János Haas

Carbon isotope anomaly and other geochemical changes at the Triassic-Jurassic boundary from a marine section in Hungary

Most mass extinctions are linked with carbon isotope excursions, implying that biotic crises are coupled with changes in the global carbon cycle. The isotopic evolution during the end-Triassic extinction is far less documented than that for the other major Phanerozoic extinctions. Here we report a sharp and short-lived 23.5‰ excursion in carbon isotope values for carbonate (d 13 Ccarb) corresponding to a 22‰ excursion in the isotopic composition of marine organic matter (d 13 Corg) and other geochemical

Significance of Late Permian-Triassic facies zones in terrane reconstructions in the Alpine-North Pannonian domain

Abstract The present-day setting of the tectonic units (terranes) making up the pre-Neogene basement of the Pannonian Basin and the West Carpathians is the result of large-scale displacements during the Alpine collisional phases. To explain this setting, based on various concepts, a number of models have been proposed in the last decade. Most of them agree in an eastward escape of the “North Pannonian terrane” from the Alpine domain towards the Pannonian during the Palaeogene-Early Miocene period. In the present paper a reconstruction of the pre-escape setting of the displaced terranes is presented based on facies zones in selected time-slices from the Late Permian to the Late Triassic. According to our reconstruction the Inner West Carpathian units were located east of the Austroalpine units forming the northern shelf of the “Euhallstatt”-Meliatic basin of the Vardar oceanic branch. The Drauzug should have been located in a position much more external than its present-day setting. The Transdanubian Range was situated in the northern neighbourhood of the Southern Alps, whereas the Bukk may have been located adjacent to the NW Dinarides. The Mid-Transdanubian zone is a major shear-zone containing elements of the Julian Alps and Sava folds nappe system and the Inner Dinaric ophiolitic melange. Although the nappe-tectonism may have played an important role in the structural evolution of the “North Pannonian terrane”, this mechanism alone can hardly produce hundreds of kilometres of facies offset on the opposite sides of strike-slip zones.

Early dolomitisation of Late Triassic platform carbonates in the Transdanubian Range (Hungary)

Abstract In the Late Triassic, a large carbonate platform system came into existence in the Transdanubian Range (TR) producing a 1.5- to 2-km-thick carbonate succession. The lower part of the platform carbonate series is made up of cyclic peritidal dolomite (Main Dolomite Formation), while the upper one consists of cyclic peritidal limestone (Dachstein Limestone Formation). However, there is a transitional member of remarkable thickness between them consisting of partially dolomitised limestone and calcitic dolomite. This study focuses on the transitional member where the process of early dolomitisation was halted at various stages. In the investigated sections the early dolomitisation was controlled by the climate and high-frequency sea-level oscillation, which led to periodic subaerial exposure of large areas and palaeo-hydrological conditions. Increasing humidity and gradual extension of the permanently inundated outer platform led to cessation of early dolomitisation in the Middle to Late Norian.

Facies analysis of the cyclic Dachstein Limestone formation (Upper Triassic) in the Bakony Mountains, Hungary

SummaryThe cyclic development of the lower Dachstein Limestones (Norian) was studied in a 410 m thick sequence intersected by the borehole Porva Po-89 in the northern Bakony Mountains. Deviations from the ideal Lofer cyclothems described by FISCHER (1964) were found for a considerable part of the total of 138 cycles. Because of very slight erosion of the regressive member of the cyclothems (algal mat bed, B′) the basic formula of the Hungarian Lofer cyclothems is d-ABCB′-d (see Fig. 1/1). Intracyclic anomalies, minor internal unconformities, or erosion may be responsible for the lack of members; most often member A is absent or strongly reduced. No megacycles comparable with those in the Northern Alps have been found.The environmental interpretation is based on macroscopic and microscopic facies criteria (see Figs. 1 and 2) and on the comparison with Recent carbonates. The rocks of member A were formed within the supratidal zone and perhaps in the uppermost part of the intertidal zone. Member B was deposited within different parts of the intertidal zone. Carbonates of member C were formed within a shallow, subtidal lagoonal environment. The cyclicity of peritidal sedimentation seems to have been caused not by world-wide eustatic changes in sea-level but rather by minor climatic changes which might have been responsible for slightly changing rates of accumulation and evaporation.ZusammenfassungDie zyklische Entwicklung der unteren Dachstein-Kalke (Nor) wurde in einer 410 m mächtigen, in der Bohrung Porva Po-89 (nördliches Bakony-Gebirge) durchteuften Karbonatfolge untersucht. Hierbei wurden in einem beträchtlichen Teil der 138 Zyklen Abweichungen von dem von FISCHER (1964) beschriebenen Modell der nordalpinen Lofer-Cyclotheme festgestellt: Bedingt durch die nur geringe Erosion des regressiven Gliedes des Cyclothems (Einheit B′, Algenmatten-Kalk) wird das generelle Sedimentationsmuster der ungarischen Cyclotheme durch die Formel d-ABCB′-d beschrieben (Abb. 1/1). Einzelne Glieder können ausfallen, veranlaßt durch kleinere interne sedimentäre Diskordanzen oder durch synsedimentäre Erosion; am häufigsten fehlt die Einheit A. Megazyklen, wie sie für die nordalpinen Loferitzyklen postuliert wurden, konnten nicht festgestellt werden.Die Milieuinterpretation stützt sich auf die Auswertung makroskopischer und mikroskopischer Fazieskriterien (Abb. 1 und 2) und auf den Vergleich mit rezenten Karbonaten. Die Gesteine der Einheit A entstanden in der Supratidalzone, möglicherweise auch im obersten Abschnitt der Intertidalzone. Die Einheit B wurde in verschiedenen Bereichen der Intertidalzone gebildet, die Karbonate der Einheit C im flachlagunären Subtidal. Das zyklische Muster der peritidalen Sedimentation dürfte nicht durch weltweite eustatische Meeresspiegelschwankungen verursacht sein, sondern durch kleinere klimatische Schwankungen, welche für wechselnde Raten von Ablagerung und Evaporation verantwortlich gewesen sein könnten.

CAPITANIAN (MIDDLE PERMIAN) MASS EXTINCTION AND RECOVERY IN WESTERN TETHYS: A FOSSIL, FACIES, AND δ13C STUDY FROM HUNGARY AND HYDRA ISLAND (GREECE)

Abstract The Capitanian (middle Permian) extinction and recovery event is examined in carbonate platform settings from western Tethys (Hungary and Hydra, Greece). The age model for these sections is poorly resolved and we have constructed a &dgr;13C chemostratigraphic correlation scheme, supported by conodont and foraminifer data, which attempts correlation with the well-dated events in China. This reveals the timing of events was similar in all Tethyan regions: extinction losses in the middle of the Capitanian produced late Capitanian assemblages in Hungary and Hydra with a distinctive late Permian character (for example, they lack large fusulinaceans). There is no evidence for an extinction event at the end of the Guadalupian (Capitanian) suggesting that previous claims for an end-Guadalupian mass extinction are based on poorly dated records of a mid-Capitanian event. Base level was stable through much of the middle–late Permian transition with the exception of a major regression within the Capitanian Stage. The subsequent transgression established widespread shallow-water carbonate deposition, such as the Episkopi Formation in Hydra and the Nagyvisnyó Limestone Formation in Hungary.

Genesis and Evolution of the Pannonian Basin

Historic-cultural precedents for the name of the Pannonian Basin can be found in the Pannonian province of the Roman Empire, whose northern and eastern boundaries were coinciding with the Danube. Telegdi-Roth (1879) created the chronostratigraphic concept of the Pannonian age for the formations of the Transdanubian region, deposited between the Sarmatian and Pleistocene, and being distinct from both of them. Anyhow, the basin-fill of the Pannonian Basin cannot be confined only to the deposits of Pannonian age; it comprises practically the whole Neogene–Quaternary rock sequence of the area.

Biodiversity evolution through the Permian-Triassic boundary event: Ostracods from the Bükk Mountains, Hungary

One of the most complete Permian-Triassic boundary sections located in the Bükk Mountains (Hungary) was sampled for ostracod study. Seventy-six species are recognized, belonging to twenty genera. Fifteen new species are described and figured: Acratia? jeanvannieri Forel sp. nov., Acratia nagyvisnyoensis Forel sp. nov., Bairdia anisongae Forel sp. nov., Bairdia davehornei Forel sp. nov., Callicythere? balvanyseptentrioensis Forel sp. nov., Cytherellina? magyarorszagensis Forel sp. nov., Eumiraculum desmaresae Forel sp. nov., Hollinella fengqinglaii Crasquin sp. nov., Hungarella gerennavarensis Crasquin sp. nov., Langdaia bullabalvanyensis Crasquin sp. nov., Liuzhinia venninae Forel sp. nov., Liuzhinia bankutensis Forel sp. nov., Microcheilinella egerensis Forel sp. nov., Reviya praecurukensis Forel sp. nov., Shemonaella? olempskaella Forel sp. nov. One species is renamed: Bairdia baudini Crasquin nom. nov. Comparison of the Bálvány North section with the Meishan section (Zhejiang Province, South China), Global Boundary Stratotype Section and Point (GSSP) of the Permian-Triassic Boundary (PTB), reveals discrepancies linked to the environmental setting and particularly to bathymetry. The stratigraphical distribution of all the species is given and diversity variations are discussed. The Bálvány North section exhibits the lowest extinction rate of all PTB sections studied for ostracods analysis associated with a high level of endemism.

Anaerobic degradation of organic matter controlled by productivity variation in a restricted Late Triassic basin

The organic-rich late Triassic Kossen Formation (Hungary) was deposited in a shallow basin, situated between a carbonate platform and the continent. A large number (107) of samples of a 240 m thick, steeply dipping core section of the Kossen Fm., built up of mostly non-bioturbated sediments have been analysed by Rock-Eval pyrolysis. Organic petrographic studies, sulphur and iron speciation (total sulphur, HCl-soluble sulphate sulphur, pyrite iron and HCl- soluble iron) and CO2 measurements have been carried out on smaller sample sets. According to Rock-Eval pyrolysis and organic petrography the immature organic matter (OM) is of dominantly marine origin throughout the section. Unicellular planktonic algae are remains of the most important organic constituents but microbial-algal mat material is also of importance. The carbonate and TOC contents and HI values display much scatter and upward decreasing trends. Type II-S OM is common in the lower third of the section and it occurs in its middle interval, too. The marked downward decrease of Tmax values is explained by the downward increase of the OM sulphur content. The original organic carbon content (TOCor) was calculated. The degree of OM preservation, expressed in term of TOC/TOCor, varies between 0.36 to 0.89 and shows an upward decreasing trend, interrupted by high values around the middle of the section. This strengthening of the degradation during the black shale event was the result of the parallel decreasing rate of sedimentation and OM deposition. The high TOC/TOCor values found around the middle of the section are mostly the result of a temporary acceleration of OM deposition. Sulphur richness of the OM shows no positive correlation with the degree of organic preservation. Sulphur partitioning between pyrite and OM was controlled by the ratio of reactive iron to OM. Average rates of planktonic productivity (Cprod) vary between 6-9 and 60-88 t Corg/m 2 /Ma. The rough covariance of the degree of preservation and Cprod suggests that variations in planktonic productivity exerted a strong control on preservation in the suboxic, low to medium productivity Kossen Formation. # 2000 Elsevier Science Ltd. All rights reserved.

GENESIS OF LATE CRETACEOUS TOE-OF-SLOPE BRECCIAS IN THE BAKONY MTS, HUNGARY

Abstract Toe-of-slope megabreccia deposits of an Upper Cretaceous rudist platform were studied in the Bakony Mountains. During the Turonian–early Senonian tectogenesis an articulated basin came into being in the area of the Bakony; depressions and highs were formed roughly parallel with the structural strike of the mountains. Inundation of the highs led to the evolution of carbonate platforms. The investigated platform shows an asymmetric architecture. In contrast to its gentle northern slope a steep erosional slope bounded the platform to the south with large, low-angle aprons, the site of deposition of megabreccias. The breccia accumulation occurred within a single 3rd-order cycle commencing in the early highstand and reaching its climax in the late highstand.

Lithofacies and age data of Jurassic foreslope and basin sediments of Rudabánya Hills (NE Hungary) and their tectonic interpretation

Lithofacies and age data of Jurassic foreslope and basin sediments of Rudabánya Hills (NE Hungary) and their tectonic interpretation Jurassic sedimentary rocks of the Telekesvölgy Complex (Bódva Series), Telekesoldal Complex (Telekesoldal Nappe) and the Csipkés Hill olistostrome in Rudabánya Hills (NE Hungary) were sampled for microfacies studies and interpretation of the depositional environments. The Telekesvölgy Complex is made up of reddish to greenish marl, occasionally containing limestone olistoliths — gradually progresses from the Norian Hallstatt Limestone of the Bódva Series — then grey marl, which may correspond to the latest Triassic Zlambach Formation. This variegated marl progresses into grey marl and calcareous marl, containing crinoid fragments. It may be interpreted as a hemipelagic facies, relatively close to submarine highs. Bajocian to Lower Bathonian black shales, rich in radiolarians and sponge spicules representing typical deep pelagic facies, are also assigned to the Telekesvölgy Complex. The Telekesoldal Complex represents a mélange-like subduction-related complex that consists of black shales, sandstone turbidites and olistostrome beds, and deposited by gravity mass flows. A relatively deep marine basin in the proximity of a submarine slope is likely to be the depositional environment of this unit. The clasts of the olistostromes are predominantly Middle to Upper Triassic pelagic limestones, rhyolite and basalt. Subduction related nappe stacking of the ocean margin during the Middle to Late Jurassic may have created suitable conditions for this sedimentation pattern. Bajocian-Callovian age of the complex was proved by the revision of the radiolarian fauna and new palynological data, the first from the Jurassic of the Aggtelek-Rudabánya Hills. The Csipkés Hill olistostrome consists of carbonate turbidite beds containing Jurassic platform derived foraminiferal and olistostrome horizons with Middle-Upper Triassic limestone clasts of red Hallstatt facies.