Neotektonika szerepe a Magyar Középhegység fiatal morfostrukturális fejlődésében = The role of neotectonics in the young morphostructural evolution of the Hungarian Mid-Mountains

A projekt keretében a Magyar Középhegység és környezetének fiatal szerkezet- és felszínfejlődését vizsgáltuk földtani, geofizikai és geomorfológiai módszerekkel. Főbb eredményeink a következők: 1) Geokronológiai vizsgálatokkal előrelépést tettünk a negyedidőszaki felszínfejlődés rekonstruálásában. A Dunakanyar sziklateraszainak kitettségi kora alapján a Duna bevágódásának üteme ~1,6 mm/év körüli volt az utolsó ~240 ka során. Barlangi ásványok alapján 0,15-0,5 mm/év kiemelkedési ráta valószínűsíthető a peremi területeken (Budai-hegység). Szélfújta felszínek kora 300-350 ka környékén szór, ami egy nagyobb léptékű lepusztulási eseményre utalhat. A lineáris erózió (folyóbevágódás) sebessége tehát jelentősen meghaladja az areális jellegű denudációs folyamatok (szélerózió) sebességét a Magyar Középhegységben. 2) A Pannon-medence szerkezeti inverziójának megfelelően a Dunántúlon a feszültségi és deformációs tér jellegzetes változékonyságot mutat. Délnyugaton a kompressziós szerkezetek dominánsak, melyek kelet felé eltolódásos, néhol transztenziós jelleget öltenek. A Dunántúl legmarkánsabb morfológiai eleme, a "meridionális" vagy sugárirányú völgyhálózat szerkezeti kontrollja valószínűleg kizárható. Az aljzat szerkezeti felépítéséhez igazodó, azok felújulásával létrejött ÉK-DNy-i csapású fiatal nyírási övek reaktivációs potenciálja nagy. Ismételt (szeizmo)tektonikus felújulásuk valószínűsíthető, ami a morfológiai képben is megjelenik ("longitudinális" völgyek a Dél-Dunántúlon). | The project aimed at the reconstruction of the young structural and landscape development of the Hungarian Mid-Mountains by means of geological, geophysical and geomorphological methods. The main results can be summarised as follow: 1) With the aid of geochronological investigations, major progress was made in the quantification of Quaternary surface processes. Exposure age of strath terraces suggests that the average incision rate of the Danube in the Danube bend was ~1.6 mm/a for the last ~240 ka. Formation of cave crystals at a more peripheral position in the Buda Hills indicates a slower uplift rate of 0.15-0.5 mm/a. Age spectrum of wind polished surfaces scatters around 300-350 ka suggesting an erosional event of regional importance. Hence, linear erosion was operating at a much higher rate than areal denudation. 2) Owing to the structural inversion in the Pannonian basin, the stress and strain fields show strong spatial variation in Transdanubia. In the southwest, compressional structures are predominant, whereas strike-slip faulting and transtension prevail more to the east. Structural control of the remarkable radial valley pattern in Transdanubia is unlikely. In contrast, the reactivation potential of NE-SW oriented shear zones, genetically connected to pre-existing basement faults, is high. Modelling results indicate that these structures are prone to repeated (seismo)tectonic reactivation, which is likely to be manifested in the morphology of South Transdanubia

(Un) Resolved contradictions in the Late Pleistocene glacial chronology of the Southern Carpathians - new samples and recalculated cosmogenic radionuclide age estimates

Application of cosmogenic nuclides in the study of Quaternary glaciations has increased rapidly during the last decade owing to the previous absence of direct dating methods of glacial landforms and sediments. Although several hundred publications have already been released on exposure age dating of glacial landforms worldwide, very few studies targeted the Carpathians so far (Kuhlemann et al, 2013a; Makos et al., 2014; Reuther et al, 2004, 2007; Rinterknecht et al. 2012).There are many unresolved or contradictory issues regarding the glacial chronology of the Romanian Carpathians. Recently, some attempts have been made to develop an improved temporal framework for the glaciations of the region using cosmogenic 10Be dating (Reuther et al. 2004, 2007, Kuhlemann et al. 2013a). However, these studies made the picture even more confusing because the local last glacial maximum, for instance, apparently occurred in asynchronous timing compared to each other and also to other dated glacial events in Europe (Hughes et al, 2013).This situation is even more interesting if we take into account that the local glacial maximum tends to agree with the global LGM derived from the Eastern Balkans (Kuhlemann et al. 2013b), while the penultimate glaciation seems to significantly overtake the LGM advance over the Western Balkans (Hughes et al. 2011).The primary candidate reasons to resolve these discrepancies are methodological, e.g. insufficient number of samples (one sample/landform) ignoring geological scatter of the data and the application of different half-lives, production rates and scaling schemes during the calculation of exposure ages. Systematic methodological uncertainties in computing exposure ages from measured nuclide concentrations have a significant impact on the conclusions concerning correlations of exposure-dated glacier chronologies with millennial scale climate changes (Balco, 2011). The changes in glacial timing generated by only using the most recent constants for the exposure age calculations has not been considered in the most recent review on the timing of the LGM (Hughes et al., 2013).Main objective of our study is to utilize the potential offered by the cosmogenic in situ produced 10Be dating to disentangle the contradictions in the available Southern Carpathian Late Pleistocene glacial chronology (Kuhlemann et al, 2013a; Reuther et al, 2004, 2007). We recalculate 10Be data published by Reuther et al. (2007) in accordance with the new half-life and production rate of 10Be. Besides, a new sample set has been collected to establish a precise chronological framework supported by in-situ exposure dating of several additional moraine generations

Revised deglaciation history of the Pietrele-Stanisoara glacial complex, Retezat Mts, Southern Carpathians, Romania

International audience\textcopyright 2015 Elsevier Ltd and INQUAAlthough geomorphological evidences of Quaternary glaciations of the Southern Carpathians were extensively studied and discussed, the limited number of chronological studies resulted in poor and controversial knowledge on the age of glaciations and deglaciation of the area. We use new and recalculated in situ produced 10Be surface exposure ages of glacial landforms to shed light on the age of the maximum glacial extent and the glacier oscillations during the last deglaciation process on the northern side of the Retezat Mountains. According to our data, the maximum ice extent documented by preserved moraines occurred around 21.0−1.5+0.8 ka, coincident with the global Last Glacial Maximum (LGM). The deglaciation process during the Lateglacial was characterized by two glacial advances at 18.6−0.8+0.9 and 16.3−0.6+0.6 ka. Inferred stabilization date of the penultimate glacial stage at 15.2−0.8+0.7 ka was closely followed by the abrupt warming at the onset of the Bølling/Allerød documented by a local chironomid-based temperature reconstruction. The last small glacier advance was dated to 13.5−0.4+0.5 ka. These recessional/readvance phases agree with other European glacial chronologies

Late Pleistocene glacial advances, equilibrium-line altitude changes and paleoclimate in the Jakupica Mts (North Macedonia)

In the Jakupica Mts a plateau glacier was reconstructed (max. area ~45 km2, max thickness: ~260 m). The study area comprises six formerly glaciated valleys, five of which were fed by the plateau glacier and one had an independent cirque when local glaciation reached its maximum ice extent (MIE). The equilibrium line altitude (ELA) of the most extended glacial phase was at 2075+37/-25 m asl. The 10Be cosmic ray exposure (CRE) age of this phase was estimated at 19.3+1.7/-1.3 ka, conformable with the Last Glacial Maximum (LGM). CRE ages from the next moraine generation placed the first phase of deglaciation to 18.2+1.0/-3.0 ka. The samples from the moraine of the penultimate deglaciation phase provided CRE ages with large scatter and biased towards old ages, which is probably the result of inherited cosmogenic nuclide concentrations within the rock. Glacio-climatological modelling was performed for the MIE, which has a well-established LGM age. The degree-day model was used to calculate the amount of accumulation required to sustain the glaciological equilibrium assuming a certain temperature drop at the ELA. The degree-day model constrained by the pollen- based July paleo-temperature reconstructions yielded an annual total melt at the LGM ELA comparable to or slightly higher than the current mean annual precipitation at the same elevation. These wetter LGM conditions inferred from the paleo-glaciological evidence in Jakupica Mts suggest an enhanced moisture advection in the region

Tectonic and climatic control on terrace formation: Coupling in situ produced 10Be depth profiles and luminescence approach, Danube River, Hungary, Central Europe

International audience\textcopyright 2015 Elsevier Ltd.The terrace sequence of the Hungarian part of the Danube valley preserves a record of varying tectonic uplift rates along the river course and throughout several climate stages. To establish the chronology of formation of these terraces, two different dating methods were used on alluvial terraces: exposure age dating using in situ produced cosmogenic 10Be and luminescence dating. Using Monte Carlo approach to model the denudation rate-corrected exposure ages, in situ produced cosmogenic 10Be samples originated from vertical depth profiles enabled the determination of both the exposure time and the denudation rate. Post-IR IRSL measurements were carried out on K-feldspar samples to obtain the ages of sedimentation.The highest terrace horizon remnants of the study area provided a best estimate erosion-corrected minimum 10Be exposure age of \textgreater700 ka. We propose that the abandonment of the highest terrace of the Hungarian Danube valley was triggered by the combined effect of the beginning tectonic uplift and the onset of major continental glaciations of Quaternary age (around MIS 22). For the lower terraces it was possible to reveal close correlation with MIS stages using IRSL ages. The new chronology enabled the distinction of tIIb (~90 ka; MIS 5b-c) and tIIIa (~140 ka; MIS 6) in the study area. Surface denudation rates were well constrained by the cosmogenic 10Be depth profiles between 5.8 m/Ma and 10.0 m/Ma for all terraces. The calculated maximum incision rates of the Danube relevant for the above determined \textgreater700 ka time span were increasing from west (\textless0.06 mm/a) to east (\textless0.13 mm/a), toward the more elevated Transdanubian Range. Late Pleistocene incision rates derived from the age of the low terraces (~0.13-0.15 mm/a) may suggest a slight acceleration of uplift towards present

A szél hatása a késő-neogén–negyedidőszaki üledékképződésre és a domborzat alakulására a Magyar-középhegységben és előterében = The effect of the wind on the late Neogene and Quaternary sedimentation and morphological evolution of the Hungarian Central Range and of its foreland

Legfontosabb kutatási eredményeink: az eolikus üledékek és felszínek elterjedésének és korának meghatározása, megayardangok és plató helyzetű eolikus képződmények leírása, valamint a defláció meghatározó szerepének kimutatása a Dunántúl mai domborzatának, így a zalai és somogyi ún. meridionális völgyrendszer kialakításában is. A szélmarta kőzetfelszínek kozmogén 10Be izotópos korát a mélységprofilok menti mintavételezési módszer alkalmazásával sikerült meghatároznunk. Ezt a módszert korábban szélcsiszolta kőzetfelszíneken még nem alkalmazták; elsőként sikerült 1,5 millió éves szélcsiszolta sziklafelszínt datálnunk Európában. A Tapolcai- és Káli-medencék negyedidőszaki deflációs alacsonyodási rátája 40-75 m/My volt, ugyanakkor a kipreparálódó kvarcittömbök csupán 2-4 m-t pusztulnak évmilliónként. A különböző korú szélmarta felszíneken mért szélkarc irányok megfeleltek a mai ÉNy-ias széliránynak. Ezzel igazoltuk az állandónak tekinthető uralkodó szélirányt a negyedidőszak során. Az OSL kormeghatározással 8-80 ezer éves üledékeket sikerült datálnunk a Vértes környezetében. Az üledékanyag szemcséit a betemetődés előtt nem érte elegendő fény ahhoz, hogy a lumineszcens szignál teljesen lenullázódjon. Ezt valószínűleg a rövid szállítási távolság okozhatta. Ezzel magyarázható, hogy a vizsgált üledékek esetében a geomorfológia és a korábbi koradatok tükrében többnyire a centrális OSL kor adja meg a betemetődés korát. | Our most important results are: determination of the distribution and age of aeolian landforms and sediments and description of megayardangs and aeolian formations in plateau position. We demonstrated that deflation played a definitive role in the formation of the topography of Transdanubia and in the development of the radial valley system of Zala and Somogy countries. Age and denudation rate of the wind-abraded rock surfaces was determined using in situ produced 10Be depth profiles. This was the first application of this method on wind-polished rock surfaces, and the first time when a 1.5 million years old wind-abraded surface was dated in Europe. Quaternary deflational surface lowering of the Tapolca and Kál Basins was 40-75 m/My, while denudation rate of the cemented quartzite rock surfaces was only 2-4 m/My. We proved long term stability of north-westerly winds by the measurement of the direction of wind striations rock surfaces of different age. OSL ages of aeolian sediments in the Vértes foreland were 8-80 ky old. The sediments were not exposed to sunlight for enough time to anneal completely the luminescence signal, most probably because of the short distance of transportation. This is the reason why the central OSL ages provide the age of sedimentation, considering the geomorphology and previous age data as well

Integrated stratigraphy of the Gusterita clay pit: a key section for the early Pannonian (late Miocene) of the Transylvanian Basin (Romania)

The Neogene Transylvanian Basin (TB), enclosed between the eastern and southern Carpathians and the Apuseni Mountains in Romania, is a significant natural gas province with a long production history. In order to improve the (bio) stratigraphic resolution, correlations and dating in the several 100-m-thick upper Miocene (Pannonian) succession of the basin, the largest and most fossiliferous outcrop at Gusterita (northeastern part of Sibiu) was investigated and set as a reference section for the Congeria banatica zone in the entire TB. Grey, laminated and massive silty marl, deposited in the deep-water environment of Lake Pannon, was exposed in the similar to 55-m-high outcrop. The uppermost 25 m of the section was sampled in high resolution (sampling per metres) for macro- and microfossils, including palynology; for authigenic Be-10/Be-9 dating and for magnetostratigraphy; in addition, macrofossils and samples for authigenic Be-10/Be-9 isotopic measurements were collected from the lower part of the section as well. The studied sedimentary record belongs to the profundal C banatica mollusc assemblage zone. The upper 25 m can be correlated to the Hemicytheria tenuistriata and Propontoniella candeo ostracod biozones, the uppermost part of the Spiniferites oblongus, the entire Pontiadinium pecsvaradense and the lowermost part of the Spiniferites hennersdorfensis organic-walled microplankton zones. All samples contained endemic Pannonian calcareous nannofossils, representing the Noelaerhabdus bozinovicae zone. Nine samples were analysed for authigenic Be-10/Be-9 isotopic measurements. The calculated age data of six samples provided a weighted mean value of 10.42 +/- 0.39 Ma. However, three samples within the section exhibited higher isotopic ratios and yielded younger apparent ages. A nearly twofold change in the initial Be-10/Be-9 ratio is a possible reason for the higher measured isotopic ratios of these samples. Magnetostratigraphic samples showed normal polarity for the entire upper part of the outcrop and can be correlated with the C5n.2n polarity chron (11.056-9.984 Ma, ATNTS2012), which is in agreement with the biostratigraphic data. Based on these newly obtained data and correlation of the biozones with other parts of the Pannonian Basin System, the Guterita section represents the similar to 11.0-10.5 Ma interval, and it is a key section for correlation of mollusc, ostracod, dinoflagellate and calcareous nannoplankton biostratigraphic records within this time interval