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Wyszukujesz frazę "Microbialites" wg kryterium: Temat


Wyświetlanie 1-3 z 3
Tytuł:
Sedimentary successions in the Middle-Upper Oxfordian reef deposits from the southern part of the Kraków-Częstochowa Upland (Southern Poland)
Autorzy:
Krajewski, M.
Olchowy, P.
Rudziński, D.
Powiązania:
https://bibliotekanauki.pl/articles/2060435.pdf
Data publikacji:
2018
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
microbialites
non-skeletal grains
reef
carbonate ramp
Oxfordian
Polska
Opis:
The sedimentary succession of the largest example of an Upper Oxfordian reef located in the southern part of the Polish sector of the northern Tethys shelf is described. Detailed sampling of exposures enabled characterization of the full succession of facies and microfacies diversity, documenting the reef evolution. The succession studied represents the maximum development of Upper Jurassic reefs in Poland corresponding to the upper Transversarium and the Bifurcatus zones, and followed by drowning of the carbonate platform in the lower Bimmamatum Zone. The reef succession comprises three types of facies, in which eight important microfacies types were distingushed, reflecting several stages of reef development. Mid-ramp, microbial-sponge frame-reefs represent a transgressive depositional sequence, up to tens of metres thick. A microbial-Crescentiella-ooid and ooid-intraclast-bioclast facies form numerous, decimetre- to metre-scale, sequences corresponding to higher-order, transgressive/regressive sea level changes. These facies represent a mid-inner ramp setting when sedimentation was dominated by bioclasts and non-skeletal grains (mainly ooids, oncoids, aggregate grains and intraclasts). The grains were stabilized by microbialites and cemented in early diagenesis, which created grain-dominated, microbial-cement supported reefs. As a result, both the mid-ramp, microbial-sponge frame-reefs and the shallow-water, grain-dominated, microbial-cement supported reefs form extensive, strongly lithified Oxfordian reef complexes in the Kraków-Częstochowa Upland.
Źródło:
Geological Quarterly; 2018, 62, 3; 653--668
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An early Middle Anisian (Middle Triassic) Tubiphytes and cement crusts-dominated reef from North Dobrogea (Romania): facies, depositional environment and diagenesis
Autorzy:
Popa, L.
Panaiotu, C. E.
Grădinaru, E.
Powiązania:
https://bibliotekanauki.pl/articles/138920.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Anisian (Middle Triassic)
Carbonate slope
Microbialites
Tubiphytes-buildup
North Dobrogea
Romania
anizyk
trias środkowy
Tubiphytes
Dobrudża
Rumunia
Opis:
A well-developed Triassic carbonate platform is exposed in the eastern part of the Tulcea Unit, in the Cimmerian North Dobrogean Orogen, southeastern Romania. Facies analysis of the 200 m thick succession of lower Middle Anisian limestones exposed in a large limestone quarry south of the village of Mahmudia suggests a transition from upper slope towards toe-of-slope carbonate facies, reflecting sea-level fluctuations and tectonic tilting. The slope is dominated by in situ microbialites in the upper portion, consisting of reefal boundstone facies, and by molluscan coquina and cement boundstones. A key role is played by the cosmopolitan micro-encruster Tubiphytes, which became common in the aftermath of the mass extinction at the Permian/Triassic boundary, and by autochthonous micrite and synsedimentary marine cement. The absence of metazoan reef builders, such as sponges and corals, reflects the fact that microbes were the first organisms to recover after the Permian/Triassic crisis under unusual marine conditions and that their main role in reef formation was sediment stabilization along the upper slopes. The lower slope is mostly detrital, being dominated by platform-derived bioclastic rudstones and crinoidal floatstones, which are interbedded with basinal carbonate hemipelagics. The toe-of-slope is composed of pelagic wackestones framed by thin tongues of intraclast breccia. All these observations are in agreement with the slopeshedding model described for the Pennsylvanian microbial margin in Asturias (northern Spain) and the Anisian– Ladinian flat-topped, steep-rimmed Latemar platform (Dolomites, Italy). As most of the Anisian reefs were described from western and eastern Tethys (Southern Alps, Hungary, China), the occurrence of the early Middle Anisian Tubiphytes-reef from North Dobrogea (Romania) contributes to resolving the puzzle of the geographic distribution of reef recovery in the Middle Triassic.
Źródło:
Acta Geologica Polonica; 2014, 64, 2; 189-206
0001-5709
Pojawia się w:
Acta Geologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Microbial laminites with coprolites from Upper Jurassic carbonate buildups (Kraków-Częstochowa Upland, Poland)
Autorzy:
Kochman, A.
Matyszkiewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/191932.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
microbialites
coprolites
carbonate buildups
nutrients
synsedimentary tectonics
Oxfordian
Opis:
The Upper Oxfordian microbial-sponge agglutinated to open-frame reef complex of the Zegarowe Crags in the Kraków-Częstochowa Upland originated upon an elevation of the Late Jurassic stable northern shelf of the Tethys. This elevation was formed, owing to a local decrease in subsidence rate during Jurassic time, induced by the presence of a Palaeozoic granitoid intrusion in the shelf substratum, and Late Jurassic, synsedimentary tectonics, which controlled the topography of the sea bottom. The Zegarowe Crags (Skały Zegarowe) complex at the top contains microbial laminites, composed of peloidal and agglutinated stromatolites, and intercalations of grainstones with indeterminable, favrenoid coprolites, occurring in large numbers. The development of stromatolites was associated with low nutrient availability. In contrast, the periodic activity of crabs, the main producers of the coprolites, forming the coprolitic grainstone intercalations, indicates periods, when nutrients were abundant in the sea water. The nutrinets most likely were associated with the occurrence of clouds of suspended matter, induced by gravity flows, generated by active, synsedimentary tectonics. The results of isotopic studies do not support the presence of warm, mineralizing solutions, connected with synsedimentary tectonics during development of the Zegarowe Crags complex in the Late Jurassic.
Źródło:
Annales Societatis Geologorum Poloniae; 2012, 82, 4; 331--347
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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