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Cryptic encrusting fauna inside invertebrate fossils from the Ordovician of Estonia

Vinn O., Ernst A., Toom U., Isakar M.

Annales Societatis Geologorum Poloniae

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2018

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Vol. 88, No. 3

285--290

EN

This is the first report of encrusted cryptic surfaces in the Ordovician of Estonia. Only bryozoans and cornulitids occurred in nautiloids and trilobites. Bryozoans were the dominant encrusters, in terms of both the number of specimens and the encrustation area. Stalked echinoderms are common on the hardgrounds in the Middle and Upper Ordovician of Baltica, but the restricted space in nautiloid living chambers and trilobites probably prevented colonization by stalked echinoderms. Cryptic surfaces in nautiloids and trilobites usually are somewhat more encrusted than the open surfaces of hardgrounds in the Ordovician of Estonia. Encrusters presumably favoured cryptic surfaces, as these were less accessible for predators and grazers. Low encrustation densities, compared to North American hard substrates, seem to be characteristic for the Ordovician Baltic Basin.

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Sedimentary history and biota of the Zechstein Limestone (Permian, Wuchiapingian) of the Jabłonna Reef in Western Poland

Peryt T. M., Raczyński P., Peryt D., Chłódek K., Mikołajewski K.

Annales Societatis Geologorum Poloniae

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2016

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Vol. 86, No. 4

379--413

EN

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.

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Bryozoans (trepostomes and fenestellids) in the Zechstein Limestone (Wuchiapingian) of the North Sudetic Basin (SW Poland : palaeoecological implications

Hara U., Słowakiewicz M., Raczyński P.

Geological Quarterly

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2013

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Vol. 57, No. 3

417-–432

EN

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.

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Sedimentological and palaeocological records of the evolution of the south west ern part of the Carpathian Foredeep (Czech Republic) during the early Badenian

Nehyba S., Tomanová Petrová P., Zágoršek K.

Geological Quarterly

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2008

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Vol. 52, No 1

45-60

EN

The depositional environment of the southern part of the Carpathian Foredeep in the Czech Republic was studied in two boreholes using sedimentological and palaeontological methods. Eight lithofacies were recognised within cores of the early Badenian deposits, comprising two facies associations, namely deposits of a coarse-grained Gilbert delta and offshore deposits. As sem blages of foraminifers document the early Badenian (Middle Miocene age). Two types of assemblages were recognised: (1) primary taphocoenoses reflecting the original environment of sedimentation, i. e. a relatively deep sublittoral (circalittoral) environment with low to normal ox ygen bottom conditions and deep-water euryoxibiont foraminifers, numerous planktonic foraminifers, agglutinated foraminifers and mixed assemblages of deep- and shallow-water foraminifers, (2) secondary taphocoenoses of shallower sublittoral (infralittoral) condition redeposited into the basin by gravity currents. These assemblages contain shallow-water foraminifers coupled with an abundant and diverse bryozoan fauna.

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Jurajskie zespoły mszywiołów: forma kolonii versus rodzaj podłoża

Hara U.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

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2008

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T. 34, z. 3/1

171-173

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Middle and Upper Jurassic bryozoan biota of the southern Poland – their diversity, palaeocology, evolution pattern and biogeography

Hara U.

Volumina Jurassica

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2006

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Vol. 4, no. 1

234-235

EN

A few distinctive bryozoan assemblages have been recognized in the Middle and Upper Jurassic sediments of the southern Poland. The Upper Callovian to Lower Oxfordian of the hardground character, epibenthic, bryozoan community at Zalas (the Kraków-Wieluf Upland) is restricted to a few cyclostomes, which are dominated by undeterminated, tubuloporinids of the fan-shaped or discoidal, bereniciform colonies, respectively (Fig. 1: 1-2), as well as to well-known Jurassic Hyporosopora and Microeciella genera. Much rarer are vine-like, uniserial runners of Stomatopora dichotoma Bronn. A moderately rich, the Early Oxfordian bryozoan biota of amielów (NW margin of the Holy Cross Mts.) occurs in the sponge biohermal facies, where the majority of colonies acquire an erect encrusting, massive, fungiform, as well as the branched colony-forms, among which the following taxa have been distinguished: Oncousoecia sp., Radicipora radiciformis (Goldfuss), Idmonea sp., Reptomultisparsa(?) sp., Mecynoecia sp., Ceriocava corymbosa (Lamouroux), Theonoa chlatrata Lamouroux and Apsendesia cristata Lamouroux. The most prolific is Radicipora radiciformis typically present in the high-diversified bryozoan assemblages, amongst marly facies, and is often accompanied by the numerous sclerosponges. The Middle-Upper Oxfordian bryozoan fauna of Ba.tów (NW of the Holy Cross Mts.), which colonizes the soft-bodied substrate, consists entirely of small, delicate, erect colonies and abundant, bereniciform, tubular-shaped zoaria (Fig. 1: 3) of the Hyporosopora baltovensis (see Hara & Taylor 1996). Palaeoecological aspects of the studied bryozoan biotas are related to the nature and relative abundance of the colonial growth forms, as well as to a substrate type, the orientation to substrate and methods of attachment. Evolution of the bryozoan biotas of Poland, during the late Middle and Late Jurassic was undoubtedly connected with the development of the favourable Callovian transgressive mostly sandy limestone facies (Calloviense-Lamberti chrons) and the shelf carbonate facies, which became prevalent in the Early Oxfordian (Cordatum Chron) as an open shelf sponge biohermal facies (amielów bryozoan biota), and replaced later during the Middle-Late Oxfordian (Transversarium-Bifurcatus chrones) by the shallower, soft-bottom coral facies (Ba.tów bryozoan fauna). Taxonomically, the Middle/Upper Oxfordian Jurassic bryozoans at Zalas show the similarities with the palaeogeographically distant Middle Jurassic shallow-water bryozoan fauna of the Carmel Formation (Utah), and the Early Oxfordian amielów bryozoans bear much of resemblance to the Middle Jurassic fauna the Saone-Rhine Basin (France) and the Swabian Basin of Germany. The moderately rich occurrence of the bryozoans in the Middle/Upper and Upper Jurassic sequences of Poland, shows the different pattern of distribution, than the biotas of the northwestern Europe which display the greatest species diversity in the Middle Jurassic (Bathonian). This fact has a great significance for an answer, weather the bryozoans of the southern Poland originated and started to radiate in the Late Jurassic, or this event was mostly connected with a facies migration from west to east. The Middle/Upper and Upper Jurassic bryozoan fauna of Poland has a key biogeographical significance, however, there is still a great patchiness in the global distribution of the Jurassic cyclostomes.