A Dunántúli-középhegység középső-triász földtörténete: medencefejlődés és vulkanizmus = Middle Triassic history of the Transdanubian Range: basin evolution and volcanism

A Dunántúli-középhegység DNy-i részén szigetplatformokkal tagolt tengermedencék jöttek létre a középső-triász során, amelyek kialakulásában jelentős szerepet játszott a szinszediment tektonika. Ezzel szemben a Kelet-Bakonytól ÉK-re lévő területet karbonátplatformok uralták, amelyek között egy kisebb méretű medence léte igazolható a Budai-hegység Ny-i előterében. A platformok épülését (a "karbonátgyár működését") alapvetően a tengerszint relatív változásai határozták meg, ezek között a globális (eusztatikus) hatások elkülöníthetőek a lokális vagy regionális (elsősorban tektonikus, illetve vulkanotektonikus) hatásoktól. A Dunántúli-középhegység középső-triász medencéinek és platformjainak fejlődésében a vulkáni működés nem játszott lényeges szerepet, szemben a Déli-Alpokkal. A késő-anisusi savanyú vulkanizmus üledékei átülepítettek, mállási termékeik azonban jelentősen hozzájárulhattak a tengervíz tápanyag-utánpótlásához. A kelet-bakonyi sekély ladin medencébe egy közeli vulkáni szárazulatról lepusztuló törmelék ugyanakkor nem mutatható ki a Déli-Bakony mélyebb nyílttengeri medencéiben, ami arra utal, hogy a két medence közötti üledékszállítást kiemelt terület gátolta. | In the southwestern part of the Transdanubian Range isolated platforms and basins were formed during the Middle Triassic, controlled by synsedimentary tectonics. The area located northeast of the Eastern Bakony Mts was dominated by carbonate platforms, only a small intraplatform basin can be reconstructed in the western foreland of the Buda Mts. The evolution of the platforms (productivity of the carbonate factory) was basically controlled by relative sea-level changes, which were provoked by global and regional or local (e.g. tectonic or volcanotectonic) influences. Contrary to the Southern Alps, volcanic activity didn't play a decisive role in the evolution of the Middle Triassic basins and platforms of the Transdanubian Range. However, the weathering material of the Late Anisian redeposited acidic volcanic sediments might have significantly supported the nutrient supply of the sea water. Eroded clasts derived from a near volcanic island into the shallow Eastern Bakony ladinian basin can?t be detected in the deeper pelagic basins of the Southern Bakony. This can be explained by the existence of an uplifted area hindering the sediment transport between the two basins

The base of the Curionii Zone (Ladinian, Triassic) in Felsőörs (Hungary): improved correlation with the Global Stratotype Section

Abstract Recent excavation and sampling in the upper part of the Felsőörs section (Balaton Highland, Hungary) yielded important ammonoid findings, identified as belonging to the genera Nevadites, Chieseiceras, Eoprotrachyceras and Falsanolcites. Several specimens of Chieseiceras chiesense were found in a dm-thick clay layer with limestone nodules, regarded as the equivalent of the “Chiesense Groove“ of the Bagolino and other sections in the Giudicarie area (North Italy). The immediately overlying limestone bed yielded Eoprotrachyceras cf. curionii and Falsanolcites cf. rieberi. Together these reliably prove the base of the Curionii Zone, corresponding to the base of the Ladinian Stage, the GSSP of which was recently established at Bagolino. The new data further improved the excellent correlation between the ammonoid records of the Felsőörs section and the Global Stratotype Section at Bagolino. Felsőörs may be considered the most important reference section for the Anisian to Ladinian boundary interval

Triász platform- és medencefáciesek kapcsolata a Pilis vonulatban = Relationship between Triassic platform and basin facies of the Pilis Range

A Pilis Dachsteini Mészkő kifejlődését peritidális és sekély szubtidális rétegtagokból felépülő, ciklusos rétegsor jellemzi, amely a biosztratigráfiai vizsgálatok szerint a nori emeletbe tartozik. A Dachsteini-platform pereméhez közeli lejtőfáciest lito- és bioklasztokból, valamint bekérgezett szemcsékből álló durvaszemcsés üledék alkotja, amely alatt a platformlagúnára és a medencére jellemző kagylók viharok által átülepített kokvinái együtt fordulnak elő. A Dachsteini Mészkővel részben heteropikus Feketehegyi Mészkő rétegsorát disztális tempesztit- és medencefáciesű rétegek váltakozása építi fel. A Feketehegyi Mészkőben található átülepített zöldalga-töredékek nori korú flórát jeleznek az egyidős Dachsteini platformon. A Pilis Dachsteini Mészkő rétegsora a Tethys selfjén kialakult sekélytengeri platform háttérlagúnájában képződött a nori során. A nori közepén aktivizálódott extenziós tektonika hatására jött létre a platformon belül a félárok-jellegű Feketehegyi-medence, amelynek lankás oldalán egyenlejtes rámpa jött létre, sekélytengeri kagyló-kolóniákkal és viharüledékekkel. A kiemelt helyzetben maradt blokkok peremét foltzátonyokkal tarkított ooid-homokdombok alkották, bekérgező szervezetekkel. A medence mélyebb régiójában ugyanakkor disztális turbiditek és medenceüledékek rakódtak le. A késő-nori legnagyobb elöntés idején a Feketehegyi-medence nyitottabbá vált, majd az ezt követő magas vízállás idején a platformlejtő előrenyomult a medence irányába a nori–rhaeti határán. | The Pilis Hills are made up predominantly of the Dachstein Limestone of Norian age. It is characterised by alternation of peritidal and shallow subtidal Lofer cycles. However, coeval basin facies with distal tempestite interlayers (Feketehegy Limestone) also occur in the Pilis. Redeposited fragments of Norian green-algae constrain the synchrony of the platform and basin facies. Proximal tempestite beds with mollusc coquina indicate the upper part of low-angle slopes between the basin and the platform. In the northern part of the Pilis, the mollusc coquina beds are overlain by thick limestone of forereef slope facies. The Dachstein Limestone of the Pilis was formed in the internal platform domain of the Dachstein platform system which developed along the margin of the Neotethys during the Late Triassic. As a result of extensional tectonic movements activated in the mid-Norian the half-graben type Feketehegy Basin came into existence. On the low-angle side of this basin a homoclynal ramp was developed where bivalve coquinas and proximal storm deposites were accumulated. Oolitic mounds with patch reefs were developed along the margin of the elevated blocks. Basinal carbonates and distal tempestites were deposited in the deepest part of the basin. At the time of the Late Norian maximum flooding the Feketehegy Basin became more open; it was probably followed by progradation of the ambient platform during the subsequent latest Norian – earliest Rhaetian highstand period

Partial dolomitization of foreslope and toe-of-slope facies of a Carnian carbonate platform, Transdanubian Range, Hungary

Partial and pervasive dolomitization of foreslope and toe-of-slope deposits of an early Carnian carbonate platform was investigated to understand the process and mechanism of dolomitization. Based on petrographic observations and C and O isotope data, the dolomitization took place in a near-surface to shallow burial setting; seawater of slightly elevated salinity was likely the dolomitizing fluid. The circulation system was maintained by reflux of evaporated sea water and geothermal heating of cold seawater derived from the surrounding deeper basin. The dolomitization was mostly controlled by the permeability of the platform-derived calcareous sediments

Genesis of Upper Triassic peritidal dolomites in the Transdanubian Range, Hungary

In the Late Triassic, a 2–3-km-thick platform carbonate succession formed along the passive margin of the Tethys Ocean. Certain parts of the succession were affected by pervasive dolomitization whereas other parts are only partially dolomitized or non-dolomitized. In the Transdanubian Range, Hungary, the Upper Triassic platform carbonates are extensively distributed and numerous data are available for the space and time relations of the dolomitized and non-dolomitized units. This geological setting provides a unique opportunity for the study of paleogeographical and diagenetic controls of dolomitization of the whole platform complex. This paper presents the characteristic features of the dolomite types of the dolomite-bearing formations and lithofacies types, with a view to interpret the dolomite-forming processes and to determine the main controlling factors of the dolomite genesis. Petrographic features and stable isotope characteristics of the studied successions suggest the predominance of penecontemporaneous and early diagenetic dolomite genesis. Study of the transitional interval between the pervasively dolomitized and the non-dolomitized sequences revealed the general presence of microcrystalline dolomite in the peritidal microbial deposits and the characteristics of partial dolomitization both in the peritidal and subtidal facies. In the peritidal facies, microbially induced Ca–Mg carbonate precipitation is inferred, which was probably complemented by penecontemporaneous mimetic dolomitization of precursor carbonates due to evaporative pumping or seepage influx. Dolomitization of the subtidal facies took place via reflux of slightly evaporated seawater. Dolomitization of the previously deposited carbonate mud commenced during subsequent subaerial exposure but the process of early diagenetic dolomitization may have continued during later exposure events. Recurring subaerial exposure is one of the factors that determine the areal extent of the early dolomitization of the platform carbonates. However, climatic conditions were also crucial. Although the sealevel-controlled, unconformity-bound cyclic facies pattern did not change significantly in the internal platform belt during the nearly 20-My-long time range, a drier climate favored dolomite formation while increasing humidity led to a gradual decreasing intensity of early dolomitization

Alteration of Triassic carbonates in the Buda Mountains —a hydrothermal model

Abstract Large, irregular volumes of altered, friable Triassic dolomite with poorly recognizable depositional fabrics crop out in the Buda Mountains, Hungary. These rock volumes are characterized by powder-like, chalky, soft, whitish gray microporous carbonates, referred to as “pulverized dolomite”. This is interpreted as the result of corrosion of carbonates along microfractures. The pulverized dolomite is commonly associated with silica and clay cementation (“silicification”) and “mineralization” of ironrich minerals, barite, sphalerite, galena, fluorite, calcite, dolomite and others, clearly pointing out hydrothermal Mississippi Valley Type (MVT) conditions. The pulverization, silicification and mineralization are considered to be a diagenetic facies association (PSM facies). Tectonic shear corridors played an important role in the development of PSM facies as carriers of hydrothermal fluids, but the geometry of the altered units is very irregular and cross-cuts different Triassic depositional facies in addition to Eocene limestone and Middle-Upper Miocene sediments. The PSM facies represents the early stages of hydrothermal alteration (i.e. the burial phase) that was later modified by thermal mixing zones. Pulverized dolomite bodies that reached the surface were strongly affected by meteoric fluids; peculiar speleo-concretions were formed by calcite cementation of the powdery dolomite clasts. The altered carbonates show major porosity development whereas the unaltered carbonates present only minor porosity. The size and lithologic contrast of the altered geobodies makes them detectable by geophysical methods of mineral and hydrocarbon exploration

Mintavételes nemlineáris rendszerek stabilitásvizsgálata: Stability analysis of sampled-data nonlinear systems

Nowadays, positioning tasks are implemented with computers, which are basically resulted in sampled-data systems. Stability is the most important aspect in designing of closed-loop control systems. Models for establishing stability criteria often approximate or neglect some physical phenomena – dry friction for example. The purpose of this paper is to study the effects of sampling and dry friction in closed-loop control using analytic methods, simulation and experiments. Kivonat A pozícionálási feladatok napjainkban számítógépek segítségével kerülnek megvalósításra, mintavételes rendszereket eredményezve. A szabályozók fő tervezési szempontja a stabilitás, melynek vizsgálatához felállított modellek bizonyos jelenségeket (például a száraz súrlódást) gyakran elhanyagolnak. Ezen cikk célja a mintavételezés és a száraz súrlódás hatásainak vizsgálata analitikus, szimulációs és kísérleti módszerek segítségével egy egyenáramú villamos motor példáján keresztül