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Microencruster-microbial framework and synsedimentary cements in the Štramberk Limestone (Carpathians, Czech Republic) : Insights into reef zonation

Hoffmann M., Kołodziej B., Skupien P.

Annales Societatis Geologorum Poloniae

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2017

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Vol. 87, No. 4

325--347

EN

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.

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The tectono-sedimentary evolution of the Pelagonian Carbonate-Platform-Complex (Late Triassic - Late Jurassic, Evvoia, Greece)

Scherreiks R., Bosence D., Boudagher-Fadel M.

Volumina Jurassica

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2006

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Vol. 4, no. 1

64-66

EN

Carbonate platforms are sensitive recorders of tectonic environments. However, the tectonosedimentary interplay between ancient carbonate platforms and ocean basins is not always recognizable as the oceans involved are not often preserved. In the case of the Pelagonian Carbonate-Platform-Complex, volcano-sedimentary successions of the one-time adjacent Maliac-Vardar Ocean (Stampfli et al. 2001) are partly preserved. These Late Triassic and Jurassic ocean floor deposits and their contemporaneous platform carbonates are being investigated in Evvoia, Greece (Fig. 1) (Scherreiks 2000; Gingins & Schauner 2005; Bosence et al. 2006). The carbonates exceed 1000 m in thickness whereas the contemporaneous oceanic succession of pillow basalt, radiolarite and pelagic carbonates is only about 100 m thick. The investigation shows that the Pelagonian platform-complex is composed of a number of different carbonate platform types (sensu Bosence 2005; Fig. 2). These evolved adjacent to five changing oceanictectonic settings which affected platform subsidence and uplift. 1. Late Triassic seafloor spreading was accompanied by the slow subsidence of a passive margin platform dominated by peritidal carbonates. 2. Late Liassic convergence coincided with stepped-up subsidence and the formation of a drowned or hemipelagic platform. 3. Initial collision during Early Kimmeridgian most likely caused platform tilting, enabling patch-reef development in the midst of the hemipelagic environment. 4. Early Tithonian obduction was contemporaneous with the formation of thrust-top platforms with associated neritic-reefal turbidite and debrite facies, intercalated in pelagic facies. 5. Advanced obduction, in the Late Tithonian, caused rapid subsidence and complete drowning of the platform complex below the CCD.

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Lofer-type cyclothems in the Upper Devonian of the Holy Cross Mts. (central Poland)

Skompski S., Szulczewski M.

Acta Geologica Polonica

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2000

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Vol. 50, no. 4

393-406

EN

Numerous horizons of carbonates changed by karstic and soil-forming processes have been recognised in upper part of the Frasnian carbonate succession in southern part of the Holy Cross Mts. These layers are included in peritidal cyclothems, characterised by mostly deepening upward pattern, similarly to the typical Triassic Lofer cyclothems. The irregular cyclothemic intervals are restricted to an interior part of the isolated, reef- and shoalrimmed Dyminy carbonate platform. The Lofer-type cyclicity correlates with syndepositional block-faulting and associated seismic shock induced features, recognised in marginal parts of the platform. The most appropriate explanation of cyclicity is differentiated, tectonically controlled subsidence of Dyminy platform, according to the stick-slip faulting model proposed by CISNE (1986) for explanation of deepening-upward cyclicity in Dachstein Formation