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The Budaörs-1 well revisited: Contributions to the Triassic stratigraphy, sedimentology, and magmatism of the southwestern part of the Buda Hills
Authors: János Haas, Tamás Budai, István Dunkl, Éva Farics, Sándor Józsa, Szilvia Kövér, Annette E. Götz, Olga Piros and Péter Szeitz

The 1,200-m-deep Budaörs-1 borehole provided important data for our understanding of the stratigraphy and tectonic setting of the southern part of the Buda Hills. Although previous reports contained valid observations and interpretations, a number of open questions remained. The importance of this borehole and the unsolved problems motivated us to revisit the archived core. The new studies confirmed the existing stratigraphic assignment for the upper dolomite unit (Budaörs Dolomite Formation) as the dasycladalean alga flora proved its late Anisian to Ladinian age assignment. An andesite dike was intersected within the Budaörs Dolomite. U–Pb age determination performed on zircon crystals revealed a Carnian age (~233 Ma), and settled the long-lasting dispute on the age of this dike, proving the existence of a Carnian volcanic activity in this area after the deposition of the Budaörs Dolomite. Palynostratigraphic studies provided evidence for a late Carnian to early Norian age of the upper part of the lower unit (Mátyáshegy Formation). This result verified an earlier assumption and reinforced the significance of the tectonic contact between the upper unit (Budaörs Formation) and the lower unit (Mátyáshegy Formation). Based on structural observations and construction of cross sections, two alternative models are presented for the structural style and kinematics of the contact zone between the Budaörs and Mátyáshegy Formations. Model A suggests a Cretaceous age for the juxtaposition, along an E–W striking sinistral transpressional fault. In contrast, model B postulates dextral transpression and an Eocene age for the deformation. The latter one is better supported by the scattered dip data; however, both scenarios are considered in this paper as possible models.

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The Late Cretaceous (Santonian) fish fauna of the Iharkút vertebrate site (Bakony Mountains, Hungary) is described here. The ichthyofauna includes the lepisosteid Atractosteus sp., the pycnodontid cf. Coelodus sp., Vidalamiinae indet., a non-vidalamiin Amiidae indet., Elopiformes indet., two indeterminate ellimmichthyiforms, cf. Salmoniformes indet., Acanthomorpha indet., at least one indeterminate teleostean, and numerous indeterminate actinopterygians (represented by teeth). Among these taxa, the Iharkút remains of Vidalamiinae and the suggested indeterminate Salmoniformes represent their first occurrence in the Late Cretaceous of Europe. The unidentifiable specimens may suggest the presence of further fish taxa. The gar remains described here further support the Atractosteus sp. affinity of the Iharkút form. Most of the Iharkút fishes are carnivorous, but durophagous taxa are also represented. Although chondrichthyan remains have not been identified in the Iharkút vertebrate material up to now, the ecological distribution of some local fish taxa presumes the possible vicinity of a marine–deltaic environment. Several Iharkút fish taxa are known from North American localities as well, suggesting that the Late Cretaceous European continental fish might have been more diverse and similar to that of North America than previously thought. The necessity of more intensive screen-washing at other European Late Cretaceous vertebrate sites is also emphasized.

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In this study, new microthermometric data of fluid inclusions distributed along planar assemblages crosscutting a metamorphic quartz lens from the Mecsekalja Zone metamorphic complex are presented. Three fluid generations are defined, none of which have previously been identified by earlier paleofluid evaluations of the study area. Petrographic description of the host quartz is provided to identify textures related to crystalloplastic deformation resulting from ductile deformation. The textural relationship of the studied assemblages to the dynamic recrystallization features is discussed. The possible affinities of the fluids introduced in this study to those identified in the region by previous authors are discussed. The affinities and timing of the fluid flow events are discussed based on the physicochemical properties of the fluids. One local carbonic (high XCO2) fluid is recognized. A high- and a moderate-salinity fluid generation are also revealed. The relationship of these fluid generations to those defined in earlier studies from the Mórágy Granite and the Baksa metamorphic complex contributes new knowledge to the recognition of the regional paleofluid evolution.

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Shock-induced alterations in the recently found H chondrite Csátalja meteorite and its implications
Authors: Ildikó Gyollai, Ákos Kereszturi, Zsolt Kereszty, Máté Szabó and Elias Chatzitheodoridis

Shock-driven annealing of pyroxene and shock deformation of olivine were analyzed in a recently found H chondrite called Csátalja. The most characteristic infrared (IR) spectral shape of shock-annealed sub-grained pyroxene was identified: the strongest peak occurs at 860 cm−1 with a smaller shoulder at 837−840 cm−1, and small bands are at 686, 635−638, and 1,044−1,050 cm−1. The appearance of forbidden bands in pyroxene and shift of band positions to a lower wave number in olivines clearly demonstrate the crystal lattice disordering due to shock metamorphism. The shock annealing produced mixed dark melt along fractures, which consists of feldspar−pyroxene and olivine−pyroxene melt. The dark shock melt at sub-grain boundaries of shocked pyroxenes and along fracture of pyroxenes is characterized by elevated Ca, Na, and Al content relative to its environment, detected by element mapping. So far, shock deformation of pyroxene and olivine was not studied by IR spectroscopy; this method has turned out to be a powerful tool in identifying the mixed composition of shock melt minerals. Further study of shock annealing of minerals, together with the context of shock melting at sub-grain boundaries, will provide a better understanding of the formation of high P–T minerals.

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Finding the optimal number of realizations to represent the model uncertainty when applying stochastic approaches is still a relevant question in geostatistics. The essence of the method is to visualize the realizations in a suitably constructed attribute space. To construct this space, the static connectivity metrics of the realizations were used. Within this framework, the creation of new realizations can be regarded as a sampling process, in which each new stochastic image is the equivalent of a new sampling point in the attribute space. The sampling process begins with the first few realizations appearing in a dispersed manner in random parts of the attribute space. The addition of more realizations causes the gradual emergence of higher point densities, which in the end, results in a point structure where most of the points are located in areas of high point densities with areas of low point densities surrounding them. High point densities represent typical realizations showing very similar connectivity characteristics, whereas low point densities correspond to atypical realizations with stronger deviations from the bulk. In this sense, reaching the optimal number of realizations is the equivalent of reaching a state in the sampling process where high- and low point densities are present at the same time, yet high point densities do not dominate the overall structure of the attribute space, as they also reflect the redundancy of the information content. This desired structure is strongly analogous to the complete spatial randomness of spatial point processes, where the points are neither dispersed nor aggregated in space. Based on this analogy, the normalized version of Ripley’s K-function and the L-function for the spatial inhomogeneous Poisson point process was applied to find the optimal number of realizations. The method is illustrated on a computed tomography slice and on the real-life data of the Tisza-2 reservoir.

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Collection of the thinnest: A unique eggshell assemblage from the Late Cretaceous vertebrate locality of Iharkút (Hungary)
Authors: Edina Prondvai, Gábor Botfalvai, Koen Stein, Zoltán Szentesi and Attila Ősi

As a result of several years of screen-washing activity, a remarkable assemblage of eggshell fragments has been recovered from the Late Cretaceous vertebrate locality of Iharkút, Hungary. Detailed investigation of the assemblage by multiple visualization techniques (scanning electron microscopy, polarizing light microscopy, X-ray micro-computed tomography), quantitative morphometric analyses, and micro X-ray fluorescence spectrometry revealed a diverse composition of five different eggshell morphotypes (MT IMT V) and three subcategories within the second morphotype (MT II/a, b, c), with MT I being by far the most abundant (83%) in the assemblage. MT I, MT III, and MT V represent theropod dinosaurian eggshells, whereas MT II and MT IV show characteristics of crocodilian and squamate eggshells, respectively. Hence, despite their fragmentary nature, these eggshells represent the first clear evidence that various sauropsid taxa had nesting sites near the ancient fluvial system of Iharkút. Besides the implied taxonomic diversity, two unique features add to the significance of this eggshell assemblage. First, it contains the thinnest rigid crocodilian (MT II/c) and squamate (MT IV) eggshells ever reported. Moreover, one of the identified theropod morphotypes, MT I, is also among the thinnest fossil dinosaurian eggshells, the thinness of which is only rivalled by the eggshells of the smallest Mesozoic avian eggs known to date. Second, the Iharkút eggshell assemblage consists exclusively of thin eggshells (≤300 µm), a condition unknown from any other fossil eggshell assemblages described to date. Combined with the knowledge acquired from skeletal remains, these peculiarities give additional insights into the paleoecology of the terrestrial sauropsid fauna once inhabiting the ancient island of Iharkút. Finally, the presence of well-preserved eggshells recovered from two different sites representing different depositional environments provides further evidence for previous taphonomic and sedimentological conclusions, and also expands our knowledge of the special conditions that allowed the preservation of these delicate eggshell fragments.

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Erratum to: Petrology and paleokarst features of the Gomba hydrocarbon reservoir (central Hungary)
Authors: Márton Bauer, Tivadar M. Tóth, Béla Raucsik and István Garaguly
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Ore geology of the copper sulfide mineralization in the Rudabánya ore-bearing complex
Authors: Norbert Németh, János Földessy and Judit Turi

The mineralized complex of Rudabánya hosts deposits of several mineral resources including base metal ores. Recent exploration provided new information on the enrichment of copper within this complex. The primary copper mineralization consists of sulfides. The paragenetic sequence starts with fahlore, continues with bornite, and concludes in chalcopyrite formation partly replacing the former phases. It is hosted by brecciated carbonate rocks, overprinting the paragenesis of the iron metasomatism. It was found to be spatially separated from zinc and lead enrichments. Oxidation and a subsequent new pulse of mineralization formed several new copper, zinc, and lead minerals, probably by the remobilization of the primary parageneses.

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Recently forming stalagmites from the Baradla Cave and their suitability assessment for climate–proxy relationships
Authors: Attila Demény, Alexandra Németh, Zoltán Kern, György Czuppon, Mihály Molnár, Szabolcs Leél-Őssy, Mihály Óvári and József Stieber

Determination of the long-term behavior of cave systems and their response to changing environmental conditions is essential for further paleoclimate analyses of cave-hosted carbonate deposits. For this purpose, four actively forming stalagmites were collected in the Baradla Cave where a three-year monitoring campaign was also conducted. Based on textural characteristics and radiocarbon analyses, the stalagmites are composed of annual laminae, whose counting was used to establish age–depth relationships. Fast and slowly growing stalagmites have different stable carbon and oxygen isotope compositions as well as trace element contents that could be attributed to differences in drip water migration pathways. The stable isotope compositions were compared with meteorological data of the last ∼100 years indicating that carbon isotope compositions of the stalagmites may reflect changes in precipitation amount, while oxygen isotope compositions are more related to temperature variations. The combined textural–geochemical–meteorological interpretation lead us to select the isotope record that can best reflect variations in environmental conditions and can be used for further evaluation of the climate–proxy relationships.

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Anisian Muschelkalk carbonates of the southern Germanic Basin containing silicified ooidal grainstone are interpreted as evidence of changing pH conditions triggered by increased bioproductivity (marine phytoplankton) and terrestrial input of plant debris during maximum flooding. Three distinct stages of calcite ooid replacement by silica were detected. Stage 1 reflects authigenic quartz development during the growth of the ooids, suggesting a change in the pH–temperature regime of the depositional environment. Stages 2 and 3 are found in silica-rich domains. The composition of silica-rich ooids shows significant Al2O3 and SrO but no FeO and MnO, indicating that late diagenetic alteration was minor. Silicified interparticle pore space is characterized by excellent preservation of marine prasinophytes; palynological slides show high abundance of terrestrial phytoclasts. The implications of our findings for basin dynamics reach from paleogeography to cyclostratigraphy and sequence stratigraphy, since changes in the seawater chemistry and sedimentary organic matter distribution reflect both the marine conditions as well as the hinterland. Basin interior changes might overprint the influence of the Tethys Ocean through the eastern and western gate areas. Stratigraphically, such changes might enhance marine flooding signals. Ongoing research needs to address the complex interaction between an intracratonic basin and an open-ocean system by comparing local and regional biotic and abiotic signals.

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