New evidence for a biostratigraphic assessment of the limestone succession comprising K‐bentonite levels exposed in the Yılanlı Formation of the Istanbul-Zonguldak Terrane are provided from conodonts at the Gavurpınarı quarry in Bartın area (NW Turkey). The succession depicts a shallow marine, nearshore facies setting that comprises rare and low diversity conodont associations mainly exemplified by the species of Ctenopolygnathus, Icriodus and Polygnathus. Conodont faunas from the lower part of the section are of late Frasnian age, including the taxa Icriodus subterminus Youngquist, 1947, Polygnathus aff. xylus Stauffer, 1940, Icriodus iowaensis iowaensis Youngquist & Peterson, 1947 and Ctenopolygnathus brevilaminus Branson & Mehl, 1934, and the upper part is assigned to early Famennian marked by the first appearance of Icriodus cornutus Sannemann, 1955. The local biostratigraphic framework of the Yılanlı Formation is correlated with the upper Frasnian Lower rhenana to the lower Famennian Middle triangularis standard conodont zonations. Considering the described species, the Frasnian-Famennian boundary corresponds to a slight change in conodont fauna and is assigned within the local Icriodus iowaensis iowaensis Zone. Accordingly, the novel K-bentonite age data potentially indicates the evidence for the Kellwasser events in northern Turkey, improving paleogeographic correlations of the Istanbul-Zonguldak Terrane with other terranes in Laurasia and Peri-Gondwana.

Late Devonian felsic magmatism in southern New Brunswick and its association with a large igneous province that may have contributed to the Frasnian-Famennian extinction

Abstract Fossil (zoo)plankton dynamics during Devonian ocean‐anoxic and extinction events can shed light on the palaeoceanographic and geochemical processes that shaped the middle Palaeozoic biosphere. However, datasets on (Upper) Devonian marine palynology, illustrating such dynamics, remain underexplored. The type section of the Sweetland Creek Shale in Iowa (USA) offers a detailed conodont zonation for the upper Frasnian and across the Frasnian–Famennian boundary, records the Upper and Lower Kellwasser events and has pristine preservation of organic material, making this an ideal section to study the effects of this catastrophic event on chitinozoan zooplankton populations. A total of 3998 specimens were recovered, imaged and classified into 12 distinct species, 10 of which were previously unknown. This study demonstrates the unrealized potential of chitinozoans as a regional biostratigraphic tool in the Upper Devonian. The Lower Kellwasser Event is characterized by a drop in chitinozoan abundance and the run up to the Upper Kellwasser Event marks a period of rapid species turnover rates. Interestingly, every assemblage in this interval is nearly monospecific. Patterns of changing spine morphologies in Fungochitina pilosa, Ramochitina sp. A and Saharochitina sp. A are herein explored as potential ecophenotypic expressions. We identify Angochitina monstrosa as a new disaster species. The discovery of two teratological chitinozoans specimens, in combination with the presence of the disaster species Angochitina monstrosa and deformation in contemporaneous conodonts, supports our previous discovery that marine teratology is a feature of many Palaeozoic extinction events, possibly triggered by the injection of hydrothermal brines into the ocean.

A new Late Devonian plant assemblage in West Junggar, Xinjiang, China and its floral evolution during the Devonian

In this paper, the research results of the sandstone thin sections of the Upper Frasnian Kodinka Formation, exposed in the middle segment of the East Ural megazone, are supplemented by data on the geochemical composition of sandstones, as well as mudstones of this formation, using modern approaches to their interpretation. It is shown that, firstly, during the accumulation of the Kodinka Formation, blocks of composite crust – island-arc and spreading complexes, as well as continental crust – were exposed to the erosion. Secondly, the sandstones of the Kodinka Formation are in many ways close in mineral and geochemical composition to coeval formations on the Southern Urals, in particular to the sandstones of the Biyagoda Formation, which has been formed due to the destruction of the Uraltau cordillera. In other words, the Kodinka Formation reflects traces of the destruction of the Late Paleozoic accretionary orogen in the area under consideration. The data obtained allow us to refine the existing estimates of the time of the onset of collision in the Middle Urals and assume that this process began no later than ~371.8 Ma ago (Frasnian-Famennian boundary according to modern concepts). On the one hand, this interval fits into the datings (367–372 Ma) presented by other authors earlier, on the other hand, we should not forget that metamorphism at the margins of the terranes that are part of the Ural folded structure, including high-pressure metamorphism, probably should have preceded the sedimentation of the Kodinka Formation in time, just as it preceded the deposition of the Zilair series in the Southern Urals.

Linking anoxia, biotic events, and basin evolution in the Late Devonian Illinois Basin, North America: A geochemical approach

Carbonate lithium isotope systematics indicate cooling triggered mass extinction during the Frasnian-Famennian transition

Trilobites showed strong resilience capacity through the Late Devonian events despite an inexorable decline

The Frasnian-Famennian boundary interval is exposed in New York State in an outcrop belt that stretches from Lake Erie eastward to Steuben County, continuing into Pennsylvania. Recent biostratigraphic examination of brachiopods and conodonts suggested that the shallower water sections to the east have been miscorrelated with the deeper water sections to the west. Revised correlations place the Upper Kellwasser extinction event (Frasnian-Famennian boundary) within the Canaseraga Formation and the Lower Kellwasser extinction event (Pipe Creek Formation) above the Wiscoy Formation. We review these revised correlations and provide additional support based on δ13Corg profiles from several sections. We also define new members in the Wiscoy Formation (Rossburg Member) and Canaseraga Formation (Hornell, Elkhorn Creek, and Crooked members) that should facilitate discussions of faunal and paleoenvironmental changes associated with the Frasnian-Famennian extinctions in the Appalachian Basin.

Organic geochemistry evidence for wildfire and elevated pO2 at the Frasnian–Famennian boundary

Mercury isotope evidence for regional volcanism during the Frasnian-Famennian transition

Through the study of conodonts, strata around the Frasnian–Famennian boundary in the Compte section were analyzed in detail. Twenty-four samples in a 12 m thick sequence yielded 13 species of conodonts belonging to Ancyrodella, Ancyrognathus, Icriodus, Palmatolepis, and Polygnathus. Besides conodonts, other groups such as foraminifers, radiolarians, brachiopods, ostracods and crinoids were also found in the sequence. The conodont record, shows the FZ13, from the uppermost Frasnian, and the minuta and crepida zones from the lower Famennian. The last Frasnian fossil was obtained from Bed 92b and the first Famennian fossil was from Bed 92d, which are separated by about 45 cm. Thus, between these two samples, the lowest three Famennian conodont zones have to be represented or missing. The absence of any stratigraphic hiatus between these levels suggests that extreme condensation took place in the early Famennian in the CP section.

The Late Devonian Frasnian–Famennian (F–F) mass extinction has been long-time debated by non-volcanic causes, extra-terrestrial impacts, and large igneous province (LIP) eruptions. To better understand the ultimate cause of the F–F mass extinction, here we investigate the chemostratigraphy of mercury (Hg) and total organic carbon (TOC) on two marine F–F strata in the Dushan area, South China. In both sections, high Hg and Hg/TOC anomalies were observed near the F–F boundary. These anomalies are in line with those recently observed in Morocco, Germany, Poland, and north Russia, suggesting a global Hg flux. The Late Devonian LIP eruptions, which are believed to have emitted massive amounts of Hg, could be responsible for the global Hg and Hg/TOC anomalies around the F–F boundary. The observed Hg and Hg/TOC anomalies coincide with the extinction of Frasnian fauna in the Dushan area, implying a causal link between the Viluy, Kola, and Pripyat-Dnieper-Donets LIP eruptions and the F–F mass extinction.

When embarking on a preparation project it is essential to consider a variety of techniques. A combination of different mechanical and chemical treatments may be necessary, even within the same formation. This article explores this principle using a case study of large accumulations of Frasnian cephalopods collected between 2015 and 2021 from the active quarry of Lompret near Chimay (province of Hainaut, Belgium). The quarry comprises strata that can be linked to the Kellwasser event, an important mass-extinction event near the Frasnian-Famennian boundary. Several of the lithological entities from this quarry require specific approaches in terms of preparation. This article will explicitly focus on preparation techniques applied to cephalopods. This informative and diverse group of macro-organisms can contribute to a better understanding of marine environmental changes during an ecological crisis. A thorough preparation of all the collected specimens from this specific location is required, as this peculiar fauna is in desperate need of a taxonomic review. We will demonstrate to what extents the uses of potassium hydroxide (KOH) and Rewoquat W 3690 PG as solvents have proven to be particularly effective in dissolving clay-rich sediments during preparation.

Upper Devonian mercury record from North America and its implications for the Frasnian–Famennian mass extinction

Late Devonian ostracods are described for the first time from the Frasnian–Famennian (F–F) transition of the Zengpiyan section, Guangxi, South China. Forty‐five ostracod species belonging to 25 genera are identified and figured and one is new: Jenningsina guilinensis sp. nov. The Frasnian–Famennian boundary (F–FB) in the Zengpiyan section is coincident with the lithological boundary between the Guilin Formation and the Dongcun Formation, and could be marked by the disappearance of Rectobairdia proximischimensis (Lethiers & Casiers, 1998) and Jenningsina guilinensis sp. nov. The ostracods belong to the Eifelian Mega‐Assemblage, which implies a shallow‐water palaeoenvironment. The ostracod fauna and sedimentary features of the Guilin and Dongcun formations at the Zengpiyan section suggest a transition from subtidal to low‐energy tidal flat on the Guilin Platform during the Frasnian‐Famennian event. The extinction rate of benthic ostracod species is about 61% during the F–F event in the Zengpiyan section. Two stages of faunal changes have been recognized in the event and the second stage is more severe than the first one.

A Devonian age for the Sarhlef Formation (Jebilet Massif, Morocco) – evidence from new biostratigraphic data based on metamorphosed conodonts

The Khoshyeilagh Formation located in the northeast of Iran yielded seven conodont species and sub-species and 19 macro- and microfossil taxa that allow recognition of two conodont biozones and one biozone based on calcareous microfossils. The latest Frasnian age (the Upper rhenana to linguiformis zones) is attributed to the topmost strata with Icriodus alternatus. Its replacement with I. cornutus indicates the Famennian (Lower triangularis to Lower crepida zones) corresponding to the Umbellina Zone. The fossil assemblages identified in the Khoshyeilagh Formation represent a shallow marine environment with a tropical climate at the time of deposition. The fossil species from the Khoshyeilagh Formation and the sedimentary basins in Algeria, Libya, Morocco, Poland, and Russia reveal a close connection between the Iranian plateau and the northern parts of Gondwana in the Late Devonian. The biofacies and lithofacies analyses show a sea-level decline at the end of Frasnian, followed by a considerable sea-level drop, as in other regions of the world. After a short time, in the Famennian, the deepening occurred in some parts of the area and the open marine facies (bioclast spicule wackestone-packstone) were deposited. This study is the first attempt to determine the Frasnian-Famennian boundary based on conodont assemblages and other fossil species such as umbellulids, tentaculites, and ostracods. The distribution of these species is interpreted in sedimentological, stratigraphic, sequence stratigraphy, and the global eustatic context. Keywords: biofacies, conodont, Frasnian-Famennian boundary, Late Devonian, NE Iran.

Famennian conodonts from the Hongguleleng Formation at the Bulongguoer stratotype section, western Junggar, Northwest China

The Devonian and Early Carboniferous brachiopod assemblages of the order Rhynchonellida from Transcaucasia (Nakhchivan Autonomous Republic of Azerbaijan and Armenia) are described. The succession of dominating rhynchonellid superfamilies and ecological types has been identified. Rhynchonellids were numerous in the Devonian; in the Early and Middle Devonian, the representatives of the superfamily Uncinuloidea prevailed. Their relict species survived up to the beginning of Famennian. The free-lying and anchoring cavern-dwelling rhynchonellids dominated in the Early and Middle Devonian. This ecological subtype is recognized for the first time. The rhynchonellid taxonomic and ecological groups changed at the Frasnian–Famennian boundary but rhynchonellids remained a significant part of the brachiopod fauna. The variability of rhynchonellids decreased at the Famennian–Tournaisian boundary but the superfamily Rhynchotrematoidea and the rhynchonellid anchoring ecological type continued to dominate starting from the Frasnian. The role of Rhynchonellida in the Early Carboniferous brachiopod fauna is insignificant. The decrease of variability within some zones is probably connected with taphonomic conditions.