Early Famennian Research Articles

CONODONT BIOSTRATIGRAPHY OF UPPER DEVONIAN TEPHRA BEARING DEPOSITS IN THE İSTANBUL-ZONGULDAK TERRANE, NW TURKEY: INSIGHTS ON THE KELLWASSER EVENTS

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.

Timing and pattern of the Devonian Nehden event: Implication for the biotic recovery following the F–F extinction event

The biotic recovery process following the Frasnian–Famennian (F–F) mass extinction played an important role in reestablishing the late Palaeozoic marine ecosystem. The Nehden event is assumed as the global biotic recovery process in the aftermath of the F–F mass extinction, but the timing and pattern of this event is still in dispute due to lack of consistent geological records. In order to recognize the Nehden event and elucidate its timing and pattern, a newly refined conodont biostratigraphic framework spanning the Palmatolepis minuta minuta Zone to the Pa. rhomboidea Zone (370.8–367 Ma) has been established in the Yangdi section, Guangxi, South China. Based on a detailed analysis of microfacies and carbon isotope of carbonates (δ13Ccarb), the start of the Nehden event has been placed at the upper part of the Pa. m. minuta Zone, marked by deposition of calcareous shales and proliferation of palmatolepid conodonts and ostracods. Two episodes of the Nehden event are recognized in this study according to integrated palaeontological, sedimentological, and geochemical data from South China and other continents. The first phase of the Nehden event is assigned at the upper part of the Pa. m. minuta Zone, characterized by radiation of conodonts, ostracods, and brachiopods, which is coincident with the minimum value of negative δ13Ccarb excursion and climate warming. The second phase is placed at the Pa. termini to Pa. glabra pectinata zones, documented by biodiversification of cheiloceratid ammonoids and phacopid trilobites, which is concurrent with climate warming and the maximum transgression during the early Famennian. The extensive development of microbial bindstone in the lower Famennian succession at Yangdi demonstrates that microbial communities occupied the vacant ecological niches left behind by metazoans after the F–F biotic crisis. The expansion of ecological niches of microbial communities and depauperation of metazoan reefs implies the bioconstructor turnover from metazoan to microbial communities following the F–F extinction. The time equivalence of biotic radiation, climate change and sea-level fluctuation in two episodes of the Nehden event indicates the early Famennian biotic recovery was favored by climate warming and transgression. The results in this study not only offer important data to constrain the timing of the Nehden event, but also provide an insight on the process of biotic recovery following the F–F mass extinction event.

Изотопный состав и условия образования фаменских карбонатолитов Центрально-Хорейверского вала (Хорейверская впадина, Печорская плита)

The article presents results of the distribution of the isotopic composition of 13C and 18O (119 samples) across four facies zones to substantiate the conditions of Famennian carbonation accumulation. The Lower Famennian carbonates of the shoal zone showed values of 13C (1.5 ± 0.15 %), 18O (25.01 ± 0.29 %) reflecting evaporative processes in a shallow basin in a warm and dry climate. For the rocks of the microbial mounds zone, the values of 13C (2.47 ± 1.12 %) and 18O (23.51 ± 1.12 %) reflect an increase in bioproductivity and some fluctuation in water salinity. In the limestones of the zone of transition to depression, the variations of isotopic composition are more distinct in the section. Thus, the Early Famennian is characterized by the average values of 13C (0.94 ± 0.59 %) and 18O (23.73 ± 2.18 %) for marine carbonates. The transition to the Middle Famennian is accompanied by isotopic weighting of 13C (1.30 ± 0.47%) and 18O (24.52 ± 1.45%), which shows an increase in evaporation processes under aridization conditions. In the Late Famennian, the isotopic composition abruptly lightens by 13C (–1.05 ± 0.66 %), which is associated with desalination under conditions of climate humidification. At the same time, the value of 18O (25.75 ± 0.31 %) corresponds to the average values for carbonates of the Devonian. The values of 13C (1.04 ± 0.89 %) and 18O (26.01 ± 0.99 %) in the carbonates of the zone slope of the carbonate bank towards the shallow shelf reflect the conditions of the normal sea basin with a slight increase in the evaporation regime during climate aridization. The obtained results indicate that the Famennian sedimentation basin characterized by fluctuations in sea level, facies, water hydrochemistry and climate.

Early Famenian Trachyandesite Magmatism of the Pripyat Paleorift, East European Platform: U–Pb Age and Petrology

On the basis of the mineralogical-petrographic and geochemical study of igneous rocks of intermediate composition of the Pripyat complex of the Late Devonian Pripyat-Dnieper magmatism area, two subphases of the Pripyat magmatism phase have been definished: late Fransian (Chernin or Skolodino-Chernin) with potassium specification and early Famennian (Turov-Drozdov (Yelets)) with potassium-sodium specification. For the first time, the U–Pb age of titanite from trachyandesites of the parametric borehole Pribor was obtained for rocks of Pripyat-Dnieper magmatism area at 364 ± 1 Ma. These data confirm the Famennian age of the Yelets subphase of the Pripyat phase of magmatism and make it possible to determine the duration of the magmatic activity of this structure at least 14 Ma taking into account the isotope dating of the earliest phases of magmatism in the Pripyat-Dnieper-Donetsk Paleorift Structure as 388 ± 12 Ma, 383.3 ± 3.8, 384.7 ± 3.9 and 383.6 ± 4.4 Ma in the Azov Region and 381 ± 2 Ma in the Pripyat-Dnieper magmatism area.

Upper Devonian “griottes” facies of the Ben-Zireg area (Bechar Basin, southwestern Algeria): Stratigraphy, microfacies analysis and paleo-environmental reconstruction

The widespread ‘griotte’ facies of the Late Devonian (Frasnian to Famennian) in the Ben-Zireg area of the Bechar basin (Southwestern Algeria) is described here from three sections (BZI, BZII and BZIII) which have been sampled bed-by-bed from the ‘Griotte’ limestone of the Ben-Zireg Formation. Based on macro- and microfacies analysis, this formation has been divided into three members: the Lower Member consists of ‘griotte’ limestone, the Median Member consists of clayey-limestone ‘griotte’, and the Upper Member consists of shales with intercalations of ‘griotte’ limestone. The ammonoid specimens recolted in this formation allow to characterize three Late Devonian biozones: the Cheiloceras Zone (UD II) of Early Famennian, the Gonioclymenia (UD V) and the Kalloclymenia (UD VI) zones of Late Famennian. Based on the field observations and the analysis of 270 thin sections, six microfacies types (MFT-1 to MFT-6) have been identified. They are dominated by biomicritic wackestones and mudstones characterizing a quiet marine environment corresponding to a distal ramp with deposits containing tempestites echoes and internalites fine grained supplies.

Iron deposition during recovery from Late Devonian oceanic anoxia: Implications of the geochemistry of the Kawame ferromanganese deposit, Nedamo Belt, Northeast Japan

The Late Devonian, during which one of the “Big Five” Phanerozoic mass extinction events occurred, was one of the most important time intervals in Earth history. Nevertheless, the paucity of deep-sea records due to subduction has hampered elucidation of the pelagic environment during the Late Devonian in Panthalassa. However, ancient hydrothermal ferromanganese sediments, which were deposited on the abyssal seafloor and then accreted onto continental margins, are preserved as umber deposits and exposed in accretionary prisms. These sediments can provide key information to characterize the paleo-ocean. An Upper Devonian (Famennian) umber deposit is exposed in Kawame Quarry, Nedamo Belt, northeastern Japan. We investigated the bulk chemical composition and osmium isotopic ratio ( 187 Os/ 188 Os) of the Kawame umber to discuss the pelagic environment of the Panthalassa Ocean during the Late Devonian. The Kawame umber shows positive correlations between Fe content and the levels of P, V, Os, and rare earth elements, suggesting that hydrothermal Fe-oxyhydroxide particles adsorbed these elements from ambient seawater in the same way as hydrothermal ferromanganese sediments in the present-day ocean. Newly obtained initial 187 Os/ 188 Os values of Late Devonian seawater are 0.49–0.57, lower than that of present-day seawater (~1.06) and comparable to Paleogene and Late Cretaceous values. One of the most remarkable characteristics of the Kawame umber is its markedly high Fe levels (up to 90 wt%) compared to present-day seafloor hydrothermal ferromanganese sediments and younger umber deposits in Japanese accretionary complexes. Because seawater 187 Os/ 188 Os values were not notably different from those during the Paleogene and Late Cretaceous, anomalously vigorous hydrothermal activity in the Late Devonian is unlikely to have caused the increased Fe deposition. The rare earth element patterns of the Kawame umber (normalized to post-Archean average Australian shale) show weaker negative Ce anomalies than those of younger umbers and present-day hydrothermal ferromanganese sediments, suggesting that the Kawame umbers were deposited under less oxidizing conditions. Considering that many red beds were deposited at ~370 Ma, during recovery from the oceanic anoxic events (OAEs) of the Late Devonian (early Famennian), the anomalous Fe enrichment in the Kawame umber likely reflects enhanced oxidization and precipitation of abundant dissolved Fe during the post-OAE transition from anoxic to oxic conditions. • Geochemistry of Late Devonian Panthalassa was reconstructed from NE Japan. • Weakly negative Ce anomaly may reflect recovery from oceanic anoxia. • Reoxygenation of seawater caused Fe-enrichment in the Kawame umber. • Late Devonian seawater 187 Os/ 188 Os ratio was 0.47–0.57.

Deciphering the morphological variation and its ontogenetic dynamics in the Late Devonian conodont Icriodus alternatus

Identification of relevant taxonomic and evolutionary units is a recurrent issue in the fossil record, and all the more for ancient fossils devoid of modern equivalents such as conodonts. Extensive morphological variation has often led to the description of numerous species, subspecies or morphotypes, which may correspond to end-member morphologies reached through ontogeny. The platform elements of the Late Devonian conodont speciesIcriodus alternatuswere characterized by rows of denticles coming into occlusion between opposite elements; each element grew by the incremental addition of lamellae and by the addition of successive triads during ontogeny. During the late Frasnian and the early Famennian, the important morphological variation within this species led to the description of three subspecies. An extensive sample of early FamennianIcriodus alternatuswas quantified using 2D biometric measurements and denticle counts on 2D pictures, showing that the subspecies mainly differed in their size range but not in their general morphology. A 3D morphometric analysis was further performed on a subsample to characterize the shape of the ontogenetically older part of the elements. During ontogeny, early valleys between denticles tended to be filled, and the asymmetry between the inner and outer side of the element increased. These ontogenetic trends are responsible for the morphologies formerly described as the subspeciesIc. alt. mawsonaeandIc. alt. helmsi. Slight discrepancies between temporal ranges of the subspecies may be achieved through variations in range of size reached by the elements as a response to environmental changes. Disparity along ontogeny seems to follow an “hourglass model” suggesting a shift from relatively loose developmental constraints to a pattern of growth modulated by functional constraints during occlusion.

Upper Frasnian and Lower Famennian (Upper Devonian) conodonts of the Compte section (Spanish Central Pyrenees)

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.

BIOSTRATIGRAPHY AND CORRELATION OF DEVONIAN DEPOSITS IN THE SOUTH-WEST SEGMENT OF THE EAST-EUROPEAN PLATFORM BY BRACHIOPODS

The main aim of the paper is to study the detailed distribution of the brachiopod fauna throughout the entire Devonian section from the Silurian-Devonian boundary at the Podilla region to the Devonian-Carboniferous boundary at the SW slope of the Dnipro-Donets Depression (DDD). The Devonian brachiopods (mainly Productids, Spiriferids and Rhynchonellids) of the south-west segment of the East-European Platform (EEP) are reviewed from the DDD, Volhyn-Podilla monocline (VPM) including the L’viv Paleozoic Trough, and Fore-Dobrogea Paleozoic Depression (FDPD). The faunas of these regions are mutually related and compared to the Devonian faunas of the EEP (Russia) and Pripyat’ Depression (Belarus). In recent years several paleontological investigations have broadened and deepened our knowledge of the Devonian biostratigraphy of Ukraine. Based on systematic studies of brachiopods from the SW segment of the EEP we recognize four successive faunas corresponding to four great marine transgressions — Early Devonian (Tiwer Series, the Monograptus uniformis Zone), Middle Devonian (Givetian Stage, the conodont varcus Zone), Late Frasnian (the conodont Upper rhenana — linguiformis Zone), and Early Famennian (the conodont triangularis-crepida Zone). The Early Devonian association includes Howellella angustiplicata, Plectodonta maria, and Daiya navicula and others which are similar to late Silurian brachiopods by their generic features (represented the genus common with the Upper Silurian). The Middle Devonian assemblages contain: Emanuella volhynica, Atrypa (Desquamatia) ventricosa, Chonetes sarcinulata, and Poloniproductus productoides at VPM sections (Givetian Stage, the varcus Zone), as well as Variatrypa sokolovae (Eifelian Stage), but in the DDD sections the impoverished association with Stringocephalus cf. burtini (Eifelian Stage) and Atrypa uralica (Givetian Stage) occur. The Late Frasnian association is represented by dominance of Theodossia tanaica, T. evlanensis, T. livnensis at all regions — VPM, DDD and FDPD (the Upper rhenana — linguiformis zones). The Early Famennian association is represented by ex Cyrtospirifer archiaci = Cyrtospirifer asiaticus and Cyrtospirifer ljachovichensis, Cyrtiopsis sp., Ptychomaletoechia zadonica, Iloerhynchus tichomirovi, Ardiviscus ex gr.herminae, Steinhagella annae etc. at DDD and by the same association plus Dmitria angustirostris at VPM (the triangularis-crepida zones). Brachiopods near the D-C boundary have been recorded so far from the black shales fossiliferous deeper water facies only in DDD: Spinocarinifera nigra, S. fallax, Sphenospira julii, Parallelora sp. (the Siphonodella praesulcata Zone). The result of our systematic study of productids, spiriferids, rhynchonellids, atrypids, and athyrids from Ukrainian sections are in perfect agreement with, and supplement to the previous investigations of Middle and Upper Devonian deposits at VPM and DDD, suggesting their important role for precising boundaries between the Devonian stages and horizons in SW segment of EEP. The essential role of brachiopods for the Devonian biostratigraphy and correlations with the East-European biozonation is confirmed.

North-Gondwana – Laurussia dynamic paleogeography challenged by magnetic susceptibility through the Famennian

Large-scale magnetic susceptibility (MS) variations in ancient sediments are usually interpreted as related to sea-level and climate changes affecting the erosional regime and the amount of detrital input. To constrain such environmental changes during the Famennian, we compared MS records in representative sections of pelagic limestones of (1) the Avalonian margin of Laurussia [Sessacker (SES) and Beringhauser Tunnel (BHT), Rhenish Slate Mountains, Germany] and (2) in Gondwana related terranes [Erfoud (ERF), Tafilalt, Morocco; Col des Tribes (CT), Montagne Noire, France; Buschteich (BU), Thuringia, Germany; Corona Mizziu (CM I, II), Sardinia and Pizzul West (PZW) in the Carnic Alps, Italy]. Very low MS values throughout the Famennian characterize sections from Avalonia. In contrast, MS values are high and oscillating in Gondwana during the early Famennian; they drop significantly all together in the middle Famennian Palmatolepis marginifera marginifera Zone to match the pattern of low MS values of the Avalonian margin thereafter. To evaluate the importance of partial diagenetic overprint, MS data were compared to hysteresis parameters and geochemical proxies in sections BU, CM I, II and CT. The degree of thermal diagenesis is estimates taking into account the Color Alteration Indices (CAI) of conodonts. Striking dissimilarities in MS records between Laurussia and Gondwana are in favor for an existing remnant oceanic barrier between these continents during early Famennian times, when the amount of detrital supplies was obviously different. Uniformity is reached after the drop of MS values in N-Gondwana, when oceanic barriers could have vanished during the early middle Famennian T-R fluctuations of the sea-level. All sites remained under a rather similar regime of detrital supply through middle to uppermost Famennian. Comparison of MS trends with trends of conodont biofacies in five sections (CT, BU, CM I, II and SES) allows emphasizing the concordance of their relationship to sea level fluctuations.

Richness of Famennian-Tournaisian (Late Devonian-early Carboniferous) bryozoans in shallow areas of Palaeotethys and Palaeoasian oceans

Based on the analysis of data on bryozoan localities in territory of modern Eurasia, changes of the bryozoan richness were calculated in detail for six time slices in the interval from the early Famennian to the late Tournaisian. Highest extinction tempo was observed for the latest Famennian, apparently linked to the Hangenberg Event. However, in the richness of bryozoans during the late-latest Famennian, an abrupt increase in the origination tempo is observed, as well as a slight decrease in the total bryozoan richness at the Devonian-Carboniferous transition. Origination of abundant narrowly specialised bryozoan genera in the orders Trepostomata and Cryptostomata at the end of the Devonian and in the beginning of the Carboniferous was caused by the combined influence of extrinsic and intrinsic factors. An observed increase in the morphological specialisation of bryozoans during the Late Devonian and early Carboniferous coincides with patterns observed in other benthic organisms such as brachiopods and rugose corals. These patterns can be explained by vacation of ecological niches and changes in the structure of the marine biota in the aftermath of the Hangenberg Event.

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

The Hongguleleng Formation, the highest and most important Devonian marine carbonate horizon in western Junggar, contains an endemic shallow-water Icriodus–Polygnathus conodont fauna with rare palmatolepids and other genera. The conodont faunas from the Bulongguoer and the Wulankeshun sections are similar, with high abundance (about 40%) of endemic taxa (13 taxa), indicating isolation of the Junggar Basin during early Famennian. Non-endemic species in the faunas suggest that the Lower Member of the Hongguleleng Formation is assignable to the Pa. rhomboidea Zone to the Pa. marginifera marginifera Zone of early Famennian, not including the Frasnian–Famennian boundary. The Upper Member may be of late Famennian–early Tournaisian in age on the basis of our preliminary faunal analysis.

Late Devonian-Early Carboniferous isolated carbonate platforms of the North of the Urals and Pay-Khoy

The article considers isolated carbonate platforms known in the Sub-Polar Urals (basin of the Bolshaya Nadota River; boreholes of the Yunyakha and Levaya Grubeyu areas) and the NW Pay-Khoy (basin of the Lymbad’yakha River and coast of the Barents Sea). The three stages of formation of the platforms (Frasnian, Famennian-Tournaisian, and Visean-Serpukhovian) are distinguished, and the sedimentological models of these platforms are developed. Subsidence curves based on the back-striping demonstrate some differences in the evolution of the studied isolated carbonate platforms. Similarities and differences in the history and structure of the platforms are observed. Formation of the intra-shelf depressions (the Kozhim Depression in the Sub-Polar Urals, and the Korotaikha Depression in the Pay-Khoy) in the Frasnian — Early Famennian caused appearance of isolated carbonate platforms. The depressions probably were formed by the regional tectonics. The following development of the carbonate platforms was controlled by eustatic fluctuations. The isolated platforms differ by stratigraphic spans (Late Frasnian — Serpukhovian for the Polar Urals Platform and Famennian-Tournaisian for the Pay-Khoy Platform), relief, facies, and size. The isolated depressions differ in size as well: the Kozhim Depression is larger than the Korotaikha Depression. Additionally, it is supposed that the Polar Urals platform was of warm-water type, but the Pay-Khoy platfrom was of cool-water type.

Morphological Evolution of Eurasian Bryozoans during Famennian–Tournaisian

The main trends in the morphological evolution of bryozoans at the Devonian-Carboniferous boundary were established when studying the Late Devonian–Early Mississippian bryozoans of Eurasia. The diversity of vertical colonies increased from Early Famennian to Late Tournaisian. An increase in their strength occurred by growth of the exozonal skeleton due to the growth of vesicular tissue in cystoporates, thickening of the autozooidal walls in trepostomates, complication of polymorphism in cryptostomates, and thickening of the branches in fenestrates. The most rapid evolutionary changes were observed in rhabdomesine bryozoans of the order Cryptostomata, expressed in the change of the spiral arrangement of autozooids to complex one and a high diversity of heterozooids and styles. The development of keels, nodes, superstructures, acanthostyles, and spines in bryozoans provide protection from predators.

The upper devonian magmatic complexes of the South-East Belarus

For the first time, the authors determined lateral-temporal series of magmatic complexes of the Late Frasnian-Early Famennian Pripyat-Dnieper Magmatic Area according to the results of petrological and geochemical study of rocks of the Pripyat-Dnieper Magmatic Area (north-western part of the Pripyat-Dnieper-Donetsk Magmatic Province) in the southwest of the East European Platform using the principles of structural-material analysis and taking into account previous studies. The series consists of four complexes, formed during stages of magmatic activity, separated by time intervals: Zhlobin Complex (Rechitsa Time, the beginning of the Late Frasnian), Uvarovichi complex (Late Voronezh Time, the middle of the Late Frasnian), Pripyat Complex (Skolodin (Skolodin-Chernin?) Time, the end of the Late Frasnian) and Loev complex (Yelets (Yelets- Petrikov?) Time, Early Famennian). The rocks of the Zhlobin Complex belong to the alkaline-ultramafic (carbonatite-kimberlite-nephelinite) formation; Uvarovichi Complex - to the alkaline-mafic formation (basaltoids and phonolites); Pripyat Complex - to the alkaline-mafic-salic formation (trachyandesites); Loev Complex - to the alkaline-ultramafic (nepheline) formation.

The first aspinothoracid arthrodire from the Late Devonian continental strata are found in western Junggar, Xinjiang

Arthrodira is the most widely distributed and diversified subgroup of Placodermi, which itself is the most diverse major group of the Devonian jawed vertebrates. Arthrodires were traditionally divided into the basal, paraphyletic “Dolichothoraci” and the highly nested monophyletic Brachythoraci, the latter of which displays reduction of body armor. Among brachythoracids, the Coccosteomorphi and Pachyosteomorphi further form a nested monophyletic Eubrachythoracidi. The sister group relationship between Coccosteomorphs and Pachyosteomorphs has been supported by most phylogenetic analyses, but the basal members and their interrelationships in these two groups are still unstable. Coccosteomorphs and pachyosteomorphs are the most diverse arthrodires in the Middle and Late Devonian. Among them, coccosteomorphs are found in strata of the lacustrine and littoral-neritic facies, while the pachyosteomorphs are mostly marine. Selenosteidae, one of the most well-known families in Pachyosteomorphi, are found in marine strata of Europe, North America, and North Africa. Junqing Wang found the nuchal plate of suspected Selenosteidae in the Xiejingsi Formation (early Famennian, Late Devonian) in Hunan Province, China, but due to the lack of identification features of the material, its exact systematic position awaits further determination. The Zhulumute Formation is a lithological unit in western Junggar, Xinjiang of northwest China and is mainly composed of conglomerates, pebbly sandstones and medium- to coarse-grained sandstones, with typical braided stream lithofacies. Channel-fill deposits are thick, with well-developed parallel bedding, scour structure, and large-scale trough, wedge and tabular cross-beddings. This part contains a large number of plant stem fossils in fragment. The fine-grained floodplain deposits are thin, with horizontal beddings and small sand ripple beddings; fine fragments of plant stems or leaves can be seen in the siltstones. These characteristics indicate that the Zhulumute Formation in the Bulongguoer area was formed in the braided stream environment. At the same time, according to the preserved plant fossil Leptophloeum rhombicum , its age is limited to the early Famennian. Here we report on a new selenosteid genus Bulongosteus , collected from the upper part of the Zhulumute Formation. The diagnostic characters of the new genus include: (1) A triangular nuchal plate with convex front edge, concave back edge and bilateral micro concave, and the side edge is overlaid with paranuchal plate; (2) the posterior margin of the paranuchal plate longer than that of the nuchal plate, and two sensory tubes were developed; (3) the preorbital plate enlarged to form the anterolateral margin of the orbit, with dense tumor spots on the surface; (4) the anterior edge of the marginal plate thickened to form the posterior margin of the orbit, and the three sensory tubes in the shape of “Y”; (5) a slender posterior ventrolateral plate. Pachyosteus , Rhinosteus , Melanosteus , and Walterosteu are similar to Bulongosteu s in Selenosteidae. In Rhinosteus , there are a few tumor spots on the surface of the bone and the distribution of the sensory tubes of the paranuchal plate is different from Bulongosteus . The posterior margin of Walterosteu is wider than Bulongosteus , and the distribution of the sensory tubes of the paranuchal plate is different. The characteristics of Pachyosteus and Melanosteus are the most similar to Bulongosteus , but the distribution of the sensory tubes in their paranuchal plate is different from Bulongosteus . And Pachyosteus has less tumor spots in the nuchal plate and has a trapezoid rostral plate. Melanosteus has some tumor spots in the preorbital and suborbital plate. Bulongosteu s is the first arthrodire reported from Xinjiang of northwest China, and also the first relatively complete aspinothoracid reported in China. Strikingly, Bulongosteu s is the first aspinothoracid arthrodire found in the continental strata in the world. The discovery of the new material significantly expands the geographical and ecological distribution of aspinothoracid arthrodires, and also shows that aspinothoracids, like many fishes in the Late Devonian, are euryhaline.

The early Famennian (Late Devonian) conodonts natural assemblages from Holy Cross Mountains (Poland)

ABSTRACT 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.

The polyphasic ontogeny of the discoidal Late Devonian ammonoid Acrimeroceras

The Late Devonian ammonoid species Acrimeroceras falcisulcatum and A. stella have similar-shaped discoidal adult conchs. Their conch morphology and its ontogenetic development are described and analysed. Despite great similarities in their adult conch morphology, they can be clearly distinguished by differences in the shape of their juvenile whorl profile and by the growth trajectories of their cardinal conch parameters: conch width index, umbilical width index and whorl expansion rate. Quantification of ontogenetic change in the two species demonstrates that the stratigraphically younger species A. falcisulcatum possesses the less complex ontogeny compared to the stratigraphically older A. stella. The closely related genus Paratornoceras (early Famennian) and the unrelated Late Visean Calygirtyoceras show juvenile conch morphology and ontogenetic trajectories very similar to Acrimeroceras stella. This similarity can be seen as iterative independent unfolding of homoplastic characters, possibly linked to size-dependence of the functional morphology of the conchs.

Results of 13c nmr and ftir spectroscopy of kerogen of the upper devonian domanik of the Timan-Pechorian basin

A kerogen samples set from organic carbon rich rocks of the Middle Frasnian Early Famennian age (Domanikites) of the Timan-Pechora basin, was characterized by the Rock-Eval pyrolysis data, solid-state 13C NMR spectroscopy and Fourier transform IR spectroscopy. Additionally, the spectral characteristics of kerogen isolated from rocks artificially maturated in an autoclave in the presence of water were investigated. In general, the direction of transformation of the kerogen structure with a natural or artificial maturation coincides. For kerogen, subjected to artificial maturation, is characterized by an increase in the concentration of terminal methyl groups in relation to the methylene units. Artificial maturation of kerogen leads to a more rapid rearrangement of aromatic clusters with the accumulation of bridgehead and protonated carbon as compared with natural maturation.

Rare representatives of new Late Devonian ammonoids from the Rhenish Mountains and the Montagne Noire

The new genera and species of the early late Famennian (Late Devonian) ammonoids Hoevelia schindewolfi n. gen. n. sp. and Beulia wunderlichi n. gen. n. sp. are described from material collected in the Rhenish Mountains and attributed to the new family Hoeveliidae. The genus Falciclymenia Schindewolf, 1923 is revised with the description of the proposed new type species Falciclymenia cabrierensis n. sp. from the Montagne Noire.