544 research outputs found
Displaced South Alpine and Dinaridic elements in the Mid-Hungarian Zone
Abstract
The Mid-Hungarian Zone is a WSW–ENE trending composite structural unit in the basement of
the Pannonian Basin that is made up of displaced crustal fragments (terranes) of South Alpine and
Dinaridic origin. In the early stage of the Alpine evolution these fragments were located in various
sectors of the NW Neotethys region, representing different paleogeographic settings from passive
margin through continental slope to oceanic basement. Middle to Late Jurassic closure of the
Neotethys led to the development of a suture zone made up of subduction-related complexes that can
be followed all along the strike of the Dinarides. During the Cretaceous compressional stages, nappe
stacks were formed from the accretionary complex and the fragments of the previously disrupted
passive margin. Eastward extrusion (escape) of the ALCAPA Mega-unit during the Oligocene to Early
Miocene led to large-scale displacement of fragments of this nappe stack, transporting them to their
present-day position, and resulted in dispersal of the northwestern segment of the suture zone. The
paper summarizes the basic characteristics of the dislocated blocks, evaluates their relationships and
determines their original setting
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
Triász platform- és medencefáciesek kapcsolata a Pilis vonulatban = Relationship between Triassic platform and basin facies of the Pilis Range
A Pilis Dachsteini MĂ©szkĹ‘ kifejlĹ‘dĂ©sĂ©t peritidális Ă©s sekĂ©ly szubtidális rĂ©tegtagokbĂłl felĂ©pĂĽlĹ‘, ciklusos rĂ©tegsor jellemzi, amely a biosztratigráfiai vizsgálatok szerint a nori emeletbe tartozik. A Dachsteini-platform peremĂ©hez közeli lejtĹ‘fáciest lito- Ă©s bioklasztokbĂłl, valamint bekĂ©rgezett szemcsĂ©kbĹ‘l állĂł durvaszemcsĂ©s ĂĽledĂ©k alkotja, amely alatt a platformlagĂşnára Ă©s a medencĂ©re jellemzĹ‘ kagylĂłk viharok által átĂĽlepĂtett kokvinái egyĂĽtt fordulnak elĹ‘. A Dachsteini MĂ©szkĹ‘vel rĂ©szben heteropikus Feketehegyi MĂ©szkĹ‘ rĂ©tegsorát disztális tempesztit- Ă©s medencefáciesű rĂ©tegek váltakozása Ă©pĂti fel. A Feketehegyi MĂ©szkĹ‘ben találhatĂł átĂĽlepĂtett zöldalga-töredĂ©kek nori korĂş flĂłrát jeleznek az egyidĹ‘s Dachsteini platformon. A Pilis Dachsteini MĂ©szkĹ‘ rĂ©tegsora a Tethys selfjĂ©n kialakult sekĂ©lytengeri platform háttĂ©rlagĂşnájában kĂ©pzĹ‘dött a nori során. A nori közepĂ©n aktivizálĂłdott extenziĂłs tektonika hatására jött lĂ©tre a platformon belĂĽl a fĂ©lárok-jellegű Feketehegyi-medence, amelynek lankás oldalán egyenlejtes rámpa jött lĂ©tre, sekĂ©lytengeri kagylĂł-kolĂłniákkal Ă©s viharĂĽledĂ©kekkel. A kiemelt helyzetben maradt blokkok peremĂ©t foltzátonyokkal tarkĂtott ooid-homokdombok alkották, bekĂ©rgezĹ‘ szervezetekkel. A medence mĂ©lyebb rĂ©giĂłjában ugyanakkor disztális turbiditek Ă©s medenceĂĽledĂ©kek rakĂłdtak le. A kĂ©sĹ‘-nori legnagyobb elöntĂ©s idejĂ©n a Feketehegyi-medence nyitottabbá vált, majd az ezt követĹ‘ magas vĂzállás idejĂ©n a platformlejtĹ‘ elĹ‘renyomult 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
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