: The Naxos monzogranite (Greece). Tectonics 37, 558–587. https://doi.org/10.1002/2017TC004801 Jolivet, L., Lecomte, E., Huet, B., Denèle, Y., Lacombe, O., Labrousse, L., Le Pourhiet, L., Mehl, C., 2010. The North Cycladic detachment system. Earth and Planetary Science Letters 289, 87–104. Leeder, M.R., Gawthorpe, R.L., 1987. Sedimentary models for extensional tilt-block/half-graben basins. In: Coward, M.P., Dewey, J.F., Hancock, P.L. (eds.), Continental Extensional Tectonics. Geological Society of London Special Publication 28, pp. 139–152.

Hévíz, Hungary, 15-19 October, 2019 page 113 of 197 International Lithosphere Program Pain, C.F., 1985. Cordilleran metamorphic core complexes in Arizona: A contribution from geomorphology. Geology 13, 871–874. Siebenaller, L., Vanderhaeghe, O., Jessell, M., Boirona, M.-C., Hibsch, C. 2016. Syntectonic fluids redistribution and circulation coupled to quartz recrystallization in the ductile crust (Naxos Island, Cyclades, Greece). Journal of Geodynamics 101, 129–141. Spencer, J. E., 2010. Structural analysis of three extensional detachment faults with data from the 2000 Space-Shuttle Radar Topography Mission. GSA Today 20, 8, 4–10, doi: 10.1130/GSATG59A.1 Vetti, V. V., Fossen, H., 2012. Origin of contrasting Devonian supradetachment basin types in the Scandinavian Caledonides. Geology 40, 571–574. doi: 10.1130/G32512.1

Hévíz, Hungary, 15-19 October, 2019 page 114 of 197 International Lithosphere Program Shift of Late Miocene to Quaternary alkaline magmatism at the Alpine-Pannonian transition: Significance for coupling of Adria plate motion with the Alpine-Carpathian front

Franz Neubauer1, Shuyun Cao1,2

1 Dept. of Geography and Geology, University of Salzburg, Austria; [email protected] 2 State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan, China; [email protected] Corresponding author: [email protected]

Within-plate migration of alkali-basaltic centers is explained generally by shifts of the lithosphere above a mantle-plume related to a largely stationary hot spot in the asthenosphere. Here, we report, for the first time, a hitherto unrecognized shift of small Late Miocene to Early Quaternary alkali-basaltic volcanic centers at the Alpine-Pannonian Basin transition (at the South Burgenland High), which spread in a regular sequence over 95 km from NNE to SSW between 11 Ma and 1.7 Ma (Fig. 1).

Fig. 1. Alkali-basalt volcanic centers along the South Burgenland High (Penninic windows are shown for reference) at the Alpine-Pannonian transition. Ages are summarized from Balogh et al. (1994), Bojar et al. (2008), Bojar et al. (2013 and references therein).

Hévíz, Hungary, 15-19 October, 2019 page 115 of 197 International Lithosphere Program In detail, we recognize three stages: Stage 1 with a ca. 55 km SSW shift of volcanism between 11 and 5 Ma, Stage 2 with ca. 34 km WSW shift between 5 and 3.5 Ma, and Stage 3 with S-directed shift of ca. 19 km between 3 and 1.7 Ma. Obviously, this area represents a unique setting where the motion directions of upper crust and mantle lithosphere are decoupled. We interpret this volcanism to have resulted from thinning of the lithosphere in the Pannonian basin (Hurai et al., 2015) over a hotspot within the ALCPA plate moving from SSW to the NNE between 11 and 1.7 Ma, interrupted by a marked eastward shift between 5 and 3.5 Ma. Fragmentary Stage 1 shift can be also observed in Western Carpathians (Hurai et al., 2011), some Stage 2 shift in the center of the Pannonian Basin (north of Lake Balaton) (Wijbrans et al., 2007). In detail, the three stages well correlate in orientation and time with regional deformation phases as well as with events of exhumation (ca. 9 – 4 Ma) and surface uplift along Alpine-Carpathian frontal areas (e.g., Kilb fault), shortening structures in West Carpathians (Beidinger and Decker, 2016) and within western Pannonian basin (Fodor et al., 2005) and south (e.g., Sava Fold Belt, peripheral Klagenfurt basin) of this volcanic trend although the entire amount of shift remains uncertain and shortening is potentially lower. Punctuated Late Miocene NNE-SSW shortening is known in the Western Carpathians as well as along southern margins of the Southalpine unit. We explain this deformation stage to monitor the Stage 1 shift. Gently W-dipping thrust faults indicate ca. WSW- ENE shortening in South Burgenland High potentially related to Stage 2 ENE-ward motion of the ALCAPA block. Finally, all these deformation events allow correlate Adria motion with deformation along frontal parts of Eastern Alps, and Western and Eastern Carpathians across the western Pannonian basin, and a semi-quantitative model is proposed for that late-stage tectonic processes in the Alpine-Carpathian-Pannonian realm.

Balogh, K., Ebner F., Ravasz, C., 1994. K/Ar Alter tertiärer Vulkanite der südöstlichen Steiermark und des südlichen Burgenlandes. In: Lobitzer, H., ed., Jubiläumsschrift 20 Jahre Geologische Zusammenarbeit Österreich-Ungarn, Geologische Bundesanstalt Wien 2, 55–72. Beidinger, A., Decker, K., 2016. Paleogene and Neogene kinematics of the Alpine-Carpathian fold-thrust belt at the Alpine-Carpathian transition. Tectonophysics 690, 263–287. Bojar, A.-V., Halas, S., Bojar, H.P., Szaran, J., 2008. Isotopic evidence for the origin of an acid sulphate alteration, Styrian basin, Austria. Terra Nova 20, 45–51. Bojar, H.-P., Bojar, A.-V., Halas, S., Wójtowicz, A., 2013. K-Ar Geochronology of Igneous Amphibole Macrocrystals of Miocene to Pliocene Volcanoclastics, Styrian Basin, Austria. Geological Quarterly 57, 405–416. Cao, S., Neubauer, F., Bernroider, M., Liu, J., Genser, J., 2013. Structures, microfabrics and textures of the Cordilleran- type Rechnitz metamorphic core complex, Eastern Alps. Tectonophysics 608, 1201–1225, Fodor, L., Bada, G., Csillag, G., Horváth, E., Ruszkiczay-Rüdiger, E., Palotás , K.,Síkhegyi, Timár, G., Cloetingh, S., Horváth, F., 2005. An outline of neotectonic structures and morphotectonics of the western and central Pannonian Basin. Tectonophysics 410, 15–41. Harangi, S., Jankovics, M. E., Sági , T., Kiss, B., Lukács, R., Soós, I., 2015. Origin and geodynamic relationships of the Late Miocene to Quaternary alkaline basalt volcanism in the Pannonian basin, eastern–central Europe. Int. J. Earth Sci. (Geol. Rundsch.) 104, 2007–2032.

Hévíz, Hungary, 15-19 October, 2019 page 116 of 197 International Lithosphere Program Hurai, V., Paquette, J.-L., M. Huraiová, M., Konečný, P. 2011. U–Th–Pb geochronology of zircon and monazite from syenite and pincinite xenoliths in Pliocene alkali basalts of the intra-Carpathian back-arc basin. J. Volcanol. Geotherm. Res. 198, 275–287. Wijbrans, J., Németh, K., Martin, U., Balogh, K., 2007. 40Ar/ 39Ar geochronology of Neogene phreatomagmatic volcanism in the western Pannonian Basin, Hungary. J. Volcanol. Geotherm. Res. 164, 193–204.

Hévíz, Hungary, 15-19 October, 2019 page 117 of 197 International Lithosphere Program Regional scale constraints on the lithosphere asthenosphere boundary (LAB) in the Carpathian Basin by electromagnetic induction

Attila Novák1, Viktor Wesztergom1, István János Kovács1, Csaba Molnár1

1 Geodetic and Geophysical Institute of Research Centre for Astronomy and Earth Sciences of Hungarian Academy of Sciences, [email protected] Corresponding author: [email protected]

The topography of the lithosphere asthenosphere boundary (LAB) and the distribution of the subsurface specific electric conductivity in the Pannonian Basin may reflect important records of its geological history. Its main features can be determined with up-to-date methods of MT investigations much more accurately than it was possible several decades ago (e.g. Ádám and Wesztergom, 2001). The more complex and unexceptional imaging of the LAB greatly contributes to the reconstruction of tectonic processes in the Carpathian Basin, also facilitating the refined localization of natural geothermal energy resources.

Figure1. Magnetotelluric database with digital and analogue MT stations (back dots - the planed MT stations between 2018-2020 in Pannon LitH2Oscope Lendület Framework, white dots - the measured MT stations in Pannon LitH2Oscope Lendület Framework (2019), lightgreen dots - the MT stations in TopoTransylvania project (2018))

In the past years several project aimed to study the LAB beneath the Carpathian-Pannonian region (Pannon LitH2Oscope Lendület Framework, TopoTransylvania project, etc.; Fig1.). To complement the electromagnetically less known region of Transylvanian Basin 6 long-term

Hévíz, Hungary, 15-19 October, 2019 page 118 of 197 International Lithosphere Program magnetotelluric soundings were carried out to cover the region between the Ciuc Basin and the eastern margain of the Great Hungarian Plain (Békés Basin) (Fig2.). In addition, the implementation of new deep MT soundings in the vicinity of the already installed seismological stations in the Transdanubian region has begun. In the future more than 50 new deep MT sounding sites are planned to explore the conductivity distribution under the Pannonian Basin.

Figure2. Magnetotelluric 1D results of TopoTransylvania project: a) Terrain map of Carpathian region with MT stations (red dots); b) 1D inversion layered models of magnerotelluric soundings (resistivity values in Ohmm)

Hévíz, Hungary, 15-19 October, 2019 page 119 of 197 International Lithosphere Program The Pannon LitH2Oscope multidisciplinary Lendület Group’s major goal is to develop a refined joint geological and geophysical map of LAB in a young continental extensional area, the Pannonian Basin. The new approach is based on the predictions of the innovative ‘pargasosphere’ concept (Kovács et.al, 2017). The dynamics of the lithosphere-asthenosphere system is associated with the occurrence of earthquakes, volcanism and determines significantly the geothermal energy potential of an area which all have outstanding importance of scientific point and great societal relevance too.

Ádám A and Wesztergom V, 2001, An attempt to map the depth of the electrical asthenosphere by deep magnetotelluric measurements in the Pannonian Basin (Hungary). ACTA GEODAETICA ET GEOPHYSICA, 44, pp.167- 192. Kovács I, Lenkey L, Green D H, Fancsik T, Falus Gy, Kiss J, Orosz L, Angyal J, Vikor Zs: The role of pargasitic amphibole in the formation of major geophysical discontinuities in the shallow upper mantle, ACTA GEODAETICA ET GEOPHYSICA 52: (2) pp. 183-204.

Hévíz, Hungary, 15-19 October, 2019 page 120 of 197 International Lithosphere Program Integrated reservoir investigations of known fields in the Zala basin

Dániel Nyíri1, Csilla Zadravecz1, Lilla Tőkés2

1 MOL Plc. 2 Eötvös University Corresponding author: [email protected]

As the Bajánsenye 3D seismic cube was reprocessed in 2018, a detailed tectonostratigraphic reconstruction was carried out. The results of this work, and the findings of previous studies led to a better understanding of the known fields in the area. Significant amount of gas and condensate were produced from both the Bajánsenye and Őriszentpéter-Dél fields, and the gradually decreasing pressure values are resulting in production issues. In this work we integrated core, well- log and seismic information to further our knowledge of the reservoir extent and quality. Based on these the remaining hydrocarbon volumes still present in the reservoirs can be estimated more accurately. The presented reservoir analysis can be used to prolong the production of these fields, as tectonics and the sedimentary structure of these fields are comlex enough to have several previously non-produced reservoir compartments.

Hévíz, Hungary, 15-19 October, 2019 page 121 of 197 International Lithosphere Program Connecting low-grade deformation and temperature data in Neotethyan meta(sediments)

Gabriella Obbágy1,2,*, Szilvia Kövér3, Béla Raucsik4, Kata Molnár1, László Fodor3, Zsolt Benkó1

1 ICER Centre, Institute for Nuclear Research, Hungarian Academy of Sciences, Debrecen, Hungary 2 Department of Mineralogy and Geology, University of Debrecen, Debrecen, Hungary 3 MTA-ELTE Geological, Geophysical and Space Science Research Group of the Hungarian Academy of Sciences, Budapest, Hungary 4 Department of Mineralogy, Geochemistry and Petrology, University of Szeged, Szeged, Hungary Corresponding author: [email protected]

Style, age and temperature of the deformation within a nappe system are crucial to constrain the evolution history of an orogen. Low-temperature deformation of sedimentary rocks at the ductile-brittle transition zone is very frequent in the upper crustal part of accretionary wedges, obduction-related lower-plates and orogenic belts. However, individual methods sensitive to this temperature range often yield ambiguous results, therefore, in this study we combined illite crystallinity, chlorite crystallinity and Raman spectroscopy of carbonaceous material (RSCM) from the same samples of well characterized structural position. The studied Bükk Mountains were located on the western passive margin of the Neotethys Ocean during the Middle Triassic – Middle Jurassic time. During the Middle Jurassic subduction and following ophiolite obduction most of the area was situated in lower plate position and suffered low-temperature deformation. The temperature of this deformation and the history of the nappe stacking is still unknown. In the present study we tried to estimate the temperature of deformation by applying the above mentioned methods simultaneously in order to separate different nappes and unravel their structural history. The succession consists of Middle to Late Jurassic dark slates, sandstones, limestones, and mixed shale-siltstone-sandstones with pillow basalts, small-scale gabbro intrusions and dykes. Previous studies differentiated three nappes within the succession (Paraautochthon, Mónosbéli and Szarvaskő Units) [1], however, some deformation features suggest that the entire succession is part of the same structural unit. The style of deformation varies from well-defined axial planar cleavage (Paraautochthon) to shear related sigmoidal foliation, which intersects the bedding in a small angle (Mónosbéli and Szarvaskői Units). We determined a range of RSCM [2] based maximum temperatures on slate samples from the three different ‘nappes’. We observed no sharp change in maximum temperature at nappe boundaries (~260 ± 30 °C) but a continuous decrease towards the upper part of the succession (220 ± 30 °C). In contrast, samples from the contact with basalts/gabbroic dykes or those from

Hévíz, Hungary, 15-19 October, 2019 page 122 of 197 International Lithosphere Program shear zones show slightly higher temperatures (~300 ± 30 °C). In summary our results show that different deformation styles in different units are not related to temperature variations between nappes. On the other hand, magmatic bodies are slightly younger than the enclosing sediments and their thermal contact is evident from temperature measurements. RSCM of the slates turned out to be a key method in temperature estimation in the investigated 200-300 °C range.

[1] Csontos (1999) Bull of the Hungarian Geol Soc, 129/4: 611-651. [2] Lünsdorf et al. (2017) Geostand Geoanal Res, 41: 593-612.

Hévíz, Hungary, 15-19 October, 2019 page 123 of 197 International Lithosphere Program Triassic salt tectonics in the Inner Western Carpathians (Silica Nappe, Aggtelek Hills): The role of inherited salt structures during the Alpine deformation

Éva Oravecz1,2, Gábor Héja2, László Fodor2

1 Eötvös Loránd University of Sciences, Department of General and Applied Geology 2 MTA-ELTE Geological, Geophysical and Space Sciences Research Group Corresponding author: [email protected]

The Permian to Lowermost Triassic Perkupa Evaporite forms the base of the enigmatic Silica Nappe which is the uppermost tectonic unit of the Inner Western Carpathians. This evaporitic sequence played the role of the main detachment level of the Silica Nape during the Cretaceous shortening. Several previous studies suggested that there may be salt diapirs rooting in this evaporitic detachment level (Grill 1989, Less 2000, Less et al. 2006, Zelenka et al. 2005) but their role in the evolution of the Silica Nappe has not been studied in details. Results of a detailed structural mapping revealed that not only simple salt diapirs but also map- scale salt walls are present in the southernmost part of the Silica Nappe (Aggtelek Hills). Slump folds, syn-sedimentary and pre-tilt normal faulting, and thickness changes observed within the Lower Triassic sequences indicate that these salt structures originally formed syn-sedimentary with the respect to the Early Triassic sedimentation when extensive salt deformation occurred. The onset of intensive salt movement can probably be dated to the Spathian (Olenekian). From this time the sedimentation occurred in minibasins, the evolution of which was controlled by the continuously growing salt structures. Salt movements were coupled with doming and drag folding along the salt structures which resulted in significant map-scale folding. The exact extent of this tilting is unknown but locally, directly next to the salt bodies even sub-vertical dips might have been reached. This means that not all folds observed presently in the Silica Nappe are related to the Cretaceous deformation but were formed much earlier in the Triassic. The kinematics and geometry of the Cretaceous deformation was strongly influenced by the pre-existing salt structures and normal faults. Firstly, secondary salt welds formed by the squeezing of diapirs and salt walls, then the welds and tilted normal faults were reactivated as oblique thrust faults. During the main NW-SE oriented shortening the E-W trending salt structures evolved into dextral tear faults zones (Jósvafő-Perkupa Fault Zone), whereas young-on-older thrust contacts evolved along the minibasin borders by the inversion of former salt structures (Jósvafő-Bódvaszilas Fault Zone). The main tectonic transport direction was to the S-SE but due to structural inheritance local deviations do occur. Consequently, the key for understanding the still debated deformation

Hévíz, Hungary, 15-19 October, 2019 page 124 of 197 International Lithosphere Program history and nappe transport direction of the Silica Nappe would be the understanding of the Triassic pre-orogen deformation geometry and its role in the Cretaceous shortening. The research was supported by the research found NKFIH OTKA 113013 and the ÚNKP-18-2 New National Excellence Program of the Ministry of Human Capacities.

Figure 1: Cross-sections through the most important structural elements of the southernmost part of the Silica Nappe (Aggtelek Hills, Inner Western Carpathians): the young-on-older contact of the Jósvafő-Bódvaszilas Fault Zone; the Jósvafő-Perkupa Salt Wall that evolved into a secondary salt weld and reactivated as a dextral tear fault during the Cretaceous shortening; the Szövetény Diapir and the Teresztenye Minibasin.

Grill J. (1989): Structural Evolution of the Aggtelek-Rudabánya Mountains, NE Hungary — Annual Report of the Hungarian Institute of Geology from 1986, pp. 69-103. Less Gy. (2000): Polyphase evolution of the structure of the Aggtelek-Rudabánya Mountains (NE Hungary), the southernmost element of the Inner Western Carpathians – a review — Slovak Geological Magazine 6/2-3, 260-268. Less Gy., Kovács S., Szentpétery I., Girll J., Róth L., Gyuricza Gy., Sásdi L., Piros O., Réti Zs., Elsholz L., Árkai P., Nagy E., Borka Zs., Harnos J. & Zelenka T. (2006): Explainatory book for the geological map of the Aggtekek-Rudabánya Mts. (1:25 000) — Hungarian Institute of Geology, Budapest. Zelenka T., Németh N. & Kaló J. (2005): The structure of the gypsum-anhydrite dome at Alsótelekes — Bulletin of the Hungarian Geologocal Society 135/4, 493-511.

Hévíz, Hungary, 15-19 October, 2019 page 125 of 197 International Lithosphere Program Determination of the thermal conductivity of Tertiaryclastic sediments in Hungary: preliminary results of elaborating a methodology using well logs

Petra Paróczi1, János Mihályka1, László Lenkey1

1 Department of Geophysics and Space Science, Eötvös Loránd University Corresponding author: [email protected]

The utilization of geothermal energy in Hungary has a long tradition, because several geothermal reservoirs exist in the Tertiarysediments and buried karstified and fractured carbonates. The heat flow density is one of the most important quantities in geothermal exploration, because it allows the prediction of subsurface temperature, and its local variations may originate from groundwater flow, which indicatesthepresence of a reservoir. Its large scale distribution is also influenced by mantle and lithospheric processes, therefore it is an important control parameter in geodynamic models. The heat flow density is determined using Fourier’s Law as the product of the thermal conductivity of rocks and the temperature gradient measured in boreholes and wells. 70% of Hungary’s surface is covered by Tertiary clastic sediments. The average sediment thickness is 1-2 km, but in the deepest troughs it reaches 5-8 km (Fig. 1.). As the thermal conductivity of clastic sediments is lower than the conductivity of the crystalline basement, the sediments have a significant influence on the temperature distribution and heat flow density. By this time in Hungary most of the temperature measurements were carried out in clastic sediments. Furthermore, the thermal conductivity of more than 300 sediment core samples were measured in laboratory conditionsandthermal conductivity-depth trends were established for shales and sandstones. We present a methodology for determining the thermal conductivity of clastic sediments using geophysical well logs. A geophysical inversion algorithm based on a weighted least squares method was created to derivethe volumetric fractions of the lithological components like shale, sand and pore-waterfrom wireline logging data such as natural gamma ray, resistivity, bulk density and neutron porosity logs. The effective thermal conductivity was computed withapplying an appropriate mixing law using the thermal conductivity values of the lithological components. The thermal conductivity derived from well logs wastested using the archive thermal conductivity measurements of core samples (Fig. 2.). Here we present our preliminary results conducted from the dataset of explorational wells like Iharosberény-I.

Hévíz, Hungary, 15-19 October, 2019 page 126 of 197 International Lithosphere Program

Figure 1. The locations of the explorational wellsin Hungarywhere core samples were taken. The color scale represents the thickness of Tertiarysediments.

Hévíz, Hungary, 15-19 October, 2019 page 127 of 197 International Lithosphere Program

Figure 2. Results of the inversion derived fromthis log combination and the calculated thermalconductivity in case of Iharosberény-I well. Thepurple circles represent the thermal conductivitymeasured on core samples.

In general, the method determining thermal conductivity from well logs bears large significance in geothermal studies in Hungary, because orders of more thermal conductivity data can be obtained than presently available. The thermal conductivities determined by high resolution in wells can be interpolated between the boreholes using seismic sections, and 3D numerical thermal models can be constructed.3Dnumerical thermal modellingusingreliable data reduces the uncertainty of temperature prediction in large depth, thusit is reduces the risk of geothermal exploration.

Hévíz, Hungary, 15-19 October, 2019 page 128 of 197 International Lithosphere Program Geological interpretation of magnetotelluric sounding in the Nógrád-Gömör Volcanic Field (Northern Pannonian Basin)

Levente Patkó1,2,3, Attila Novák2, Rita Klébesz4, Nóra Liptai2, Károly Hidas5, Carlos J. Garrido5, István János Kovács2, Viktor Wesztergom4, Csaba Szabó1,4

1Lithosphere Fluid Research Lab, Institute of Geography and Earth Sciences, Eötvös Loránd University, Budapest, Hungary 2 Lendület Pannon LitH2Oscope Research Group, Geodetic and Geophysical institute, MTA CSFK, Sopron, Hungary 3Isotope Climatology and Environmental Research Centre, Institute for Nuclear Research, MTA, Debrecen, Hungary 4Geodetic and Geophysical Institute, MTA CSFK, Sopron, Hungary 5Instituto Andaluz de Ciencias de la Tierra, CSIC and UGR, Granada (Armilla), Spain

Corresponding author: [email protected]

The Nógrád-Gömör Volcanic Field (NGVF) is one of the five mantle xenolith bearing Neogene alkaline basalt occurrences in the Carpathian-Pannonian region. In addition to the dominant lherzolite xenoliths, petrographic and geochemical evidence (i.e. newly formed clinopyroxene and olivine grains, Ti, Al, Fe, Mn and LREE enrichment in rock-forming minerals) suggests that a portion of the upper mantle was transformed to wehrlite beneath the NGVF by upward migrating mafic melts. The nature of the metasomatic agent is fairly well constrained with compositions similar to the host alkali basalt (Patkó et al., 2015). However, the spatial distribution of the metasomatized mantle domain is unclear, although wehrlites only appear in the central NGVF suggesting a restricted dimension. Recently acquired magnetotelluric (MT) data may shed light on the extent of the metasomatism. Long period MT data were collected at 14 locations along a ~50 km long NNW-SSE profile in the NGVF. The lithosphere-asthenosphere boundary was detected at depths of 60-80 km. A low resistivity anomaly (~5-10 Ωm) was observed at 30-45 km depth below the central part of the NNW-SSE profile, indicating the presence of a conductive body just below the Moho. To test the origin of this low resistivity anomaly, model calculations were carried out. We applied the excel worksheet composed by Kovács et al. (2018) for the estimation of the mantle conductivity values. This estimation follows the methodology of Fullea (2017). The results revealed lower electric resistivity for wehrlites (50 - 68 with an average of 60 Ωm) compared to lherzolites (47 - 1486 with an average of 399 Ωm). However, the resistivity values estimated for wehrlites are higher than those measured by magnetotellurics. The discrepancy can be explained by the presence of melts, which were not taken into account during modelling. Therefore, we suggest that the low resistivity body is explained by the presence of residual, melt network and the conductivity differences between the lherzolitic and wehrlitic mantle domain resulting from different chemical composition and rock-forming mineral ratio.

References Fullea (2017). Surveys in Geophysics, 38(5), 963-1004. Kovács et al. (2018) Acta Geodaetica et Geophysica, 53(3), 415–438. Patkó et al. (2015) Goldschmidt2015 Abstracts

Hévíz, Hungary, 15-19 October, 2019 page 129 of 197 International Lithosphere Program Strain localization during the negative inversion of thrust wedges: a case study from the Aegean and constraints from numerical simulations

Kristof Porkolab1, Ernst Willingshofer1, Dimitrios Sokoutis1, Jan Wijbrans2

1 Utrecht University, Netherlands 2 Vrije Universiteit Amsterdam, Netherlands Corresponding author: [email protected]

The role of pre-existing structures and rheological stratification during the extension (negative inversion) of a thrust wedge may be significant in localizing extensional deformation and thus controlling the lithospheric and thermal structure of a region. We present a field geological analysis supplemented by Ar/Ar dating from the islands of the Northern Sporades (Greece) focusing on strain localization from micro-to regional scale, and extrapolate our key observations to lithospheric-scale numerical models. Tectonic burial of the Northern Sporades initiated in the latest Cretaceous – Early Paleocene, as a result of collision between Pelagonia/Adria and Rhodopia(Eurasia). All the formations were buried to the depth of greenschist facies conditions, where shortening was largely accommodated by the formation of top-S to SW reverse-sense shear zones. We show that these shear zones largely localized within the Triassic and Cretaceous shallow-water carbonates that outcrop on the islands. This implies that rheological differences in the original sedimentary succession might have played a key role in localizing shortening. Between the shear zones, distributed shearing is observed with identical kinematics. Mylonitic sericite foliations from top-S-SW shear zones yield 50-60Ma Ar/Ar ages. Top-SW thrusting was followed by top-NE shearing similarly under greenschist facies conditions. Top-NE shear zones localized at pre-existing stratigraphical and tectonic contacts, and are subparallel with the main foliation. Partial resetting of the Ar-system in the sericitic foliation of these shear zones occurred from around 40 Ma suggesting that the onset of extension (negative inversion) is Eocene. These shear zones may have a minor to medium (few 100 or 1000 m) displacement and consequently do not cut out major parts of the stratigraphy. However, they triggered distributed top-NE shearing between the shear zones that is especially characteristic on Skopelos. Ductile top-NE shearing was gradually replaced by top-NE to top-NW semi-brittle and eventually fully brittle normal faulting. Asymmetric normal faulting (simple shear) along pre-existing ductile shear zones evolved into more symmetric (pure shear) mode of extension as evidenced by major sets of NE-SW and NW-SE trending normal faults. Our findings support the idea that initial stratigraphy of the upper crust can substantially influence the

Hévíz, Hungary, 15-19 October, 2019 page 130 of 197 International Lithosphere Program distribution of shortening in a thrust wedge, which in turn influences the localization of extension during negative inversion. We present preliminary results of thermomechanical numerical experiments that show how initial upper crust rheology is a key factor in understanding exhumed thrust wedges in nature.

Hévíz, Hungary, 15-19 October, 2019 page 131 of 197 International Lithosphere Program Uplift of the Transdanubian Range, Pannonian Basin: How fast and why?

Zsófia Ruszkiczay-Rüdiger1, Attila Balázs2, Gábor Csillag3, Guy Drijkoningen4, László Fodor3

1 Hungarian Academy of Sciences (MTA), Research Centre for Astronomy and Earth Sciences, Institute for Geological and Geochemical Research, [email protected] 2 Department of Sciences, Università degli Studi Roma Tre, [email protected] 3 MTA-ELTE Geological, Geophysical and Space Science Research Group, [email protected]; [email protected] 4 Faculty of Civil Engineering and Geosciences, Delft University of Technology, [email protected] Corresponding author: [email protected]

The quantification of the incision rates of the Danube River is provided and interpreted in terms of geodynamic processes and Quaternary climate-driven surface processes. Recently published cosmogenic nuclide- and luminescence-based terrace ages, together with revised paleontological data (Ruszkiczay-Rüdiger et al., 2016, 2018) were combined to yield a comprehensive uplift history of the study area. The age-elevation data pairs record the incision of the Danube. They present the best approximation for the uplift history of the northern Transdanubian Range (TR). The calculated incision/uplift rates are 50-70 m/Ma over the last 3 Ma. A change in the uplift rates was identified at ~300 ka from 423 m/Ma before, to 1997 m/Ma after this time (Fig.1). It is still a matter of debate whether the acceleration in incision implies an acceleration of uplift rates or it is just an artefact of the integration of geochronological data over a shorter timescale. In the latter case the incision rate of 423 m/Ma should be considered as a good approximation for the entire incision history.

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Fig. 1. Temporal uplift rates in the Gerecse Hills quantified by terrace ages plotted against terrace elevations. Trend-lines were fitted to the datasets before and after the breakpoint at ~300 ka, (the fQ3b terrace; I>300ka and I<300ka, respectively).

Considering the spatial pattern and geochronological data of the Danube terraces, an enlargement of the uplifting area, a result of the onset of uplift at the eastern margin of the Danube Basin, was reconstructed not later than ~1.1 Ma. The recorded pattern of vertical deformation is interpreted as large-scale tilting and folding of the lithosphere (Balàzs et al. 2017; Dombrádi et al. 2010). The observed upper crustal neotectonic faults are not sufficient to accommodate the deformation necessary for the reported Quaternary vertical motion. Previous geodynamic models considering only compression-related large-scale folding of a homogenous lithosphere or solely thermal effects are neither suitable to reproduce the observed hundreds of kilometres wavelength of uplift and subsidence. We suggest that vertical motions can be reconciled by models if rheological heterogeneities, i.e., pre-existing structures of the lithosphere and sediment redistribution by erosion and accumulation are considered. This hypotesis would emphasize the role of deep lithosphere and asthenosphere dynamics in neotectonic deformation of the Pannonian Basin (Fig.2).

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Fig. 2. A simplified lithospheric-scale cross-section over the western part of the Pannonian Basin, with the most important tectonic and surface processes. The red dashed rectangle indicates the study area. DrB – Dráva Basin, TR – Transdanubian Range, DB – Danube Basin, LAB – lithosphere- asthenosphere boundary, M1-M2: Lower- to Middle Miocene; M3-Q: Late Miocene to Quaternary.

Acknowledgement: The research was supported by the following NKFIH-OTKA projects 83610, 113013, 83400, 106197, 124807.

Balázs, A., Burov, E., Mațenco, L., Vogt, K., Francois, T., Cloetingh, S., 2017. Symmetry during the syn- and post-rift evolution of extensional back-arc basins: the role of inherited orogenic structures. Earth Planet. Sci. Lett. 462, 86– 98. Dombrádi, E., Sokoutis, D., Bada, G., Cloetingh, S., Horváth, H., 2010. Modelling recent deformation of the Pannonian lithosphere: lithospheric folding and tectonic topography. Tectonophysics 484 (1-4), 103-118. Ruszkiczay-Rüdiger, Zs., Braucher, R., Novothny, Á., Csillag, G., Fodor, L., Molnár, G., Madarász, B., ASTER Team. 2016. Tectonic and climatic forcing on terrace formation: coupling in situ produced 10Be depth profiles and luminescence approach, Danube River, Hungary, Central Europe. Quaternary Science Reviews 131, 127-147. Ruszkiczay-Rüdiger, Zs., Csillag, G., Fodor, L., Braucher, R., Novothny, Á., Thamó-Bozsó, E., Virág A., Pazonyi, P., Timár, G., ASTER Team. 2018. Integration of new and revised chronological data to constrain the terrace evolution of the Danube River (Gerecse Hills, Pannonian Basin). Quaternary Geochronology 48. 148-170.

Hévíz, Hungary, 15-19 October, 2019 page 134 of 197 International Lithosphere Program Geothermal potential of Sedimentary Basins, especially of the Swiss Molasse Basin

Ladislaus Rybach1,2

1 Institute of Geophysics ETHZ, Zurich/Switzerland, [email protected] 2 Geowatt AG, Zurich/Switzerland, [email protected]

Sedimentary basins usually have significant geothermal potential. Deep aquifers are key components. The factors, conditions, and processes that define and control the potential are: processes during basin formation like sedimentation, karstification, fracturing; rock porosity, permeability/fluid content; depth/temperature; hydrogeology; production sustainability. They are demonstrated on selected examples: USA basins, Paris Basin, Molasse Basin. Of the latter, the French, German and Austrian parts are treated first and then the Swiss Molasse Basin (SMB) in more detail. An example of a Swiss potential map is given below:

Geothermal productivity (MWth/m) in the SMB, based on the deep aquifers Topmost fractured crystalline basement, Upper Marine Molasse and Upper Muschelkalk. The various efforts undertaken to assess and quantify the SMB potential are described, example maps presented. The realizations of the SMB potential so far are really modest: of 10 deep drilling projects performed in various locations to date only two are successful, one is a partial success. The official Swiss energy strategy EN2050 includes electricity supply in the future; this assigns

Hévíz, Hungary, 15-19 October, 2019 page 135 of 197 International Lithosphere Program 4.4 TWh to geothermal sources in 2050. This would be delivered form geothermal power plants, foreseen are 250 MWe installed capacity from hydrothermal reservoirs, and another 250 MWe from petrothermal (EGS) sources. Only the SMB could host hydrothermal resources; the current data don’t make much hope. In principle, EGS plants could take heat (and convert it to electricity) from below the SMB. The EGS technology itself has great potential but it is still in the proof of concept stage. Intensive R&D is ongoing in several countries; however very substantial funding will be needed to answer the many questions still open.

Hévíz, Hungary, 15-19 October, 2019 page 136 of 197 International Lithosphere Program 3D density distribution and thermal field of the Alps and their forelands

M. Scheck-Wenderoth 1,2, C. Spooner 1, J. Bott 1, H.J. Götze 3, J. Ebbing 3

1 Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Germany 2 RWTH Aachen University, Aachen, Germany 3 2Christian-Albrechts-Universität zu Kiel, Institut für Geowissenschaften, Germany Corresponding author: [email protected]

The present day physical state of the European Alps is still a matter of debate as is their evolution in response to the continental collision of Europe and Africa in the Cenozoic. A steadily increasing amount of geological and geophysical observations in this region over the past few decades fed various hypotheses on the present- day and past drivers of deformation of the system. Major scientific questions remain on the lateral distribution of strength or the partitioning of deformation from the orogen to the two foreland systems: the Molasse basin in the North and the Po-Basin in the south. Within the DFG-priority program “Mountain building processes in 4D” we aim to derive a 3D description of the present-day physical state of the orogenic system through integration of numerous available geoscientific datasets including previous seismic and seismological experiments, observed gravity and existing 3D models. The resulting integrated model differentiates vertically between sedimentary layers (unconsolidated and consolidated), crystalline crustal layers (upper and lower) and mantle layers (lithospheric and asthenosphere). We find that the European crystalline crust is less dense and thicker (~2820 kg/m3, ~27.5 km) than the Adriatic crust (~2920 kg/m3, ~22.5 km). We find that some lateral density contrasts within the crust of the two plates correspond to features expressed at the surface, such as faults but also boundaries between domains of different deformation intensity. Using the lithological interpretations derived from the seismically and gravity constrained 3D model, we also calculate the 3D conductive thermal field and the variations in integrated strength and assess related consequences for the deformation regime.

Hévíz, Hungary, 15-19 October, 2019 page 137 of 197 International Lithosphere Program Tectonic units of the Alpine collision zone between Eastern Alps and western Turkey

Stefan M. Schmid 1, Bernhard Fügenschuh 2, Alexandre Kounov 3, Liviu Mațenco 4, Peter Nievergelt 5, Roland Oberhänsli 6, Jan Pleuger 7, Senecio Schefer 3, Ralf Schuster 8, Bruno Tomljenović 9, Kamil Ustaszewski 10 and Douwe J.J. van Hinsbergen 4

1 Institute of Geophysics ETH Zürich, Switzerland, [email protected] 2 Department of Geology Universität Innsbruck, Austria, [email protected] 3 Department of Environmental Sciences, Universität Basel, Switzerland, [email protected] 4 Faculty of Geosciences, Universiteit Utrecht, The Netherlands, [email protected] 5 Institute of Geochemistry and Petrology ETH, Zürich, Switzerland, [email protected] 6 Department of Earth and Environmental Sciences, Potsdam, Germany, [email protected] potsdam.de 7 Institute of Geological Sciences, Freie Universität Berlin, Germany, [email protected] 8 Geologische Bundesanstalt, Wien, Austria, [email protected] 9 Faculty of Mining, Geology and Petroleum Engineering, Zagreb, Croatia, [email protected] 10 Institute of Geological Sciences, University Jena, Germany, [email protected] Corresponding author: [email protected]

We present a map that correlates tectonic units between Alps and western Turkey accompanied by a text providing access to literature data, explaining the concepts used for defining the mapped tectonic units, and first-order paleogeographic inferences. Along-strike similarities and differences of the Alpine-Eastern Mediterranean orogenic system are discussed. The map allows (1) for superimposing additional information, such as e.g., post-tectonic sedimentary basins, manifestations of magmatic activity, onto a coherent tectonic framework and (2) for outlining the major features of the Alpine-Eastern Mediterranean orogen. Dinarides-Hellenides, Anatolides and Taurides are orogens of opposite subduction polarity and direction of major transport with respect to Alps and Carpathians, and polarity switches across the Mid-Hungarian fault zone. The Dinarides- Hellenides-Taurides (and Apennines) consist of nappes detached from the Greater Adriatic continental margin during Cretaceous and Cenozoic orogeny. Internal units form composite nappes that passively carry ophiolites obducted in the latest Jurassic–earliest Cretaceous or during the Late Cretaceous on top of the Greater Adriatic margin successions. The ophiolites on top of composite nappes do not represent oceanic sutures zones, but root in the suture zones of Neotethys that formed after obduction. Suturing between Greater Adria and the northern and eastern Neotethys margin occupied by the Tisza and Dacia mega-units and the Pontides occurred in the latest Cretaceous along the Sava-İzmir-Ankara-Erzincan suture zones. The Rhodopian orogen is interpreted as a deep-crustal nappe stack formed in tandem with the Carpatho-Balkanides fold-

Hévíz, Hungary, 15-19 October, 2019 page 138 of 197 International Lithosphere Program thrust belt, now exposed in a giant core complex exhumed in late Eocene to Miocene times from below the Carpatho-Balkan orogen and the Circum-Rhodope unit. Its tectonic position is similar to that of the Sakarya unit of the Pontides. We infer that the Rhodope nappe stack formed due to north-directed thrusting. Both Rhodopes and Pontides are suspected to preserve the westernmost relics of the suture zone of Paleotethys.

Figure: Simplified overview of the major units showing the traces of profiles presented in the poster.

Full text and figures available as Gondwana Research preprint under: https://doi.org/10.1016/j.gr.2019.07.005

Hévíz, Hungary, 15-19 October, 2019 page 139 of 197 International Lithosphere Program A regional overview of Upper Miocene Lake Pannon deposits in a tectonic framework in the Mecsek region, SW Hungary

Krisztina Sebe1, Imre Magyar2

1 University of Pécs, Department of Geology and Meteorology, Hungary, [email protected] 2 MOL Plc. & MTA-MTM-ELTE Research Group for Paleontology, Budapest, Hungary, [email protected] Corresponding author: [email protected]

Upper Miocene deposits of the brackish Lake Pannon were deposited during the post-rift phase and the onset of inversion of the Pannonian Basin on an inherited, relatively rugged topography. We investigated these deposits on a regional scale from litho- and biostratigraphic aspects in a tectonic framework to study the influence of structural movements (fault activity and geodynamic background) on topography and sedimentation. The rock succession was evaluated using borehole data. These were collected for the whole area, arranged in a geodatabase, and obvious spatial errors were corrected. The successions were then re-interpreted following a uniform lithostratigraphic framework, using the original borehole documentations where necessary. Maps of under- and overlying formations of the Upper Miocene stratigraphic units were compiled to study the succession of sedimentation. The sediments were dated using biostratigraphy. All published data on possibly age-indicating fossil groups and new, own data were gathered from the region and included mollusc, dinocyst and ostracod sites and taxon lists. The fossil sites were georeferenced in a geographic information system using various geological maps, aerial photos, and documents and maps in the municipal archives. The spatial and temporal evolution of sedimentation was evaluated on the background of known faults. Across the Sarmatian-Pannonian boundary sedimentation was continuous only in local basin centres including the Drava Basin and along the SE boundary fault zone of the Mecsek Mts. Mostly offshore calcareous marls accumulated during this period. Until ~8 Ma, the medium-elevation areas between basins and mountains gradually became flooded by Lake Pannon, still with the deposition of offshore marls and carbonaceous silts. Marginal clastics only accumulated in restricted areas and time intervals. Sedimentation was disturbed by several deformation events along the main boundary fault zone and in small basins, first of transtensional, later, after ~10 Ma of compressional character. Basement highs like the Villány Hills and the Mecsek Mts. and their axial continuations were subaerial during this time. The Mecsek area became flooded synchronously, between ~7.6-7 Ma, in the Prosodacnomya dainellii and P. vutskitsi littoral mollusc biochrons. Flooding was rapid, indicating a fast increase of local relative lake level. Submergence

Hévíz, Hungary, 15-19 October, 2019 page 140 of 197 International Lithosphere Program happened right before the arrival of the distal, Alp-Carpathian delta system upfilling the lake and affected the entire or nearly the entire area of the basement highs. From then on, tectonic activity was characterised by reverse and strike-slip faulting and folding mostly related to large basement faults. Paleontological investigations were extended to the southern margin of the Drava Basin. They showed that after a significant intra-Pannonian unconformity, a W-E-striking area in northern Croatia, Bosnia and Herzegovina and Serbia was flooded coevally, similarly to the Mecsek region, but a biochron later, in the latest Miocene or in the earliest Pliocene (in the P. vodopici littoral mollusc biochron, after 6 Ma). The submerged lands were covered by the delta sediments here as well. The synchronous submergence of roughly parallel stripes of land and the southward migration of the flooding in time suggests that there was a regional geodynamic driver behind submersion of given areas in this part of the Pannonian Basin. To achieve a better spatial and temporal resolution of the events, the published mollusc assemblages should be revised in the museum collections according to the up-to-date taxonomical and biostratigraphic knowledge. Work was supported by the Hungarian Scientific Research Fund (OTKA/NKFIH) projects PD104937 and 116618 and by the Hungarian-Croatian bilateral project TÉT_16-1-2016-0004.

Hévíz, Hungary, 15-19 October, 2019 page 141 of 197 International Lithosphere Program A review of the geodynamic setting of the volcanic provinces in the Carpathian-Pannonian region

Ioan Seghedi1

1 Institute of Geodynamics Sabba S. Stefanescu, Romanian Academy, Bucharest, Romania Corresponding author: [email protected]

The Carpathian-Pannonian region (CPR) area, as part of the Alpine–Himalayan orogenic belt shows a complex late Cenozoic-Quaternary geodynamic evolution of the magmatism. However, the relationship between geodynamic processes and magmatism remains controversial. The magmatism starts with ‘orogenic’ magmas and end with ‘anorogenic’ ones. Since the formation of most of the ‘orogenic’ volcanic rocks postdates the active subduction process the ‘subduction-related’ geochemical character of the volcanic rocks is supposed to be inherited from the mantle source regions modified previously by fluids or sediments released from subducted slabs. Post-collisional extension of the lithosphere could result in the decompression melting of the hydrous portion of the lithospheric mantle followed by the melting of the deeper asthenosphere. Ignimbrite flare-up is characteristic for the inception of extensional tectonic processes in CPR, followed by a variety of subalkaline, potassic or ultrapotassic (orogenic) magmas suggesting a progressive dehydration and “de-fertilization” of the lithospheric mantle source. The latest magmas are less voluminous, silica-undersaturated and sodic-alkaline in composition (anorogenic), suggesting a transition from lithosphere to asthenosphere melting in the orogenic environment. We do know that there is a relationship of the volcanoes with regional tectonic setting since volcanoes generally lay along or near major faults or within severely faulted areas, however we do not really tell the triggering mechanism of the eruptions. Large, initial ash-flow calderas that may imply a huge size, now hidden by the younger events raise a lot of questions about their relationships with regional geological framework, especially how such vast material was accumulated or how the eruptions were triggered. The Subalkaline magmatism is constantly younging from west to east, as connected with different local basins, suggesting a NE-ward time- dependent migration that followed the trend of extensional tectonics in each basin; various tectonic processes were suggested: lateral extrusion, wide rift or core complex extension, or transpressional-transtensional tectonics. Juxtaposition in both space and time suggests that the rate of volcanic activity should be related to the rate of tectonic activity. Much of the present contribution is an update review of the relationship between the volcanism and tectonic activity in CPR. Few additional subjective suggestions can be used in the

Hévíz, Hungary, 15-19 October, 2019 page 142 of 197 International Lithosphere Program future for a petrological-geophysical multidisciplinary approach to investigate the premises how volcanism is related to the tectonically controlled accumulation and storage of magmas in releasing structures that could be themselves oriented for eruption or are associated with such structures. This work was supported for IS by a grant of Ministry of Research and Innovation, CNCS – UEFISCDI, project number PN-III-P4-ID-PCCF-2016-4-0014, within PNCDI III.

Hévíz, Hungary, 15-19 October, 2019 page 143 of 197 International Lithosphere Program Preliminary Paleoreconstructional model for Basin development from Middle Miocene: a summary of seismic interpretations from Western Hungary

Balázs Soós1, László Fodor2, Dániel Nyíri1, Csilla Zadravecz1, Orsolya Magyari1, Imre Magyar1, Katalin Ujszaszi1, András Németh1

1 MOL Plc, [email protected] 2 MTA-ELTE Geological, Geophysical and Space Sciences Research Group

The aim of the presentation is to summarize the results of recent seismic interpretations of MOL Plc at Southwest-Hungary. The outcomes of the study were 3D paleo-reconstruction models to visualize the connections between Miocene sub-basins in time and spatial context.

However, in large scale the Pannonian Basin system could be interpreted as a complex, but individual basin in the Upper Miocene-Pliocene - the post-rift phase of Royden and Horváth (1988), in the Early-Middle Miocene we have to deal with relatively small sub-basins, with high tectonic control.

This study is focusing the tectonic development of these sub-basins in the upper crust of Southwest-Hungary with the interpretation and visualisation of the relation between the visible tectonic structures on seismic and the changes of accommodation space in time.

Hévíz, Hungary, 15-19 October, 2019 page 144 of 197 International Lithosphere Program The architecture of an intracontinental sedimentary basin (Parnaíba Basin, northeast Brazil) and its relationship with underlying crustal and upper mantle structure

Randell Stephenson1, José E.P. Soares2, Marcus V.A.G. De Lima3 and Reinhardt A. Fuck2

1 School of Geosciences, University of Aberdeen, Scotland 2 Instituto de Geociências, Universidade de Brasília, Brazil 3 Universidade Federal do Pampa, Caçapava do Sul/RS, Brazil Corresponding author: [email protected]

The Parnaíba Basin is one of a set of Palaeozoic intraplate basins within the South America plate (others include the Amazonas-Solimões, Parecis and Paraná basins). Its sedimentary record comprises Silurian to Cenozoic strata and its character is often compared to other Palaeozoic intraplate basins such as the Williston and Illinois basins in North America, the Congo and Taoudeni basins in Africa and the Siberian basin in Russia. PBAP (the Parnaíba Basin Analysis Program) was a multidisciplinary, multinational activity aimed at learning about the processes involved in forming intracontinental basins. On the geophysical side, it included wide-angle reflection-refraction (WARR) data acquisition as well as near-vertical, deep seismic reflection (DSR) profiling and complementary passive seismological studies. The results of the first of these is the focus of this report but it also incorporates insights derived from comparing the WARR and DSR datasets. There is a spatial correlation between acoustically transparent crust in the DSR image and highly reflective crust indicated by the WARR shot records. Seismic modelling experiments suggest that this is explicable by the presence of fine-scale lithological heterogeneity. The relevant crustal segment where this occurs is the Grajaú domain, which is where the Cretaceous sub-basin of the Parnaíba Basin is preserved. The Grajaú domain presents a thick crust (~43 km) including a mafic crustal underplate (the crustal segment indicated by the stippling in the figure, below).

Hévíz, Hungary, 15-19 October, 2019 page 145 of 197 International Lithosphere Program The present-day upper mantle and crystalline crustal structure is the result of the tectonic processes assembling lithosphere in the Precambrian and redesigning it in the Phanerozoic. The architecture of the sedimentary succession overlying the crystalline crust is the result of the vertical dynamic effects of these but also illustrates the role of isostatic equilibration in preserving sedimentary basins in intracontinental settings.

Hévíz, Hungary, 15-19 October, 2019 page 146 of 197 International Lithosphere Program Young Uplift at the Eastern End of the Alps.

Evidence for Uplift Unrelated to the Inversion of the Pannonian Basin? Kurt Stüwe1, Jörg Robl2

1 Department of Earth Science, Graz University, Austria [email protected] 2 Department of Geography and Geology, Salzburg University, Austria [email protected] Corresponding author: [email protected]

The eastern end of the Alps features a series of low relief surfaces at elevations up to 2500 m (Fig. 1). These surfaces have long been known to reflect uplifted planation surfaces that have not yet been dissected by fluvial processes and thus preserve a strong geomorphic dis-equilibrium. While their age would present a good handle on the surface uplift history of the Eastern Alps, these surfaces are barely dated and their age is only indirectly inferred to reflect the Miocene and Pliocene uplift history.

Figure 1: Elevated low relief surface at around 1800 m sea level on the Hohe Veitsch in the Mürztaler Alpen. Note the successive dissection of the plateau from the side and the dolines on the plateau itself.

Recent geomorphological cosmogenic nuclei-based studies have shown that these surfaces may record up to 1000 m of surface uplift in the last 5 Ma (Wagner et al., 2010; 2011; Legrain et al., 2015; Dertnig et al., 2017). Such a distinct uplift event in the recent past is surprising and needs to be interpreted. Interestingly, this time frame appears not to be accompanied by crustal shortening and the standard hypothesis about the inversion of the Pannonian Basin as the underlying cause needs to be questioned.

Hévíz, Hungary, 15-19 October, 2019 page 147 of 197 International Lithosphere Program In order to get a better handle on the nature of this young uplift event and its overriding driver it is crucial to understand its spatial extent. However, much of the Eastern Alps was glaciated in the Pleistocene and currently several studies suggest that elevated low-relief landscapes were shaped by the glacial buzz-saw, instead of interpreting them in terms of fluvial prematurity of recently uplifted planation surfaces (Fig. 2). The models of glacial erosion versus fluvial prematurity as the formation agent of the low-relief surfaces can be discerned if it can be shown that the surfaces formed prior to the Pleistocene.

Figure 2: The nature of low relief surfaces at high elevations is debated. In the glaciated parts of the Alps, glacial erosion and fluvial prematurity may both produce similar slope-elevation distributions.

In a currently operating research project we employ cosmogenic nuclei burial dating on a substantial part of the entire Eastern Alps to derive the age of these surfaces. We use the burial age of siliceous sediments in caves formed at the phreatic-vadose transition as a proxy. Correlation of cave levels with low-relief surfaces and their mapping in t he field is an integral part of the project. This paper reports about the current progress of this project.

Dertnig F., Stüwe K., Woodhead J., Stuart F.M., Spötl C., (2017). Constraints on the Miocene landscape evolution of the Eastern Alps from the Kalkspitze region, Niedere Tauern (Austria). Geomorphology, 299, p. 24-38. Legrain N., Dixon J., Stüwe K., von Blanckenburg F., Kubik P., (2015) Post-Miocene landscape rejuvenation at the eastern end of the Alps. Lithosphere. V.7(1), p. 3-13. Doi: 10.1130/L391.1

Hévíz, Hungary, 15-19 October, 2019 page 148 of 197 International Lithosphere Program Wagner T., Fritz H., Stüwe K., Nestroy O., Rodnight H., Hellstrom J., and Benischke R., (2011). Correlations of cave levels, stream terraces and palnation surfaces along the river Mur – Timing of landscape evolution along the eastern margin of the Alps. Geomorphology, vol. 134, p. 62–78. DOI: 10.1016/j.geomorph.2011.04.024. Wagner T., Fabel D., Fiebig M., Häuselmann P., Sahy D., Sheng X., Stüwe K., (2010). Young uplift in the non-glaciated parts of the Eastern Alps. Earth and Planetary Science Letters, v. 295, p. 159-169.

Hévíz, Hungary, 15-19 October, 2019 page 149 of 197 International Lithosphere Program Evaluation of fluid flow systems for hydrocarbon and geothermal exploration – A case study from Eastern Hungary

Zsóka Szabó, Brigitta Zentai-Czauner, Judit Mádl-Szőnyi

József and Erzsébet Tóth Endowed Hydrogeology Chair, Department of Geology, Eötvös Loránd University, Budapest, Hungary Corresponding author: Zsóka Szabó ([email protected])

Groundwater flow mobilises, transports and accumulates matter and heat, thus the evaluation of recent fluid flow systems can contribute to hydrocarbon and geothermal exploration, among others (Tóth, 1999). The main focus of our research was the mapping of hydraulically favourable places for hydrocarbon trapping and preservation in an Eastern Hungarian study area and comparing the results with the already known hydrocarbon fields. The aims were the following: to understand the recent fluid flow systems and regional pressure field in the broader area of Debrecen, Eastern Hungary (approx. 8000 km2), to find potential areas for hydraulic trapping in the study area, to explore the hydraulic connection between Hajdúszoboszló and Ebes gas fields and their surroundings. First the hydrostratigraphic build-up was determined based on borehole sequences, seismic horizons and sections. Then mapping of the fluid-potential field was carried out based on measured hydraulic (pressure and hydraulic head) data by pressure vs. elevation profiles, tomographic fluid-potential maps, and hydraulic cross sections. This evaluation was complemented by water chemical and temperature data analyses by TDS (total dissolved solids content) and temperature vs. elevation profiles, tomographic isoconcentration and isotherm maps, as well as cross sections. Based on the results of the data processing two distinct flow systems were identified and characterized, namely the nearly hydrostatic, gravitational, and the overpressured flow system, which are well known in the Pannonian Basin (eg. Tóth & Almási, 2001). Beneath the main recharge area (Nyírség), gravitational downward flow is superimposed to the deeper upward flow and thus a potential minimum zone evolves. This zone can function as a hydraulic trap, so this can be the upper limit of vertical hydrocarbon migration (Czauner & Mádl-Szőnyi, 2013). As the aim of this research, the connection between the flow systems and the areas of Hajdúszoboszló and Ebes gas fields were analysed in detail. The favourable hydraulic conditions of entrapment and

Hévíz, Hungary, 15-19 October, 2019 page 150 of 197 International Lithosphere Program accumulation right here are provided by coincidences of different factors. Namely, in the area of the Hajdúszoboszló gas field upward gravity-driven flow dominates from the elevated Pre-Neogene basement, which may focus flows of the underpinning overpressured system from the South, up to the land surface. This upward flow zone could force the dominantly horizontal SW-directed gravitational flows to turn upward, whilst pressure and temperature drop, as well as salinity increases and these together decrease the solubility of hydrocarbons in groundwater. Furthermore, the differences related to the topography of the Pre-Neogene basement between the Hajdúszoboszló–Ebes High and the Derecske Trough were described, as they determine the pressure and heat dissipation and secondary migration pathways as well. In addition, these findings can help to find geothermal resources with greater economical confidence (Mádl-Szőnyi & Simon, 2016). These conclusions demonstrate the significance of hydraulic studies in the understanding of secondary hydrocarbon migration and accumulation. Combining these methods with the otherwise used industrial practice as a hand-in-hand experience, they can help to reach better scores in hydrocarbon exploration, as well as in geothermal research. These results are part of a project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 810980 and was supported by József and Erzsébet Tóth Endowed Hydrogeology Chair and Fundation, as well as Vermilion Hungary Ltd.

CZAUNER, B., MÁDL-SZŐNYI, J. (2013): Regional hydraulic behavior of structural zones and sedimentological heterogeneities in an overpressured sedimentary basin. Marine and Petroleum Geology 48, pp. 260-274. MÁDL-SZŐNYI, J., SIMON, SZ. (2016): Involvement of preliminary regional fluid pressure evaluation into the reconnaissance geothermal exploration – Example of an overpressured and gravity-driven basin. Geothermics 60, 156-174. TÓTH, J. (1999): Groundwater as a geologic agent: an overview of the causes, processes, and manifestations. Hydrogeology Journal 7, 1–14. TÓTH, J., ALMÁSI, I. (2001): Interpretation of observed fluid potential patterns in a deep sedimentary basin under tectonic compression: Hungarian Great Plain, Pannonian Basin. Geofluids 1.1, pp. 11-36.

Hévíz, Hungary, 15-19 October, 2019 page 151 of 197 International Lithosphere Program The TOPO TRANSYLVANIA Project: An Introduction

Alexandru Szakács1,2, Andrei Bălă3, Felix Borleanu3, István Bozsó4, Ágnes Gál5, Orsolya Gelencsér6, Thomas Pieter Lange6, Elena Manea3, Attila Novák4, Laura Petrescu3, Mihaela Popa3, Mircea Radulian3, 7, Csaba Szabó6, Eszter Szűcs4, Viktor Wesztergom4

1Institute of Geodynamics, Romanian Academy, Bucharest, Romania 2Sapientia University, Cluj-Napoca, Romania 3 National Institute of Physics of the Earth (INFP), Bucharest, Romania 4Geodetic and Geophysical Institute, Hungarian Academy of Science, Sopron, Hungary 5 Babeș-Bolyai University, Institute of Geology, Cluj-Napoca, Romania 6 Eötvös Loránd University (ELTE), Budapest, Hungary 7Academy of Romanian Scientists, Bucharest, Romania

Initiated as an informal cooperation between a few Hungarian and Romanian researchers looking for a test-area to apply original satellite-based geodetic techniques developed at the MTA CSFK Geodetic and Geophysical Institute (Sopron, Hungary), the original idea evolved into a multi- and inter-disciplinary project proposal aiming at the multidisciplinary monitoring of the geodynamically most active part of Europe, the internal part of the Carpathian bend area in Romania and adjacent parts of the Transylvanian Basin. It is the site where a number of ongoing and geologically recent processes (seismicity, recent volcanism, “post-volcanic” phenomena, focused geothermalism) converge in space and time. TOPO TRANSYLVANIA now involves a large number of scientists representing a spectrum of Earth-science expertise, and a number of institutions from Romania and Hungary with the cooperation of the Tectonics Group, University of Utrecht (Netherlands) under the aegis of the broader TOPO EUROPE project. It addresses the following research topics and scientific objectives: 1) coupling deep earth kinematics to surface evolution/topographic changes; 2) process-oriented understanding of landform evolution and linking it to the timescales of relevant geodynamical processes; 3) evaluating the societal relevance of this geodynamically highly active area; 4) supporting decision making related to of georisk management and mitigation; 5) assessing vulnerability and sensitivity of the target area with respect to geohazards. The investigation and modelling of the ongoing geodynamic processes in the target area will be accomplished by the integrated application of a number of research methods and techniques: 1) monitoring Earth’s surface dynamics by using high-resolution space geodetic techniques, and integrating the results with ground-based geochemical and geophysical observations; 2) investigation of lithospheric architecture by means of seismic tomography based on a densified seismic network and electromagnetic deep-sounding, also benefiting from the

Hévíz, Hungary, 15-19 October, 2019 page 152 of 197 International Lithosphere Program available potential field analysis; 3) the physical and chemical state of the lithosphere will be investigated either by a) petrographic and geochemical investigation of mantle materials (mantle xenoliths), study of cryptic “water” content of anhydrous rock-forming minerals of volcanic formations, b) observation and monitoring of ongoing “post-volcanic” processes by obtaining time series of parameters such as focused and diffuse gas fluxes and compositions (including Radon), changes in chemical compositions and temperatures of mineral water, in relation with external (atmospheric) and internal (geodynamics-related) causes and modulations, and c) paleo- geothermal studies on fluid-inclusions in post-emplacement minerals of volcanic rocks; 4) analogue and numerical modelling fostering better understanding of the coupling between volcanism, “post- volcanic” phenomena and tectonics using thermochemical models as well as constructing the linkage between the refined lithospheric architecture and dynamical observation; 5) inventory and evaluation of the natural resources in the area with special consideration of geothermal energy; 6) evaluation of geohazards of natural (volcanic, tectonic) and anthropogenic (induced and triggered seismicity) origin. This unfolding, poorly-founded but enthusiastically conducted, project started with emplacement of two arrays of satellite-signal reflectors for space geodetic measurements and monitoring of subtle topographic changes at the Praid salt diapir and on the most recently erupted Ciomadul volcano. Experimental space-geodetic studies, using existent natural reflectors, were completed for the same two areas to assess background values of displacements in the broader target areas. Samples of mantle xenoliths and their host basalts were collected for in-depth petrographic, geochemical, and fluid-inclusion studies in the Perșani Mts., as well as samples in the Harghita Mts. for investigation of the “water” content of nominally anhydrous minerals in volcanic rocks. Salt-rock samples were collected from the Praid underground mine for fluid inclusion and salt-deformation studies currently underway. Radon-flux monitoring is prepared in a mofette at Covasna. A broad-band seismic array is planned to be installed at/around Ciomadul volcano to understand and monitor its magma-plumbing system. Once the whole multidisciplinary monitoring system is in place, then decades-long monitoring of a large number of measured parameters is envisaged, allowing this way to achieve time series relevant to, and interpretable in terms of, ongoing geodynamic processes in this critical area of Europe.

Hévíz, Hungary, 15-19 October, 2019 page 153 of 197 International Lithosphere Program Extinct or dormant? The activity status of Ciomadul volcano: what we know and what we don’t?

Alexandru Szakács1, 2

1Institute of Geodynamics, Romanian Academy, Bucharest 2 Sapientia University, Dept. of Environmental Sciences, Cluj-Napoca [email protected]

Located at the southeastern end of the Miocene-Pleistocene Calimani-Gurghiu-Harghita volcanic range, Ciomadul (Csomád) volcano consists of a dominantly dacitic dome complex: a central group of tightly packed domes penetrated by two explosion craters, and surrounded by a number of isolated peripheral domes. It is subjected to intense study during the last few decades because 1) its location in the geodynamically most active part of Carpathian-Pannonian Region, at the Carpathian bend interior in Romania, 2) its most recent eruption occurred at ca. 29 Ka ago, and 3) the presence of residual magma in its mid-crustal magma chamber. The time-space evolution and eruptive history includes a long-lasting dome-building stage and a short late phase of dominantly explosive activity (phreatomagmatic and sub-Plinian eruptions through the two craters, Mohos and Sf. Ana). The magma output rates varied through time from low during the ~850 to 450 Ka time interval to higher in the ~200 to <30 Ka interval. Due to these unique (in the Carpathian-Pannonian Region) characteristics Ciomadul poses the question of its activity status: is it definitely extinct or it is only dormant (i.e. capable of further eruptions). This question was addressed since at least 25 years ago based on the evidence of presence of residual magma beneath the volcano, as pointed out early in the 1980’s. The earliest statement on this subject, that a future eruption of Ciomadul cannot be ruled out completely, is still valid today and no significant progress was made in solving the problem of the activity status (i.e extinct or dormant?) of the volcano despite the numerous and notable results obtained through intense research in the last few decades. Actually, what we know for sure in this respect is merely that the crustal magma plumbing system of Ciomadul still hosts non-erupted residual melt in the form of a crystal mush-filled magma reservoir located at ca. 8-12 km crustal depths, confirmed bygeophysical studies. A recent study, based on numerical modeling using a large number of estimated input parameters, claims that the residual magma beneath Ciomadul forms 20-58% of the rock volume hosting it and it sums up at a total volume of 20-58 km3. However, such a large volume of upper crust-hosted magma has no equivalent surface thermal expression as it would be expected. For this reason, beyond others, this magma volume figure appears unrealistic.

Hévíz, Hungary, 15-19 October, 2019 page 154 of 197 International Lithosphere Program Irrespective of the melt volumes present beneath Ciomadul, the capability to erupt of that residual magma is practically unknown, as is the current state of the magma-hosting rock body (i.e. of the magma reservoir) itself: is it a continuously cooling, freezing and shrinking (after the last eruption) body or it is being gradually melt-receiving (from below), warming and inflating feature? There is no any positive evidence that the latter is the case at present. However, as it was convincingly pointed out on petrologic grounds, Ciomadul has precedents of eruptions triggered by re- activation of its cooling-down magma chamber hosting residual dacitic magma by input (from below) of a new batch of more mafic magma. Therefore, the next question to be posed is: is there any new magma being currently generated at the lithospheric mantle (or asthenosphere) level able to ascend into, and activate the currently cooling/freezing, hence currently non-eruptible, magma reservoir of Ciomadul? The correct answer to this question is: we don’t know. In the light of current knowledge on the characteristics and time-space evolution of volcanism at regional scale (i.e. in the Carpathian-Pannonian Region megastructure of Europe), with no any active volcanism occurring, the balance seems to incline rather towards the “extinct” side against the “dormant” (i.e .capable of future eruptions) one. However, some uncertainties still remain until convincing evidence will be obtained supporting one or another of the two hypotheses. What is needed to get the final answer to the question of the activity status (extinct or dormant) of Ciomadul volcano is a specially designed geophysical/geochemical investigation (including seismics, MT, geothermics, fluid/gas geochemistry) followed by continuous decades-long monitoring of the magma-plumbing system to understand its current state and dynamics at both crustal and sub-crustal levels. This is exactly what one segment of the Topo Transylvania Project proposes to do. Until that, the old statement, saying that a future eruption of Ciomadul cannot be ruled out completely, remains valid.

Hévíz, Hungary, 15-19 October, 2019 page 155 of 197 International Lithosphere Program Well-log re-processing and re-interpretation in boreholes from the Mihályi High

Ágnes Szamosfalvi 1, László Zilahi-Sebess 2, Csilla Király 3, György Falus 4,5

1 Mining and Geological Survey of Hungary, [email protected] 2 Mining and Geological Survey of Hungary, [email protected] 3 Research Centre for Astronomy and Earth Sciences, HAS, [email protected] 4 Mining and Geological Survey of Hungary, [email protected] 5 Research Institute of Applied Earth Sciences, Miskolc University Corresponding author: [email protected]

The Mihályi High (Figure 1.) in the Little Hungarian Plain, Western Hungary has been long in the focus of geophysical exploration and geological modelling. It is generally accepted that the Late Miocene sedimentary sequence filling the basin from NW is largely incomplete on the high implying syn-sedimentary erosion or condensed sedimentation due to its elevated position.

Figure 1. Location of the investigated wells in the Little Hungarian Plain - plotted on the bottom depth map of Pannonian sediments (asl (m))

Hévíz, Hungary, 15-19 October, 2019 page 156 of 197 International Lithosphere Program More recent studies have concluded that some elements of the Late Miocene sequence, comprising of pelagic clay marl, turbiditic sandstones and aleurolites covered silty, clayey lithology are partially present (Magyar et al., 2004; Vető et al, 2014; Sztanó et al., 2016). Detailed analysis including digitalization, re-processing and re-interpretation, using advanced computation methodology, of archive paper-based geophysical well logs of more than 20 wells drilled in the area evidence that the Late Miocene all over the Mihályi High represents similar sedimentary facies, comparable also in thickness to other Late Miocene sequences in deep basin environment (Figure 2.). This may indicate that models describing the Late Miocene evolution of the NW Pannonian Basin should be revisited (e.g. Sztanó et al. 2016).

Figure 2. Possible correlation between the wells (RM24, RM40) from Mihályi High and Mihályi- 28 well (Sztanó et al. 2016) from the Csapodi Trough

Hévíz, Hungary, 15-19 October, 2019 page 157 of 197 International Lithosphere Program Magyar I., Juhász G., Szuromi-Korecz A., Sütő-Szentai M. 2004: The Tótkomlós Calcareous Marl Member of the Lake Pannon sedimentary sequence in the Battonya-Pusztaföldvár region, SE Hungary. Földtani Közlöny, 133, 521–540 (in Hungarian with English abstract) Sztanó O., Kováč M., Magyar I., Šujan M., László Fodor, Uhrin A, Rybár S., Csillag G., Tőkés L. Late Miocene sedimentary record of the Danube / Kisalföld Basin: interregional correlation of depositional systems, stratigraphy and structural evolution. Geologica Carpathica, 2016, 67, 6, 525 – 542 Vető I., Csizmeg J., Sajgó Cs. 2014: Mantle-related CO2, metasedimentary HC–N2 gas and oil traces in the Repcelak and Mihalyi accumulations, W-Hungary – mixing of three fluids of very different origin. Central Europian Geology, 57, 1. 53–59.

Hévíz, Hungary, 15-19 October, 2019 page 158 of 197 International Lithosphere Program Permian felsic volcanism in the Tisza Mega-unit (basement of the Pannonian Basin and Apuseni Mts) – Zircon U-Pb dating and geotectonic implications from a regional marker horizon

Máté Szemerédi1,2, Réka Lukács1,2, Andrea Varga1, István Dunkl3, Ioan Seghedi4, Elemér Pál- Molnár1,2, Szabolcs Harangi2,5 (underline presenting author)

1Department of Mineralogy, Geochemistry and Petrology, ‘Vulcano” Petrology and Geochemistry Research Group, University of Szeged, Szeged, Hungary 2MTA-ELTE Volcanology Research Group, Budapest, Hungary 3Geoscience Center, Department of Sedimentology and Environmental Geology, University of Göttingen, Göttingen, Germany 4Institute of Geodynamics, Romanian Academy, Bucharest, Romania 5Department of Petrology and Geochemistry, Eötvös Loránd University, Budapest, Hungary Corresponding author: [email protected]

During the Permo-Carboniferous several intramontane sedimentary basins were formed along the European Variscan Orogenic Belt controlled by a post-collisional to extensional tectonic setting. This extension was associated with intense magmatic activity exposed in various parts of the European Variscides including outcrops of the Tisza Mega-unit (Mecsek Mts, Hungary and Apuseni Mts, Romania) as well as boreholes in S Transdanubia and the eastern Pannonian Basin (Great Hungarian Plain, Hungary). Permian felsic volcanic rocks appear in all the three Alpine facies zones of the mega-unit (Mecsek, Villány and Békés Units) and also in the Codru and Biharia Nappe Systems (Apuseni Mts), and were gathered under the name of Gyűrűfű Rhyolite Formation in the Hungarian lithostratigraphy (Fülöp 1994). These felsic volcanic rocks, as the only magmatic assemblage within the thick Permo-Carboniferous sedimentary sequences (molasses type siliciclastic rocks and continental red beds), were used as a Lower Permian marker horizon in the local to subregional stratigraphy. As most of the descriptions and interpretations were related to archive reports of uranium ore and hydrocarbon explorations, a modern research of the Permian felsic volcanism was started a couple of years before, involving petrographic reinterpretations, whole-rock geochemical analyses and zircon U-Pb dating. Despite being interpreted as lavas in the former reports (e.g. Szepesházy 1967; Barabásné Stuhl 1988) felsic rocks are dominantly ignimbrites that consist of flattened devitrified pumices, resorbed quartz, feldspar and hematitized biotite. In some pyroclastic rocks strongly altered pyroxene and garnet are also present. Lavas are subordinate with the same main mineral assemblage as ignimbrites and have various recrystallized textures. Most of the samples were affected by various post-magmatic alterations (K-metasomatism, hydrothermal alteration, Alpine low-grade metamorphism) and their major element composition were modified. Thus, immobile elements

Hévíz, Hungary, 15-19 October, 2019 page 159 of 197 International Lithosphere Program were used for the rock classification (Zr/TiO2 vs. Nb/Y), showing rhyolitic–rhyodacitic/dacitic compositions. Chondrite-normalized REE patterns (Fig. 1a) and multi-element spider diagrams are similar in case of all Permian felsic volcanic rocks. The former show higher enrichment in LREEs, slighter enrichment in HREEs and a negative Eu anomaly (‘seagull’ pattern, typical for hot-dry- reduced magmas referring to continental rifting; Bachmann & Bergantz 2008; Fig. 1a), while the latter show enrichment in Rb, Th and U and depletion in Ba, Nb, Sr and Ti. In the LaN/YbN vs. LaN diagram felsic rocks follow a positive linear trend that could be explained by fractional crystallization. In the Y–Nb and Yb–Ta discrimination diagrams (Fig. 1b) most of the studied volcanic rocks fall into the border between the volcanic-arc granite (VAG) and within-plate granite fields (WPG), however, some samples from the eastern Pannonian Basin plot in the within-plate granite field. Zircon U-Pb TuffZirc ages (representing the youngest coherent age group, being closest to the eruption age) range between 267.0 +0.90 -1.70 Ma and 259.35 +0.85 -1.45 Ma, showing Middle Permian (Guadalupian) volcanism in the Tisza Mega-unit.

1. Figure: Chondrite-normalized REE (‘seagull’) pattern (a) and Yb–Ta discrimination diagram (b) of the Permian felsic volcanic rocks referring to their geotectonic setting

All petrographic, geochemical and geochronological results show that Permian felsic volcanic rocks in the Tisza Mega-unit represent the same rhyolitic–rhyodacitic/dacitic, <10 Myr-long volcanic activity associated with a post-collisional to extensional (continental rifting) tectonic regime. However, this ~270–260 Ma magmatic activity is much younger than it was previously supposed and handled (as a Lower Permian marker horizon) in the local to subregional stratigraphy. Thus, the reconsideration of ages in the whole Permian sedimentary and volcanosedimentary sequences of the Tisza Mega-unit is necessary. On the other hand radiometric ages are significantly younger from the well known parts of the European Variscides (e.g. Intra-

Hévíz, Hungary, 15-19 October, 2019 page 160 of 197 International Lithosphere Program Sudetic Basin, NE Germany) where much older ages (300–280 Ma; Breitkreuz & Kennedy 1999; Słodczyk et al. 2018, etc.) were performed. This project was (K 108375; PD 121048) was financed by the NRDIF (Hungary)

Bachmann, O. & Bergantz, G.W. (2008). Journal of Petrology, 49(12), 2277–2285. Barabásné Stuhl, Á (1988). Final report (former Mecsek Ore Mining Company), 100–213. Breitkreuz, C. & Kennedy, A. (1999). Tectonophysics, 302, 307–326. Fülöp, J. (1994). Geology of Hungary, Palaeozoic II., 445 pp. Słodczyk, E, Pietranik, A., Glynn, S., Wiedenbeck, M., Breitkreuz, C., Dhuime, B. (2018). International Journal of Earth Sciences, 107:2065–2081. Szepesházy, K. (1967). Annual report of the Geological Institute of Hungary 1967, 227–266.

Hévíz, Hungary, 15-19 October, 2019 page 161 of 197 International Lithosphere Program Roles of different driving forces in groundwater flow from theoretical models to the Buda Thermal Karst

Márk Szijártó1,3, Attila Galsa1, Ádám Tóth2,3, Tímea Havril2,3, László Lenkey1, Judit Mádl-Szőnyi2,3

1 Eötvös Loránd University, Department of Geophysics and Space Science, [email protected], [email protected], [email protected] 2 Eötvös Loránd University, Department of Physical and Applied Geology, [email protected], [email protected], [email protected] 3 József and Erzsébet Tóth Endowed Hydrogeology Chair Corresponding author: [email protected]

Numerical model calculations were carried out in order to investigate the relevance of the interaction of water table configuration and heat transfer as driving forces of regional groundwater flow (Szijártó et al., 2019). Effect of the growing geothermal gradient, regional relief, model depth and anisotropy of hydraulic conductivity were examined on the groundwater flow pattern and the temperature field corresponding to the thermal Rayleigh number (Ra=0–6336) and the modified Péclet number (Pe*=0–323). Transition from topography-driven forced thermal convection to mixed thermal convection system appears when the Rayleigh and the modified Péclet number is Ra=500–1100, and Pe*=10–20, respectively. Below these intervals, advective heat transfer is the dominant driving force, thus the flow converges towards a steady-state solution (Fig. 1).

Fig. 1. Rayleigh number (Ra) versus modified Péclet number (Pe*) for simulations with varying geothermal gradient, regional relief, model depth and anisotropy of hydraulic conductivity.

Hévíz, Hungary, 15-19 October, 2019 page 162 of 197 International Lithosphere Program However, above those intervals, additional effect of buoyancy force (free thermal convection) increases the vigorousness of the flow system, which causes time-dependent mixed thermal convection in the numerical models. Obviously, free thermal convection is facilitated by higher geothermal gradient and greater model depth, while increasing regional relief and anisotropy strengthen the formation of forced thermal convection. Besides these systematic investigations, influence of artificial thermal and flow boundary conditions were tested along the sides, on the top and the bottom of the model. Based on conclusions of the theoretical studies, combined effect of the two mentioned driving forces was examined along a two-dimensional west-east geological section across Buda Hills (Rózsadomb) to Gödöllő Hills (Fodor, 2011). Three simulation scenarios were carried out to investigate the effect of driving forces separately: (a) a purely topography-driven groundwater flow, (b) a topography-driven groundwater flow with forced thermal convection and (c) a time- dependent groundwater flow with mixed thermal convection. The verification of the model was completed in agreement with the annual amount of precipitation, the estimated heat fluxes and the result of basin-scale hydraulic evaluation of Mádl-Szőnyi (2019). Generally, the thermal convection increases the heat flux compared to the conductive model which is shown by the non- dimensional Nusselt number from 1.5 to 5 in model (b) and (c), respectively. Forced thermal convection causes a large hot upwelling with a surface temperature of 50–70 °C beneath the River Danube in agreement with the interpreted temperature depth profiles and appearances of thermal springs (Mádl-Szőnyi, 2019). The buoyancy force also facilitates the formation of small hot upwellings and convection cells in the Mesozoic carbonate sequences (Fig. 2). Mixed thermal convection induces a time-dependent, but quasi-stationary groundwater flow in the model, which might elucidate the heat anomalies in temperature maps and profiles. Calculated temperature depth profiles and measured data were compared along three vertical sections in the numerical model. This study draws attention to the importance of theoretical and ‘practical’ investigation of different driving forces in groundwater flow systems. Comparison of the numerical results and the observation data could improve understanding the fluid-matrix interaction caused by mixed thermal convection in karstified carbonate sequences and adjoining siliciclastic sedimentary basins. However, there are still some open questions: how can the climate change influence a complex groundwater flow pattern; how can we improve the understanding of the influence of geological evolution on fluid flow, temperature and solute transport processes etc.?

Hévíz, Hungary, 15-19 October, 2019 page 163 of 197 International Lithosphere Program

Fig. 2. A snapshot of the temperature distribution (T) along a hydrostratigraphic section of the Buda Thermal Karst, Hungary (based on the geological section interpreted by Fodor (2011)) at time of t=20 kyr

This research is a part of a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 810980. The project was supported by the Hungarian Scientific Research Fund (K 129279).

Fodor, L. (2011) Geological sections across Budapest E-W. In: Mindszenty, A. (2013), Budapest: geological values and man – urbangeological studies, Eötvös University Press, Budapest, pp. 20. Mádl-Szőnyi J. (2019) Pattern of groundwater flow at the boundary of unconfined and confined carbonate systems on the example of Buda Thermal Karst and its surroundings. DSc thesis. p. 150. (in Hungarian) Szijártó, M., Galsa, A., Tóth, Á. and Mádl-Szőnyi, J. (2019) Numerical investigation of the combined effect of forced and free thermal convection in synthetic groundwater basins. Journal of Hydrology, 572, 364-379.

Hévíz, Hungary, 15-19 October, 2019 page 164 of 197 International Lithosphere Program High resolution correlation of deltaic cycles: an example of lateral and temporal variablity

Orsolya Sztanó1, Imre Magyar2, Krisztina Sebe3, Lajos Katona4

1 Eötvös Loránd University, [email protected] 2 MTA-MTM-ELTE Research Group for Paleontolog, [email protected] 3 University of Pécs, [email protected] 4 MTM Bakony Natural History Museum, [email protected] Corresponding author: [email protected]

The endorheic, brackish Late Miocene Lake Pannon was filled by open-water marls, different types of turbidite systems, slope shales, stacked deltaic lobes and alluvial sediments. Both sand- prone turbidites and delatic succession are reservoirs and pathways of subsurface fluids. Therefore, the high-resolution correlation of sand bodies and interfingering of low-permeability mudstones or lignites are of prime importance. Sequence stratigraphy offers an option of correlation through the analysis of parasequence stacking pattern, though ever since its methodology has been developed it was challenged e.g. by lateral variability of the feeder systems. We have a chance to test correlation of the deltaic successions in 5 fully cored wells from a 15km*30km area in the central part of the Pannonian Basin. More than 2800 m core was investigated, the thickness of the continuous deltaic record in each core varies between 280-450 m. Detailed (dm-scale) analysis of sedimentary facies and fossils helped the environmental interpretation. Bio-, magneto- and seismic stratigraphy supported correlation. The study area is situated over a basement high and on the flank of a depression, therefore the lacutrine succession is only 900-500 m thick. This area was flooded only about 9 Ma ago, and the topmost sediments have an age of 6.5 Ma, unconformably overlain by Quaternary gravel. The open-water marls are overlain by siltstones with thin sandy intercalations, which represent the 150-200 m high shelf-margin slope, prograding from NW to SE across the area between 8.4-7.9 Ma. Afterwards, progradational deltaic lobes developed, comprising shallowing upwards cycles, i.e. parasequences, on the scale of 15-43 m thickness (Fig.1). The prodelta is represented by often laminated mudstones or mud-rich heterolithic facies. The increasing ratio of massive or cross- laminated sand, slump folds up to 3 m thick and water escape structures indicate the distal delta front. Few meter thick sand-dominated successions with cross-bedding and plane lamination point to mouth bars on the proximal delta front. The lower delta plain (inter-distributary bays) is characterized by heterolithics, organic-rich silts and sands, intense burrowing, and mottling. Variegated clays and lignite beds are more common on the upper delta plain. Delta plain successions are cut by few meter deep channels, filled by fining-up series of cross-bedded sand. In

Hévíz, Hungary, 15-19 October, 2019 page 165 of 197 International Lithosphere Program addition, 10-33 m thick, cross-bedded, medium to coarse-grained sands represent major conduits of transport, which were occasionally deeply incised even into the delta front successions.

Fig.1. Correlation of parasequences and 4th-order sequences.

In the lower and/or lakeward part of the succession, cycles are made up of alternations of prodelta and delta-front deposits, often separated by shell-beds above the parasequence boundary. In the upper and/or landward part, deltaic cycles are represented by alternations of mouth bar, lower to upper delta plain and channel-fill deposits. In many parasequences interfingering of highly variable delta plain deposits with sandy delta front is documented within a distance of 8-12 km. In each well 15-20 parasequences were recognized, but their stacking pattern shows a great lateral variability on this spatial scale. No major sand body, including incised valley- fills, neither major shales nor lignite seams can be used as stratigraphic markers. The location of maximum regression also shifts in space and time. All of theses might be related to avulsions, lateral variations in sediment input rates and locations. As a consequence, correlation could not have been carried out without the support of seismic and magnetostratigraphy. Recognition of

Hévíz, Hungary, 15-19 October, 2019 page 166 of 197 International Lithosphere Program fourth-order sequences in the shallow-water sediments is based on a combination of features, as incised valley-fills or maximum lakeward and major landward shifts of facies. Due to lateral lithological variability, neither the small- nor the large-scale stacking patterns are reflected by the well-logs. This high-resolution example demonstrates the risk and challenge of purely log-based correlations of deltaic deposits even within distances of a few km. The research was funded by NKFI 116618. Financial support from TÉT 16_16-1-2016-0004 project is acknowledged.

Hévíz, Hungary, 15-19 October, 2019 page 167 of 197 International Lithosphere Program Title: The role of space-based observations in understanding active tectonics with special emphasis on recent initiatives in Hungary

Eszter Szűcs1, Ferenc Horváth†,2, Alexandru Szakács1,3, Zoltán Wéber1, Viktor Wesztergom1

1 MTA CSFK Geodetic and Geophysical Institute, Hungary 2 deceased, Geomega Ltd. Hungary 3 Institute of Geodynamics, Romanian Academy, Bucharest, Romania Corresponding author: [email protected]

Geological structures are sensitive recorders of the dynamic processes controlling the deformation of the lithosphere. Understanding past deformation events by using geological approaches unravels the time evolution of tectonic processes. However, the study of the recent deformation of the Earth’s surface, reflecting deep-seated geodynamic processes, is challenging due to 1) the limited capacity of traditional field-based geodetic methods, 2) the coarse resolution of the Global Positioning System (GPS) measurements, and 3) the very small magnitude (i.e. long characteristic time) of the ongoing processes. Recent remote sensing methods such as satellite radar interferometry (InSAR) and optical imaging with coordinated and systematic large-scale observations of the globe mark a new era in Earth Observation studies. InSAR is a complementary technique to GPS and seismology to map and study the deformation of the Earth’s surface topography caused either of natural (earthquakes, strain accumulation along faults, volcano deformation, landslides) or anthropogenic (triggered and induced seismicity, man-made disasters) origin. European Space Agency’s Sentinel-1 twin satellite constellation with a short revisit period of 6 days (from 2016 fall) enables to capture the time dependence of surface deformation relative to historic missions. Further advantages of the mission, as compared to heritage ones, are the wide area coverage, high quality data due to stringent orbit control and open data policy which make Sentinel-1 the main tool for measuring crustal deformation reflected in topographic changes at small magnitudes over a large area for the next two decades. In this contribution we present two initiatives, currently evolved to projects, inspired by, and built upon satellite radar interferometry. TopoTransylvania was initiated by complementary research interest of a few Hungarian and Romanian researchers who sought an active area to investigate the resolution power of the newly developed artificial targets (backscatters) for Sentinel-1, on the one hand, and to obtain a quantitative measure of ongoing geodynamic processes related to recent volcanic and actual post- volcanic (gas emanation) activities in order to couple deep and surface processes, on the other hand. Since then the initiative evolved into a multidisciplinary project which aims at the complex

Hévíz, Hungary, 15-19 October, 2019 page 168 of 197 International Lithosphere Program observation and monitoring of the Carpathian Bend area (Romania) by means of seismic tomography, electromagnetic deep-sounding and space geodesy, where several geodynamical processes (increased seismicity, volcanic and post-volcanic activity, salt tectonics, active vertical motions) converge. The other project targets the development and analysis of the seismotectonic model of Hungary and was initiated by, amongst others, Frank Horváth. In the framework of the National Excellence Program project launched in January 2019 the seismotectonic vulnerability of Hungary will be determined based on the analysis and interpretation of seismogenic structures connected to neotectonic/active fault zones, assessment of local stress field, seismic tomography based on a dense broadband seismic network and more accurate epicenter determination of earthquakes, surface velocity field estimation along capable faults using Sentinel-1 space geodesy as well as taking into account local geological features and processes.

Hévíz, Hungary, 15-19 October, 2019 page 169 of 197 International Lithosphere Program A regional Alpine graphite décollement level beneath the NW Pannonian Basin

Gábor Tari1, Viktoria Németh2, Frank Horváth3 and Viktor Wesztergom4

1OMV, Vienna, Austria 2 Geomega, Budapest, Hungary 3Eötvös University, Budapest, Hungary, deceased 4 Széchenyi István Geophysical Observatory of the Hungarian Academy of Sciences, Sopron, Hungary

The so-called Transdanubian Conductivity Anomaly (TCA) of the Hungarian part of the NW Pannonian Basin has been well known for more than five decades. The exceptionally low resistivity (i.e. 1-2 Ωm) zone has a very large areal extent (on the order a few thousand km2) and it is an entirely subsurface anomaly occurring at depth between circa 3-15 km, with no corresponding outcrops. Various geological explanations of this enigmatic crustal-scale geophysical anomaly range from invoking sub-horizontal Alpine nappe contacts to subvertical dikes with graphite and/or saline fluid content. Only one possible analogue outcrop area was considered for the high conductivity anomaly so far, namely the Drauzug/Gailtal area of the Eastern Alps in Austria, some 300 km to the West from the TCA area. Previous attempts to find correspondence between the TCA and prominent seismic reflectors seen on 2D seismic reflection profiles were based on data acquired by research institutions. This study systematically correlates, for the first time, the TCA with 2D industry seismic reflection data in the same area. Our new results show a very strong correlation between the subsurface extent and location of the TCA with various sub-horizontally oriented Cretaceous Alpine nappe surfaces. In addition, we draw on the latest structural correlation of the Alpine nappe stack of the Transdanubian Central Range with its proper tectonic counterpart in the Eastern Alps. At the southern edge of the Upper Austroalpine units in northern Styria, in the Veitsch Nappe of the Greywacke Zone, numerous graphite localities are known historically. These laterally extensive graphite units in NW Styria formed as the result of greenschist-grade metamorphism of a Carboniferous coal sequence during the Cretaceous. For the first time, we describe here one well penetration of possibly age-equivalent graphitic units in NW Hungary. Correlation of the magnetotelluric anomaly with the distinct reflection seismic signature suggests that the same Paleozoic graphite-bearing Upper Austroalpine units should be present at 3-15 km depth in our study area. Therefore, we propose that the best explanation for the observed extent and geometry of the

Hévíz, Hungary, 15-19 October, 2019 page 170 of 197 International Lithosphere Program TCA is the presence of graphite in subhorizontal, tectonically thinned detachment surfaces at the base of the Upper Austroalpine nappe edifice of NW Hungary. Keywords: magnetotellurics, graphite, Alpine, décollement, Pannonian Basin, Austria, Hungary

Hévíz, Hungary, 15-19 October, 2019 page 171 of 197 International Lithosphere Program A die-hard structure in the Alpine-Pannonian junction: the Rába Line

Gabor Tari

OMV Upstream, Vienna, Austria Corresponding author: [email protected]

The much debated Rába Line trends to the NE beneath the center of the Hungarian part of the Danube Basin. The Rába Line as such was introduced by Scheffer and Kántás (1949) and Scheffer (1959). In the description of Körössy (1958, 1965) the Rába Line is "a fault of uncertain origin" in the pre-Tertiary basement separating a metamorphosed Paleozoic area in the NW (e.g. Mihályi, Ikervár, Takácsi highs) from an unmetamorphosed area in the SE (e.g. Dabrony, Vasvár, Borgáta highs, etc.). Based on reflection seismic data, Ádám et al. (1984) interpreted a SE-dipping fault at the southeastern flank of the Mihályi high as the Rába Line separating Paleozoic rocks from probable Triassic rocks in the basement. Horváth et al. (1987) further interpreted this fault as a major Neogene flower structure using a deep seismic reflection line suggesting oblique-slip movements, i.e. a combination of normal and sinistral strike-slip faulting. Another line of thought is represented by Balázs (1971, 1975), Árkai et al. (1987) and Árkai and Balogh (1989). These authors view the Rába Line as a fault separating low-grade metamorphosed Paleozoic rocks (e.g. Mihályi high) from very low-grade metamorphosed Paleozoic (e.g. Takácsi, Ikervár highs) to unmetamorphosed Mesozoic rocks. Further confusion emerged from a different attempt to locate the Rába Line. Magnetotelluric surveys in the Danube Basin revealed a highly conductive intrabasement layer (conductivity: 1-2 m). Based on several magnetotelluric transects across the area, the Rába Line was defined as the boundary of the good basement conductor to the NW. The structural feature determined in this way (e.g. Pápa et al., 1990; Nemesi et al., 1994), however, does not coincide with the Rába Line of others. Balla et al. (1990) followed this latter, magnetotelluric approach to argue that the Rába Line is not located at the southeastern flank of the Mihályi high in the center of the Danube basin but rather some 8 km to the SE, where the good intrabasement conductor seems to terminate. Moreover, Balla et al. (1990) identified the Rába Line as a "dislocation zone" on the deep reflection seismic line running along the transect. This boundary, however, does not seem visible on the seismic data (cf. Tari, 1994). Balla et al. (1990) further interpreted the Rába Line as a major subvertical to vertical fault crossing the whole crust offsetting even the Moho(!) based entirely on

Hévíz, Hungary, 15-19 October, 2019 page 172 of 197 International Lithosphere Program gravity model calculations. According to their view, the Rába Line is the most important tectonic lineament of the Little Hungarian Plain separating two crustal domains with completely different internal structures and thicknesses. Balla (1994) further proposed that the Rába Line was accompanied from the northwest by a NE-trending, intra-crustal, high-density body, similarly to the Ivrea zone of the Western Alps. In this paper we re-emphasize the simple fact that the Rába "Line" is just a one of many SE- dipping low-angle normal faults beneath the Danube Basin (Horváth, 1993; Tari, 1994), obliquely cutting across the pre-existing Eo-Alpine structural fabric (Tari, 1996; Szafián et al., 1997). Therefore, the continuing use and abuse of the Rába "Line" in numerous large-scale tectonic models and paleogeographic reconstructions (e.g. Schmid et al., 2008) is totally unjustified. The Rába "Line" as such simply does not exist and, after exactly 70 years of its inception, the entire international geoscience community should stop referring to it.

Ádám, A., Haas, J., Nemesi, L., R-Tátrai, M., Ráner, G. and Varga, G., 1984. Regional study of the tectonics of Transdanubia. In Hungarian with English summary. Annu. Rep. Eötvös L. Geophys. Inst. Hung., 1983: 37-44. Árkai, P. and Balogh, K., 1989. The age of metamorphism of the East Alpine type basement, Little Plain, W-Hungary: K- Ar dating of K-white micas from very low- and low-grade metamorphic rocks. Acta Geol. Hung., 32: 131-147. Árkai, P., Horváth, Z.A. and Tóth, M.N., 1987. Regional metamorphism of the East Alpine type Paleozoic basement, Little Plain, W-Hungary: mineral assemblages, illite crystallinity, -bo and coal rank data. Acta Geol. Hung., 30: 153- 175. Balázs, E., 1971. Altpaläozoische Gesteine des Beckenuntergrundes der Kleinen Ungarischen Tiefebene. In Hungarian with German summary. Annu. Rep. Hung. Geol. Inst. 1969: 659-673. Balázs, E., 1975. Paleozoic formations of the basement of the Little Hungarian Plain. In Hungarian. Földtani Kutatás, 18: 17-25. Balla, Z., 1994. Basement tectonics of the Danube lowlands. Geologica Carpathica, 45: 271-281. Balla, Z., Dudko, A. and Kövesi, G., 1990. The Rába Line and the interpretation of gravity anomalies along the MK-1 reflection seismic line. In Hungarian with English summary. Ann. Rep. Eötvös L. Geophys. Inst. Hung., 1988-89: 19- 47. Horváth, F., 1993. Towards a mechanical model for the formation of the Pannonian basin. Tectonophysics, 226: 333- 357. Horváth, F., Ádám, A. and Stanley, W.D., 1987. New geophysical data: evidence for the allochthony of the Transdanubian Central Range. Rend. Soc. Geol. It., 9: 123-130. Körössy, L., 1958. Some data concerning the subsurface geology of the Kisalföld (Little Hungarian Basin). In Hungarian with English summary. Földt. Közl., 88: 291-298. Körössy, L., 1965. Stratigraphischer und tectonischer Bau der westungarischen Becken. In Hungarian with German summary. Földt. Közl., 95: 22-36. Nemesi, L., Hobot, J., Kovácsvölgyi, S., Milánkovich, A., Pápa, A., Stomfai, R. and Varga, G., 1994. Investigation of the basin basement and crust structure beneath the Kisalföld (performed in ELGI between 1982 and 1990). In Hungarian with English summary. Geophys. Trans., 39: 193-223. Pápa, A., Ráner, G., Tátrai M. and Varga, G., 1990. Seismic and magnetotelluric investigation on a network of base lines. Acta Geod., Geophys. et Mont. Hung., 25: 309-323. Scheffer, V., 1959. Contributions to the problem of the "median mass". In Hungarian with English abstract. Geofiz. Közl., 9: 55-68. Scheffer, V. and Kántás, K., 1949. Die regionale Geophysik Transdanubien. In Hungarian with German summary. Földt. Közl., 79: 327-360. Schmid, S. M., Bernoulli, D. Fügenschuh, B., Matenco, M., Schefer, S., Schuster, R., Tischler, M.and Ustaszewski, K., 2008. The Alpine-Carpathian-Dinaridic orogenic system: correlation and evolution of tectonic units. Swiss Journal of

Hévíz, Hungary, 15-19 October, 2019 page 173 of 197 International Lithosphere Program Geosciences, 101:139-183. Szafián, P., Tari, G., Horváth, F. and Cloetingh, S. (1999). Crustal structure of the Alpine-Pannonian junction: combined seismic and gravity study. Int. Journal Earth Sciences, 88: 98-110. Tari, G., 1994. Alpine Tectonics of the Pannonian Basin. Unpublished Ph.D. thesis, Rice University, Houston, Texas, 501 p. Tari, G. 1996. Neoalpine tectonics of the Danube Basin (NW Pannonian Basin, Hungary). In: P. Ziegler and F. Horváth, (eds), Peri-Tethys Memoir 2: Structure and Prospects of Alpine Basins and Forelands. Mém. Mus. natn. Hist. nat., 170: 439-454. Tari, G., Horváth, F. and Rumpler, J., 1992. Styles of extension in the Pannonian Basin. Tectonophysics, 208: 203-219.

Hévíz, Hungary, 15-19 October, 2019 page 174 of 197 International Lithosphere Program Strength and effective elastic thickness of the Australian lithosphere

Magdala Tesauro 1,2 Mikhail K. Kaban 3,4, Alexey G. Petrunin3,4, Alan Aitken5

1 Trieste University, Italy 2 University of Utrecht, Utrecht, Netherlands 3 German Research Centre for Geosciences (GFZ) Potsdam, Germany 4 Schmidt Institute of Physics of the Earth, Moscow 5 University of Western Australia Corresponding author: [email protected]

The Australian plate is composed of tectonic features showing an age progression from dominantly Phanerozoic in the east, Proterozoic in the centre, and Archean in the west. Precambrian Australia has been divided into three main Archean cratons: the West, North, and South Australian cratons, which are separated from each other by Proterozoic orogenic belts and/or Phanerozoic sedimentary basins. The Phanerozoic Tasmanides in the east of Australia were accreted onto the eastern margin of the Precambrian craton in the late Palaeozoic in a series of stages.

Fig. 1 From left to right: Integrated strength distribution in the lithosphere, in the crust, and mantle lithosphere, percentage of the crustal strength.

We used the surface heat flow values recently published and the crustal seismic velocity provided by the tomography model AuSRem (http://rses.anu.edu.au/seismology/AuSREM/index.php), to calculate the lateral and vertical variations of heat generation and construct a crustal thermal model, assuming steady state conditions. The results have been combined with the mantle temperatures distribution obtained applying an iterative technique, which jointly interprets seismic tomography and gravity data, to construct a complete lithospheric thermal model. The largest thermal crustal anomalies are

Hévíz, Hungary, 15-19 October, 2019 page 175 of 197 International Lithosphere Program located in the North Australian craton, on account of the high concentration of radiogenic elements, while the hottest part of the upper mantle corresponds to the Phanerozoic areas. We used the new thermal model as input for calculation of the strength and effective elastic thickness (EET) of the lithosphere. For the same purpose, we assigned a stiff or weak rheology to the crust on the base of the seismic velocity variations and we used strain rate values obtained from a global mantle flow model, constrained by seismic and gravity data. The strength is prevalently concentrated in the mantle lithosphere of the West Australian Craton, characterized by coupling conditions of the crust and upper mantle. In the other parts of the continent, the strength is mostly located in the crust, which is mostly decoupled from the upper mantle. We observe a good correspondence between the areas having a sharp lateral crustal strength and EET variations and the location of the intraplate earthquakes, supporting the hypothesis that a change in the lithospheric rigidity can localize the stress.

Hévíz, Hungary, 15-19 October, 2019 page 176 of 197 International Lithosphere Program Start of Frank's scientific career: from Doppler geodesy to plate tectonics

Gábor Timár

Dept. of Geophysics and Space Science, ELTE Eötvös University, Budapest

Perhaps it is less known that the very start of Frank Horvath’s scientific career, still as a university student of geophysics, is connected to space geodesy. It was a very young branch of science, as the first Soviet satellite was launched in 1957 and the first American one, already applied in the Earth shape computations, followed it in 1958. The Hungarian Doppler geodesy satellite measurements have been started in the second half of the 1960s, as a cooperation of the newly founded Space Research Group (first in the Technical University of Budapest, then at the Department of Geophysics of the ELTE Eötvös University), with significant contribution of students, like Frank. The goal of these studies was to determine coordinates of distinct terrain points in an Earth-centered Earth-fixed geodetic coordinate system. The accuracy of the coordinate determination was in the same range as the locating of the control stations of the American space programs in the Mercury datum. This project was the kickoff of the research career of Frank Horvath. The figure of the Earth, namely the geoid computations have been connected to isostasy and geodynamic as early as late 1940s, as one of W. Heiskanen’s students, L. Tanni (1948) provided a geoid model of the Mediterranean region and its explanation in terms of isostasy model of Vening Meinesz (1931). Upon the new global satellite geodesy-based geoid models, these explanations were extended by Kaula (1967, 1972) to global level. Later, the largest undulation of the geoid was considered to be connected to the largest mantle convection stuctures by Chase (1979). Thus, Frank’s scope of interest turned to this direction: how to use the data, also his very own ones (Horváth, 1968; Ferencz et al., 1970) in the geo-dynamical way, also in terms of plate tectonics. He became the first Hungarian author of the subject (Horváth, 1973), turning his main attention to this directions, to run a brilliant scientific career in these latter subjects.

Chase, C. G. (1979): Subduction, the geoid, and lower mantle convection. Nature 282: 464-468. Ferencz, Cs., Drahoz D., Ferencz, I., Horváth, F. & Tarcsai, Gy. (1970): Some theoretical contributions concerning Doppler-geodetical measurements. Space Research, 10: 43-53. Horváth, F. (1968): The gravity field of the Earth as determined by satellite observations and some of its geophysical implications. Annales Universitatis Scientiarum Budapestinensis de Rolando Eötvös Nominatae – Sectio Geologica, 13: 43-52. Horváth F. (1973): Lemeztektonika és a globális gravitációs tér. MTA X. Osztály Közleményei 6, 293-298. Kaula, W. M. (1967): Geophysical implications of satellite determinations of the Earth’s gravitational field. Space Science Reviews, 7(5-6): 769-794. Kaula, W. M. (1972): Global gravity and tectonics. In: Robertson, E. C. (ed.): The nature of the solid Earth. McGraw-Hill,

Hévíz, Hungary, 15-19 October, 2019 page 177 of 197 International Lithosphere Program New York NY, 385 p. Tanni, L. (1948): On the continental undulation of the geoid as determined from present gravity materials. — Publications of the Isostatic Institute of I.A.G., 18: 1-78. Vening Meinesz, F. A. (1931): Une nouvelle méthode pour la réduction isostatique régionale de l’intensité de la pesanteur. Bulletin Geodésique 29: 33-54.

Hévíz, Hungary, 15-19 October, 2019 page 178 of 197 International Lithosphere Program Cycles of erosion, aggradation and abandonment: architecture of deep-water channels and lobes, Transylvanian Basin, Romania

Lilla Tőkés1, István Róbert Bartha2, Lóránd Silye3, Csaba Krézsek4, Orsolya Sztanó1

1 Department of Geology, Eötvös Loránd University, Budapest, Hungary, [email protected] 2 Department of Geology, Eötvös Loránd University, Budapest, Hungary 3 Department of Geology, Babeș-Bolyai University, Cluj-Napoca, Romania, [email protected] 4 OMV Petrom S.A., Bucharest, Romania 5 Department of Geology, Eötvös Loránd University, Budapest, Hungary Corresponding author: [email protected]

Near seismic-scale exposures of deep-water architectural elements from the late Miocene of the Transylvanian Basin, Romania offer an insight into the dynamics of erosional and depositional processes in contemporaneous channels and lobes. The detailed facies analysis, gamma-ray logging, and mapping of stratal patterns and channel-form surfaces revealed the development of the internal anatomy of the elements. Seven facies have been determined, recording hemipelagic settling, dilute muddy turbidity currents, low-density sandy, high-density sandy and gravelly turbidity currents. The mud-prone facies association corresponds to a slope environment, the mixed sand-mud and the sand-prone facies associations characterize channel fills and lobes (Fig. 2).

Fig. 2 Conceptual model of the turbidite system and their architectural elements in the southern Transylvanian Basin.

Although the studied outcrops are of slightly different age within a narrow time range and represent different parts of the system, they clearly mirror the spatial and temporal evolution of the deep-water depositional environment from deep compound slope channels to shallow sandy channels with levees, connected to channelized proximal, axial lobes to distal lobe fringes. 1)

Hévíz, Hungary, 15-19 October, 2019 page 179 of 197 International Lithosphere Program Gușterița and Daia, 2) Tău, 3a) Micăsasa (upper part), Seica Mare, 3b) Ocna Sibiului, 4) and 5) Micăsasa (lower part). A deep slope channel went through multiple cut-and-fill phases: erosion, bypass and coarse lag deposition, sedimentation from gravelly and sandy turbidity currents in the channel axis was repeated on three hierarchical levels (Fig. 3). First lateral migration, then vertical aggradation was more dominant. Backsets also occur, interpreted as cyclic steps. An erosionally based, shallow sandy compound channel fill shows more lateral migration. The isolated channel formed in response to avulsions and low aggradation rate. Amalgamated pebbly sandstones of lobes record high aggradation rate. Scour surfaces suggest channelized lobes: a proximal axial or medial axial part of a lobe. Erosionally based, upward thinning cycles are attributed to lateral or upstream stepping of lobe elements. A proximal lobe fringe setting is manifested by laterally varying bed thickness in a mixed sand-mud facies association.

Fig. 3 Sequence of cut-and fill patterns both in channels and lobes due to cycles of erosion, lateral displacement, aggradation and abandonment in relation with repeated waxing and waning flow energy of the successive turbidity currents.

Hévíz, Hungary, 15-19 October, 2019 page 180 of 197 International Lithosphere Program These diverse architectural elements could develop in one turbidite system, reflecting downstream and along strike variations (Fig. 2). The scarcely documented late Miocene turbidite system in the Transylvanian Basin developed in close relationship with the uplifting Carpathians fringing the basin. Tectonic pulses in the source area may have controlled deposition, but no direct link has been revealed so far. Cyclic waxing and waning flow conditions of successive turbidity currents influenced the evolution of both channels and lobes (Fig. 3). This work was supported by the Papp Simon Foundation, the Koch Antal Geological Society and the Hungarian National Research, Development and Innovation Office (NKFIH – 116618).

Hévíz, Hungary, 15-19 October, 2019 page 181 of 197 International Lithosphere Program Neogene collision between the ALCAPA plate and Europe and the Origin of the Tatra – Fatra Mountains

Čestmír Tomek1

1 Earth Science Institute of the Slovak Academy of Sciences, Dubravska cesta 9, Bratislava

Feri Horváth was my close friend in our young and best ages from September 1975. Last time we had a lunch at Balaton Lake in april 2017. Feri devoted the most significant scientific effort to the Pannonian basin. The unique terrestrial one all back-arc basin of the Mediterranean system. I contributed to all his books and conferences in the eighties with my view on the Czechoslovakian part of the Pannonian realm. This presentation is devoted to the antithesis of the Pannonian system, the 150 km long mountain chain in Slovakia and Poland originated during 16 Ma – Recent time interval. The uplifted area is 150 km long and 60 km wide and crustal crustal thickening took place there after Sarmatian final docking of the ALCAPA subplate to the European foreland. This thick crust is isostatically compensated according to an excellent isostasy study by Popelář (1965). As the convergence of both plates is still going on, I conclude that steady state uplift and erosion is still compensated by arrival of the material from the SW and its compressive (collisional) amalgamation above the sharply bent European plate with very low effective elastic thickness. Geodynamic development of the Tatra - Fatra mountain system in their recent form started in the Badenian about 16 Ma ago. The first five Ma until early Pannonian (11 Ma) were coeval with oceanic subduction in the East Carpathians and were dominated by large-scale orogen-parallel extension elsewhere (rift stage of Royden – Horváth publications). During this time significant amount of the CCP basin sediments were extended and exhumed. The thickness of that time inverted basin about 6 – 7 km thick was significantly reduced, at least 30%. Also the megafold of the Tatra Mts. was formed during this period as an extensional dome. The Tatra mountains are composed of two parts, the West Tatra Mts. and the High Tatra Mts. They form dominant mountain system of the West Carpathians. Even though they are only 53 km long and 15 km wide, the Tatras are the highest mountains of the whole recent Carpathian arc. On all sides except the SW, they are surrounded by thick sedimentary complexes of inverted Central Carpathian Paleogene (CCP) basin. The Late Pliocene and Quaternary cold climate and mainly last 900 ky of seven severe ice ages shaped Tatras to recent face that is very different from previous post-Sarmatian to late Pliocene times. Extreme erosional exhumation due to cold climate and glaciations gave rise to 2 km high

Hévíz, Hungary, 15-19 October, 2019 page 182 of 197 International Lithosphere Program rugged mountains and different, gravels dominated, sedimentation around described precisely by Tokarski. I hypothesize that the amount of uplift due to crustal thickening was nearly the same during the last 11 Ma but exhumation was severe during the last 2 to 3 Ma. So before Quaternary, all area of crustal thickening was a high plateau with mild erosion giving rise to basins like the Orava basin where pre-Quaternary sediments are of pelitic nature. The sedimentation in the Orava basin started 11,8 Ma ago exactly when two different tectonic regimes changed. Uplift rate in the very center of the thickening area was measured precisely by AFT method in deep borehole Bukowina Tatrzaňska PIG-1 by Anckiewicz and others (2013). Rate of erosion was 400 m/Ma between 10 Ma to 6 Ma. If the uplift would be steady state, than about 4 km of material was removed during the last 11 Ma when large scale thickening started. This large amount of removed Paleogene and Neogene sediments of the CCP (Central Carpathian Paleogene) is in accordance with previous study by Srodoň and others 2008) based on illite – smectite study of shales of the CCP. Partially exhumed Tatra Mts. were completely stripped of CCP sediments and, beacause of cold climate, very rugged mountaineous relief developed as in many other mountains during this period (Molnar, 2003). The souther fault of the Tatra – Fatra Mts., we follow in several seismic sections crossing the fault. The line 2T North crossed the fault in the central area of the Choč Mts. It revealed that the Liptov basin filled by sediments of the CCP is a syncline and that the Paleogene sediments did not dip under the Choč Mts. Instead, they are turning up above the Choč. Further to the E, seismic lines start subsequently release the thrust image of the fault. The High Tatras behaved therefore during the first phases of collision as a megaanticline that was later cut by thrust fault in the southeast.

Hévíz, Hungary, 15-19 October, 2019 page 183 of 197 International Lithosphere Program Structural constraints of groundwater flow and heat transport in the Lake Balaton region

Ádám Tóth1, Judit Mádl-Szőnyi1

1 József & Erzsébet Tóth Endowed Hydrogeology Chair, Department of Geology, ELTE Eötvös Loránd University Corresponding author: [email protected]

Naturally discharging springs and water wells have been providing high-quality water as a local drinking water resource in the Bakony Mts. – Balaton Highland area (Central Hungary, Europe) for centuries. On the other hand, the Balaton Highland – Lake Balaton region is a popular tourist destination with an outstanding ecological value of the Lake Balaton and the surrounding wetlands. For the proper and sustainable water management, we need to reveal the groundwater flow systems of the Bakony Mts. – Balaton Highland – Lake Balaton region. It means the understanding of hydraulic connection between the subareas of it, quantity and areal distribution of groundwater recharge, subsurface flow paths through the mainly carbonate formations and also the exploitable amount of groundwater which, meets the human and ecological needs. Therefore, the main aim of the study was to disclose the natural hydrogeological processes in the Lake Balaton region, applying the modern theory of basin hydraulics, considering the special behaviour of carbonate systems and the structural constraints. Hydraulic and hydrochemical connection among Bakony Mts., Balaton Highland, Lake Balaton and Somogy Hills were examined. Water management-related issues were also discussed regarding drinking water resources, sustainable water use and geothermal potential. The study area consists of ~2-3 km thick carbonate formations with hydraulic conductivity of 10- 6–10-5 m/s. Two main tectonic events have played important role in determining the hydrogeological conditions: the first has resulted syncline structures before the Late Cretaceous and the second one has produced ~200 km horizontal displacement along strike slip faults during the Miocene. The hydrostratigraphy and the basin geometry modify the flow pattern. The folded basement aquitard restricted the groundwater flow at the boundary of the Bakony Mts. (~5 km deep) and Balaton Highland (0.5–1-km-deep basin) and it caused intensified flow toward the area of the Lake Balaton. The low-permeability thrust-fault caused a hydraulic head drop of 10–30 m at the footwall. South of the Lake Balaton, the carbonates are covered by a <2-km-thick siliciclastic cover. The intensity of groundwater flow is low in this confining layer, and groundwater is directed toward the Lake Balaton because of the water table difference. This could result in a subsurface

Hévíz, Hungary, 15-19 October, 2019 page 184 of 197 International Lithosphere Program convergence zone of groundwater flowing from the Northern and Southern basin. Subsurface temperature field reflected the advective heat transport caused by the groundwater flow. The recharging cold water could infiltrate and move down to –3 000 m asl under the Bakony Mts., thermal water (>30 °C) could be found in deeper parts of the basin, except the two near-surface heat accumulations under the boundary of Bakony Mts. and Balaton Highland and under the basin of Lake Balaton. Slightly elevated water temperature (20–23°C) can be found in the region of the Lake Balaton. The regional-scale numerical simulation and hydraulic data evaluation could disclose flow components from the North and South; revealed an asymmetric flow pattern caused by different topographic settings in the Northern and Southern basins; the hydraulic regimes in the broader vicinity of the Lake Balaton; and the groundwater discharge through the lakebed of the Lake Balaton. The constraints of the groundwater flow and heat transport are provided by the distinctly different hydrostratigraphic configuration, basin depth and topographic settings determined by structural evolutionary events. This research is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 810980.

Hévíz, Hungary, 15-19 October, 2019 page 185 of 197 International Lithosphere Program From alluvial plain to shallow sea: The evolution of the southern part of the Gulf of Trieste since the Last Glacial

Ana Trobec1, Andrej Šmuc1, Sašo Poglajen2, Marko Vrabec1

1 University of Ljubljana, Faculty of Natural Sciences and Engineering, Department of Geology, [email protected], [email protected] 2 Sirio d.o.o., [email protected] Corresponding author: [email protected]

Rapid sea-level rise following the last glacial maximum submerged extensive areas of shallow continental shelves. One such area is the northern Adriatic which was a vast alluvial plain prior to the Holocene transgression. We present a compilation of our recent research efforts focused on the Late Pleistocene-Holocene transition in the Slovenian part of the Gulf of Trieste, the northeasternmost part of the Adriatic Sea. High-resolution bathymetric surveys of this area show a complex seafloor morphology which reveals the well-preserved paleotopography of the submerged and subsequently buried pre-transgressional fluvial features. We used high-resolution parametric sub-bottom sonar profiling and established the acoustic stratigraphy of the seabed sediments. We obtained samples of the seabed sediments with a gravity corer. We dated the sediment samples and analysed their granulometric characteristics. We correlated the granulometric characteristics with the determined acoustic facies and established the geological evolution of the studied area since the Last Glacial. The oldest sampled sediment (approx. 30 ky cal BP) is represented by fluvio-aeolian sandy mud for which chaotic low-amplitude reflection geometries are characteristic. Floods later redeposited this sediment in the form of graded deposits (sandy mud grading into clay) which exhibit distinct subhorizontal high-amplitude and high-frequency reflections in the geophysical profiles. These deposits were covered by fine-grained (mud and clay) floodplain sediments which were depositing during the Last and Late Glacial. These fine-grained sediments are generally acoustically transparent, but contain individual discontinuous low- to middle-amplitude reflections. Within the floodplain deposits two sinuous fluvial channels can be resolved from the geophysical data. The youngest channel is exceptionally well-preserved and can be recognised in the seafloor morphology even though it is buried by up to 10 meters of younger sediment. Above the floodplain sediments a thin layer of Early Holocene transgressive muds and sandy muds containing brackish fauna was deposited. In the geophysical record these sediments are characterised by continuous subhorizontal or slightly undulating middle- to low- amplitude reflections. The youngest deposits are represented by Holocene-to-recent marine mud and sandy mud with an average thickness of approximately 5 meters. These sediments produce a

Hévíz, Hungary, 15-19 October, 2019 page 186 of 197 International Lithosphere Program characteristic acoustically transparent acoustic facies. The demonstrated relatively continuous sedimentation since the Last Glacial make our study area in the Slovenian part of the Gulf of Trieste an ideal natural laboratory for future studies of the Late Pleistocene-Holocene transition. Our work represents the first correlation of the acoustic and sedimentary facies of a well-preserved Late Quaternary alluvial plain transgressed during the Holocene.

Hévíz, Hungary, 15-19 October, 2019 page 187 of 197 International Lithosphere Program Towards a new era in seismological imaging of the lithosphere beneath the Pannonian Basin

Zoltán Wéber1,2, Bálint Süle1,2, Tibor Czifra1,2 Zoltán Gráczer1,2, István János Kovács1,2, Antje Schlömer3, Gyöngyvér Szanyi1,2, Eszter Szűcs1, Viktor Wesztergom1

1 Geodetic and Geophysical Institute, MTA CSFK 2 MTA CSFK Pannon LitH2Oscope Research Group 3 Geophysical Observatory, Department of Earth and Environmental Sciences, Munich University Corresponding author: [email protected]

Earthquake-generated elastic waves travel across the Earth’s interior in all directions, so they are especially suitable for probing the subsurface for lithosphere structure. Detailed three-dimensional (3D) imaging of the lithosphere, however, requires a dense seismic network on the surface. From July 2019, in cooperation with the German Seismological Broadband Array (DSEBRA) consortium, the Kövesligethy Radó Seismological Observatory (KRSO) operates more than 40 broadband seismic stations covering the whole territory of Hungary (Fig. 1). Fifteen permanent stations constitute the Hungarian National Seismological Network (HNSN) which is supplemented by eleven temporary deployments operating till the end of 2021. In addition, 15 temporary stations are equipped and financed by the German DSEBRA consortium and are to be operated till the end of 2020. This network is somewhat a continuation and extension of the Hungarian part of the earlier AlpArray Seismic Network operated till March 31, 2019 in the western half of Hungary (Transdanubia). Hungary, and for that matter the Pannonian basin, has never been covered by such an unprecedentedly dense seismic network before.

Hévíz, Hungary, 15-19 October, 2019 page 188 of 197 International Lithosphere Program Figure 1: Map showing the locations of seismic stations operating in Hungary

The overall objective of these deployments is to provide the observational basis for high- resolution 3D imaging of the physical properties of the lithosphere and a more refined identification of discontinuities in and between the main tectonic microplates of the lithosphere and the underlying asthenosphere. The detailed images provided by this dense seismological network will vastly improve our understanding on the structure and geodynamics of the Carpathian-Pannonian region. Three ongoing research projects supported by the National Research, Development and Innovation Fund (NRDI) and the Hungarian Academy of Sciences (HAS) contribute to and benefit from the large amount of high-quality data produced by this seismic network: 1) A thematic research project (Grant No. NRDI K124241) whose aim is to create detailed 3D P- and S-wave velocity images of the crust and upper mantle beneath the Pannonian basin and to map the topography of the Moho and the lithosphere-asthenosphere boundary (LAB). 2) A National Excellence Programme (Grant No. NRDI 2018-1.2.1-NKP-2018-00007) which is about to develop and evaluate a novel seismotectonic hazard map of Hungary.

3) The MTA CSFK Lendület Pannon LitH2Oscope grant (Grant No. LP2018-5/2018) which aims to develop a novel petrophyscial model for the lithosphere-asthenoshpere boundary including the role what tiny amount water plays in regulating the melting properties of the upper mantle (also

Hévíz, Hungary, 15-19 October, 2019 page 189 of 197 International Lithosphere Program referred to as the new ‘pargasosphere’ concept). This concept has several empirically testable predictions on the behaviour of seismic waves at the LAB, and the Carpathian-Pannonian Region offers a unique natural laboratory for this globally relevant ‘experiment’. The outputs of these projects will expectedly shed light on several, presently unresolved scientific questions. This presentation provides an overview of this seismic network outlining its instrumentation and typical configuration, furthermore shows its noise characteristics and the sensitivity estimate of the network.

Hévíz, Hungary, 15-19 October, 2019 page 190 of 197 International Lithosphere Program Combinations and an interaction of mechanisms of formation of the folded and the mountain structure of the Greater Caucasus in scales of (a) the sedimentary cover and (b) the Earth crust (to the problem of planning of geodynamic modeling)

Fedor L. Yakovlev

Institute of physics of the Earth of RAS, Moscow, Russia, [email protected]

Introduction. The study of the mechanisms of formation of folded structures of the internal parts of the folded-thrust structures is important, because they lead to growth of the continental crust, and are involved in the formation of mountain building. The presented material was collected during realization of several types of research, and it can be used for integrated planning of experiments on modeling of complex structure on the example of the Greater Caucasus. Materials and basic method of studying of a folding. The folded structure of the Greater Caucasus is characterized by a large amount of information in 24 structural profiles of more than 500 km total length. At least four hierarchic levels of structure (from seven ones, [Yakovlev, 2015]) were used in a study. The structure of each profile was divided into domains (level III of hierarchy) that combine folds with homogeneous morphology. Deformation of the domain is described by structural elements associated with the strain ellipsoid (fig. 1A). A method of balanced section reconstruction [Yakovlev, 2017], based "on geometry of folded domains", was used. Pre-folded states of domains were combined into "structural cells" (level IV), which allow to measure the shortening value of “cells” (Fig. 1B). The method [Yakovlev, 2017] allows also to determine the depths of the basement top for structural cells (for the pre-folded, post-folded and modern stages) and the amplitudes of uplift after folding and mountain building (Fig. 1B, sign 6). The geometry of the structure in the scale of the sedimentary cover. At the scale of the “structural cells” (for 78 cells), the shortening values were determined in range from 0.63 to 0.33 for the Eastern part of the Greater Caucasus with average shortening 0.43, 0.45 and 0.51 for three “tectonic zones” (level V of hierarchy). The estimated depths of the basement top after folding and neotectonic uplift for the present stage of development for the same structures are, for example, -10.2 km, -12.0 km and -20.5 km (with range -13.6 ÷ -26.3). It was determined that in many cases the cells are separated by subvertical faults with the displacement amplitude on the level of basement top up to 10-15 km (Fig 1 B, sections 6, 5, 4). The reproduction of these parameters of particular natural structures can be planned as the purpose of physical or computing experiment. Compilation of a list of possible mechanisms for the formation of the folding of a sedimentary cover; a decision-making. The concept of "folded domains" description in form of a strain ellipsoid

Hévíz, Hungary, 15-19 October, 2019 page 191 of 197 International Lithosphere Program [Yakovlev, 2015] made it possible to clarify the problem of diagnostics of the mechanisms of structure formation (Fig. 2). Several series of physical models of mechanisms from literature, such as “lateral pressure”, “gravitational sliding”, “diapiric” and “convective” structures were investigated. Own cinematic models "advection plus the shortening (flattening)", "quasi-buckling" on the scale of the sedimentary cover, as well as a local "thrust related” mechanism [Yakovlev, 2015] were studied also. It was determined that each mechanism is characterized by its specific path of displacement (trends) in the feature field (Ax, En, K). Comparison of natural structures with reference mechanisms, using the same quantitative parameters of morphology, allows us to give a list of mechanisms, acting in nature. The natural structures of the three tectonic zones of the Eastern Caucasus showed a good similarity of their contours in the most developed domains (Fig. 2, blue arrows), as it shown in the diagrams by the letters "A, B, C, F, G, J, K". Folded structures are cinematically well described by a combination of the synthetic model “advection plus shortening” (Fig. 2, sign 4) with “inclined zones of simple ductile shearing”, i.e. “thrust-related” mechanism (Fig. 2, sign 5, 6). These data as well as the shortening values of natural structures (noted above) may be used for a planning of folded structures simulation. The “mechanism” of displacement on the vertical faults (fig. 1B) remains unknown at this stage of study of the folding process. The geometry of the structure at the scale of the crust. The structure of the Greater Caucasus on the scale of the crust and the upper mantle (“folded system”, level VI) for different stages of development can be obtained by summarizing the above data in the scale of tectonic zones. Formation of a folded structure with an average shortening 0.50, as well as the growth of the mountain structure can take place only with an increase in the density of a large volume of crust rocks up to the density of mantle one [Yakovlev, 2012]. Recognition of mechanisms in the scale of the crust and upper mantle. Six parameters of the structure on the “cells” scale relates to the geodynamics of Greater Caucasus formation (fig. 1B, sign 6). The study of their pair correlations and the use of factor analysis [Yakovlev, Gorbatov, 2018] allowed to identify two main factors, i.e. geodynamic mechanisms. First factor (F1, "isostasy") shows the dependence of the modern depth of the basement top from its depth at the pre-folded stage. It is associated finally with an increasing of the density of crustal rocks up to the "mantle" values. The second factor (F2, "shortening") shows the dependence of the neotectonic uplift value (stage 3) on the shortening value (stage 2). Relationship of mechanisms on the scale of the sedimentary cover and mechanisms on the scale

Hévíz, Hungary, 15-19 October, 2019 page 192 of 197 International Lithosphere Program of the crust and the upper mantle. Data on the mechanism of "isostasy" (which acts constantly) well explains the vertical movement of crust blocks, including large displacements of basement top along vertical faults (fig. 1B). Thus, the possibility of a detailed description of the mechanisms of the structure formation acting in different scales and in a certain way interconnected is revealed. The geodynamic nature of the horizontal shortening (acting episodically) in these scales of generalization has not yet been explained.

Yakovlev F.L. (2012). Reconstruction of the balanced structure of the eastern part of alpine Greater Caucasus using data from quantitative analysis of linear folding – case study // Bulletin of “KRAESC”. Earth Sciences. No. 1 (19), pp. 191- 214. [in Russian]. Yakovlev F.L. (2015). Multirank strain analysis of linear folding on the example of the Alpine Greater Caucasus. Doctoral thesis. Moscow, IPE RAS. Manuscript. 472 P. [in Russian]. Yakovlev F.L. (2017). Reconstruction of folded and faulted structures in zones of the linear folding using structural cross-sections / Moscow: Published in IPE RAS. 60 p. [in Russian]. Yakovlev F.L., Gorbatov E.S. (2018). On using the factor analysis to study the geodynamic processes of formation of the Greater Caucasus. Geodynamics & Tectonophysics, 9 (3), 909–926. [in Russian].

Hévíz, Hungary, 15-19 October, 2019 page 193 of 197 International Lithosphere Program Tentative results of the analysis of the main geodynamic processes of formation of the crust and the upper mantle structure of the Greater Caucasus; their spatial variability

Fedor L. Yakovlev, Evgenii S. Gorbatov

Institute of physics of the Earth of RAS, Moscow, Russia, [email protected], [email protected] Corresponding author: [email protected]

Introduction. The main problems of tectonics and geodynamics are connected with uncertainty of mechanics of continental crust formation and development, including the subsidence of crust blocks, folding formation and mechanisms of mountains uplift. In this study, the methods of structural geology and tectonophysics are used for a collection of reliable data on the development of the active Alpine region. The model of the sedimentary cover, which is balanced on volumes of sediments. The material of detailed structural profiles was transformed into a quasi 3-D model of the structure of the sedimentary cover of the Greater Caucasus [Yakovlev, 2015] using the method of balanced section compilation "on the geometry of folded domains" [Yakovlev, 2017]. The main data were obtained by measuring the morphology of "folded domains", occupying a space of 0.5-2 km along the profile and consisting from several folds. Pre-folded states of several domains combined into "structural cells" (with a length 5-7 km), which allow obtaining the shortening values for them. The structure of sedimentary cover for three stages of the Caucasus development – pre-folded (J1 – Pg2), post- folded (Pg3 – N1) and post-uplifted (N1 – Q) was reconstructed. After additional operations, six parameters for each "structural cell", which are relevant to the geodynamic processes of the Greater Caucasus, were obtained (table 1): the depth of the basement top at all three stages (1, 3, 4,), the value of shortening (2), the amplitude of the uplift and erosion (5), as well as the difference in the depth of the basement top between the first and third stages (6). The material of 24 structural profiles with a total length of more than 500 km was divided into 505 domains, which were combined into 78 structural cells after the reconstruction of the structure. Some strong pair correlations between these several parameters were found; obviously, they have a genetic meaning [Yakovlev, 2015]. It was also found that the depth of the basement top from the pre- folded stage to the present one, consistently passing through the processes of folding and mountains building, tends to come back to the initial level [Yakovlev, 2015]. Factor analysis was used for the complex analysis of those processes that led to the appearance of a certain combination of values of six parameters in 78 cells [Yakovlev, Gorbatov, 2017, 2018]. It was found that the totality of all dispersions of values is determined by two factors, which were

Hévíz, Hungary, 15-19 October, 2019 page 194 of 197 International Lithosphere Program interpreted as two processes (not a one or three). There are (table 1; columns 1, 2): F1, weight 47%, "Isostasy", associated with the stability of the basement top depth and changes of the crust rocks in the density up to mantles meanings, and F2, weight 40%, “Shortening”, in which the neotectonic uplift is determined by the shortening value. Clarification of the history of the formation of the crust structure. Based on the idea that isostasy is acting all the time, and based on the facts of the geological development of the region, parameters of the changes of the crust thickness for Chiaur zone for all stages of development were calculated [Yakovlev, Gorbatov, 2018] (Fig. 1). The initial thickness of the crust at the beginning of the sediments accumulation was 40 km, during the accumulation of 15 km of sediments, the crystalline crust degraded and it had a new thickness of 14 km; from the rocks of the former crust, a layer of a new mantle with a thickness of 26 km was formed. The isostatic balance of the modern structure showed that the depth of the sedimentary cover bottom is 20 km; the crystalline crust thickness is 19 km. In case that the uplift of the structure at stage 3 was in its pure form after shortening and full subsidence at stage 2, the modern crust thickness of 19 km includes 15 km belonged to the new mantle (appeared at the stage 2), which, during uplift and erosion (stage 3), acquired the density of the crust rocks again (Fig. 1). Thus, significant amounts of crystalline crust rocks during the formation of folding and growth of mountains eventually experienced compaction (about 15%, 2.83 / 3.30 g/cm3). The growth of mountains at the last stage is accompanied by decompaction, of course.

Regional stability of the result. To clarify the limits of the variety of manifestations of the identified processes, the structures of Dagestan (13 cells) were studied additionally at further investigation; also, the structures of the North-Western Caucasus (NWC, 42 cells) and the Eastern Caucasus (EC, 36 cells) were considered separately and in combinations with Dagestan cells (table 1, columns 3-10). Statistically correct existence of both processes for 78 cells (“b3–b1” in average is -0.5 km) are fixing

Hévíz, Hungary, 15-19 October, 2019 page 195 of 197 International Lithosphere Program by loadings larger than 0.7 (bold) for the leading parameters #1 and #2 and by a contrast of these loadings for factors (0.790 vs 0.022, for instance). NWC (42 cells) has very similar result (“b3–b1” is - 0.13 km). The separation of two processes/factors for EC (36 cells) is not quite reliable – parameters #1 and #2 are weak and non-contrasting, possible, due to a sharp subsidence of the Chiaur zone (“b3–b1” is -5.2 km here). The addition of 13 cells to the EC distorted the result much more. The reason of result distortion may be in large box-shape folds of Dagestan (instead of small folds in common Caucasus structure), and in the uprising of the region (“b3–b1” is +4.5 km).

Fig. 1. Model of development of the Greater Caucasus crust structure ([Yakovlev, Gorbatov, 2018], with changes). A – The structure of the crust of the Chiaur zone, the beginning of sedimentation; B – The structure of the crust before a folding; C – The modern structure of the crust and mantle of the Greater Caucasus and of the surrounding blocks. 1-5 – Sedimentary rocks of different age; 6 – Crystalline crust; 7 – Pre-Alpine mantle rocks; 8 – mantle rocks (on density) formed during of the development; 9 – the estimated amount of crust, which was formed at the uplift stage from the mantle; 10 – Moho borders of different ages; 11 – calculated boundaries of the change of rocks density; 12 – tectonic zones (1 – Chiaur, 2 –Tfan, 3 – Shakhdag); 13 – the scale of the densities of the rocks, which were used in the calculations of “isostatic” models.

Conclusions and discussion. Factor analysis revealed a statistically reliable existence of the phenomenon of compaction of the rocks of the earth's crust to the mantle density in the processes of folding in the Greater Caucasus (on about 15% of the initial density) and mantle rocks decompaction during the mountains uplift. The mantle rocks decompaction partly has relation to the previous shortening of the structure. Regional changes in the proportion of such processes can be strong. The four main mechanisms are widely used in widespread publications to explain the

Hévíz, Hungary, 15-19 October, 2019 page 196 of 197 International Lithosphere Program subsidence and sedimentation in basins (e.g. [Teixell et al. 2009]); their main postulate is the constant volume of continental crust rocks (or their constant density). There are, briefly: 1) a stretching during the rifting, 2) the temperature cooling, 3) overlay of the structure by sediments or by nappes, 4) the local structure near a strike-slip faults (pull-apart). The materials, presented in this study, make it possible to supply this list with important mechanisms of vertical movements by compacting the crust rocks to “mantle” values of densities and decompaction of mantle rocks to “crust” densities. References Teixell A., Bertotti G., de Lamotte D. F., Charroud M. (2009). The geology of vertical movements of the lithosphere: An overview // Tectonophysics, 475, 1-8. Yakovlev F.L. (2015). Multirank strain analysis of linear folding on the example of the Alpine Greater Caucasus. Doctoral thesis. Moscow, IPE RAS. Manuscript. 472 P. [in Russian]. http://yak.ifz.ru/Yak- folding-publ.html Yakovlev F.L. (2017). Reconstruction of folded and faulted structures in zones of the linear folding using structural cross-sections / Moscow: Published in IPE RAS, 60 p. [in Russian]. Yakovlev F.L., Gorbatov E.S. (2017). The first experience in diagnosing the geodynamic mechanisms of folding by the factor analysis of folded structure parameters (Greater Caucasus) // Geodynamics & Tectonophysics, 8 (4), pp. 999–1019. [in Russian]. Yakovlev F.L., Gorbatov E.S. (2018). On using the factor analysis to study the geodynamic processes of formation of the Greater Caucasus // Geodynamics & Tectonophysics, 9 (3), pp. 909–926. [in Russian].

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