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Wyszukujesz frazę "bryozoans" wg kryterium: Temat


Wyświetlanie 1-2 z 2
Tytuł:
Bryozoans (trepostomes and fenestellids) in the Zechstein Limestone (Wuchiapingian) of the North Sudetic Basin (SW Poland : palaeoecological implications
Autorzy:
Hara, U.
Słowakiewicz, M.
Raczyński, P.
Powiązania:
https://bibliotekanauki.pl/articles/2060558.pdf
Data publikacji:
2013
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
bryozoans
Late Permian
Zechstein
taxonomy
ecology
Opis:
A recently investigated Zechstein Limestone (Ca1, Wuchiapingian) bryozoan fauna from the Polish part of the Southern Permian Basin (SW Poland) is dominated volumetrically and taxonomically by fenestellids. In total six species from five genera are recognized, comprising two species of trepostomes belonging to Dyscritella Girty, 1911 and four fenestellids attributed to Kingopora Morozova, 1970, Kalvariella Morozova, 1970, Acanthocladia King, 1849 and Spinofenestella Termier and Termier, 1971. The greatest biodiversity of the bryozoans in the Ca1 profiles studied is within the slope facies where large, fan-shaped and funnel-shaped reticulate fenestellid colonies up to 10 cm high dominate. In contrast, bryozoans in the marginal (proximal) parts of the basin mostly comprise trepostomes, represented by encrusting plate-like or coil-shaped colonies of Dyscritella Girty, and commonly broken branched colonies of Acanthocladia King. The changes in the biotic composition of the bryozoans and the presence of a dominant colony growth form in the stratigraphical profile of the Ca1 reflect the depositional environment and water energy. These factors stimulate the successive stages of the development of the biota and their settlement, marked by the rich productid-fenestellid assemblages typical of the offshore setting, with the maximum depth in the middle part of the Ca1 in the Grodziec Syncline. The proximal tempestites and foreshore facies of the upper part of the Ca1 (Leszczyna Syncline) terminate the sedimentary cycle of the Ca1, with the remnant, broken bryozoans of Acanthocladia and fenestellids. The relationship between the taxonomic composition, colony growth-patterns, associated biota, and sedimentary structures points to slow sedimentation rate on slope and basin floor of the Ca1 carbonate platform. The fenestellids which are dominated in the studied biota by the reticulate and pinnate colonies of Spinofenestella, Kingopora, Kalvariella and Acanthocladia mark a close palaeogeographical link with the Zechstein (Ca1) bryozoans of Great Britain, Germany and the southern Baltic region.
Źródło:
Geological Quarterly; 2013, 57, 3; 417--432
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sedimentary history and biota of the Zechstein Limestone (Permian, Wuchiapingian) of the Jabłonna Reef in Western Poland
Autorzy:
Peryt, T. M.
Raczyński, P.
Peryt, D.
Chłódek, K.
Mikołajewski, K.
Powiązania:
https://bibliotekanauki.pl/articles/191254.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
Wuchiapingian
reefs
Zechstein
bryozoans
stromatolites
aragonite cementation
neptunian dykes
carbon and oxygen isotopes
Opis:
The Jabłonna Reef, one of the reefs formed in Wuchiapingian time in the western part of the Wolsztyn palaeo-High (SW Poland), is characterized by quite irregular outlines and consists of three separate reef bodies (ca. 0.5–1.5 km2 each; the thickness of the reef complex is usually >60 m). It is penetrated by four boreholes, which show two distinct phases of bryozoan reef development during deposition of the the Zechstein Limestone. The first one occurred early in the depositional history and botryoidal aragonitic cementation played a very important role in reef formation. This phase of bryozoan reef development terminated suddenly; one possible reason was that a relative change of sea level – first a fall and then a rise – disturbed the upwelling circulation. Consequently, bioclastic deposition predominated for a relatively long time until the second phase of bryozoan reef development occurred, but the latter was not accompanied by dubious early cementation. During this second phase, reticular fenestellid bryozoans were predominant. Subsequently, microbial reefs developed and abound in the upper part of the Zechstein Limestone sections. The general shallowing-upward nature of deposition in the Jab³onna Reef area resulted in reef-flat conditions with ubiquitous, microbial deposits, in the central part of the Jab³onna Reef. Then, the reef-flat started to prograde and eventually the entire Jab³onna Reef area became the site of very shallow, subaqueous deposition. Five biofacies are distinguished in the Jab³onna Reef sections: the Acanthocladia biofacies at the base, then mollusc-crinoid, brachiopod-bryozoan, Rectifenestella and at the top, stromatolite biofacies. They represent a shallowing-upward cycle, possibly with some important fluctuation recorded as the distinctive lithofacies boundary, corresponding to the Acanthocladia/mollusc-crinoid biofacies boundary. The 13C curves of the Jab³onna 2 and Jab³onna 4 boreholes permit correlation of the trends in the middle parts of both sections and confirm the strong diachroneity of the biofacies boundaries, with the exception of the roughly isochronous Acanthocladia/ mollusc-crinoid biofacies boundary. The presence of echinoderms and strophomenid brachiopods indicates that until deposition of the lower part of the Rectifenestella biofacies, conditions were clearly stenohaline. The subsequent elimination of stenohaline organisms and progressively poorer taxonomic differentiation of the faunal assemblage are characteristic for a slight, gradual rise in salinity. The taxonomic composition of organisms forming the Jab³onna Reef shows a similarity to reefs described from England and Germany, as well as the marginal carbonate platform of SW Poland. Filled fissures were recorded in the lower part of the Jabłonna Reef. The aragonite cementation recorded in some fissure fillings implies that they originated in rocks exposed on the sea floor and are neptunian dykes.
Źródło:
Annales Societatis Geologorum Poloniae; 2016, 86, 4; 379-413
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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