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Denayer, Julien, et Izzet Hoşgör. « First report of Devonian corals from the Bitlis-Pötürge Massif (SE Turkey) : a rare occurrence of corals on the northern margin of Gondwana ». Geologica Acta 19 (28 janvier 2021) : 1–11. http://dx.doi.org/10.1344/geologicaacta2021.19.1.
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The Bitlis-Pötürge Massif of SE Turkey is a metamorphic belt separating the Arabian Plate from the Taurides. It includes a non-metamorphic Palaeozoic sequence that contains locally fossiliferous strata. Here is reported for the first time an assemblage of Upper Devonian rugose and tabulate corals from the Meydan Formation, composed of the rugose Frechastraea schafferi (PENECKE), Peneckiella cf. teicherti HILL, Pseudopexiphyllum supradevonicum (PENECKE), and Macgeea desioi VON SCHOUPPÉ, and the tabulate Thamnopora reticulata (DE BLAINVILLE), Alveolites ex. gr. suborbicularis and Scoliopora sp. The rugose corals suggest a Late Frasnian age. The palaeobiogeographic affinities of corals are discussed. The species F. schafferi and the genus Pseudopexiphyllum –so far only reported from Turkey, Iran and Afghanistan– are probably limited to the northern margin of Gondwana and therefore diagnostic for this palaeogeographic area. Until now, the northern margin of Gondwana yielded very few Upper Devonian corals so this occurrence in SE Turkey is particularly important to estimate the relationship between these corals and the ones from the northern margin of the Palaeotethys Ocean.
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Wright, Anthony J., Yves Plusquellec et Rémy Gourvennec. « Devonian operculate corals (Calceolidae, Cnidaria) from the Massif Armoricain, France ». Alcheringa : An Australasian Journal of Palaeontology 40, no 3 (15 février 2016) : 313–40. http://dx.doi.org/10.1080/03115518.2016.1132866.
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Kossovaya, Olga Leonidovna, et Elena Ivanovna Kulagina. « Пермские кораллы из рифовых массивов в районе г. Стерлитамака (PERMIAN CORALS FROM REEF MASSIFS IN THE STERLITAMAK AREA) ». Geologicheskii vestnik, no 2 (14 juillet 2023) : 66–84. http://dx.doi.org/10.31084/2619-0087/2023-2-5.
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История изучения кораллов из Стерлитамакских шиханов началась в середине 19 века. Новый подъем исследований в 30–40 годы 20 века был связан с открытием башкирской нефти. Кораллы пермских рифов представлены одиночными и колониальным формами и чрезвычайно разнообразны. Предшествующие исследования позволяют определять возрастной интервал видов и на этой основе выделить несколько разновозрастных комплексов. Для ассельской части характерны редкие колониальные Protowentzelella и Kleopatrina. Одиночные амплексокаринии и каниноидные кораллы встречаются в ассельской части Куштау, Тратау, Шахтау. Разнообразие астреоидных форм увеличивается в верхней части тастубского горизонта. Таксономически наиболее разнообразен тастубский комплекс шихана Юрактау, в составе которого определены цериоидные и астреоидные формы. Получена характеристика местонахождений «на коралловой тропе» и в юго-западной части массива, причем в последнем астреоидные кораллы преобладают. Впервые обнаружены кораллы на шихане Куштау. По сохранности колоний и их таксономи- ческому разнообразию местонахождение кораллов в шихане Юрактау является уникальным, представляя «музей под открытым небом», сравнимый по сохранности с Большим барьерным рифом Австралии.
The history of the coral research in Sterlitamak shikhans began in the middle of the 19th century. A new rise in investigation in the 30–40 years of the 20th century was triggered by the discovery of the Bashkirian oil. The coral assemblage of the Permian reef is represented by solitary and colonial forms and is extremely diverse. The preceding studies allow the determination of the species age-range and distinguish several assemblages of different age. The Asselian part is characterized by rare colonial Protowentzelella and Kleopatrina. Solitary Amplexocarinia and caninoid corals are also found in the Asselian deposits of Kushtau, Toratau, and Shakhtau. The variety of asteroid colonies increases in the upper part of the Tastubian horizon (Sakmarian). Taxonomically, the Tastubian assemblage of Yuraktau Shikhan is the most diverse; its composition includes cerioid and astreoid forms. Locations «on the coral path» and in the southwestern part of the massif have been sampled and studied. In the second occurrence, the astreoid corals prevail. Corals were first discovered in Kushtau shikhan. According to the preservation of the colonial corals and their taxonomic diversity, the assemblage of Yuraktau Shikhan is unique, representing an «open-air museum», comparable to the modern Australian barrier reef.
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Bohatý, Jan, William I. Ausich, Elise Nardin, Christian Nyhuis et Stefan Schröder. « Coral-crinoid biocoenosis and resulting trace fossils from the Middle Devonian of the Eifel Synclines (Rhenish Massif, Germany) ». Journal of Paleontology 86, no 2 (mars 2012) : 282–301. http://dx.doi.org/10.1666/11-007.1.
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Fossil echinoderms are a rich source of information concerning biotic interactions. In this study we analyzed the premortem encrustation of the highly specialized Middle Devonian rugose coralsAspasmophyllum crinophilumand ?“Adradosia” sp. on camerate crinoid stems.Aspasmophylluminfested living crinoid stems by sclerenchymal outgrowth that formed a skeletal ring but ?“Adradosia” sp. encrusted the stems rapidly, without building a ring. These coral-crinoid biocoenoses indicate a settlement advantage for the rugose corals within densely populated communities of the lower Givetian. The corals could be interpreted as large epizoozoans that benefited as secondary tierers reaching relatively high tiering levels. It also suggests the ability for the affected crinoids to repel the coral by overgrowing the corallite with a local increased stereomic growth. Because the crinoid axial canals are not penetrated, the corals cannot be considered as predators or parasites of crinoids. Therefore, the described biocoenosis is interpreted as commensalism. The speciesA. crinophilumis redescribed, and a neotype is defined, because of the loss of the initial types. Two types of ichnofossils can be attributed to the premortem encrustation of both corals. They are described asOstiocavichnusn. ichnogen. and are attributed to the stereomic response of the infested hosts. These swellings are characterized as either elliptical (Ostiocavichnus ovalisn. ichnogen. n. ichnosp. due to the assumed reaction ofA. crinophilum) or subcircular concavities (O. rotundatusn. ichnogen. n. ichnosp. due to the reaction of ?“Adradosiasp.”).
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McLean, Ross A. « Frasnian rugose corals of western Canada Part 3A : The massive Phillipsastreidae Phillipsastrea, Chuanbeiphyllum ». Palaeontographica Abteilung A 230, no 1-3 (31 janvier 1994) : 39–76. http://dx.doi.org/10.1127/pala/230/1994/39.
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McLean, Ross A. « Frasnian rugose corals of western Canada Part 3B : The massive Phillipsastreidae - Pachyphyllum, Smithicyathus, Frechastraea ». Palaeontographica Abteilung A 230, no 4-6 (19 avril 1994) : 77–96. http://dx.doi.org/10.1127/pala/230/1994/77.
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Motai, Satoko, Jun Kawano, Takaya Nagai, Kohki Sowa et Tsuyoshi Watanabe. « Precipitation of halite during calcification of the massive reef-building coral Porites lobata ». European Journal of Mineralogy 28, no 2 (25 mai 2016) : 265–71. http://dx.doi.org/10.1127/ejm/2016/0028-2521.
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Kossovaya, Olga L., et Dieter Weyer. « Lopingian corals from the Omolon Massif (Eastern Siberia), the northernmost Permian boreal Rugosa community ». Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 287, no 2 (1 février 2018) : 167–94. http://dx.doi.org/10.1127/njgpa/2018/0711.
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Lütte, Bernd-Peter, et Klernens Oekentorp. « Rugose corals from the Cürten-Formation (Givetian) of the Sötenich syncline (Rhenish Massif, North-Eifel) ». Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 176, no 2 (15 avril 1988) : 213–43. http://dx.doi.org/10.1127/njgpa/176/1988/213.
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Aretz, Markus. « Rugose corals from the upper Viséan (Carboniferous) of the Jerada Massif (NE Morocco) : taxonomy, biostratigraphy, facies and palaeobiogeography ». Paläontologische Zeitschrift 84, no 3 (25 novembre 2009) : 323–44. http://dx.doi.org/10.1007/s12542-009-0046-0.
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Ehiro, Masayuki, Daishi Nogi, Kei Mori, Goichi Kawashima, Noritoshi Suzuki et Ken Yoshihara. « Discovery of scleractinian corals from the limestone conglomerate in the Kuzumaki-Kamaishi Belt, Northern Kitakami Massif, Northeast Japan and its significance. » Journal of the Geological Society of Japan 107, no 8 (2001) : 531–34. http://dx.doi.org/10.5575/geosoc.107.531.
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Long, D. G. F., et Paul Copper. « Late Ordovician sand-wave complexes on Anticosti Island, Quebec : a marine tidal embayment ? » Canadian Journal of Earth Sciences 24, no 9 (1 septembre 1987) : 1821–32. http://dx.doi.org/10.1139/e87-173.
Texte intégralRésumé :
Laterally discontinuous, mixed carbonate–siliciclastic sandstones in the upper Vaureal and lower Ellis Bay formations of Anticosti Island were deposited on an equatorial carbonate ramp with a slope of less than 1°. The 10–18 m thick sandstones are interpreted as subaqueous sand-wave complexes analogous to detached parts of modern shoreface-connected sand ridges. These record storm-enhanced, tidal modification of a northerly derived shoal retreat massif that may have formed in response to recovery from global sea-level lowstands in the Late Ordovician (Ashgill: late Rawtheyan – Hirnantian). The sand-wave complexes formed within a tidal embayment that was confined by the Precambrian Shield to the north and northwest by rising tectonic highlands of the Humber Zone in Newfoundland to the east, and by active tectonic highlands in the Quebec Appalachians (Gaspésie) to the south. Paleocurrent distributions, parallel to the western margins of the Strait of Belle Isle, suggest that the north end of the embayment was closed in Late Ordovician time. Low-diversity faunas within the sand units consist mostly of sowerbyellid, strophomenid, and rhynchonellid brachiopods, bivalves, gastropods, large aulacerid stromatoporoids, and large, domed favositid corals. These "sandy fades" faunas belong to communities significantly different from those found in the laterally interfingering and overlying carbonates and shales, suggesting that the sand waves played an important role in local community modification.
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Hohenegger, J. A. « Status and Conservation of the Saker Falcon in Austria ». Raptors Conservation, no 2 (2023) : 443–46. http://dx.doi.org/10.19074/1814-8654-2023-2-443-446.
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The short lecture summarizes the results of a conservation program for the Saker Falcon (Falco cherrug) in Austria for the years 2011–2022. The species reaches the western limit of its global distribution in Austria. Therefore, it is restricted to the east of the country and naturally a scarce species with high conservation concern. When Saker Falcons showed a growing tendency to nest in abandoned corvid nests on high-voltage power lines from the late 1990s on, the Austrian Ornithological Center (AOC, formerly Vetmeduni) and Austrian Power Grid (APG) supported the species from 2007 onward by providing artificial nesting sites on several powerlines within the known breeding range. AOC and BirdLife Austria have been conducting a joint nation-wide conservation program since 2011. This includes a yearly survey of all known breeding sites, ringing Saker chicks (carried out since 2015), and monitoring reasons for mortality and potential threats. Within the surveyed period (2011–2022), the species showed a clear increase in breeding pairs, successfully breeding pairs, and fledged young per breeding attempt. The clearly positive trend in all population parameters surveyed may be attributed to several factors such as nest site availability, nest site selection, and changing weather conditions. The number of artificial nesting sites has been increased; while the conservation program began with the installation of breeding platforms, from 2014 on all additionally installed artificial aids have been nest boxes. Since then, we have observed a steep increase in the number of pairs breeding in these boxes, which most probably contributed to the population growth as well as the rising proportion of successfully breeding pairs. Despite the prospering population, the breeding range of the species has not increased significantly and is still limited to the low-lying Pannonian region in eastern Austria. Contrary to other recovering raptor species in the region (e.g. Imperial Eagle Aquila heliaca and Red Kite Milvus milvus), no clear westward expansion of the Saker’s range could be observed. Rather a rising concentration of pairs in the long-known range led to population growth. Interestingly, the most westerly historic breeding sites on the edge of the Alps and of the Bohemian Massif have been abandoned for decades. The Pannonian basin hosts a single transboundary population of Saker Falcon and the birds move regularly between the different countries. This is also true for the Austrian part of the range: Most recoveries of banded Austrian birds have been made abroad and prove the exchange of birds between Austria, Slovakia, Hungary, and Serbia. Other interesting records of Austrian ringed birds comprise a recovery from Algeria and one from Poland. Currently, we know of no threats impacting the Saker Falcon in Austria on the population level. Nevertheless, our results show some potential threats that must be closely monitored in the future to secure the species. Proven, human-caused mortality reasons comprise collisions with power line infrastructure, wind power plants and vehicles, electrocution, and deliberate shooting. Intentional as well as unintentional poisoning is highly likely to occur at least occasionally but has not yet been investigated thoroughly. Our results give rise to several research topics that should be considered in the future, including the influence of wind power development, possible nest site competition between Eagle Owl (Bubo bubo) or Northern Raven (Corvus corax) and Saker Falcon or the effects of sublethal rodenticide poisoning on the bird’s health and mortality risk.
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Dupont, Nicolas, Yves Quinif, Caroline Dubois, Hai Cheng et Olivier Kaufmann. « Le système karstique de Sprimont (Belgique). Holotype d’une spéléogenèse par fantômisation ». BSGF - Earth Sciences Bulletin 189, no 1 (2018) : 1. http://dx.doi.org/10.1051/bsgf/2017205.
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Le système karstique de Sprimont est riche de phénomènes karstiques variés dans un contexte géologique bien défini : un synclinal de carbonates carbonifères entourés au nord, à l’est et au sud par des formations famenniennes imperméables. À l’ouest, l’Ourthe recoupe le synclinal perpendiculairement à son axe d’allongement dans le cadre d’un relief appalachien typique et constitue le niveau de base karstique. Le relief consiste en un vallon orienté est-ouest dont l’axe coïncide avec celui du synclinal. Les ruisseaux qui descendent des hauteurs imperméables vers le vallon se perdent après leur entrée dans le domaine calcaire. Ces ruisseaux confluent sous terre pour résurger au « Trou Bleu », unique résurgence du système, non loin du talweg de l’Ourthe. Le système compte de nombreuses grottes, de dimensions souvent décamétriques. Quelques-unes sont de plus grande ampleur, dont la grotte du « Noû Bleû » récemment découverte, qui est un regard sur la rivière souterraine à quelques dizaines de mètres en amont de la résurgence. Les carrières ont dévoilé en plus de diverses grottes des phénomènes karstiques de type fantôme de roche. La karstogenèse de type fantôme de roche consiste en une altération modérée des carbonates produisant une séparation de phase. D’une part, la phase soluble comprend essentiellement le calcium, le magnésium, le bicarbonate et la silice colloïdale. Elle sort du système par la voie souterraine. D’autre part, une altérite résiduelle constitue la phase solide restante comprenant une partie des carbonates cinétiquement moins solubles comme la calcite sparitique et la dolomie pro parte, les insolubles comme les minéraux argileux, le quartz, et la matière organique. Cette phase solide évolue de façon isovolume lors d’une première étape et voit donc sa porosité augmenter, de même que sa fragilité mécanique. Cette première étape se déroule durant une période géologique où le potentiel hydrodynamique est très réduit, la fantômisation s’exerçant grâce à des circulations phréatiques très lentes mais chimiquement agressives. On obtient ainsi des volumes soit totalement circonscrits dans la masse rocheuse (pseudoendokarsts) soit sous forme de couloirs descendant du toit de la roche mère, remplis par l’altérite résiduelle. À Sprimont, la carrière du Coreux a dévoilé ces fantômes de roche. Durant une seconde phase, lorsqu’apparaît un potentiel hydrodynamique suite à une surrection et à l’incision des rivières, l’altérite peut être mécaniquement érodée par des circulations fluviatiles : les grottes « spéléologiques » se forment. Dans le site étudié, une cavité, la grotte « Nico », a été ouverte par l’avancée du front de la carrière. On y trouve une coupe sédimentaire montrant l’altérite résiduelle ravinée par des formations fluviatiles. Cet article décrit la coupe levée dans ces formations au travers de la lithostratigraphie, de la granulométrie et de la minéralogie des grains. La grotte « Nico » résulte de la coalescence de deux grottes superposées, le plancher rocheux séparant les deux cavités étant fantômisé et affaissé. Les parois et le sol sont des fantômes de roche dont l’altérite résiduelle est essentiellement formée de grains dolomitiques, tels les encrines dolomitisées. Les formations fluviatiles ravinent l’altérite suivant une surface chenalisante. Les grains sont constitués de grains remaniés d’altérite, calcite et dolomite, et d’une faible partie d’insolubles tels des grains de muscovite et de quartz en provenance des psammites famenniens. La série détritique est coiffée par un plancher stalagmitiques dont deux échantillons ont été datés de 53 851 ± 2493 et 61 542 ± 1235 ans B.P. ce qui situe l’érosion de l’altérite à une date relativement récente dans le Pléistocène supérieur. Ces phénomènes éclairent d’un jour nouveau la formation des grottes en Haute Belgique. L’évolution du karst de Sprimont trouve son origine dans un massif fantômisé partiellement érodé au cours de la surrection plio-quaternaire. L’apparition du potentiel hydrodynamique responsable de cette érosion trouve son origine dans les différences d’altitude entre pertes supérieures et résurgence à l’aval par enfoncement du niveau de base : la rivière Ourthe. Nous sommes confrontés à un holotype de spéléogenèse dans le cadre d’un relief appalachien. La grotte « Nico » et les phénomènes associés permettent de concevoir un modèle d’évolution des karsts de la Haute Belgique. Enfin, cet exemple montre aussi qu’une distinction claire peut être faite entre le terme karstogenèse qui englobe la fantômisation de celui de spéléogenèse qui ne concerne que le creusement des grottes spéléologiques par érosion mécanique de l’altérite résiduelle.
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Rodríguez-Castro, Isabel, et Sergio Rodríguez. « Palaeogeographic significance of rugose corals : El Guadiato Area (Southwestern Spain) as a case study ». Journal of Iberian Geology, 30 juin 2022. http://dx.doi.org/10.1007/s41513-022-00194-3.
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AbstractCarboniferous rugose corals are useful for palaeoecological, palaeoenvironmental and palaeogeographic studies. However, most analyses are qualitative and/or comprise corals from long stratigraphical intervals, and detailed palaeogeographic studies in the Carboniferous from western Palaeotethys are scarce. This report presents a quantitative analysis of the late Visean coral assemblages from the El Guadiato Area (Southwestern Spain), which has been thoroughly studied during the last 30 years. This case study aims to check the utility of rugose corals in detailed palaeogeographic studies, reconstructing tectonic movements in the suture zone between the Ossa Morena and Centroiberian domains in the Iberian Massif. Sixty-one rugose coral species from the El Guadiato Area were included in the analyses. Moreover, two other late Visean rugose coral faunas have been added as an external reference: Los Santos de Maimona (Southwestern Spain) and Kingscourt (Ireland). The presence/absence datasets have been treated with paired group (UPGMA) Hierarchical Clustering and a Detrended Correspondence Analysis. The results of this study support previous observations about the palaeogeography of the El Guadiato Area, backing the hypothesis that the strike slip faults of the area produced large lateral displacements. The results of analyses conducted at this level of detail appear to be conditioned by palaeoenvironmental differences, but the results of the comparison with Los Santos de Maimona and with Kingscourt’s faunas look promising for future larger comparisons between different basins.
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Königshof, Peter, Steffen Loos et Julia Rutkowski. « Lithofacies variability and facies analysis of a Givetian reef in the southwestern Lahn Syncline (Rhenish Massif, Germany) ». Palaeobiodiversity and Palaeoenvironments, 19 septembre 2023. http://dx.doi.org/10.1007/s12549-023-00585-z.
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AbstractA 200 m thick drill core penetrating the Givetian Hahnstätten Reef in the southwestern Lahn Syncline (Rhenish Massif) was investigated. A range of different depositional environments is described based on lithofacies and microfacies analysis. All in all, nine lithofacies types (FTs) are distinguished, which can include subfacies types. The majority of lithofacies of these ultrapure carbonates is represented by lime mudstone and fenestral microbialites, all pointing to shallow subtidal, intertidal to even supratidal low-energy palaeoenvironments. In contrast, more high-energy parts of the reef were dominated by bioclastic rubble deposits (e.g. rudstone). Autochthonous, reef-building carbonates are represented by bafflestone and framestone. Diversity of reef building organisms (stromatoporoids and corals) is low and is dominated by Stachyodes, Actinostroma, Stromatopora, and Thamnopora and alveolitids, respectively. Other bioclasts are brachiopods, gastropods, ostracods, foraminifera, echinoderms, trilobites, and conodonts in descending order. Development of the Hahnstätten Reef is interpreted as having been controlled mainly by synsedimentary tectonics and volcanism with contributions from eustasy. The occurrence of Stringocephalus burtini in the entire section and conodont findings, which provide more precise biostratigraphic data confirm an early to middle Givetian age (Polygnathus rhenanus/varcus Zone to Polygnathus ansatus Zone) of the succession. The average quality of the ultrapure carbonates lies at 97.68% CaO (excl. loss of ignition), with 70% of the core ranging between 98% and 99% CaO. This extremely high purity makes it difficult to identify correlations between lithofacies and geochemical data.
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Hartenfels, Sven, Ralph Thomas Becker, Hans-Georg Herbig, Wenkun Qie, Tomáš Kumpan, David De Vleeschouwer, Dieter Weyer et Jiří Kalvoda. « The Devonian-Carboniferous transition at Borkewehr near Wocklum (northern Rhenish Massif, Germany) – a potential GSSP section ». Palaeobiodiversity and Palaeoenvironments, 30 juillet 2022. http://dx.doi.org/10.1007/s12549-022-00531-5.
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AbstractThe Borkewehr section near Balve at the southeastern end of the Remscheid-Altena Anticline is currently the best and most complete Devonian/Carboniferous Boundary (DCB) succession of the Rhenish Massif, Germany. Based on a multidisciplinary approach, focusing on refined conodont and ammonoid biostratigraphy, microfacies analyses, sequence stratigraphy, carbon isotopes (Corg and Ccarb), trace element geochemistry, including REE data, and cyclostratigraphy, the section is proposed as a candidate for the new basal Carboniferous GSSP. The succession represents a pelagic “seamount” setting. It spans the upper Famennian to lower Viséan, with a condensed development of most Rhenish lithostratigraphic units and sedimentary sequences. It is the type-section of the oxic and strongly cyclic, fossiliferous Wocklum Limestone and of important uppermost Famennian and basal Carboniferous index species. The First Appearance Datum (FAD) of Protognathodus kockeli s.str., in a phylogenetic succession from the ancestral Pr. semikockeli n. sp., is proposed as future GSSP level. This FAD is sandwiched between many other marker levels for global correlation. Below are, from base to top, the transgressive base of the at least partly anoxic Hangenberg Black Shale (base Lower Hangenberg Crisis Interval), the Hangenberg Regression (onset of siltstones of the basal Middle Crisis Interval), the level of maximum regression, indicated by maximum Zr/Al values, and the initial transgression of the basal Upper Crisis Interval, marked by the re-onset of carbonate deposition. Above follow the locally cryptogenic FAD of Siphonodella (Eosiphonodella) sulcata s.l. at the base of the post-Crisis Interval (Hangenberg Limestone), associated with a conodont biofacies shift, the FAD of Si. (Eo.) bransoni, and, much higher, the sharp Lower Alum Shale Event at the base of the classical middle Tournaisian. The significance of the section is greatly enlarged by its precise correlation with numerous other Rhenish DCB sections that provide important additional data on faunas, geochemistry, geochronological ages, and magnetic susceptibility. The new Borkewehr data suggest changes of weathering intensity, based on Rb/K and K/Al trends, and Milankovitch cyclicity associated with the climate changes of the Hangenberg Crisis. The local conodont extinction rate at the top of the Wocklum Limestone lies at 57 % while there are no survivors in ammonoids, trilobites, or deep-water corals. Positive carbon isotopic shifts of carbonate in the Upper Crisis Interval and of Corg in the Middle Crisis Interval are decoupled, which suggests complex underlying processes that are not yet understood.
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Löw, Mieke, Till Söte, Ralph Thomas Becker, Sören Stichling, Andreas May, Zhor Sarah Aboussalam et Simon Felix Zoppe. « The initial phase of the Hönne Valley Reef at Binolen (northern Rhenish Massif, Middle Devonian) ». Palaeobiodiversity and Palaeoenvironments, 20 juillet 2022. http://dx.doi.org/10.1007/s12549-022-00540-4.
Texte intégralRésumé :
AbstractThe Hagen-Balve Reef Complex of the northern Rhenish Massif, Germany, is one of the best examples for the globally widespread Givetian to Frasnian reefs. At its eastern end, in the Hönne Valley, it reaches up to 1000 metres in thickness. In general, there is limited knowledge concerning the faunas and palaeoecology of Rhenish initial reef phases. A unique section at Binolen exposes the sharp boundary between the underlying, siliciclastic Upper Honsel Formation and the lower part of the reefal Hagen-Balve Formation. A ca. 14 m thick succession is assigned to the new Binolen Member and investigated in terms of carbonate microfacies, micro-, and macrofaunas. Seven microfacies types (MF) characterise a crinoidal coral-stromatoporoid garden setting (MF-2 to MF-6) or allobiostrome of an initial open platform turning upsection into a coral parabiostrome (MF-7/8). The base of the Asbeck Member is locally defined by the appearance of back-reef facies types, such as fenestral limestones (MF-9), which indicate the transformation into a bioherm. Low-diversity conodont faunas prove an influx of open shelf organisms for the Binolen Member and suggest a lower Givetian age (probably Polygnathus timorensis Zone). There are two new Givetian conodont biofacies types characteristic for open biostrome settings, the Bipennatus Biofacies and a Simple Cone Biofacies. Thin sections reveal over 40 different reef builders (rugose and tabulate corals, stromatoporoids, and chaetetid sponges). Around 4200 microfossils from conodont residues consist of agglutinating foraminifers, calcareous sponge spicules (e.g. Heteractinida), scolecodonts, echinoderms (mostly crinoid ossicles and holothurian sclerites), pyritised benthic ostracods, assumed calcified moulds of chitinozoans, subordinate microvertebrates, and other groups. They were analysed quantitatively in order to document changing distribution patterns and environments through time. We distinguish six microfossil-based biofacies types (BF), namely the Ostracoda Biofacies (BF-O), Foraminifera Biofacies (BF-F), Scolecodont Biofacies (BF-S), Chitinozoa Biofacies (BF-C), Porifera-Scolecodont Biofacies (BF-PS), and Porifera-Echinodermata Biofacies (BF-PE). Microfacies and microfossil assemblages led to a reconstruction of the local facies development, consisting of seven successive depophases with further subdivisions. At the base, the sudden termination of siliciclastic influx enabled a proliferation of reef builders and microfaunas (Depophase I), followed by a longer deepening phase characterised by exclusive bioclastic wackestones (Depophase II). Depophase III is a short regressive phase with crinoidal coral-stromatoporoid floatstones. Depophase IV is characterised by fluctuations in facies and relative sea-level, which results in three subphases. Depophase V resembles Depophase III, but with argillaceous interbeds and more abundant scolecodonts. It is followed by an interval with coral-stromatoporoid rudstones, which grade into coral-dominated bafflestones of an (auto)parabiostrome (both Depophase VI). Depophase VII represent the back-reef facies, including fenestral pack-bindstones of the basal Asbeck Member. The systematic analysis of reefal microfaunas represents pioneer work that should be tested and expanded to other reefs of the Rhenish Massif and beyond.
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Stichling, Sören, Ralph Thomas Becker, Sven Hartenfels, Zhor Sarah Aboussalam et Andreas May. « Drowning, extinction, and subsequent facies development of the Devonian Hönne Valley Reef (northern Rhenish Massif, Germany) ». Palaeobiodiversity and Palaeoenvironments, 17 septembre 2022. http://dx.doi.org/10.1007/s12549-022-00539-x.
Texte intégralRésumé :
AbstractThe Hagen-Balve Reef is one of the largest Devonian carbonate complexes in the Rhenish Massif exposed in many former or active, economically significant quarries, especially in the Hönne Valley region at its eastern end. The timing and patterns of reef drowning, final extinction, and the middle Frasnian to middle Famennian post-reefal facies history, including details of the global Kellwasser Crisis, were studied based on two boreholes (HON_1101 and B102) and one outcrop at the Beul near Eisborn. More than 100 conodont samples provided a fine biostratigraphic framework and included new forms left in open nomenclature. The ca. upper 80 m of the new Asbeck Member of the Hagen-Balve Formation consists of relatively monotonous lagoonal successions assigned to four microfacies types. The local diversity of reef builders, mostly stromatoporoids, is low. Fenestral microbialites indicate very shallow and rather hostile back-reef settings. Near the Middle/Upper Devonian boundary, the eustatic pulses of the global Frasnes Events led to a significant backstepping of the reef margin, with reef core/outer slope facies overlying lagoonal facies. This flooding drastically reduced the carbonate accumulation rate and enabled the invasion of drowned back-reef areas by open-water organisms, such as polygnathid conodonts. Within this Eisborn Member, five microfacies types and numerous subtypes are distinguished including low-diversity “coral gardens” and a final, top lower Frasnian parabiostrome dominated by tabulate and colonial rugose corals. There was no cap stage (“Iberg Facies”). Two phases of the Basal Frasnes Event are marked by dark, organic rich limestones with subordinate reef builders. Based on conodont fauna from overlying nodular limestones of the new, (hemi-)pelagic Beul Formation, the final Hönne Valley reef extinction was caused by the eustatic Middlesex Event at the lower/middle Frasnian boundary. Within the Beul Formation, eight subphotic submarine rise microfacies types are distinguished. After a lower middle Frasnian phase of extreme condensation, rich conodont faunas enable the recognition of most upper Frasnian to middle Famennian zones. The global semichatovae Event led to a regionally unique intercalation by four phases of organic-rich, laminated black shales and intervening thin limestones in core HON_1101. The Lower Kellwasser Event is represented in HON_1101 by atypical, moderately Corg-rich, recrystallized, peloidal ostracod-mollusk pack-grainstones. The Upper Kellwasser level begins with an ostracod bloom, followed either by recrystallized mollusk wacke-packstones (HON_1101) or laminated, argillaceous mudstones (B102). The first indicates a rarely documented shallow subphotic, better oxygenated setting than typical Upper Kellwasser facies. As elsewhere, the top-Frasnian conodont extinction was severe. The lower/middle Famennian carbonate microfacies of the Beul Formation is relatively monotonous and typical for an oxic, pelagic submarine rise. The youngest recorded nodular limestones fall in the Palmatolepis marginifera utahensis Zone. Regionally uniform lydites of the Hardt Formation show that the local palaeotopography was levelled before the base of the Viséan. The Hönne Valley case study and comparisons with western parts of the Hagen-Balve Reef and other Rhenish reefs underline the significance of Givetian to middle Frasnian eustatic and anoxic events as causes for reef extinctions.