Biostratigraphy of Middle and Upper Devonian Carbonates of Moravia Czechoslovakia
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Abstract This paper discusses contemporaneous knowledge of conodont, foraminiferal, stromatoporoid, tabulate and rugosan faunas through the Devonian carbonate platform of Moravia. In basal parts of the Moravian Devonian, upper Emsian to lowermost Eifelian is documented by conodonts in the Jeseniky Mts. Conodonts are rare in the Middle Devonian and the Middle/Upper Devonian boundary is not yet documented by conodonts. The most important change in the conodont assemblage lies in the upper part of the Pa. triangularis Zone in Moravia; for detailed zonation of Famennian, the system based on phylogeny of Palmatolepis is accepted. Five foraminiferal zones correlated with the standard conodont zonation are distinguished in the Upper Devonian. Several stromatoporoid assemblages were distinguished in the interval from Eifelian to Frasnian; stromatoporoids pass into the Famennian. Eight tabulate coral biozones are known at present, some of which are capable of more detailed division. Biostratigraphically significant tabulates range from Eifelian to the Famennian Pa. crepida Zone. Seven rugose coral biozones are described, ranging from Eifelian to the upper Frasnian Pa. gigas or Pa. triangularis Zones with a local fauna known from the Famennian Pa. crepida Zone. Stromatoporoid and coral faunas are correlated with standard conodont zonation of the Upper Devonian. Stromatoporoid and coral shallow water faunas locally pass from upper Frasnian to Famennian without pronounced systematic changes. However, both diversity and abundance of coral and stromatoporoid faunas decrease noticeably across the Frasnian/Famennian boundary beds.Keywords:
Conodont
Devonian
Biozone
Tournaisian
Late Devonian extinction
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Conodont
Tournaisian
Stratotype
Late Devonian extinction
Devonian
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Conodont
Section (typography)
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Abstract Late Devonian conodont sequences across the Frasnian — Famennian boundary interval at two sections in cratonal Western Canada (Medicine Lake, Alberta; Trout River, Northwest Territories) are described. These are compared with isolated faunas from the epicratonal Selwyn Basin-Kechika Trough, and from allochthonous terranes of the Western Cordillera. Current conodont zonations loosely constrain the age of the boundary between Upper rhenana Zone, and the undifferentiated Upper triangularis — Lower crepida zones. Broad synchroneity of the ‘event horizon’ at Medicine Lake and Trout River is supported by several faunal links, but precise age assignment is precluded due to poor conodont yield and, at Trout River, the presence of a hiatus at the boundary. The appearance of Palmatolepis canadensis sp. nov. provides a particularly useful datum in the early Famennian of Western Canada. The phylogenetic relationships of the new species are discussed.
Conodont
Late Devonian extinction
Devonian
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On the western slope of the Southern Urals, a continuous conodont zone sequence within different facies of the Frasnian-Famennian (F-F) boundary beds is documented. In all the sections the boundary between both stages runs within lithologically uniform successions and can be determined only by a sharp faunal change. In brachiopod facies, it is placed within brachiopod shell beds and relates to the base of the Barma Beds, i.e., the level marked by a simultaneous appearance of the index brachiopod species Pugnoides(?) markovskii and the zonal conodont species Palmatolepis triangularis. In goniatite facies, the F-F boundary can be traced by the disappearance of diverse Frasnian conodonts and goniatites of the genus Manticoceras, coupled with the first occurrence of the conodont Pa. triangularis; the sequence shows also the well-known icriodid blooms in the earliest Famennian. Finds of Famennian goniatites (representatives of the genus Cheiloceras) are confined to the crepida zones. In the sections of the West-Zilair, where the F-F boundary passage consists of siliceous-terrigenous deposits, the boundary can be established only by a change in conodont assemblages. In all the sections under investigation the F-F boundary level shows a drastic faunal change that corresponds to the global Kellwasser Event.
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Sequence (biology)
Terrigenous sediment
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Tournaisian
Conodont
Devonian
Late Devonian extinction
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Dynamics of the conodont diversity in the Late Devonian–Early Carboniferous (Famennian–Serpukhovian)
Subject. The article is aimed to evaluate of the conodont diversity dynamics at the species level in the Famennian – Serpukhovian interval. Materials and methods . The database compiled from the published and original data contains information on the stratigraphic ranges of 389 Famennian-Serpukhovian conodont species ( https://1drv.ms/x/s!AvPFMTPL Pc7T4nFU81CaO5UJ6nlw). Conodont zones compose the geochronological basis of the database. The conodont diversity, origination, extinction, and diversification were calculated. Dynamics of these parameters in the Late Devonian–Early Carboniferous was analyzed. Results. The Famennian-Serpukhovian conodonts demonstrate four cycles in the diversity: the early Famennian (triangularis-early postera zones), the late Famennian (late postera-praesulcata zones), the Tournaisian (sulcata-anchoralis zones), and the Visean-Serpukhovian (texanus-bollandensis zones). The cycles are separated by the low-diversity episodes. The highest diversity (80 species) is detected in the early and late marginifera zones (Famennian). Conclusions . The successive decreasing in diversity comprises interval from the late Famennian through Serpukhovian. The global events gave little influence on the conodont diversity except for the Frasnian/Famennian (about 70% conodont species became extinct) and Devonian/Carboniferous extinction events. Conodont diversity demonstrates weak dependence form the global sea level fluctuations. The transition from the green-house to ice-house climate at the beginning of the Carboniferous and successive changes in the marine ecosystems are considered as main probable cause of the decline in conodont diversity in the late Tournaisian-Serpukhovian.
Conodont
Tournaisian
Late Devonian extinction
Devonian
Diversity index
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Tournaisian
Conodont
Biozone
Devonian
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Conodont
Stratotype
Late Devonian extinction
Devonian
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The Frasnian-Famennian (F-F) boundary in Central Iran has been investigated on the basis of conodont faunas (34 species and subspecies) from four sections: Chahriseh near Esfahan, and Kal-e-Sardar, Howz-e-Dorah and Ghale-Kalaghu near Tabas. The F-F boundary in the Chahriseh section is located in a one-metre interval between beds EX1 and F-F9 whereas in the Kal-e-Sardar section it is at the base of bed Cly1. The F-F boundary cannot be recognized in the Howz-e-Dorah and Ghale-Kalaghu sections because of unconformable relationships and erosion of the uppermost late Frasnian beds indicated incidentally by reworked boulders (indicating contemporaneous tectonic activity) and by the abrupt appearance of contrasting environments, including tempestites at the base of the lower Famennian. The best conodont and palaeoenvironmental data were obtained from the Kal-e-Sardar section where a deeper marine environment prevailed during the late Frasnian, becoming shallower in the early Famennian; the Chahriseh section displays small fluctuations in sea level during the early Famennian. The conodont faunas display the inception of the Polygnathus communis group in the late Frasnian (rhenana-linguiformis zones) and the appearance of Icriodus alternatus mawsonae in the Late rhenana Zone. A new age-range is suggested for Polygnathus aequalis Klapper and Lane, from the transitans to the linguiformis zones. Three conodont biozones are represented in the late Frasnian to early Famennian of the Chahriseh section, two late Frasnian and one early Famennian in the Kal-e-Sardar section and two biozones in the late Frasnian and early Famennian of both the Howz-e-Dorah and Ghale-Kalaghu sections. Two new species are described: Polygnathus tabasianus (Early to Late crepida zones) and Polygnathus vachiki (Late rhenana-linguiformis zones).
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The early Famennian (Late Devonian) conodonts natural assemblages from Holy Cross Mountains (Poland)
Two early Famennian natural assemblages of conodont elements were found in a marly shale bed within a limestone and shale sequence representing the Palmatolepis triangularis conodont zone at the Kowala quarry in the Holy Cross Mountains, Poland. The most complete of these assemblages, identified as Ctenopolygnathus brevilamina, contained nine skeletally preserved elements and four imprints on the rock bedding plane. A peculiar aspect of the apparatus was the disposition of S4 elements with respect to other S-array elements. Moreover, the denticles of S4 elements were unusually robust and slightly twisted towards the caudal side, which may have resulted from a mode of food processing different from those of other conodonts known from natural assemblages. Moreover, the location of S0 was not consistent with the hypothetical arrangements of similar apparatuses proposed by previous authors. The second assemblage, representing an unidentified palmatolepidid, contained scattered two fragmentary elements and four imprints.
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Devonian
Tournaisian
Assemblage (archaeology)
Sequence (biology)
Late Devonian extinction
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