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Wyświetlanie 1-2 z 2
Tytuł:
Microencruster-microbial framework and synsedimentary cements in the Štramberk Limestone (Carpathians, Czech Republic) : Insights into reef zonation
Autorzy:
Hoffmann, M.
Kołodziej, B.
Skupien, P.
Powiązania:
https://bibliotekanauki.pl/articles/191832.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
coral reefs
carbonate platforms
microframework
sedimentary breccia
Moravia
Jurassic
Cretaceous
Opis:
The Štramberk Limestone (Tithonian–lower Berriasian) was developed on a northerly located, isolated intra-Tethyan carbonate platform. It is composed of various facies that can be observed in olistoliths and blocks embedded in the Cretaceous flysch of the Outer Carpathians in Moravia (Czech Republic). Corals, microbialites, microencrusters and synsedimentary cements contributed on various scales to the reef framework. The importance of corals and some microencrusters to the formation of the Štramberk reef complex is well recognized, while other components received less attention in previous studies. Two end members of boundstone types are described from the Kotouč Quarry, near Štramberk. Boundstone type A is dominated by phaceloid (branching-type) corals, encrusted by microbialites and microencrusters, in particular photophile species (“Lithocodium-Bacinella”, Koskinobullina socialis Cherchi et Schroeder, Iberopora bodeuri Granier et Berthou). Boundstone type B is composed of microencrusters, microbialites and synsedimentary isopachous fibrous cements, while corals are absent or subordinate. Microencrusters [Crescentiella morronensis (Crescenti), Labes atramentosa Eliášová, Perturbatacrusta leini Schlagintweit et Gawlick, Radiomura cautica Senowbari-Daryan et Schäfer, thin encrusting calcified sponges] are main biotic components of the microencruster-cement boundstone. Some identified microencrusters are known only or mostly from intra-Tethyan carbonate platforms. Except for C. morronensis, other common microencrusters in the coral-microbial boundstone (type A) are rare in the microencruster-cement boundstone (type B). The depositional setting of boundstone type A corresponds to a low-energy environment of an inner platform. Boundstone type B, until now not recognized in the Štramberk Limestone, was developed in a high-energy, upper fore-reef slope environment. Other important facies in the Kotouč Quarry are reef-derived breccias: matrix-supported breccia and clast-supported breccia with radiaxial-fibrous cement (showing some similarities to Triassic “evinosponges” cement), interpreted as being dominantly synsedimentary (pre-burial). The preliminary studies by the present authors, supported by observations under cathodoluminescence, highlight the significance of synsedimentary cementation for the formation of a boundstone framework (type B) and the stabilization of fore-reef, slope deposits.
Źródło:
Annales Societatis Geologorum Poloniae; 2017, 87, 4; 325-347
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oxfordian to Valanginian palaeoenviron- mental evolution on the western Moesian Carbonate Platform: a case study from SW Bulgaria
Autorzy:
Ivanova, D.
Kołodziej, B.
Koleva-Rekalova, E.
Roniewicz, E.
Powiązania:
https://bibliotekanauki.pl/articles/191387.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Geologiczne
Tematy:
Oxfordian-Valanginian
biostratigraphy
carbonate sedimentology
reefs
Moesian Platform
Lyubash unit
Bulgaria
Opis:
Three sections (Rebro, Lyalintsi and Velinovo) of the Upper Jurassic-Lower Cretaceous carbonate sequences from the Lyubash unit (Srednogorie, Balkanides, SW Bulgaria) have been studied for elucidation of biostratigraphy and palaeoenvironmental evolution. Palaeontological studies of foraminifera, supplemented by studies of calcareous dinoflagellate cysts and corals, enabled the determination of the Oxfordian-Valanginian age of the analysed sequences. They were deposited on the Dragoman Block (western part of the Moesian Platform), and during Mid-Late Cretaceous included to the Srednogorie. A possible Middle to Late Callovian age of the lowermost part (overlying the Bajocian-Lower Bathonian Polaten Formation) of the studied sections assumed till now has not been confirmed by the present studies. Eleven facies have been distinguished and attributed to depositional environments. Marine sedimentation on a homoclinal ramp started in the Oxfordian and till the Early Kimmeridgian - in all three sections - was dominated by fine-grained peloidal-bioclastic wackestones to grainstones. Since the Late Kimmeridgian, when a rimmed platform established, facies pattern underwent differentiation into (i) the inner platform (lagoon and tidal flat facies) - only in Velinovo, (ii) reef and peri-reef facies/bioclastic shoals - mainly in Lyalintsi, and (iii) platform slope - mainly in Rebro. Sedimentation generally displays a shallowing-upward trend. Two stages in evolution of the rimmed platform are postulated. The mobile stage lasting till the Tithonian/Berriasian boundary was followed by a more stable stage in the Berriasian to Valanginian time. Reefs are developed mainly as coral-microbial biostromes, lower coral bioherms or coral thickets, in the environment of moderate energy and sedimentation. They contain highly diversified corals (72 species). Micro- bialites contributed to the reef framework, but they never dominated. Locally, microencrusters and cement crusts formed important part of reefal framework. During the mobile stage of the platform evolution a relative sea-level rise interrupted reef development, as evidenced by intercalations of limestones with Saccocoma. During the second stage high carbonate production and/or regressive eustatic events, not balanced by subsidence, decreased accommodation space, limiting reef growth and enhancing carbonate export to distal parts of the platform.
Źródło:
Annales Societatis Geologorum Poloniae; 2008, 78, No 2; 65-90
0208-9068
Pojawia się w:
Annales Societatis Geologorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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