Statistical analysis of the Late Miocene sequences on the southeastern Danube Basin margin based on borehole data

The strata of lacustrine, deltaic and alluvial sequences of the southeastern Danube Basin (se DB) deposited during the Pannonian were reached by numerous boreholes. Even though the large amount of available data there are inconsistencies in recent knowledge, concerning distribution of different formations in the basin fill as well as the interpretation of their surficial occurrences. The purpose of this study is to utilize the full strength of available borehole data to characterize the spatial distribution and internal architecture of each penetrated sedimentary formation defined by Kováč et al. (2011). The used database contains more than 700 boreholes reaching average depth of 300 m, which lithological logs were digitalized according to main grain size in each described stratum and considering the origin of the layer. The resulting database comprises up to 16 000 documented layers. For purposes of the statistical analysis were created (1) pie charts of percentual share of each described lithotype (clays, fine sands, sands, gravels) for individual stratigraphic unit; (2) histograms of the percentual content of coarse (sandy and gravely) layers in a lithological column for each strat. unit; (3) histograms of single unit/stratum thickness for each lithotype in each strat. unit; and (4) interpolated maps of spatial distribution of coarse layers (percentual content) in each strat. unit. Area of the se DB, bordering with the Transdanubian Range Mts. (TR), represented before the regression of the Lake Pannon a submerged basement high. Specific depositional conditions occurred, because main input of sediment from the Western Carpathians on the northeast and from the paleo-Danube delta on the northwest fell into the offshore depocenter in the central depression of the DB. Lacustrine strata of the Ivanka Fm. deposited there mainly in a sublittoral zone contain therefore highly bioturbated clays and silts, while sand or coarser sediment is almost absent. This succession described only from core material and well-logs of deep boreholes is comparable to the Szák Fm. described in the Hungarian part of the basin. Subsequent regression of the Lake Pannon took place through mentioned deltaic systems prograding from the North. The shelf slope prograded to studied area across the offshore environment of the central depression before ca. 9.0 Ma. The deltaic sequence, considered as the Beladice Fm., is widely documented by studied boreholes. It is typical with alternating occurrence of brackish and freshwater to terrestrial mollusk fauna and common layers of lignite. Lithological composition of the sequence is highly fine grained: 88% clays, 6% silts/very fine sands, 6% sands. Layers coarser than clays form usually 3-18% of a lithological column. Majority of very fine sands and sands form units 1-9 m thick with peak thickness in 2-6 m. A single rhythm of lithological change, which could be assumed as parasequence according to Sztanó & Magyar (2007), reaches thickness 10-35 m with most frequent value of ca. 25 m. Based on observed situation we can expect, that mouth bars, beach ridges and channels representing the thickest sandy bodies form a minor part of the volume, while the main part of upward coarsening cycles were formed by filling of interdistributary bays and lagoons on the delta plain. On the basis of used data was identified a distinct sedimentary unit, which underlies the deltaic Beladice Fm. in the transitional zone between the se DB and the TR, named the complex of shelfal sands. The strata consist of sublittoral Congeria czjzeki mollusk alternated with littoral fauna. Average lithology of the complex consists of 57% clays, 16% fine sands, 22% sands and 5% gravels. However, the complex is laterally variable and single borehole may consist up to 90% of sandy and gravely layers. The thickness of individual sandy unit is unclear due to amalgamation. Described lithology is interpreted as a result of sedimentary trap formed between deltaic lobes on the North and partially subaerial exposed islands of the TR on the South. While the deltaic Beladice Fm. consists almost no gravely layers, the gravel described in the complex was probably derived from the TR. Distinguishing of the alluvial Volkovce Fm. from the underlying deltaic Beladice Fm. could be concluded by absence of the brackish mollusk fauna, but it is difficult to exclude the possibility of missing information. The alluvial sequence consists of significantly lower portion of coal layers. Clays form 79%, fine sands 6.5%, sands 14%, 0.5% gravels. Individual well profile consists usually of 5-30% coarse layers. Sandy bodies reach thickness 3-15 m with peak thickness in 5-11 m, fine sands form bodies 1-8 m thick. We can assume that the main portion of the sandy deposits in studied alluvial sequence is bound to meandering channel belts ca. 8 m thick, which are occasionally amalgamated. The few meters thick sandy and fine sandy units represent levees and crevasse splays. Alluvial facial associations with described parameters were documented also on outcrops. Spatial correlation indicates prevailing orientation of sandy bodies in NW-SE direction, while paleocurrent analysis from field denotes direction from N and NW. The majority of documented sandy bodies are located in the western part of the studied area. The boundary between deltaic and alluvial sequences is despite the wealth of data not easy to correlate. The similarity of depositional processes and resulting geological setting of both sequences lead to conclusion that interpreting an outcrop assignment to formation based on lithofacies without precise paleontological analysis and control by boreholes, could be groundless

Early Pleistocene age of fluvial sediment in the Stará Garda Cave revealed by 26Al/10Be burial dating: implications for geomorphic evolution of the Malé Karpaty Mts. (Western Carpathians)

Assessment of vertical movements of tectonically boundedblocks is crucial for determination of geohazards in denselyinhabited zones, such as the border zone of western Slovakiaand eastern Austria. The morphostructure of the Malé KarpatyMts. divides the Vienna and Danube basins in the WesternCarpathian – Eastern Alpine junction, and its neotectonicactivity is of high importance. This study was focused on26Al/10Be burial dating of fluvial sediment in the Stará GardaCave, located in the central part of the mountains. The structuralresearch revealed predisposition of forming of horizontalpassages in low angle to subhorizontal bedrock stratificationtogether with low-grade metamorphic foliation. Fluvial originof the passages was inferred from mezoscale erosional featureson the bedrock as well as from facies character of the well preservedsedimentary profile. Cave sediment was according topetrographic analysis derived from a watershed comparableto recent one of the Stupavský Potok Stream. Three analyseddating samples provided low values of isotopic concentrations,allowing us only to calculate the minimum burial age of thedeposit of 1.72 Ma. Assuming the low position of the caveabove recent surface streams, resulting maximum incision rateof 26 m/Ma indicates very low uplift of the mountains horstduring the Quaternary. The slow incision of the river network is in good agreement with a widespread preservation of theplanation surface called "Mid-mountain level". In contrast arerelatively high values of palaeodenudation rates inferred fromisotopic concentrations. Generally, our results indicate that theMalé Karpaty Mts. horst underwent relatively intense but shortuplift in the Early Pleistocene, followed by very moderate upliftup to the recent.Key words: Western Carpathians, Malé Karpaty Mts., fluvialcave sediment, burial dating, Early Pleistocene, neotectonics.Zgodnja pleistocenska starost fluvialnihsedimentov v jami Stará Garda, ki jo je dala 26Al/10Be datacija:uporabnost za geomorfni razvoj Nizkih Karpatov (ZahodniKarpati)Ocena vertikalnih premikov tektonsko omejenih blokov jeključna za določitev geohazardov v gosto naseljenih območjih.Morfostruktura Malih Karpatov deli Dunajski in Donavski bazenna stičišču Zahodnih Karpatov – Vzhodnih Alp in njegovaneotektonska aktivnost je zelo pomembna. Študija se je posvetila26Al/10Be dataciji fluvialnih sedimentov v jami Stará Gardav osrednjem delu gorovja. Strukturna raziskava je razkrilapredispozicijooblikovanja vodoravnih jamskih rovov pod nizkimkotom v odvisnosti od subhorozontalne stratifikacije kamnineter tudi z nizko stopnjo metamorfne foliacije. Na fluvialnoporeklo rovov smo sklepali iz srednje velikih erozijskih oblik nanjihovih stenah kot tudi iz lastnosti faciesov dobro ohranjenegasedimentnega profila. Glede na petrografske analizejamskisediment izhaja iz povodja, ki je primerljiv z recentnim povodjempotoka Stupavský. Trije analizirani vzorci so nam dalinizke vrednosti koncentracij izotopov, ki so nam omogočilele izračun najnižje pokopne starosti sedimenta, ki je znašala1,72 Ma. Če upoštevamo, da leži jama nizko nad recentnimivodnimi tokovi, dobimo maksimalno hitrost vrezovanja dolinsamo 26 m/Ma, kar kaže na zelo majhen tektonski dvig v časukvartarja. Počasno vrezovanje rečne mreže se dobro ujema sširoko ohranjenim uravnanim površjem, imenovanim »Srednjegorskauravnava«. V nasprotju pa so sorazmerno visoke vrednosti hitrosti paleodenudacije, ki izhajajo iz koncentracijizotopov. Na splošno naši rezultati kažejo, da je bil horst NizkihKarpatov podvržen relativno močnemu, toda kratkemu dvigovanjuv spodnjem pleistocenu, ki mu je sledil zmeren dvig dosedanjosti.Ključne besede: Zahodni Karpati, Nizki Karpati, fluvialnijamski sedimenti, pokopna datacija, starejši pleistocen, neotektonika.

Evolution of depositional systems and sedimentary cycles in Želiezovce Depression of the Danube Basin

Five deep wells (Pozba4, Pozba3, Dubnik1, Nová Vieska1, Modrany1), drilled in the Želiezovce depression of the south-east Danube Basin penetrate the Cenozoic sedimentary record in overall thickness ranging from 1000 m up to 3000 m, the total thickness gradually increases from South to the North. This area is well known for the complex geological structure related to the Central Western Carpathians and Transdanubian Range junction along the Hurbanovo – Diösjenö line. Many authors have studied this area in the past,  nevertheless Depositional systems, sedimentary cycles and the development of sedimentary facies were never understood in detail. The Re-evaluation of biostratigraphy, paleoecology, sedimentology and the Re-interpretation of e-logs ware all incorporated into well correlations, what resulted in definition of four main sedimentary cycles: (1) The Lowermost Oligocene cycle, consisting of mudstones with occasional sandstone intercalations, associated with slope to offshore marine environment what is supported by the presence of the NP 22 calcareous nannoplankton zone. (2) The transgressive Langhian (Lower Badenian) deposits, composed of mudstones with epiclastic volcanic material and tuffite beds ware associated with shelfall to offshore environement the age is supported by the NN4 - NN5 calcareous nannoplankton zone. (3) The Serravallian (Upper Badenian - Sarmatian) cycle is composed mainly by mudstones with abundant Lithothamnium fragments associated with brackish coastal pain environment, supported by the NN6 calcareous nannoplankton zone and by the mass occurrence of fish scales and  Ervilia dissita (Eichwald) bivalves. (4) The overlying strata are represent the Tortonian-Pliocene (Pannonian-Pliocene) cycle, consists mostly from claystone which are overlain by sandstone and siltstones layers is associated with lake, deltaic and alluvial plain environment. 

Late Miocene fluvial distributary system in the northern Danube Basin (Pannonian Basin System): depositional processes, stratigraphic architecture and controlling factors of the Piešťany Member (Volkovce Formation)

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Surviving from transgression to regression of Lake Pannon: Fan deltas of the Nemčiňany Fm. persisted across the rifting until the post-rift stage of the Danube Basin, western Slovakia

International audienceSuccessions deposited under rifting and post-rift settings of an isolated epicontinental basin often exhibit contrasting characteristics. Facies linked to transgression during basin rifting are typically locally sourced fan deltas transporting coarse-grained sediment, whereas the post-rift setup generally involves a normal regression marked by more extensive catchments, sediment sourced from greater distances, and an overall decrease in average grain size compared to the transgressive facies. In this study, we present a specific scenario based on a sedimentological, stratigraphic, and authigenic 10 Be/ 9 Be analysis of the Nemčiňany Formation, an Upper Miocene fan deltaic succession in the eastern Danube Basin, Slovakia. Deposition of the Nemčiňany Fm. was initiated shortly after ~11.6 Ma by the fourth rifting phase of the Pannonian Basin System, triggering the transgression of Lake Pannon. The depositional system persisted until ~9.6 Ma, likely balancing the increased accommodation rate with sediment supply in the shallow lake area situated on a basement high. Subsequently, a relative decrease in the accommodation rate prompted the progradation of shelf-slope scale clinoforms, originating from the Nemčiňany depositional system, toward the center of the Komjatice depression at ~9.4 Ma, resulting in a normal regression of Lake Pannon. The persistence of the Nemčiňany fan delta system, unlike common stratigraphic patterns, was associated to the high sediment supply yielded by the paleo-Hron river, which entered the basin in the study area. These observations underscore the need for caution in predicting provenance shifts during changes in geodynamic stages of a basin

The tectono-sedimentary evolution of a major seismogenic zone with low slip rate activity: A geochronological and sedimentological investigation of the Dobrá Voda Depression (Western Carpathians)

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Effects of spatially variable accommodation rate on channel belt distribution in an alluvial sequence: Authigenic 10Be/9Be-based Bayesian age-depth models applied to the upper Miocene Volkovce Fm. (northern Pannonian Basin System, Slovakia)

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Dependence of Gully Networks on Faults and Lineaments Networks, Case Study from Hronska Pahorkatina Hill Land

In this paper we analyse the dependence between gully networks, networks of valleys and faults in the area of Hronska pahorkatina Hill Land. The work is based on the analysis of directions and densities of these three networks in the study area and subunits of lower hierarchical level. The coincidence of all three networks is rare. This scenario occurs when networks of gullies are situated on the bottom of shallow valleys which are conditioned by the presence of faults. More often scenario is only the coincidence of network of valleys and gullies. The last scenario appears in areas with low fault density. The most specific scenario is perpendicularity between network of gullies and network of gullies. Gullies are situated on steep slopes of incised valleys in this case. The last scenario appears the most frequently and was also proven by findings from other studies. We propose three comprehensive explanations of the possible dependence between network of gullies and faults. We also suggest the draft of the possible dependence between network of valleys and gullies

The age and paleoenvironment of a late Miocene floodplain alongside Lake Pannon: Rodent and mollusk biostratigraphy coupled with authigenic 10Be/9Be dating in the northern Danube Basin of Slovakia

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