Kinga Hips

Lower Triassic storm-dominated ramp sequence in northern Hungary: an example of evolution from homoclinal through distally steepened ramp to Middle Triassic flat-topped platform

Abstract Lower Triassic formations were studied in sections of the overthrust Silicicum, in the Aggtelek-Rudabánya Mountains, in northern Hungary. The sequence is represented by evaporitic, siliciclastic, mixed siliciclastic-carbonate, and carbonate rocks c. 800 m in thickness. Sixteen facies, from tidal flat to outer ramp, were documented in three succeeding depositional systems. They are as follows: wave- and storm-dominated siliciclastic ramp, mixed high-energy storm-dominated ramp, and low-energy carbonate ramp. Based on the vertical stacking patterns of the metre-scale cycles, five depositional units were defined within the Scythian sequence. Each depositional unit is composed of a deepening- and a shallowing-upward part. Occasionally, a lowermost transitional part is also recognized from the top of the previous depositional unit. There is a good correlation between these units and the Scythian depositional sequences of western Tethys. In Early Triassic time, the following main ramp stages were recorded: (1) homoclinal ramp with siliciclastic sedimentation; (2) homoclinal ramp with siliciclastic sedimentation and incipient oolite shoals on the inner ramp; (3) homoclinal to distally steepened ramp with mixed sedimentation; (4) distally steepened ramp with mixed and subsequent carbonate sedimentation; (5) drowning and gradual restriction of carbonate ramp. The following Anisian development is briefly summarized. In Early Anisian time, the restricted outer ramp filled up, which allowed shallow-water carbonates to advance laterally. In Mid-Anisian time, a tectonically preformed flat-topped platform began to develop. As a consequence of Mid-Triassic rifting, a deep pelagic basin was formed. Reef-building organisms, which first appeared in Late Anisian time after the Permian-Triassic boundary extinction, colonized the faulted margins. The sedimentation on the Scythian ramp was controlled by several factors. The gently sloping ramp was formed by slow thermal subsidence. Absence of frame-builders because of the Permian-Triassic boundary crisis played an important role in maintenance of the ramp morphology. The climate significantly influenced the terrigenous influx and carbonate production. Owing to the windward palaeogeographical position of the Aggtelek ramp, storms had a particularly important role in the sediment transport.

BIVALVES AND BRACHIOPODS NEAR THE PERMIAN-TRIASSIC BOUNDARY FROM THE BÜKK MOUNTAINS (BÁLVÁNY-NORTH SECTION, NORTHERN HUNGARY)

In the Bukk Mountains the Upper Permian is represented by the Nagyvisnyo Limestone, which contains very rich marine assemblages. It is overlain by the Gerennavar Limestone (uppermost Permian-Lower Triassic) which records the effects of the Permo-Triassic mass extinction with a dramatic decrease in diversity and abundance of fossils. The basal Gerennavar Limestone is represented by a clayey marl unit (basal beds) deposited in a quiet, low-energy marine environment below the storm wave-base, whose maximum thickness, about one meter, is recorded in the Balvany-North section. From this locality a relatively diversified and abundant marine benthonic assemblage has been collected, and is here described. Bivalves are represented by: Bakevellia cf. ceratophaga (Schlotheim), ? Pterinopectinidae gen. et sp. indet., Eumorphotis lorigae sp. n., the most abundant species, Entolium piriformis (Liu) and Pernopecten latangulatus Yin. Brachiopods are less frequent, and the following four species have been identified: Spinomarginifera sp., Orthothetina ladina (Stache), Ombonia tirolensis (Stache) and Orbicoelia tschernyschewi (Likharew). An exact age of this fauna, based on conodonts, is not yet available, but the strong affinities with those of the lower Tesero Member (Dolomites) and the Lower Kathwai Member (Pakistan) suggest a latest Permian age (? Hindeodus praeparvus Zone). If so, the Balvany-North section becomes one of the few in the world which records the last bioevents of the Palaeozoic.

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.

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.

Hydrothermal dolomitization of basinal deposits controlled by a synsedimentary fault system in Triassic extensional setting, Hungary

Dolomitization of relatively thick carbonate successions occurs via an effective fluid circulation mechanism, since the replacement process requires a large amount of Mg-rich fluid interacting with the CaCO3 precursor. In the western end of the Neotethys, fault-controlled extensional basins developed during the Late Triassic spreading stage. In the Buda Hills and Danube-East blocks, distinct parts of silica and organic matter-rich slope and basinal deposits are dolomitized. Petrographic, geochemical, and fluid inclusion data distinguished two dolomite types: (1) finely to medium crystalline and (2) medium to coarsely crystalline. They commonly co-occur and show a gradual transition. Both exhibit breccia fabric under microscope. Dolomite texture reveals that the breccia fabric is not inherited from the precursor carbonates but was formed during the dolomitization process and under the influence of repeated seismic shocks. Dolomitization within the slope and basinal succession as well as within the breccia zones of the underlying basement block is interpreted as being related to fluid originated from the detachment zone and channelled along synsedimentary normal faults. The proposed conceptual model of dolomitization suggests that pervasive dolomitization occurred not only within and near the fault zones. Permeable beds have channelled the fluid towards the basin centre where the fluid was capable of partial dolomitization. The fluid inclusion data, compared with vitrinite reflectance and maturation data of organic matter, suggest that the ascending fluid was likely hydrothermal which cooled down via mixing with marine-derived pore fluid. Thermal gradient is considered as a potential driving force for fluid flow.

Hettangian (Early Jurassic) Dinosaur Tracksites from the Mecsek Mountains, Hungary

Isolated theropod dinosaur tracks were first collected in Hungary from Hettangian (Lower Jurassic) beds of the Mecsek Coal Formation in 1966 and described as Komlosaurus carbonis Kordos, 1983. Our study is based on newly collected material from additional track-bearing beds. The description of the two largest preserved surfaces containing a total of 102 tracks that can be referred to as 21 trackways is provided here. This represents the first attempt to measure, map and compare the tracks of these bipedal, functionally tridactyl dinosaurs in several associated trackways. Significant morphological variability can be observed (e.g., depth, presence or absence of a metatarsal impression, digit length, digit divarication angle) that is explained by differences in physical parameters of the substrate. The mean of pes length is 16.3 cm in tracksite PB1 and 19.9 cm in tracksite PB2. Stride length of trackways usually ranges between 120 and 170 cm; pace angulation is 160–175°. The speed of the trackmaker is calculated to range between 6 and 14 km/h. Imprints are diagnosed by a pes length/width ratio lower than 2.0; metatarsal pads and hallux impressions are frequent. Based on the similarity of several morphological characters, the herein described tracks are referred to the ichnotaxon Komlosaurus carbonis, which is clearly distinct from Grallator and Kayentapus.

Processes and controlling factors of polygenetic dolomite formation in the Transdanubian Range, Hungary: a synopsis

In the Transdanubian Range (Hungary), dolostone and dolomitic limestone appear in a number of sedimentary successions formed from the Late Permian to the Late Triassic in various depositional settings and under various diagenetic conditions, whereas only a negligible amount of dolomite was detected in the post-Triassic formations. Seven dolomite-bearing units representing ramp, small and large carbonate platforms, and intraplatform basin settings are presented in this synopsis. In most cases, multi-stage and polygenetic dolomitization was inferred. The main mass of the dolostones was formed via near-surface diagenetic processes, which were commonly preceded by the formation of synsedimentary dolomite. Accordingly, surficial conditions that prevailed during sediment deposition controlled the dolomite-forming processes and thus the lateral extension and the time span of dolomitization. The area of episodic subaerial exposure was a critical controlling factor of the lateral extension of the near-surface dolomite genesis, whereas its temporal extension was mostly governed by climate. Burial diagenesis usually resulted in only moderate dolomitization, either in connection with compactional fluid flow or via thermal convection. The Triassic fault zones provided conduits for fluid flow that led to both replacive dolomitization and dolomite cement precipitation. In the Late Triassic extensional basins, synsedimentary fault-controlled dolomitization of basinal deposits was reconstructed.