Klement Fordinál’s research while affiliated with State Geological Institute of Dionyz Stur and other places

Long-term research of the Vienna Basin (Central Europe) has resulted in multiple stratigraphic concepts, though these are at least in part mutually exclusive. This contribution aims to reconsider the available information on the northeastern Vienna Basin, located in Slovakia, to create a consistent stratigraphic model. Lithostratigraphic correlations based on benthic taxa - widely used elsewhere - are omitted, since these include inherently diachronous paleoecological zones. This presumption of diachroneity is further supported by the evidence of shelf-slope scale clinoforms. The following sequences were identified: (1) the Early Miocene wedge-top basin, genetically unrelated to the subsequently formed Vienna Basin; Eggenburgian-Ottnangian cycles are still obscured, and the Karpatian includes two transgressive-regressive cycles; (2) Middle Miocene early Badenian rifting including the Kúty Fm. lowstand and Lanžhot Fm., together with the Devínska Nová Ves Fm., comprising transgression and a highstand; (3) Middle Miocene late Badenian rifting including lowstand offshore Jakubov Mb. and transgressive littoral Stupava Fm., followed by the highstand offshore Studienka Mb. passing to normal regressive Matzen delta; (4) Middle Miocene Sarmatian rifting including the basal Kopčany and Radimov mbs., the offshore transgressive to regressive Holíč Fm. and the highstand normal regressive deltaic Skalica Fm.; (5) supposed Late Miocene rifting with Lake Pannon transgression resulting in the lacustrine Bzenec Fm., followed by the highstand normal regressive deltaic Čáry and alluvial Gbely fms.

This review aims to present an updated lithostratigraphic framework of the northern Danube Basin in Slovakia, consistent with recent shifts in geochronology and depositional system redefinitions based on sedimentology and seismic stratigraphy. Several transgressive-regressive sequences are distinguished: Lower Badenian (Middle Miocene), represented by the Špačince Fm., mainly occurred in peripheral Blatné and Želiezovce sub-basins. The central part of the Danube Basin formed an elevation during this period, coinciding with the onset of intermediate volcanic activity. Upper Badenian (Middle Miocene), encompassed within the Pozba Fm., saw the flooding of the central Danube Basin, signifying a change in transport direction. The inception of this cycle is well constrained by recently published multiple ⁴⁰ Ar/ ³⁹ Ar dating to ∼13.8 Ma. Sarmatian deposition (Middle Miocene), characterized by the Vráble Fm., occurred also in newly significantly deepened Komjatice and Rišňovce sub-basins, coinciding with a gradual cessation of calc-alkaline volcanism, observed only at the basin's eastern edge. Pannonian (Upper Miocene) deposition includes lacustrine Ivanka, deltaic Beladice, and alluvial Volkovce fms., representing interconnected depositional systems prograding towards Lake Pannon. The subsequent evolution entails a post-rift stage (9.5-6 Ma), primarily marked by the alluvial Volkovce Fm. deposition, and basin inversion, with alluvial deposition mostly confined to the basin centre and differentially eroded basin margins (from 6 Ma to the present).

Región Podunajská nížina-juhovýchodná časť je zo západu obmedzený spojnicou miest Nové Zámky a Komárno, severným ohraničením je spojnica medzi mestom Nové Zámky a obcou Ipeľský Sokolec. Južné a východné ohraničenie tvorí štátna hranica s Maďarskou republikou, reprezentovaná riekami Dunaj a Ipeľ. Z tohto územia bola zostavená regionálna geologická mapa v mierke 1 : 50 000 s textovými vysvetlivkami. Vo vysvetlivkách sú opísané jednotky neogénneho a kvartérneho veku zobrazené na geologickej mape, geologické jednotky predkenozoického podložia Dunajskej panvy a jej sedimentárnej výplne a litostratigrafické jednotky oligocénneho veku Budínskej panvy. Súčasťou vysvetliviek je aj charakteristika tektonických pomerov, opis geologického a tektonického vývoja územia, zhodnotenie získaných geofyzikálnych údajov, hydrogeologických pomerov a geofaktorov životného prostredia, opis recentného pôdneho pokryvu, ložísk nerastných surovín a významných geologických lokalít. Na území juhovýchodnej časti Podunajskej nížiny sa nachádza časť kenozoickej depresie Dunajskej panvy, ktorá je súčasťou panónskeho panvového systému. Z regionálnogeologického hľadiska skúmaná oblasť zahŕňa hlavne okraje gabčíkovskej panvy a želiezovskú priehlbinu Dunajskej panvy. Okrajovo (na SZ) je sú časťou regiónu aj komjatická priehlbina Dunajskej panvy. Na geologickej stavbe juhovýchodnej časti územia sa podieľajú horniny budínskeho paleogénu a v najvýchodnejšej časti neogénne vulkanity Burdy. Na stavbe predkenozoického podložia sa podieľajú horniny dvoch odlišných tektonických jednotiek. Se verne od hurbanovského zlomu sa nachádza južné veporikum. Tvoria ho prevažne horniny kryštalického fun damentu, a to metamorfity (muskoviticko-chloritické bridlice, amfibolity, zelené bridlice) a granitoidy. Južne od uvedeného zlomu je transdanubikum, zložené z hornín paleozoického a mezozoického veku. Oligocénne sedimenty Budínskej panvy (štúrovský paleogén) sú na študovanom území reprezento vané usadeninami kišcelského a egerského veku. Sedimenty kišcelského veku boli začlenené do súvrstvia Csatka, kišcelského súvrstvia a háršhedského súvrstvia s ostrihomskými vrstvami. V ich nadloží sú sedimenty egerského veku reprezentované mányským a törökbálintským súvrstvím s kováčovskými vrstvami a séčénskym súvrstvím. Neogénnu sedimentárnu a vulkanicko-sedimentárnu výplň Dunajskej panvy tvoria miocénne (stredný až vrchný) a pliocénne usadeniny. Strednomiocénne sedimenty reprezentuje bajtavské, pozbianske, zbrojnícke a vrábeľské súvrstvie. Vrchno- miocénne usadeniny sú zastúpené nemčinianskym, ivanským, beladickým a volkovským súvrstvím. Pliocénne sedimenty reprezentuje kolárovské súvrstvie. Kvartérne sedimenty pokrývajú takmer celú časť Podunajskej nížiny zobrazenú na mape. Z celkovej škály genetických typov kvartérnych sedimentov z hľadiska genézy, objemu hmoty, plošného rozsahu, stratigrafie a morfometrickej pozície výskytu majú dominantné postavenie fluviálne akumulácie hlavných vodných tokov Váhu, Nitry, Žitavy, Dunaja, Hrona a Ipľa. S fluviálnou akumuláciou sú úzko geneticky späté proluviálne akumulácie náplavových vejárov, ktoré majú na zobrazenom území len nepatrné zastúpenie. Oveľa väčšie plošné zastúpenie majú deluviálno-fluviálne splachy, ktoré nadväzujú na holocénne nivné výplne dna dolín potokov. Na deluviálno-fluviálne sedimenty v smere do pahorkatín a do pohoria Burda nadväzujú rôzne subtypy deluviálnych sedimentov. S deluviálnymi a deluviálno-fluviálnymi sedimentmi sú úzko geneticky späté deluviálno-proluviálne výplavy kužeľov na rovinaté územia povrchu riečnych terás aj priamo do nív hlavných tokov. Druhým plošne najväčším a objemovo najmohutnejším genetickým typom sú rozsiahle akumulácie sprašových sérií a sprašových hlín. Ďalším dôležitým fenoménom, najmä v západnej časti územia, sú eolické akumulácie pieskov vo forme dún a presypov, transportovaných na rôznu vzdialenosť od primárnych deflačných zón. Eolické piesky najčastejšie tvoria povrch vrchno- až strednopleistocénnych fluviálnych terás Váhu, Nitry, Žitavy, Dunaja a Ipľa. V rozsahu aluviálnych nív je povrch poznačený sieťou mŕtvych a slepých ramien aj občasne prietočných korýt dokazujúcich výraznú holocénnu laterálnu dynamiku fluviálneho vývoja riečnej siete územia. Vo výplniach mŕtvych ramien a iných zníženinách reliéfu sa vyvinuli fluviálno-organické a organogénne a palustrické sedimenty, slatinné rašeliny a humolity. Hydrogeologické pomery regiónu Podunajská nížina-juhovýchodná časť sú podmienené jeho geologicko-tektonickou stavbou a morfologickými, klimatickými a hydrologickými podmienkami. Tieto základné faktory ovplyvňujú vznik podzemnej vody, jej obeh a akumuláciu v hydrogeologických štruktúrach a formujú jej fyzikálno-chemické vlastnosti. Ako vyplýva z geologickej stavby územia, v skúmanom území prevláda medzizrnová, prípadne puklinová priepustnosť horninového prostredia. Hlavnými kolektormi obyčajnej podzemnej vody sú kvartérne piesčité štrky a piesky, neogénne piesky a pieskovce, ale aj vulkanické tufy a tufity. Hlavnými kolek tormi geotermálnej podzemnej vody sú neogénne piesky, pieskovce a karbonáty mezozoického veku. Geofaktory životného prostredia sú vlastnosti zložiek geologického prostredia, ktoré významne ovplyvňujú životné prostredie a možnosti jeho využitia. Rozdeľujú sa na geopotenciály a geobariéry. Geopotenciály sú tie geofaktory, ktoré umožňujú istý spôsob využitia územia. Ku geobariéram patria tie geofaktory, ktoré ohrozujú životné prostredie a obmedzujú alebo znemožňujú istú formu využitia životného prostredia. Z hľadiska regionálneho inžinierskogeologického členenia Západných Karpát patrí prevažná časť mapo vaného územia juhovýchodnej časti Podunajskej nížiny do regiónu neogénnych tektonických vkleslín, do oblasti vnútrokarpatských nížin. Len juhovýchodná časť skúmaného územia v pohorí Burda patrí do regiónu neogénnych vulkanitov, k oblasti vulkanických vrchovín. Pôdny pokryv juhovýchodnej časti Podunajskej nížiny je výrazne ovplyvnený geologickou stavbou, genézou a typom morfoštruktúrnych parametrov georeliéfu, erózno-akumulačnými procesmi a bioklimatickými faktormi v priebehu pleistocénu, a najmä holocénu. Pôdy vznikali v procese geologického vývoja v dôsledku interakcie medzi geologickými, klimatickými a biotickými faktormi.

This study examines the suitability of the authigenic 10Be/9Be dating method to the dating of the deposits of an incising river, taking as an example the Nová Vieska river terrace, which accumulated during the neotectonic inversion of the Danube Basin (western Slovakia). The succession was formed by a wandering river with minor preservation of proximal floodplain muds. The frequent occurrence of mud intraclasts reflects significant input of eroded material from underlying, older successions. The ages of 13 authigenic 10Be/9Be dating samples formed three groups: (1) samples from below the base of the river terrace yielded dates of ~4.13–3.70 Ma (including uncertainties); (2) muddy intraclasts from the river terrace gave an age range of ~2.79–1.96 Ma; and (3) in situ muddy layers had ages in the range of ~1.91–1.39 Ma. The large mammal fossil assemblage from channel thalweg deposits yielded a biostratigraphic age of ~3.6–2.2 Ma, matching the age of intraclasts, and thus emphasising the redeposited origin of those fossils. The relatively wide range of authigenic 10Be/9Be dating ages is interpreted as a result of the redeposition of mud from older strata on three scales: decimetre‐scale intraclasts, millimetre‐scale rip‐up clasts mixed into the newly formed beds, and formation of two authigenic rims with different age and 10Be/9Be records around individual particles. Considering these observations, an age range of in situ layers of ~1.91–1.39 Ma is proposed as the depositional age of the river terrace, with the most probable age falling within the most recent part of this interval. The effect of redeposition is thus shown to be potentially limiting to the application of authigenic 10Be/9Be dating to incising rivers, and stands in marked contrast to aggrading river settings, where redeposition of older sediments is limited and the degree of 10Be/9Be variability is low.

This study examines the suitability of the authigenic 10Be/9Be dating method to the dating of the deposits of an incising river, taking as an example the Nová Vieska river terrace, which accumulated during the neotectonic inversion of the Danube Basin (western Slovakia). The succession was formed by a wandering river with minor preservation of proximal floodplain muds. The frequent occurrence of mud intraclasts reflects a significant input of eroded material from underlying, older successions. The ages of 13 authigenic 10Be/9Be dating samples formed three groups: (1) samples from below the base of the river terrace yielded dates of ~4.13–3.70 Ma; (2) muddy intraclasts from the river terrace an age range of ~2.79–1.96 Ma; and (3) in situ muddy layers had ages in the range of ~1.91–1.39 Ma. The large mammal fossil assemblage from channel thalweg deposits yielded a biostratigraphic age of ~3.6–2.2 Ma, matching the age of intraclasts, and thus emphasizing the redeposited origin of those fossils. The relatively wide range of authigenic 10Be/9Be dating ages is interpreted as a result of the redeposition of mud from older strata on three scales: decimeter-scale intraclasts, millimeter-scale rip-up clasts mixed into the newly formed beds, and formation of two authigenic rims with different age and 10Be/9Be record around individual particles. Considering these observations, an age range of in situ layers of ~1.91–1.39 Ma is proposed as the depositional age of the river terrace. The effect of redeposition is thus shown to be potentially limiting to the application of authigenic 10Be/9Be dating to incising rivers, and stands in marked contrast with aggrading river settings, where redeposition of older sediment is limited and the degree of 10Be/9Be variability is low.

The authigenic 10Be/9Be ratio provides an important geochronological tool to date a depositional age of clay bearing sediment, nevertheless, recent studies showed that the initial 10Be/9Be ratio might be affected by changes in paleoenvironmental conditions and post-depositional processes. The method is based on the ratio of atmospheric cosmogenic radionuclide 10Be transported to a sedimentary environment by meteoric precipitation and of stable 9Be derived by weathering of rock massifs. This study examines suitability of the method to date river terrace sediments, accumulated during incision of a river. The Nová Vieska river terrace selected for the case study was deposited during the inversion of the Danube Basin (western Slovakia). The facies analysis implies accumulation by a wandering river, comprising both lateral- and downstream-accreted sandy-gravelly bars, apart from thalweg basal coarse lag strata and minor oxbow lake and proximal floodplain facies, sampled for the authigenic 10Be/9Be dating. A high variability of flow speed, turbulence and sediment concentration is implied by the range of lithofacies. An extensive presence of mud intraclasts mirrors significant input of eroded material from below-lying older successions. The ages of 13 authigenic 10Be/9Be dating samples form three groups: (1) samples below the base of the river terrace yielded ~4.13–3.70 Ma, (2) muddy intraclasts present in the river terrace with ages ranging in ~2.79–1.96 Ma and (3) in situ muddy layers from the river terrace representing oxbow lake or proximal floodplain facies, which provide ages in the range of ~1.91–1.39 Ma. The large mammal fossil assemblage from channel thalweg deposits yields biostratigraphic age of ~2.56–1.85 Ma, what fits to the age of intraclasts, emphasizing redeposited origin of fossils. The relatively wide range of authigenic 10Be/9Be dating ages is interpreted as a result of redeposition of mud derived from below lying Upper Miocene, Pliocene and Lower Pleistocene alluvial strata. It is expected to appear at three scales: (1) decimeter-scale intraclasts, (2) millimeter-scale rip-up clasts mixed to the newly formed beds, and (3) mixing of individual clay particles, which have preserved internal older authigenic rim and newly formed outer rim, differing by 10Be/9Be record. Considering the mentioned settings, the age range of in situ layers reaching 1.91–1.39 Ma is proposed as the depositional age of the river terrace. The effect of redeposition limits application of the authigenic 10Be/9Be dating to incising rivers, in contrast with settings of aggrading rivers, where redeposition of older sediment is limited and the 10Be/9Be variability is low. The study was supported by the Slovak Research and Development Agency (SRDA/APVV) under contracts No. APVV-16-0121 and APVV-20-0120.

The depocenters of epicontinental basins usually comprise relatively continuous depositional records, and these can be used in the determination of sediment routing and paleogeographic changes via a set of various geophysical, sedimentological, biostratigraphic and geochronological approaches. Although the margins of such basins will have a major role as constraints for that sediment routing, their depositional records are typically scarce and incomplete, posing a common challenge in terms of gaining information about them. The present study focuses on the upper Miocene succession present in the Malé Karpaty Mts., a pre-Cenozoic horst dividing the Vienna and Danube basins (Central Europe). The data gained by facies analysis, biostratigraphy, shallow seismic survey, authigenic 10Be/9Be dating and correlation of archival borehole profiles reveals, that the succession under consideration represents a record of the Lake Pannon transgression, which appeared in the study area at ~10.9–10.6 Ma. The subaerially exposed granitic massif and Middle Miocene successions sourced a shoal water delta, which intercalated with wave-induced dunes and open lacustrine muds in brackish sublittoral to marginal littoral environments. The granitic massif was probably also exposed later, during the regression of Lake Pannon at ~10.2–10.0 Ma, as a result of the progradation of the paleo-Danube delta from the Vienna Basin southeastwards. The depositional record of the regressive sequence was documented and dated in well-cores from the nearby Danube Basin margin. The documented scenario of transgression preceding the overall regression of the paleo-Danube delta system by a relatively short period is characteristic of several other localities across the Pannonian Basin System, and may imply that the progradation of depositional system caused a base-level rise on account of sediment loading-induced subsidence.

The study focuses on the upper Miocene colluvial to alluvial fan deposits of the Modrová Mb., which accumulated on the marginal blocks of the Považský Inovec Mts., transitional to surrounding depressions of the Danube Basin. These blocks are delimited tectonically according to the geophysical evidence, and the late Miocene normal faulting produced fault scarps causing rapid sediment supply. However, the supply of coarse clastics composed mostly of Mesozoic dolomites was of intensity sufficient only to fill the accommodation of the marginal blocks. The sediment input to the surrounding Danube Basin is on the both sides of the Považský Inovec Mts. not traceable, probably due to an overwhelming alluvial redistribution. Facies analysis of the Modrová Mb. implies an environment of colluvial fans with prevalence of cohesive debris flow deposition, associated with less frequent rockfall, grain flow and sheetwash processes on the western side of the mountains in the area of Modrová village. In contrary, the easterly situated area of Tesáre village exhibits dominance of debris flow deposition with more than one third of the succession deposited by channelized and unchannelized shallow traction currents, indicating sedimentary environment of an alluvial fan close to its transition to colluvial sediment-feeder system. Petrographical and geochemical study showed extremely low content of siliciclastic component in the colluvial deposits of the Modrová area. Dolomite clasts form a major part of the sediment and are covered by a coating of clay minerals. The coatings and sediment matrix contain iron oxides possibly derived by fersiallitic weathering and by oxidation of pyrite scattered within the matrix. Geochemistry of muddy layers in the Tesáre succession implies either cold or dry weathering conditions. However, weathering proxies are considered to be biased due to the rapid denudation in the colluvial to alluvial fan environment, since observed facies and published regional studies imply rather warm and humid climate. Several examples of simultaneous comparable depositional settings in the broader region imply, that these colluvial to alluvial fan successions could be related to a mild phase of regional tectonic activity at ~8 Ma.

The ratio of channel belt to overbank deposits in alluvial sequences and the variability in channel belt distribution are the most important characteristics of alluvial stratigraphic architecture. The ratio of floodplain facies to channel fills is determined by the sediment supply to accommodation rate ratio, yet the relation is probably more complex than previously thought, since aggradation rate and channel-deposit density do not exhibit a simple negative dependence. Examples of experimental and depositional research reveal that a decrease of sediment supply to accommodation ratio along the drainage axis increases the preservation of floodplain facies and decreases channel belt amalgamation. The evolution of ideas explaining the changes in the sediment supply to accommodation ratio perpendicular to the basin drainage axis has proven very complex (Nádor & Sztanó, 2011: SEPM Spec. Pub.). A review of published research points to the existence of several factors which interact in resulting location of channel belts in an alluvial depositional system under conditions of differential accommodation, for example topographic gradient, substrate erodibility, avulsion rate or dominant grain-size of transported sediment (e.g., Hickson et al., 2005: J. Sediment. Res.; Nádor and Sztanó, 2011). The pioneering “LAB models” established that variable lateral accommodation rate results in attracting the channels to area within the drainage basin where maximum subsidence is found (e.g. Bridge & Leeder, 1979: Sedimentology; Alexander & Leeder, 1987: SEPM Spec. Pub.). Following research implied, that interplay of slopes parallel and perpendicular to the drainage axis has major control over channel location, and differential subsidence might not affect lateral distribution of channel belts (Mackey & Bridge, 1995: J. Sediment. Res.; Hickson et al., 2005). A case study of Nádor & Sztanó (2011) showed that only up to double times higher spatial difference in accommodation documented in the Quaternary succession of the southern Pannonian Basin System resulted in location of main channel belts in the marginal part of the depocenter. In contrary, Hickson et al. (2005) showed experimentally that ca. three times higher spatial difference in accommodation rate is associated by homogeneous distribution of channel deposits in a distributary fluvial system regardless the position within the system. The same magnitude of differential accommodation caused dominant channel belt deposition on the margin of a depocenter in the sequence documented by Foix et al. (2013: Sed. Geol.). Our case study is based on depositional record of the late Miocene alluvial Volkovce Fm. in the northern Pannonian Basin System (Slovakia) (Šujan et al., 2020: Sed. Geol.). The results indicate that the up to four times higher accommodation rate affects the drainage network by capturing the channel belts into the area of maximum subsidence. This is most likely due to topographic confinement which prevents basin-scale avulsion from relocating the channels in a lower accommodation rate area. Hence, our study show that the four times higher accommodation rate might be close to boundary conditions needed to relocate the channel belts to the area of maximum subsidence. Acknowledgement: This work was financially supported by the Slovak Research and Development Agency under contract No. APVV-16-0121.