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Warunki depozycji szczątków kręgowców w osadach środowisk okołopływowych dolnego wapienia muszlowego (anizyku) w kopalni „Stare Gliny” koło Olkusza

Matysik M., Surmik D.

Przegląd Geologiczny

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2016

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Vol. 64, nr 7

495--503

EN

A detailed sedimentological study of the Lower-Middle Muschelkalk (Middle Triassic) carbonate succession exposed at the “Stare Gliny” quarry near Olkusz (Kraków-Silesia region, southern Poland) revealed numerous vertebrate remains within its lowermost sedimentary unit. This 7-m-thick package onlaps a gently-inclined surface of a paleoisland made of the Devonian (Givetian) dolostones, and was deposited during a transgressive phase of the second Middle Triassic transgression onto the southern Poland. The package consists largely of: 1) unfossiliferous dolosiltites and fine-grained dolarenites, the tops of which commonly contain root molds and small-scale karstic forms; 2) breccias (minor conglomerates) with lithoclasts of Givetian dolostones; 3) dolocretes; and 4) dolomitic shales. This lithofacies association represents a restricted lagoon which experienced longer periods of emersion. A minor occurrence of cryptalgal laminites reflects only temporary sedimentation in the intertidal zone of a tidal flat. The bone fragments occur within all types of lithofacies, but the macroscopically distinguishable specimens have been found exclusively in the dolocretes. The poor preservation and advanced disarticulation of bones hinder unequivocal assessment of their affinity. The small size of bones suggests that they represent prolacertiforms (perhaps juvenile Macrocnemus) or other small archosauromorphs similar in sizes to Protorosaurus or Czatkowiella whose remains were found in the 1950s within cave deposits, in the same outcrop. Macrocnemus widely inhabited Middle Triassic lagoons and tidal flats across Paleo-Europe and thus seems to fit well to the peritidal setting surrounding the “Stare Gliny” paleoisland. The bone-bearing package occurs 30 metres below the 5-m-thick oncolitic package that is widely regarded as a correlation horizon over the entire Kraków-Silesia region, and 15 metres below the sequence boundary marking the top of the Górażdże Beds in the Opole region and the Olkusz Bedsin the Kraków-Silesiaregion.On the basis of the secor relations,a conclusion can be made that the vertebrate assemblage is Bithynian/Pelsonian (middle Anisian) in age.

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An early Middle Anisian (Middle Triassic) Tubiphytes and cement crusts-dominated reef from North Dobrogea (Romania): facies, depositional environment and diagenesis

Popa L., Panaiotu C. E., Grădinaru E.

Acta Geologica Polonica

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2014

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Vol. 64, no. 2

189--206

EN

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.

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The Anisian carbonate ramp system of Central Europe (Peri-Tethys Basin): sequences and reservoir characteristics

Gotz A., Lenhardt N.

Acta Geologica Polonica

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2011

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Vol. 61, no. 1

59-70

EN

During Middle Triassic times, the Peri-Tethys Basin bordered the north-western Tethys shelf and was connected to the open Tethys Ocean via three seaways. Today, Lower Muschelkalk carbonates of this epeiric sea cover large parts of Central Europe, documenting the evolution of a low-relief, homoclinal, mud-dominated ramp system during the Anisian. In view of their geotectonic/climatic setting, depositional processes, facies architecture, and distribution, the rocks are considered as an outcrop analogue for layer-cake reservoirs of world-wide importance, e.g. the Permo-Triassic Khuff or Jurassic Arab carbonates in the Middle East. In general, two different reservoir types and their interplay might be considered: The proximal stacks of muddy dolostones (NW part of the basin) and the more distally developed grainy limestones (central and SE part of the basin). The rather uncommon depositional setting with minor relief and minimal accommodation contributed to both, the stratal and lateral facies development, and to unusual and possibly even "inverted" facies patterns with thick, grainy facies found in the more distal environments. Based on litho- and microfacies analyses, six main facies types are distinguished, building characteristic cyclic facies successions of different hierarchies. The stratal architecture of small-scale depositional sequ ences systematically changes in relation to their relative proximal-distal position on the Muschelkalk ramp system. Here, we present porosity and permeability data of the different facies types and within the basin-wide sequence stratigraphic framework. Dolo-wacke-/packstones and peloid grainstones attain the highest porosities of up to 24%, whereas bioclastic grainstones show porosities of up to 8%. The platy and nodular mud-/wackestone and most of the bioclastic wacke-/packstones typically show porosities below 2%. Even in the most porous strata, permeabilities do not exceed 10 mD, and only a few carbonates show higher permeabilities up to 90 mD. Within large-scale, third-order depositional sequences late highstand deposits represent the most permeable sediments.