Conodonts across the Devonian/Carboniferous boundary: a review and implication for the redefinition of the boundary and a proposal for an updated conodont zonation

This paper is a contribution to the redefinition of the base of Carboniferous system. At present the criterion for the definition of the Devonian\u2013Carboniferous boundary is the first occurrence of a conodont species. In order to evaluate the stratigraphic potential for new criteria for the definition of the Devonian\u2013Carboniferous boundary, the distribution of conodont species of Bispathodus, Branmehla, Palmatolepis, Polygnathus, Protognathodus, Pseudopolygnathus and Siphonodella across the boundary is presented and discussed. An updated biozonation scheme across the boundary based on the First Appearance of Bispathodus ac. aculeatus, Bispathodus costatus, Bispathodus ultimus, Protognathodus kockeli, Siphonodella bransoni and Siphonodella duplicata is proposed, and it is suggested that the new criterion for the definition of the base of the Carboniferous system be the First Appearance Datum of Pr. kockeli or Si. bransoni

Conodonts across the Devonian/Carboniferous boundary in SE Sardinia (Italy)

The Bruncu Bullai section, located in SE Sardinia, exposes limestones from the styriacus Zone (upper Famennian) to the Upper duplicata Zone (Tournaisian), but the Upper praesulcata Zone is not documented; at the Devonian/Carboniferous boundary a black shales level, equivalent to the Hangenberg Shales, is present. Fifty-six conodont taxa were recovered, three of which are here described as new species: Polygnathus bicristatus, Po. nuragicus, Pseudopolygnathus granulobatus; two more species, probably new, are described, but left in open nomenclature because of the low number of specimens collected. The relative high abundance of Protognathodus and low abundance of Siphonodella in some levels and the opposite in others is discussed, and a new hypothesis on the occurrences of protognathodids as influenced by ecological factors is suggested. The early phase of the Hangenberg crisis is testified by a faunal turnover in an impoverished fauna within the deposition of limestones of the Lower praesulcata Zone

The Devonian/Carboniferous boundary in Sardinia (Italy)

In Sardinia (Italy) two sections, located in the southeastern part of the island, expose the Devonian/Carboniferous Boundary: the Monte Taccu Section and the Bruncu Bullai section. Both expose limestones from the middle Famennian to the lower Tournaisian Siphonodella jii Zone. The limestone sequence is interrupted by a thin level of shales representing the Hangenberg Event. Data on conodont biostratigraphy and magnetic susceptibility across the Devonian/Carboniferous Boundary are here summarised and reviewed

Subaerial exposures in the Tournaisian (Lower Carboniferous) of the central Carnic Alps (Italy)

The documentation of a palaeodoline and the recovery of a loose block with shrinkage cracks in the Rio Sglirs area (central Carnic Alps) suggest subaerial exposure during the late Tournaisian. Both structures have been dated to the anchoralis conodont zone. This episode occurredwell before the globally documented sequence boundary at the Tournaisian-Visean boundary. These data, combinedwith other evidence from different areas in the CarnicAlps suggest that the evolution of the Carnic Basinwas influenced by high frequency sealevel fluctuations during the late Tournaisian

Two new early balognathid conodont genera from the Ordovician of Oman and comments on the early evolution of prioniodontid conodonts

<p>Reports of Ordovician conodonts from the Arabian region of the Gondwanan margin are extremely rare. Here we provide a description of the apparatus of two new conodont genera and species, <i>Aldridgeognathus manniki</i> and <i>Omanognathus daiqaensis</i>, based on discrete elements recovered from the Am5 Member of the Amdeh Formation, Darriwilian, Ordovician of the Sultanate of Oman. The apparatuses contain 17 and 15 elements, respectively, and both possess three pairs of P elements. The apparatus structure of <i>Omanognathus</i> is similar to the bedding plane assemblage-defined genus <i>Notiodella</i> (= <i>Icriodella</i>) but differs in that as yet only 15 elements rather than 17 have been identified. <i>Aldridgeognathus</i> has similar P elements to the early Silurian apparatus <i>Pranognathus</i> but differs in the possession of a geniculate M element and a <i>Baltoniodus</i>-like S element array. <i>Aldridgeognathus</i> does not easily fit with either the 17-element <i>Notiodella</i> (<i>Icriodella</i>) or the 19-element <i>Promissum</i> templates and suggests that there may be other 17-element Ordovician apparatus templates with very similar or duplicated elements in the P element positions. A cladistic analysis based on the data set of Donoghue (2008) confirms that both new genera should be classified with the Balognathidae and suggests that they, along with another newly described three P element bearing genus <i>Arianagnathus</i>, are more derived than <i>Baltioniodus</i> and <i>Prioniodus</i> but ancestral to <i>Icriodella</i>, <i>Sagittodontina</i>, <i>Promissum</i> and <i>Notiodella</i>. The exact position of <i>Aldridgeognathus</i> is not well resolved in respect to the newly described <i>Arianagnathus</i> or <i>Omanognathus</i>. These new taxa add little to attempts to correlate the Arabian Peninsula with other palaeogeographic regions, but may prove useful for future correlation within the region and provide data to test the hypothesis of Dzik (2015) that the origins for prioniodontid conodonts lie in high latitudes during the Ordovician.</p> <p><a href="http://zoobank.org/urn:lsid:zoobank.org:pub:84C8267D-76E8-4DD3-92F3-0B72CA976DEC" target="_blank">http://zoobank.org/urn:lsid:zoobank.org:pub:84C8267D-76E8-4DD3-92F3-0B72CA976DEC</a></p

Depositional evolution of a lower Paleozoic portion of the Southalpine domain: the Mt. Pizzul area (Carnic Alps, Italy)

he Carnic Alps represent the best exposed Paleozoic succession within the Alpine domain being fossiliferous, mostly non-metamorphic and largely complete. This study focuses on the area around Mt. Pizzul, because the bedrocks record well the basin dynamics and most of the units are conodont bearing. Our aims were to contribute to the procedure of formalization of the lithostratigraphic units and to understand the depositional and deformation history of the study area. The area has been mapped, tectonic overprint constrained and the successions described, measured and dated. As a second-order aim, we discuss these data to infer the relations with other parts of the Carnic basin and to recognize the global controls on sedimentation. The depositional evolution can be sketched as follows: pre-Hirnantian ramp-type margin; Hirnantian glacioeustatic-related deposits and unconformity; pelagic deposition in a ramp-type margin (Přídolí–Eifelian); slope formation and differentiation in buildup, foreslope and pelagic environments (Eifelian–Frasnian); transgression and reef drowning (Frasnian–Visean); probable subaerial exposures likely during in uppermost Famennian and Visean times; and turbidite deposition (Visean). Global controls or deposits suggesting a global control are documented, including the Boda Event, the Hirnantian glaciation, the Middle Devonian reef growth, the Kačák Event, and the high-frequency sea-level fluctuations around the Devonian–Carboniferous boundary. The drowning of the buildups here and elsewhere in the Carnic Alps started during the Frasnian, unlike observed globally. This suggests that local tectonics lead to progressive deepening up to the transition to turbidite deposition

Freikofel Formation

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