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The iron (Fe)-oxide deposits of the Lahn-Dill-type are composed of haematite-quartz and rare siderite-haematite ores. These ores formed as marine chemical sediments on top of volcaniclastic rocks near the Middle to Late Devonian boundary (∼ 380 Ma). As such, their trace element fractionation patterns provide key information on venting style, ocean chemistry, particle-solution interaction, and depositional environment at the time of ore formation. This study combines WDXRF and ICP-MS/OES whole-rock geochemistry with complementary in-situ LA-ICP-MS analysis, and TEM element mapping of ore samples from the Fortuna Mine (Rhenish Massif, Germany). In-situ measurments were conducted on quartz-haematite, haematite, and siderite-haematite microdomains. Bulk major element contents of the ores indicate (volcani)clastic contamination and post-depositional hydrothermal alteration. Microdomain trace element distributions reveal four different trace element signatures, which are related to: (1) syngenetic apatite formation due to sorption of P and REY from seawater; (2) Fe-(oxyhydr)oxide-specific trace element scavenging and fractionation within the seawater column; (3) diagenetic Fe(III) reduction and trace element mobilisation in pore water; and (4) simultaneous deposition of (volcani)clastic material and Fe-(oxyhydr)oxides. These results show that Lahn-Dill-type iron ore formation resulted from mixing of a low-temperature vent fluid with ambient seawater at high seawater to vent fluid ratios. This likely was related to an environment in which diffuse venting dominated over focused venting, and in which quick Fe-particle precipitation led to formation of haematite-quartz ores. Local diagenetic Fe(III) reduction resulted in post-depositional siderite-haematite ore formation during which trace elements were partially remobilised in pore water. [ABSTRACT FROM AUTHOR]

Problems related to the classification of species are common in the field of palaeontology. The family Homalonotidae (Phacopida; Trilobites), in the Devonian period of the Malvinoxhosan Realm, can be included in this issue, since of its 22 species described since the 19th century, only half are considered valid today. This is mainly due to the existence of not very distinct diagnoses, the lack of comparisons between species and/or the lack of more up-to-date concepts. In order to demonstrate some of these problems and propose plausible solutions, this work was based on a bibliographic survey of the literature on the subject. The surveys showed the existence of 11 species of Homalonotidae, of the genera Burmeisteria, Burmeisterella, Digonus and Dipleura. The analyses indicated that some species were very similar (e.g. Burmeisteria accraensis and B. notica), while others had no distinguishable characteristics (e.g. Burmeisteria oiara). Thus, new analyses and classifications were proposed based on the specificity of each case and the use of more up-to-date concepts (e.g. taphotaxon), as well as the application of a phylogeny of morphological characters, in order to better understand the relationship between the taxa studied. [ABSTRACT FROM AUTHOR]

Premise: Cladoxylopsids, one of the first lineages with complex organization to rise from the plexus of structurally simple plants that comprised the earliest euphyllophyte floras, are moniliformopsid euphyllophytes. They formed Earth's earliest forests by the Middle Devonian and are thought to have given rise to the equisetopsids and probably some fern lineages. The Lower Devonian (Emsian) Battery Point Formation (Quebec, Canada) contains previously unrecognized cladoxylopsids preserved anatomically. One of these provides new data on structural evolution among euphyllophytes and is described here. Methods: The anatomy and morphology of permineralized axes of the new plant were studied with light and electron microscopy on sections produced using the cellulose acetate peel technique. Morphological comparisons and phylogenetic analysis were used for taxonomic placement of the plant. Results: The plant represents a new species, Paracladoxylon kespekianum Chu et Tomescu, gen. et sp. nov., that has tracheids with modern‐looking bordered pits and the complex cauline vascular architecture characteristic of the genus Cladoxylon. Its dissected ultimate appendages have complex regular taxis and a pattern of vascularization that suggests bilateral symmetry. Conclusions: Paracladoxylon kespekianum is one of the largest Early Devonian euphyllophytes, among the oldest representatives of the cladoxylopsid group, and older than any species of the closely related Cladoxylon by at least 35 million years. It is also one of the oldest anatomically preserved representatives of the cladoxylopsid group. Its anatomical organization pushes the rise of complex vascular architecture among moniliformopsid euphyllophytes deeper in time than previously recognized. [ABSTRACT FROM AUTHOR]

Background: The sea spiders (Pycnogonida Latreille, 1810) of the Hunsrück Slate (Lower Devonian, ~400 million years ago) are iconic in their abundance, exquisite pyritic preservation, and in their distinctive body plan compared to extant sea spiders (Pantopoda Gerstäcker, 1863). Consequently, the Hunsrück sea spiders are important in understanding the deep evolutionary history of Pycnogonida, yet they remain poorly characterised, impacting upon attempts to establish a time-calibrated phylogeny of sea spiders. Methods: Here, we investigated previously described and new material representing four of the five Hunsrück pycnogonids: Flagellopantopus blocki Poschmann & Dunlop, 2006; Palaeoisopus problematicus Broili, 1928; Palaeopantopus maucheri Broili, 1929; and Pentapantopus vogteli Kühl, Poschmann & Rust, 2013; as well as a few unidentified specimens. Using X-ray microtomography and Reflectance Transformation Imaging, we describe new fossils, provide evidence for newly revealed anatomical features, and interpret these data in comparison to extant species. We also reinterpret the previously published illustration of the (probably lost) holotype of Palaeothea devonica Bergström, Stürmer & Winter, 1980. Results: We provide the first detailed description of the cephalic appendages of Palaeoisopus problematicus and revise the interpretation of the organisation of its ocular tubercle. Furthermore, we provide new insights into the structure of the legs and the proboscis of Palaeopantopus maucheri, the first description of the body of Flagellopantopus blocki and describe a new specimen of Pentapantopus vogteli, demonstrating that it had eight legs, in contrast to previous interpretations. We argue that, contrary to previous suggestions, Palaeothea devonica probably had a different body plan from extant pantopods. We discuss the ecological traits of the Hunsrück pycnogonids based on their morphological adaptations, and conclude that there is no compelling evidence of Pantopoda in the Devonian. Through comparative interpretation of the legs as well as general morphology, we can divide the Hunsrück pycnogonids into two morphological groups, while Pantopoda constitutes a third morphological group. [ABSTRACT FROM AUTHOR]

Three collections of clam shrimp from the Lower Devonian (upper lower Emsian) Klerf Formation of Willwerath and Waxweiler in the western Eifel Mountains are herein studied. Four discernible morphotypes are present in the Willwerath assemblage. These morphotypes correspond to the previously described species from this locality: Pseudestheria diensti (Gross), Pseudestheria subcircularis Raymond, and Palaeolimnadiopsis? eifelensis Raymond. The fourth morphotype also closely corresponds to Pseudestheria diensti, but is slightly different in outline. Asmussia willweratica (Novozhilov) is an objective synonym of Pseudestheria subcircularis. In the Willwerath clam shrimp sample, it is difficult to disentangle taphonomic/preservational versus ontogenetic/sexual variation. If taphonomic/preservational causes could be confirmed, all the Willwerath specimens may represent just one taxon and Pseudestheria subcircularis and Palaeolimnadiopsis? eifelensis would be potential subjective synonyms of Pseudestheria diensti. However, we refrain from a formal taxonomic act, which requires a larger number of specimens to be analysed. In addition, we investigated two samples from Waxweiler, which originate from distinct centimetre-thick layers and therefore represent associations. One of these associations comprises two discernible clam shrimp morphotypes. Because of limited preservation of morphological characters, one is here left in open nomenclature as Spinicaudata incertae sedis, whereas the other is recognised as a new species of the family Palaeolimnadiopseidae, Palaeolimnadiopsis frankeorum sp. nov. The second association from Waxweiler comprises at least four, possibly six different clam shrimp taxa. In addition to Pseudestheria diensti, Palaeolimnadiopsis sp., and poorly preserved Asmussia- and Ulugkemia-like specimens, two taxa can be described as new, namely the vertexiid Cornia wasvilrensis sp. nov. and the leaiine Eicheleaia wenndorfi gen. nov. et sp. nov. Altogether, the Klerf Formation at Waxweiler yields a total of at least five (possibly eight) clam shrimp taxa. The palaeoenvironment of these early clam shrimp from the Klerf Formation is interpreted as a non-marine, relatively proximal deltaic setting with no or very minor marine influence, such as a deltaic freshwater pond or lake. The comparatively high diversity of these lower Devonian clam shrimp suggests a considerably earlier origin and cryptic evolution of the group. [ABSTRACT FROM AUTHOR]

Svalbard has long been thought to represent the easternmost realm of the Ellesmerian Orogeny in the late Devonian or early Mississippian (Svalbardian tectonic event). Several authors do not agree and present alternative interpretations of the observed structures in older and more recent articles. This article discusses a number of issues that, in our opinion, are not sufficiently considered in those works, but which are essential for the understanding of the Svalbardian tectonic event: (1) the possibility of re-deposited palynomorphs in the discussion of the deformational ages, (2) the age and structural setting of the crucial Adriabukta Formation in southern Spitsbergen, and (3) the presence and nature of the Svalbardian angular unconformity in central and southern Spitsbergen.

The protective structures of bryozoans representing four orders—Trepostomata, Cryptostomata, Fenestrata, and Cheilostomata—were analyzed and classified for the first time based on functional criteria. The proposed classification includes five groups of protective structures responsible for: 1) reducing water pressure; 2) increasing the feeding area by expanding the distance between the autozooecia apertures, as well as strengthening the colony’s stability and integrity; 3) physically protecting the polypide and providing attachment points for muscles; 4) scaring off predators; and 5) enabling physical protection against predators while also cleaning the colony from sediments, larvae, and small invertebrates. The study of the development of heterozooids, stylets, and avicularia in fossil bryozoans revealed the emergence of persistent, effective polymorphs in the Early Ordovician, Late Devonian, and Early Cretaceous. The evolutionary changes in bryozoans were primarily driven by fluctuations in the levels of the World Ocean, climate, phytoplankton biomass, and predator composition, among other complex interplays between abiotic and biotic factors. To shield themselves from predation threats, bryozoans evolved acanthostyles protruding above colony surfaces and various types of heterozooids physically protecting them from being eaten (caverno-, para-, cyclo-, lepto-, and allozooids in the old groups, along with avicularia in cheilostomates). Avicularia and similar structures occurred repeatedly in different orders: in fenestrates during the Early Ordovician and Early Devonian, in cryptostomates during the Middle Carboniferous, and in cheilostomates during the Early Cretaceous.

Devonian successions in the Calliope and Yarrol provinces of the northern New England Orogen in central to northern Queensland have a lithological assemblage and depositional environments indicative of a close association with a subduction-related volcanic arc. These rocks have been interpreted as related to island arc and backarc settings based on geochemical characteristics of magmatic rocks. We present new detrital zircon ages from the Devonian to lower Carboniferous successions of the Calliope and Yarrol province successions. Most samples have no or relatively few zircon grains extracted except for samples of quartz-rich sandstone in the Middle Devonian Erebus beds of Hunter Island, located 160 km north-northwest of Rockhampton and another sample in the Rockhampton district. The samples with abundant zircon, and some with less common zircon, have prominent peaks of mid Cambrian to Ordovician ages and are consistent with derivation from the northern Thomson Orogen where igneous rocks of this age are documented in the Charters Towers Province. These data indicate a connection between the Devonian arc-flank deposits of the northern New England Orogen and the Thomson Orogen, which had previously been well established for Carboniferous deep-marine sandstones of the subduction complex (e.g. Shoalwater Formation). These results favour an east-facing continental margin arc setting in the Devonian contra to intra-oceanic island arc settings previously proposed. Detrital zircon age spectra from sampled early Carboniferous units of northern New England Orogen association indicate a pulse of felsic magmatism of that age. KEY POINTS: Devonian quartz-rich sandstones from the northern New England Orogen have abundant detrital zircon ages of mid Cambrian to Ordovician indicating a provenance connection with the Charters Towers Province of the northern Thomson Orogen. These results confirm a provenance linkage to Gondwana and imply that the Devonian tectonic setting was a continental margin arc and associated forearc basinal infill. Geochemical comparisons suggesting an island arc setting have overly influenced previous tectonic interpretations. [ABSTRACT FROM AUTHOR]

• A diverse assemblage of anatomically preserved plants is described from Oum El Jerane. • The euphyllophytes include one iridopterid, two cladoxylopsids and two aneurophytales. • Arachnoxylon and Triloboxylon are recorded for the first time in Gondwana. • The new plant assemblage may belong to a drier phytochorion than the Laurussia one. The Middle Devonian is a transitional period for the first vascular plants, which acquire modern vegetative and reproductive structures, diversify considerably and, within the euphyllophytes, evolve the first representatives of modern plant groups, the monilophytes and lignophytes. However, the dynamics of this diversification across the different paleocontinents remains obscure, particularly within Gondwana. The upper Givetian locality of Oum el Jerane, in southeastern Morocco, has yielded a new assemblage of anatomically preserved plant remains whose description contributes to a better understanding of the floras of the northern margin of Gondwana during the Middle Devonian. The euphyllophytes include one iridopterid, Arachnoxylon minor , two cladoxylopsids, one of which represents the new genus Jerana , and two aneurophytales affiliated with the genus Triloboxylon. The cladoxylopsid remains from Oum el Jerane correspond to relatively small plants compared to the well-known coeval cladoxylopsids of Laurussia. Compared to the taxonomic composition of the four phytochoria recently defined for the Middle Devonian, the Oum el Jerane plant assemblage corresponds to the 'subtropical' phytochorion, which is close to the 'Laurussia' phytochorion, but which would correspond to drier environmental conditions. [ABSTRACT FROM AUTHOR]

This paper presents the first contribution to the study of bryozoans from the Frasnian–lower Famennian successions of Armenia. The latter were examined in two distinct localities (Ertych and Noravank) of Central Armenia; abundant fragments of branched ramose and encrusting bryozoans were observed in them, belonging to the orders Trepostomata and Cryptostomata. Their taxonomic assessment led us to recognize four species: two cryptostomes – Euthyrhombopora tenuis Ernst et al., 2017 and Bigeyella indigena (Morozova and Weiss in Morozova et al., 2002) from the Noravank section (Frasnian) – and two trepostomes – Eostenopora sp. and Eridotrypella sp. from the Ertych section (lower Famennian). No cystoporate and fenestrate bryozoans were observed. The identified bryozoans are characteristic of shallow marine or middle shelf paleoenvironments. The presence of Euthyrhombopora tenuis and Bigeyella indigena suggests palaeobiogeographic affinities to contemporary faunas from Iran and Poland, respectively. In addition to our results, an overview of previously published data reveals that the upper Famennian assemblages of bryozoans from the Lesser Caucasus contain more endemic species than those known from the Frasnian and the lowermost Famennian. [ABSTRACT FROM AUTHOR]

The Devonian-Carboniferous (D-C; 359 Ma) boundary is marked by widespread deposition of organic-matter-rich black shales associated with the Hangenberg mass extinction event. The Exshaw Formation spans the D-C boundary in the Western Canada Sedimentary Basin (WCSB) and includes the basal Exshaw Shale deposited under broadly anoxic waters. The sediments at the base of the Exshaw Shale were deposited synchronously during a transgressive event across the WCSB, spanning the geographic variability of the basin. The variable Corg content of the shale was affected by local nutrient upwelling and paleotectonic features impacting water depth and circulation. To characterize the link between paleogeography and nutrient cycling, geographic (N = 20 locations) and stratigraphic (N = 6 locations) trends of δ13^^ and δ15^^ were examined throughout the WCSB, representing a range of depositional settings. The δ15^^ values range between 0.0 and 6.3%" and δ13^^ from -29.5 to -26.8%. Phytoplankton production in focused upwelling zones acquired a relatively 15N-depleted signature through isotopic fractionation during nutrient assimilation, and the residual nutrient pool was 15N-enriched. The advection of surface waters away from the location of upwelling supported additional phytoplankton growth and the deposition of sediments with higher δ1^ values. The stratigraphic sections include black laminated and burrowed mudrock sequences that record changes in paleoredox conditions, water depth, and tectonism over time. Up-core from the base of the Exshaw, the Corg content decreases and simultaneously δ15^^ increases, suggesting a decrease in eutrophic conditions. Variable δ13^^ and δ15^^ trends demonstrate that there is no "type" isotopic profile spanning the D-C boundary in the WCSB. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study including LA-ICP-MS zircon U-Pb dating, geochemical, zircon Hf isotope, and whole rock Sr-Nd isotope analysis of magmatic rocks from the Yitong County, Jilin Province, NE China. These data are used to better constrain the Middle Silurian–Middle Devonian tectonic evolution in the eastern segment of the northern margin of the North China Craton (NCC). Zircon U-Pb dating results show that the Ximangzhang tonalite formed in the Late Silurian (425 ± 6 Ma); the basalt, andesite, and metamorphic olivine-bearing basalt in the Fangniugou volcanic rocks formed in the Middle Silurian (428 ± 6.6 Ma) and Middle Devonian (388.4 ± 3.9 Ma, and 384.1 ± 4.9 Ma). The Late Silurian tonalites are characterized by high SiO2 and Na2O and low K2O, MgO, FeOT, and TiO2, with an A/CNK ratio of 0.91–1.00, characteristic of calc-alkaline I-type granite. They are enriched in Rb, Ba, Th, U, and K, and depleted in Nb, Sr, P, and Ti, with positive εNd(t) (+0.35) and εHf(t) (+0.44 to +6.31) values, suggesting that they mainly originated from the partial melting of Meso–Neoproterozoic accretionary lower crustal material (basalt). The Middle Silurian basalts are characterized by low SiO2, P2O5, TiO2, and Na2O and high Al2O3, FeOT, and K2O, enriched in Rb, Ba, Th, U, and K and depleted in Nb, Ta, Sr, P, and Ti, indicative of shoshonitic basalt. The Late Silurian tonalites have positive εNd(t) (+4.91 to +6.18) values and primarily originated from depleted mantle magmas metasomatized by subduction fluids, supplemented by a small amount of subducted sediments and crustal materials. The Middle Devonian volcanic rocks exhibit low SiO2, TiO2, and Na2O and high K2O, and MgO, enriched in Rb, K, and LREEs and depleted in Nb, Ta, Sr, and HREEs, characteristic of shoshonitic volcanic rocks. Their εNd(t) (+2.11 to +3.77) and εHf(t) (+5.90 to +11.73) values are positive. These characteristics indicate that the Middle Devonian volcanic rocks primarily originated from depleted mantle magmas metasomatized by subduction fluids, with the addition of crustal materials or subducted sediments during their formation. Based on regional geological data, it is believed that the study area underwent the following evolutionary stages during the Silurian–Devonian period: (1) active continental margin stage of southward subduction of the Paleo–Asian Ocean (PAO) (443–419 Ma); (2) arc-continent collision stage (419–405 Ma); (3) post-collision extension stage (404–375 Ma); (4) active continental margin stage, with the PAO plate subducting southward once again (375–360 Ma). [ABSTRACT FROM AUTHOR]

The sedimentary column at the Rechitsa oilfield in the Pripyat rift basin, Belarus, is dominated by an Upper Devonian synrift succession. The succession includes uppermost Frasnian and mid‐Famennian salt units which are about 1000 m and 2000 m thick respectively. Reservoir rocks consist of sandstones and carbonates in the intra‐, inter‐ and sub‐salt successions. In this paper, the geochemical analysis of 15 oil samples from different stratigraphic intervals at the Rechitsa field is used as a basis for reservoir characterisation. Geochemical studies included biomarker and stable C, N and S isotope analyses. Four genetic oil groups were identified and are referred to as Groups A to D. Oils in Group A came from upper intra‐ and inter‐salt reservoir rocks; the oils are early mature, enriched in heavy (C36+) hydrocarbons, heteroatoms, aryl‐isoprenoids and gammacerane, with low Pr/Ph = 0.6 and a sulphur isotope composition averaging 22.7‰ CDT. Oils in Group B were from sub‐salt reservoirs and are at peak maturity with Pr/Ph = 1, an increased proportion of C27 regular steranes, and a sulphur isotope composition of 8.1‰ CDT. The single oil sample in Group C was from a Proterozoic reservoir. The oil was overmature with a low content of heavy fractions, heteroatoms and steranes; its hopanes composition indicated that it was generated by the same source rock as the oils in Group B. Oils in Group D came from inter‐salt reservoir rocks and were composed of a mixture of Groups A and B oils in roughly equal proportions, as indicated by their average isotope, molecular and biomarker compositions. Observed differences in oil composition were explained in terms of contributions from at least two different source rocks together with variations in source rock maturity. Group A oils were interpreted to have been generated by Famennian carbonate‐rich source rocks containing dominantly marine and bacterial organic matter deposited in an anoxic evaporitic setting. Source rocks for Groups B and C oils were suggested to be composed of OM‐rich marine shales of Frasnian age or older. The geochemical characteristics of the Devonian oils from Rechitsa field, and the oil‐oil and oil‐ source rock correlations reported, will contribute to a better understanding of the petroleum system in the Pripyat Basin although direct oil‐ source rock correlations are not yet available. The presence of at least two source rocks for the Rechitsa oils has been suggested, respectively comprising carbonates in the inter‐salt succession and marine shales and/or carbonates in the sub‐salt succession. The main controls on oil composition in the Devonian reservoir units were the varying contributions from the different source rocks and differences in source rock thermal maturity associated with variations in burial depth and tectonics, together with the stratigraphic distribution of reservoir units which was in turn controlled by the presence of the thick Frasnian and Famennian salt units. [ABSTRACT FROM AUTHOR]

Blastoids underwent a revolution in respiration in the Devonian. Emsian blastoid faunas were dominated by fissiculates such as Pentremitidea, giving rise to a transitional spiraculate, Conuloblastus. Hyperoblastus and a mosaic of spiraculates followed; they featured a more advanced respiratory system and were dominant until the Permian. This diversification occurred just prior to or during the Stony Point and Kačák Events, major ecological disruptions of marine ecosystems. Most new spiraculate blastoids were endemic and short lived, but Hyperoblastus survived the major extinction events, lasting into the Famennian. Material from Germany, Spain and North America enables us to trace the diversification of the spiraculates during the Devonian. We erect the new family Conuloblastidae, including Hreggoblastus differentialis gen. et sp. nov.; also Altusoblastus (type species Pentatrematites eifeliensis) with new species A. eremitus, A. palliolatus, A. sp. 1 and A. sp. 2 in the Hyperoblastidae. Pentremitidea roemeri and Hyperoblastus schultzei are assigned to Altusoblastus. Hyperoblastus batheri is declared the type species of Absensoblastus gen. nov.; H. ludwigi sp. nov. is assigned to Hyperoblastus. Pentahedronoblastus gen. nov. (type species P. giesdorfensis sp. nov.) is described. The fissiculate nymphaeoblastid genus Pentremitella (including P. osoleae and ?P. sp. 1) is redescibed. We recognize the eleutherozoic Freisoblastus gen. nov. (type species F. hemisphaericus sp. nov.), Dissimiloblastus gen. nov. (type species D. inequalis sp. nov.) and non‐eleutherozoic Lotusoblastus gen. nov. (type species Pentremitidea medusa) (order and family incertae sedis). We recognize 13 American species of Hyperoblastus. [ABSTRACT FROM AUTHOR]

The swellability of mudstone has important influence on slope stability and other geotechnical engineering. Lianhuashan Formation of the Devonian is developed in Cenxi City, central of southeast Guangxi. It is mainly distributed in a small scale in the low hill area of the stripped and dissolved ridges and valleys geomorphologic area. In order to find out the dilatability of the mudstone in this area, this study has carried out geological mapping, drilling, field test, laboratory geotechnical test and X-ray diffraction analysis to determine the macro-characteristics and physical and mechanical properties of the mudstone. The swelling property of mudstone is studied by the comprehensive evaluation method of macroscopic preliminary judgment—physical and mechanical indexes quantitative initial judgment—Gaussian process quantitative detailed judgment. The physical and mechanical indexes are selected as effective montmorillonite content, < 2 μm colloidal content, liquid limit, plastic index and total swelling and shrinkage ratio, and the quantitative criterion of swelling property is given. The five indexes of mudstone in the study area are 22%-33%, 20%-33%, 46. 8%-78. 0%, 24. 1-42. 9 and 1. 3%-5. 2%, respectively. It is concluded that the mudstone in the study area has moderate to strong swellability. [ABSTRACT FROM AUTHOR]

The Changning-Menglian suture zone is a critical tectonic belt pivotal to the evolution of the Paleo-Tethys. The Wenquan Formation, characterized as turbidite deposited on the western side of the Changning-Menglian suture zone as well as the eastern edge of the Baoshan Block. Analysis of detrital zircons from the Wenquan Formation reveals two significant age peaks approximately at 440 and 980 Ma, with additional age populations around 600, 780, and 2 500 Ma. The major age peak at about 440 Ma is come from the andesitic-dominant volcanic arc within the Lancang Block and the western Simao Block, corroborated by the presence of andesite fragments in thin section studies. Meanwhile, the zircons that form the secondary age peak at ∼980 Ma and other older age groups probably originate from the Baoshan Block. Deposited on the western side of the Paleo-Tethyan ophiolites, the Wenquan Formation received detrital materials from the continental margin on the opposite side. Thus, the main Paleo-Tethyan Ocean basin was not sufficiently broad enough to cut off the transference of detrital materials. It was a relatively narrow basin in the Early Devonian. [ABSTRACT FROM AUTHOR]

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Background The present contribution reexamines the geometry of a segment of a presumably long-lived fault in Svalbard, the Balliolbreen Fault segment of the Billefjorden Fault Zone, along which presumably two basement terranes of Svalbard accreted in the early–mid Paleozoic after thousands of kilometers strike-slip displacement. Methods We performed structural fieldwork to Billefjorden in central Spitsbergen and interpreted satellite images. Results Field observations demonstrate that the Balliolbreen Fault formed as a top-west thrust fault in the early Cenozoic and that weak sedimentary units such as shales of the Lower Devonian Wood Bay Formation and coals of the uppermost Devonian–Mississippian Billefjorden Group partitioned deformation, resulting in significant contrast in deformation intensity between stratigraphic units. For example, tight early Cenozoic folds are localized in shales of the Wood Bay Formation and contemporaneous top-west brittle–ductile thrusts within coals of the Billefjorden Group, whereas Pennsylvanian deposits of the Hultberget (and/or Ebbadalen?) Formation are simply folded into gentle open folds. Rheological contrasts also resulted in the development of décollements locally, e.g., between tightly folded strata of the Wood Bay Formation and Billefjorden Group and flat-lying, brecciated limestone-dominated strata of the Wordiekammen Formation. Despite the limited quality and continuity of outcrops in the area, the eastward-thickening character (i.e., away from the fault) of Pennsylvanian deposits of the Hultberget, Ebbadalen, and Minkinfjellet formations suggests that the fault did not act as a normal fault in Pennsylvanian times. Conclusions The study suggests that strain partitioning of early Cenozoic Eurekan contraction alone may explain the deformation patterns in Paleozoic rock units in central Spitsbergen, i.e., that Late Devonian Svalbardian contraction is not required, and that a major segment of the Billefjorden Fault Zone formed in the early Cenozoic. The present work illustrates the crucial need for interdisciplinary approaches and composite educational backgrounds in science.

Background The sea spiders (Pycnogonida Latreille, 1810) of the Hunsrück Slate (Lower Devonian, ~400 million years ago) are iconic in their abundance, exquisite pyritic preservation, and in their distinctive body plan compared to extant sea spiders (Pantopoda Gerstäcker, 1863). Consequently, the Hunsrück sea spiders are important in understanding the deep evolutionary history of Pycnogonida, yet they remain poorly characterised, impacting upon attempts to establish a time-calibrated phylogeny of sea spiders. Methods Here, we investigated previously described and new material representing four of the five Hunsrück pycnogonids: Flagellopantopus blocki Poschmann & Dunlop, 2006; Palaeoisopus problematicus Broili, 1928; Palaeopantopus maucheri Broili, 1929; and Pentapantopus vogteli Kühl, Poschmann & Rust, 2013; as well as a few unidentified specimens. Using X-ray microtomography and Reflectance Transformation Imaging, we describe new fossils, provide evidence for newly revealed anatomical features, and interpret these data in comparison to extant species. We also reinterpret the previously published illustration of the (probably lost) holotype of Palaeothea devonica Bergström, Stürmer & Winter, 1980. Results We provide the first detailed description of the cephalic appendages of Palaeoisopus problematicus and revise the interpretation of the organisation of its ocular tubercle. Furthermore, we provide new insights into the structure of the legs and the proboscis of Palaeopantopus maucheri, the first description of the body of Flagellopantopus blocki and describe a new specimen of Pentapantopus vogteli, demonstrating that it had eight legs, in contrast to previous interpretations. We argue that, contrary to previous suggestions, Palaeothea devonica probably had a different body plan from extant pantopods. We discuss the ecological traits of the Hunsrück pycnogonids based on their morphological adaptations, and conclude that there is no compelling evidence of Pantopoda in the Devonian. Through comparative interpretation of the legs as well as general morphology, we can divide the Hunsrück pycnogonids into two morphological groups, while Pantopoda constitutes a third morphological group.

Information about changes to the depositaries for some holotypes of Paleozoic bryozoans from different localities of Russia and Kazakhstan is provided. [ABSTRACT FROM AUTHOR]

The Pashyian Regional stage (horizon) is the main productive unit of the middle Devonian clastic succession of the South Tatar arch. This article presents, for the first time, maps of the lower and upper parts of the Pashyian, including data on sand-shale ratio, number of sand layers (reservoirs) and thickness, based on the analysis of logging data from 25,000 wells. The maps were created by spatial interpolation of Natural Neighbor and ArcGIS Pro software.The model of sedimentation of the Pashyian Regional stage reflects the interpretation of the plotted maps as well as the synthesis of the results of detailed core investigations (lithological, sedimentological, ichnotextural, petrophysical, etc.) and analysis of archive and published materials.The main points of the proposed model are as follows. The Pashyian sediments were formed in a marine basin, in an environment comparable to that of the middle shelf of modern seas – in an offshore zone dominated by current activity. The basin floor was a relatively flat plateau, on which sandy, silty and clay sediments were simultaneously accumulated. Sediments of all types accumulated during sea transgression. Sea regression caused erosion and destruction of the already formed sediments.Positive landforms of seabed relief, composed predominantly of sandy well-sorted material, comprised autochthonous underwater sand bars, formed by constant currents parallel to the bathymetric contour of the seabed. Underwater sand bars formed extensive systems nearly throughout the entire territory of the modern South Tatar arch. At the same time, allochthonous, poorly sorted, less mature sediments were formed in underwater troughs produced by transversal currents (directed from the shore towards the sea).The proposed model explains the consistent thickness of the Pashyian Regional stage, the mosaic distribution of sand bodies over the area, and the lens-like shape of the sand and siltstone reservoirs. The model can be extrapolated to other stratigraphic intervals of the Devonian clastic succession with similar sedimentological features.

This study describes an assemblage of Dzieduszyckia brachiopods preserved in sedimentary barite deposits from the Famennian, Upper Devonian of Nevada, USA. The brachiopods lived in a methane-seep environment like those described from Sonora, Mexico, and the Western Meseta, Morocco. Although the original carbonate fabrics are not preserved, pockets of limestone within the brachiopod barite are depleted in with δ13C values ranging from -31.1 to -27.3‰ VPDB. The fossils are preserved as internal and external molds only but record enough detail to demonstrate key internal features of Dzieduszyckia such as a pronounced dorsal septum, septalium, and vertical dental plates. The lack of common bifurcation or trifurcation of the costae as well as larger size of the shells recommends against inclusion within D. sonora as previously published. Based on the number of costae per width of shell, it is possible that there are two distinct species in Nevada, like other localities in Morocco, the Urals, and South China. These new data expand the body of knowledge of these earliest dimerelloids and it is hypothesized that this seep-dwelling macrofauna arose from depauperate-successful lineages between the Famennian biotic crises. As nearly all global Dzieduszyckia deposits are associated with active tectonic margins, it is also suggested that tectonically-driven methane expulsion in low nutrient waters spurred the evolution of dimerelloids.

The Devonian outcrops of the Azrou-Khenifra Basin are located in the eastern band of the Moroccan Central Massif. They are characterized by a high geodiversity since they show sedimentary, stratigraphic, paleontological, tectonic and geomorphological aspects. Those outcrops allow the understanding of the evolution and geodynamic of the area during the Devonian. This proves their relevant in term of scientific value. In addition, they also have educational and touristic interests. The objectives of this work are making the inventory and quantitative assessment as well as the mapping of nine Devonian geosites. To approach the topic, the method proposed by Brilha (2016) have been used which based on qualitative and quantitative criteria. The results show that the geosite Famennian zebra griottes limestones of Ziyar has the highest scientific value (345) while the others are characterized by scientific, educational and tourist values ranging from moderate to high. Regarding the degradation risk, the geosites have a low value. This work could be considered as the base of any geoconservation strategy and geotourism action plan in the area since it focused on the two first steps of it. This may help improve the sustainable development through the establishment of geopark consequently and enhance economical level of people living the Azrou-Khenifra area.

The iso‐ or diachronous character of a geologic unit is scale‐dependent, especially for time‐specific facies. The Usseln Limestone is a Late Devonian time‐specific facies from Germany, occurring immediately below the Lower Kellwasser black shale. Here, we investigate whether cm‐scale rhythmical bands within the Usseln Limestone are correlatable across its depositional basin. Its facies were studied at three locations ca. 50 km apart, representing different depositional settings. Its cm‐scale alternations in lithological facies and elemental content (μXRF) form an excellent target for correlations on millennial timescales. Correlation attempts failed to converge to a solution at the cm‐scale of individual rhythmites. Dynamic Time Warping, however, provided convincing correlations at the dm‐scale, supporting its use as a high‐resolution correlation tool. The Usseln Limestone base may be diachronous, but the top is likely isochronous. This finding is in agreement with sudden basin‐wide black shale deposition at the onset of the Kellwasser Crisis. Plain Language Summary: A time‐specific facies is a rock unit that can be recognized in different places and always represents the same specific moment in Earth history. Here, we study the Usseln Limestone from the Rhenish Massif in Germany. This time‐specific facies is intruiging, as it is characterized by internal cm‐ and dm‐scale rhythmites. We sampled the Usseln Limestone at three different locations and assessed how consistently individual rhythmites occur across the basin, with approximately 50 km between sites. To do this, we first obtained mm‐resolution geochemical elemental data from all samples. Subsequently, the mathemathical method "Dynamic Time Warping" was applied to attempt correlation. At the cm‐level, our correlation attempt failed. Depositional differences between the three sites were too substantial for precise correlations at the scale of individual rhythmites. However, we successfully made stratigraphic correlations at the decimeter‐scale of the rhythmite bundles. These correlations suggest that while the base of the Usseln Limestone might have formed at different times in different places, the top of this time‐specific facies likely is synchronous throughout the basin. This is important, because the top of the Usseln Limestone aligns with the sudden appearance of a widespread black shale layer, marking the start of a major biotic crisis in Earth history. Key Points: This case study illustrates how the isochronony of a time‐specific facies breaks down at smaller thickness scalesDynamic Time Warping applied to an ensemble of proxies is demonstrated to be a useful high‐resolution correlation toolThe inferred isochronous top of the Usseln Limestone is in line with a rapid onset of Lower Kellwasser black shale deposition [ABSTRACT FROM AUTHOR]

Premise of research. The fossil record shows that seed plants appeared during the Devonian and started to become dominant in the Mississippian. However, the identity of their closest relatives remains uncertain with three candidates: Stenokoleales, Archeopteridalean progymnosperms, and Aneurophytalean progymnosperms. To clarify the relationships of these groups, it is necessary to document as many Devonian-Mississippian taxa as possible and increase taxon sampling in phylogenetic analyses. In this context, Stauroxylon beckii Galtier 1970 from Mississippian deposits of France is particularly interesting because of its similarities with both seed plants and some of their potential closest relatives. Here, we provide an updated description of Stauroxylon and discuss its affinities using morphoanatomical comparisons and phylogenetic analyses. Methodology. The holotype of S. beckii and a new specimen from the same formation are described using thin sections, cellulose acetate peels, and polished surfaces. The morphoanatomy of the specimens is compared with that of early seed plants and their putative relatives. Stauroxylon is also included in phylogenetic analyses of the radiatopses based on Toledo and colleague's matrix. Pivotal results. Stauroxylon beckii possess a cruciform protostele with protoxylem strands at the tips of the ribs, a central protoxylem strand, and produces second- and third-order axes in perpendicular planes. The new specimen differs by characters interpreted as developmental differences or intraspecific plasticity (organotaxis, secondary growth) and is also assigned to S. beckii. Both comparative approaches and phylogenetic analyses place Stauroxylon within the Aneurophytalean progymnosperms, a group previously only known in the Devonian. The inclusion of Stauroxylon strengthens previously established relationships within the radiatopsids. Stauroxylon also displays structural fingerprints important for leaf and pith evolution. Conclusions. Stauroxylon is interpreted as a Mississippian representative of the Aneurophytales. It provides new information on the relationships and morphoanatomical diversity of early seed plants and their closest relatives. [ABSTRACT FROM AUTHOR]

Dispersal, whether active or passive, plays a crucial role in biogeography by facilitating the movement of propagules away from their original location. Botanical geographical zonation, resulting from the co‐evolution of plants and their environment, has been established since the remarkable plant diversification during the Devonian Period (c. 419–359 Ma). However, a significant knowledge gap exists in understanding plant dispersal between living and fossil organisms due to the rarity of opportunities for tracing plant dispersal in geological history. In this study, we present evidence of two plant dispersal routes and verify their occurrence through the examination of geographical zonation, changes in plant diversity, and latitudinal and longitudinal gradients during the Devonian. We analyse global occurrence data from widely‐distributed and extensively‐studied Devonian plants. The two dispersal routes, namely clockwise and anticlockwise, connect the South China and Euramerica–Siberia realms. These routes clearly demonstrate inland and inter‐land dispersal models, closely linked to Devonian sea–land topography and dispersal vectors such as wind and ocean currents. Moreover, these models probably apply to all Devonian plants. Our comprehensive synthesis of plant dispersal in deep time reveals that propagule diversity and dispersal vectors have progressively increased and become more complex over time, facilitating plant colonization and diversity changes. Importantly, our study unveils the dispersal models of fossil plants, demonstrating the equivalent models observed in extant plants that have been established since the Devonian Period. [ABSTRACT FROM AUTHOR]

The late Famennian Sarcheshmeh Member of the Khoshyeilagh Formation contains a sizeable rhynchonellide component comprised of eight genera and ten species, including Golestanirhynchus golestanicus sp. nov. Petasmaria sartenaeri sp. nov. Tilabadirhynchus azadshahrensis gen. et sp. nov. Tilabadirhynchus qeshlaqensis gen. et sp. nov. and Megalopterorhynchus chanakchiensis giganteus subsp. nov. The characters of brachiopod biostratigraphical distribution in the Sarcheshmeh Member and correlation with conodont biozonation suggest that Megalopterorhynchus chanakchiensis giganteus does not cross the lower boundary of the Bispathodus ultimus Zone, while Araratella anatolica is probably confined to it. The pugnacoidean genus Petasmaria is reported for the first time outside of North America. The broad paleobiogeographic affinities of the late Fammenian rhynchonellide assemblages from the Sarcheshmeh Member of the Alborz Region with the contemporaneous brachiopod faunas of Central Iran, Afghanistan and Transcaucasia corroborate the well-established pattern of increasing cosmopolitanism of the brachiopod faunas towards the end of the Devonian Period. [ABSTRACT FROM AUTHOR]

Lithuania is located on the East of Baltic sedimentary basin and has a geothermal anomaly situated in the southwestern region of the country. There are two primary geothermal complexes within the anomaly, composed of Cambrian and Devonian aquifers. The Cambrian formation is composed of sandstones that have a reservoir temperature reaching up to 96 °C (depth > 2000 m). The Devonian aquifer is composed of unconsolidated sands of Parnu–Kemeri and has a reservoir temperature of up to 46 °C (depth > 1000 m). Historically, both formations have been investigated for geothermal energy production. In this article, we present a detailed literature review of the geothermal work carried out on both formations, including past, present, and some possible future studies. The study presented in this paper highlights the key findings of previous research work, summarizes the research gaps, and then elaborates on the possible applications of emerging technologies to bridge the research gaps and improve our understanding of geothermal complexes in Lithuania. Although it is not the main aim of this article, this article also touches upon the important need to develop 2D/3D numerical models, to quantify uncertainties, in the evaluation of the geothermal potential in Lithuania for commercial development. This study also highlights possibilities of extending geothermal development to depleted hydrocarbon reservoirs through repurposing the high-water-production wells. Moreover, from the literature review, it can be concluded that the Lithuanian geothermal aquifers are hyper-saline in nature and temperature changes lead to the deposition of salts both upstream and downstream of the reservoir. Therefore, there is a need for developing multiphysics thermo-mechanical–chemical (THMC) models for evaluation of reservoir behavior. The literature also describes the potential use and development of the THMC model as a part of future work that must be carried out. [ABSTRACT FROM AUTHOR]

The Devonian System in the Qinghai-Tibetan Plateau and its surrounding areas is widely distributed, diverse in lithotypes and rich in fossils. It records the crucial processes of continuous subduction and reduction of the Paleo-Asian Ocean in the northern hemisphere and the transformation of the Proto-Tethys Ocean into the Paleo-Tethys Ocean in the southern hemisphere. Thus, it is of great significance for explaining the global paleogeographic evolution, tectonic activities and biodiversity changes during this critical period. The blocks on both sides of the southern Tienshan suture zone and the Longmu Co-Shuanghu-Changning-Menglian suture zone belong to different sedimentary systems and paleobiogeographic realms and regions, showing important tectonic paleogeographic partitioning significance. The two suture zones represent the main branches of the Paleo-Asian Ocean and the Paleo-Tethys Ocean, respectively, and on this basis the Devonian System can be subdivided into three types: the Tienshan type, the Tethys type and the Gondwana type. Based on recent research progress on the Devonian stratigraphy and paleontology in combining provenance analysis and biotic characteristics in the Qinghai-Tibetan Plateau and surrounding areas, this paper aims to establish the latest integrative stratigraphic framework and conduct paleogeographic reconstruction, providing foundation for exploring the geological evolution and dynamic mechanisms of various terranes and blocks in the northern margin of Gondwana. The results indicate that the North Qiangtang, South Qiangtang, Simao, Baoshan and Tengchong terranes, as well as the Himalaya Tethys Zone and the South China Block have affinities with the Indian Block, while the Lhasa Terrane has affinities with the Australian Block, and may be located between the South China and Australian blocks. In the Emsian (Early Devonian), the South China Block separated from the northern margin of Gondwana, a process that was accompanied by the opening of the Jinshajiang-Ailaoshan Ocean. In the Middle Devonian, the mid-oceanic ridge of the Paleo-Tethys Ocean expanded rapidly, corresponding with a global sea-level rise, the widespread development of carbonate platforms and nadir values of Devonian seawater strontium isotopes. By the Late Devonian, the Paleo-Tethys Ocean had reached a considerable size, leading to abundant occurrences of Upper Devonian radiolarian cherts in the Paleo-Tethys suture zones. [ABSTRACT FROM AUTHOR]

This study provides new constraints on the causes of the chemical and isotopic variability in the central Victorian, Devonian, silicic, magmatic rocks and relates these to crustal architecture in the region. Synthesising present and previous work, it is concluded that the Selwyn Block, which forms the main source region for the Devonian silicic magmas (granitic and silicic volcanic rocks), is heterogeneous in three dimensions, on scales of 1 km and less. The sources of both the I- and S-type magmas were formed in Paleoproterozoic to Mesoproterozoic times, in the distal back-arc region of an Andean-type margin, in a basin that was extending and deepening eastward with time. The prominent rock types are high-grade metamorphosed greywackes, potassic andesites and dacites, with smaller volumes of pelitic rocks. The metasediment-dominated source rocks generally lie at deeper levels and reached higher metamorphic grades than the sources of the I-type magmas. This means that the I-type magmas were generally at lower temperatures and were also more hydrous than the S-type magmas. Heat for the metamorphism and partial melting of the source rocks of the silicic magmas was advected into the crust by mantle-derived magmas. These probably formed an underplate, to drive the regional metamorphism, but numerous, scattered, sill-like mafic bodies caused local contact anatexis and silicic magma production. Along with the emplacement of mafic magma bodies, the ascent of the silicic magmas to the upper crust rendered the deeper parts of the Selwyn Block denser and more mafic. The largely unexposed Selwyn Block, which forms the crustal basement in central Victoria, is heterogeneous in three dimensions, on scales of 1 km and less. The sources of the Devonian I- and S-type silicic magmas here formed in the Paleoproterozoic to Mesoproterozoic distal back-arc of an Andean-type margin. The metasedimentary S-type source rocks lie at deeper levels and reached higher metamorphic grades than the sources of the I-type magmas. Heat for the metamorphism and partial melting was advected by both underplating and numerous sill-like mafic bodies scattered throughout the deep crust. [ABSTRACT FROM AUTHOR]

The first chitinozoan assemblages from the middle–late Silurian and Early Devonian strata of the Copo Formation in the Rivadavia borehole, Salta province, Argentina, are described. The studied interval was considered deposited in an offshore shelf environment and composed of micaceous dark-gray shales with pyrrhotite intercalated with fine-grained quartzitic sandstones. Thirty-nine core samples were processed, and 11 yielded chitinozoan specimens that allowed taxonomic classification. Seven genera and 13 species were identified; four were retained in open nomenclature, and the new species Cingulochitina chacoparanaense sp. nov. is erected. Three chitinozoan assemblages were recognized: Chitinozoan assemblage I of a middle–late Silurian age, Chitinozoan assemblage II of a late Silurian age, and Chitinozoan assemblage III of a late Lochkovian (Early Devonian) age. A new upper Lochkovian chitinozoan concurrent range biozone of Cingulochitina striata and Ancyrochitina asterigis is proposed for northwestern Argentina. The chitinozoan assemblages support Gondwanan affinities from the middle Silurian to Early Devonian of the Chacoparaná Basin. Se han descripto las primeras asociaciones de quitinozoos del Silúrico medio–tardío y Devónico Temprano de la Formación Copo en el pozo Rivadavia, provincia de Salta, Argentina. El intervalo estudiado fue depositado en un ambiente marino de plataforma y está compuesto por lutitas micáceas de color gris oscuro con pirrotina e intercalaciones de areniscas cuarcíticas de grano fino. Se procesaron 39 muestras de testigo corona, de las cuales en 11 se obtuvieron especímenes de quitinozoos que permitieron el estudio taxonómico. Se identificaron siete géneros y 13 especies, cuatro de ellas en nomenclatura abierta y se creó la nueva especie Cingulochitina chacoparanaense sp. nov. Se reconocieron tres asociaciones de quitinozoos: Asociación de quitinozoos I del Silúrico medio–tardío, Asociación de quitinozoos II del Silúrico tardío, Asociación de quitinozoos III del Lochkoviano tardío (Devónico Temprano). Se propone la nueva biozona de quitinozoos, de extensión coincidente, Cingulochitina striata y Ancyrochitina asterigis para el Lochkoviano superior del noroeste argentino. Las asociaciones de quitinozoos sugieren afinidades gondwánicas desde el Silúrico medio al Devónico Temprano para la cuenca Chacoparaná. [ABSTRACT FROM AUTHOR]

Attempts to explain the origin and diversification of vertebrates have commonly invoked the evolution of feeding ecology, contrasting the passive suspension feeding of invertebrate chordates and larval lampreys with active predation in living jawed vertebrates. Of the extinct jawless vertebrates that phylogenetically intercalate these living groups, the feeding apparatus is well-preserved only in the early diverging stem-gnathostome heterostracans. However, its anatomy remains poorly understood. Here, we use X-ray microtomography to characterize the feeding apparatus of the pteraspid heterostracan Rhinopteraspis dunensis (Roemer, 1855). The apparatus is composed of 13 plates arranged approximately bilaterally, most of which articulate from the postoral plate. Our reconstruction shows that the oral plates were capable of rotating around the transverse axis, but likely with limited movement. It also suggests the nasohypophyseal organs opened internally, into the pharynx. The functional morphology of the apparatus in Rhinopteraspis precludes all proposed interpretations of feeding except for suspension/deposit feeding and we interpret the apparatus as having served primarily to moderate the oral gape. This is consistent with evidence that at least some early jawless gnathostomes were suspension feeders and runs contrary to macroecological scenarios that envisage early vertebrate evolution as characterized by a directional trend towards increasingly active food acquisition. [ABSTRACT FROM AUTHOR]

The Devonian outcrops of the Azrou-Khenifra Basin are located in the eastern band of the Moroccan Central Massif. They are characterized by a high geodiversity since they show sedimentary, stratigraphic, paleontological, tectonic and geomorphological aspects. Those outcrops allow the understanding of the evolution and geodynamic of the area during the Devonian. This proves their relevant in term of scientific value. In addition, they also have educational and touristic interests. The objectives of this work are making the inventory and quantitative assessment as well as the mapping of nine Devonian geosites. To approach the topic, the method proposed by Brilha (2016) have been used which based on qualitative and quantitative criteria. The results show that the geosite Famennian zebra griottes limestones of Ziyar has the highest scientific value (345) while the others are characterized by scientific, educational and tourist values ranging from moderate to high. Regarding the degradation risk, the geosites have a low value. This work could be considered as the base of any geoconservation strategy and geotourism action plan in the area since it focused on the two first steps of it. This may help improve the sustainable development through the establishment of geopark consequently and enhance economical level of people living the Azrou-Khenifra area. [ABSTRACT FROM AUTHOR]

Three ichnospecies of Lophoctenium (L. comosum , L. richteri and L. cf. haudimmineri) are reported from the Upper Devonian Argiles de Marhouma Formation (southwestern Algeria) for the first time. This formation contains a diverse assemblage of trace fossils belonging to the Nereites ichnofacies. We describe three ichnospecies of Lophoctenium that correspond to three different feeding strategies among the diverse ichnofauna of the Argiles de Marhouma Formation. The strategy of L. comosum evidences food-rich sediments as it maximises the amount of collected food per foraged distance. The strategy of L. richteri is probably most efficient for feeding in slightly less nutrient rich sediment, but gives the opportunity to discover more prolific feeding sites by moving on longer distances. The strategy with a straight central burrow and probes on both sides of the main burrow with long interspaces (L. cf. haudimmineri) was presumably used in the least food rich sediment. It seems that the Lophoctenium was widespread in the Devonian, but restricted to seas surrounding Gondwana. [ABSTRACT FROM AUTHOR]

The matter of photosymbiosis in Paleozoic corals remains unresolved as it is not possible to directly check for the presence of algal symbionts in fossil corals. However, present-day photosymbiotic corals are characterised by a number of features that can be evaluated in fossil corals as well, such as large, highly integrated colonies, growth banding, and platy growth forms in mesophotic conditions. The present study aims to evaluate these features in heliolitid corals. Heliolitids were relatively highly integrated, compared to other Paleozoic corals and could produce large colonies, over 1 m in diameter. In this study, heliolitid corals from different outcrops from the Silurian (~ 444 to 419 ma) of Gotland (Sweden) were analysed, and additional Devonian (~ 419 to 359 ma) specimens from Belgium, Poland and Morocco, featuring cyclic growth banding, were also included. Overall, over 60% of studied specimens from Lower Visby Formation in Ireviken and over 80% from Eke Formation in Lau Käldu are platy or tabular. Those outcrops represent environments that were mesophotic. Specimens from the shallower Upper Visby Formation in Ygne are dominated by branching forms instead. The apparent light-related skeletal plasticity, high colony integration, growth banding, and the absence of heliolitids in deep water environments implies that some of these corals were most likely photosymbiotic. [ABSTRACT FROM AUTHOR]

This study describes an assemblage of Dzieduszyckia brachiopods preserved in sedimentary barite deposits from the Famennian, Upper Devonian of Nevada, USA. The brachiopods lived in a methane-seep environment like those described from Sonora, Mexico, and the Western Meseta, Morocco. Although the original carbonate fabrics are not preserved, pockets of limestone within the brachiopod barite are depleted in with δ13C values ranging from -31.1 to -27.3‰ VPDB. The fossils are preserved as internal and external molds only but record enough detail to demonstrate key internal features of Dzieduszyckia such as a pronounced dorsal septum, septalium, and vertical dental plates. The lack of common bifurcation or trifurcation of the costae as well as larger size of the shells recommends against inclusion within D. sonora as previously published. Based on the number of costae per width of shell, it is possible that there are two distinct species in Nevada, like other localities in Morocco, the Urals, and South China. These new data expand the body of knowledge of these earliest dimerelloids and it is hypothesized that this seep-dwelling macrofauna arose from depauperate-successful lineages between the Famennian biotic crises. As nearly all global Dzieduszyckia deposits are associated with active tectonic margins, it is also suggested that tectonically-driven methane expulsion in low nutrient waters spurred the evolution of dimerelloids. [ABSTRACT FROM AUTHOR]

The discovery of this group of gymnosperms from the Palaeozoic era is one of the notable achievements of the palaeobotanist and it was of immense value to the palaeobotany & in phylogeny. It includes fernlike plants which were dominant in the Devonian period. They extend into the beginning of the Mesozoic era, later on, there was a mass extinction of the pteridospermales, due to the misconception, that they were initially considered ferns and fern-like plants. Williamson (1897) first considered these plants as an intermediate of the ferns and cycads due to the morphological and anatomical similarity of the organs. H. Potonie (1899) was the first to give their names as the Cycadofilicales. Oliver and Scott (1904) named this group as pteridospermales due to the similarity between the ferns and spermatophytes. In this review article features of the order pteridospermales and their phylogeny have been discussed. [ABSTRACT FROM AUTHOR]

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 distinguished: 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 Pribor borehole was estimated 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 estimate the duration of the magmatic activity of this structure at least 14 m.y. taking into account the isotope dating of the earliest phases of magmatism in the Pripyat–Dnieper–Donetsk Paleorift Structure as 388 ± 12, 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. [ABSTRACT FROM AUTHOR]

Lithology of the Lower Frasnian (Upper Devonian) sections, including the Zhelon Regional Stage and the Saria Beds of the Sargaevo Regional Stage, exposed in the basin of the Saryanka River, the Latvian Saddle, is described. The complete lithological description of the Sargaevo and Semiluki deposits (Frasnian) in the Gralevo quarry of the Vitebsk Region, Orsha Depression is presented. Photographic images of macro- and micro-dimensional remains of heterostracans, placoderms, acanthodians, sarcopterygians, actinopterygians, as well as scolecodonts and conodonts found in the Lower Frasnian deposits are presented. For the first time, the Sr isotope composition was measured in remains of ichthyofauna from the Zhelon and Sargaevo deposits of Belarus. Paleoichthyological and taphonomic data, lithology and Sr isotope composition of ichthyofauna fragments, depositional environments in the Zhelon and Saria times were clarified, and the distant sections were correlated. The 87Sr/86Sr values in ichthyofauna samples from the Saria Beds in sections of the Latvian Saddle (sections of Kalyuty 5a and 6, Virenka 1) and the Orsha Depression (Gralevo quarry) lie within similar ranges: 0.70825–0.70842 and 0.70837–0.70856, respectively. The 87Sr/86Sr values in ichthyofauna from the Zhelon deposits in the Kalyuty 2 and Obukhovo 1 sections (Latvian Saddle) vary within 0.70898–0.70932 and 0.71065–0.71102, respectively. High 87Sr/86Sr values in the fossil ichthyofauna of both regional stages suggest that the Early Frasnian paleobasin was significantly desalinated, while the salinity in the Saria paleobasin was comparable to the salinity of the modern Baltic Sea. [ABSTRACT FROM AUTHOR]

Dolomitization is one of the most substantial diagenetic reactions in carbonate systems, occurring where calcite (CaCO3) is replaced by dolomite (CaMg(CO3)2) under a wide range of crystallization temperatures and fluids. This approach led to investigating and documenting field characteristics related to the petrography and geochemistry of the Devonian carbonates in the Peshawar basin, Pakistan. Two hundred samples were collected from various types of dolomitization and studied their petrographic properties, while the geochemical compositions were examined using XRD and carbon–oxygen isotope analyses. These analyses were conducted to understand the diagenetic processes, the dolomitization, hydrothermal fluids, and their development. Dolomitized bodies are randomly distributed within the host limestone, which can be observed in the field where outcrops extend north east-south west in the study region from Kali Shilman to Bara Fort and have been changed by hydrothermal fluids and magmatic intrusions. This research aims to understand the origin, diagenetic evolution, and sedimentary features of the dolomites that make up the Khyber Limestone Formation and provide pertinent knowledge for comprehending the dolomitization-processes in the alteration of hydrothermal-related Devonian carbonates within the Khyber Limestone. Field relationships, petrographic studies, and geochemical analyses helped us understand the paragenetic history of carbonate rocks and their relationship to igneous intrusions. The phenomenon of fluid-rock interaction has received significant attention because hot fluids (hydrothermal) alter the composition of the host limestone in contact. Field observations indicate the host limestone to have thick, numerous mafic intrusions. In the study area, host limestone is altered into dolomite and marble due to these igneous intrusions (mafic composition). A petrographic study demonstrated host limestone alteration, resulting in digenetic alteration and metamorphism. The formation of marble as a result of contact metamorphism has also been observed to act as a barrier against the host limestone being altered by dolomitizing fluids. Field observations, hand specimen examinations, and thin-section studies show that the altered carbonate rocks are also exceptionally finely to moderately to coarsely crystalline. Five distinct types of dolomite rock textures are identified and classified as “planar” and “non-planar” dolomite based on the distribution of crystal sizes and the shape of the crystal boundaries. Planer dolomite crystals have straight boundaries and are divided into euhedral Dol-III and subhedral Dol-IV textures. In contrast, non-planar dolomite crystals (Dol-I) have arched, lobate, ridged, obscure, or irregular intercrystalline boundaries. Planar-subhedral dolomite has a unimodal mosaic structure and is subhedral to anhedral shape with straight compromise boundaries and numerous crystal-face junctions, while planar-euhedral dolomite (Dol-III) is composed of fine to coarse dolomite crystals with dense hazy rhombs. The bulk mineralogy was ascertained using XRD studies. Mostly dolomite and calcite were present along with other minerals like putoranite (Cu17(Fe,Ni)18S32), mangano calcite (Ca,Mn)CO3, quartz, and copper, which can be formed when magmatic activity occurs, so because of some copper-bearing fluids, they were deposited. The C and O isotopic variations of ancient ocean water demonstrate the effects of various diagenetic processes resulting from magmatic emplacement, hydrothermal fluids’ impact, and the consequent on the dolomitization of the Khyber Limestone. [ABSTRACT FROM AUTHOR]

A styliolinid limestone is described from a trench northwest of Bad Laasphe in the southwestern Wittgenstein Syncline. All limestones from the trench contained conodonts and representatives of other microfaunal groups. These lower Frasnian assemblages fall in an interval ranging from the Upper falsiovalis to the transitans Zone. Origin and genesis of the styliolinid limestone remain unclear. [ABSTRACT FROM AUTHOR]

Two bryozoan species belonging to the Family Semicosciniidae Morozova, 1987 are described from the Middle Devonian of the Eifel—Bigeyina winteri (Bornemann, 1884) and Loculipora alvearis (Maurer, 1885). The two species are endemic to the Middle Devonian (Eifelian–Givetian) of the Eifel. Morphology and taxonomical assignment of the studied bryozoans are discussed. The Family Fenestraporidae Xia, 2002 is considered to be invalid. [ABSTRACT FROM AUTHOR]

Abstract The iso‐ or diachronous character of a geologic unit is scale‐dependent, especially for time‐specific facies. The Usseln Limestone is a Late Devonian time‐specific facies from Germany, occurring immediately below the Lower Kellwasser black shale. Here, we investigate whether cm‐scale rhythmical bands within the Usseln Limestone are correlatable across its depositional basin. Its facies were studied at three locations ca. 50 km apart, representing different depositional settings. Its cm‐scale alternations in lithological facies and elemental content (μXRF) form an excellent target for correlations on millennial timescales. Correlation attempts failed to converge to a solution at the cm‐scale of individual rhythmites. Dynamic Time Warping, however, provided convincing correlations at the dm‐scale, supporting its use as a high‐resolution correlation tool. The Usseln Limestone base may be diachronous, but the top is likely isochronous. This finding is in agreement with sudden basin‐wide black shale deposition at the onset of the Kellwasser Crisis.

Explanations for major catastrophes in the history of life commonly focus on their time-spans. Less biotic crises are worth attention as well, however, which requires their investigation in a longer-lasting context. The present study relates the Taghanic (Givetian) and mid-Carboniferous (Serpukhovian) biotic crises to some long-term changes in their environmental developments. The trends in these developments are interpreted on the basis of changes of the global sea level, the global average temperatures, the total surface area of exposed land, the total number of lithospheric plates, and the concentration of atmospheric oxygen. It is found that the Taghanic and mid-Carboniferous biotic crises can be related directly or indirectly to some long-term environmental changes.

Siliciclastic deposits and dolostones of the Å Ä·ervelis Formation in southwestern Latvia were studied in outcrops, polished slabs, thin sections, and by geochemical methods, including stable isotope analyses. Siliciclastic fluvial deposits alternate with soils and carbonates. As the soil processes became dominant, up to 6 m thick dolocretes formed, but they still preserve remnant sedimentary structures and textures. The strong role of soil processes is indicated by the presence of ooids and pisoids together with fine laminar layers, chert and phosphatic inclusions, rhizoids, and stable isotope values. Peculiar vertical clay-dolomite structures, up to 1.7 m long, are root structures or their combination with Vertisol-like soil development. The extensive development of soil processes and formation of the vertical structures was stimulated by seasonally wet monsoon climate. The scarcity of fossils in the studied deposits does not allow their age to be determined precisely, but probably the thick dolocrete unit in the upper part of the studied succession formed during the end-Devonian glaciation and the period of related sea regression.

A new asterolepidoid antiarch, Sherbonaspis talimaae sp. nov., is described based on the disarticulated skeletal elements from several boreholes in Belarus, from the Lepel Beds of the Vitebsk Formation, which has been assigned to an Early Devonian, late Emsian age. New information is provided on the structure of the paranuchal plate previously unknown in Sherbonaspis. Data on the remains of the other fossil vertebrates, and the characteristics of the fossil-bearing rocks are provided. These data add information on the taxonomic composition of the late Emsian–early Eifelian fish fauna from the western part of the East European Platform. The new cladistic analysis of the Euantiarcha provides results more reliable in comparison with the analysis of all antiarchs together, and supports traditional subdivision of the group into Bothriolepidoidei and Asterolepidoidei. However, further analysis demonstrates unresolved polytomy close to the base of the Asterolepidoidei, and supports the hypothesis that the family Pterichthyodidae is polyphyletic. Until the phylogenetic relationships of Asterolepidoidei are more clearly resolved, Sherbonaspis is attributed to Pterichthyodidae. Comparison of the sections of the Lepel Beds of Belarus with the age-equivalent deposits in Estonia, Lithuania, and Latvia supports a late Emsian or possibly early Eifelian age for the Lepel Beds.

This paper presents a detailed study including LA-ICP-MS zircon U-Pb dating, geochemical, zircon Hf isotope, and whole rock Sr-Nd isotope analysis of magmatic rocks from the Yitong County, Jilin Province, NE China. These data are used to better constrain the Middle Silurian–Middle Devonian tectonic evolution in the eastern segment of the northern margin of the North China Craton (NCC). Zircon U-Pb dating results show that the Ximangzhang tonalite formed in the Late Silurian (425 ± 6 Ma); the basalt, andesite, and metamorphic olivine-bearing basalt in the Fangniugou volcanic rocks formed in the Middle Silurian (428 ± 6.6 Ma) and Middle Devonian (388.4 ± 3.9 Ma, and 384.1 ± 4.9 Ma). The Late Silurian tonalites are characterized by high SiO2 and Na2O and low K2O, MgO, FeOT, and TiO2, with an A/CNK ratio of 0.91–1.00, characteristic of calc-alkaline I-type granite. They are enriched in Rb, Ba, Th, U, and K, and depleted in Nb, Sr, P, and Ti, with positive εNd(t) (+0.35) and εHf(t) (+0.44 to +6.31) values, suggesting that they mainly originated from the partial melting of Meso–Neoproterozoic accretionary lower crustal material (basalt). The Middle Silurian basalts are characterized by low SiO2, P2O5, TiO2, and Na2O and high Al2O3, FeOT, and K2O, enriched in Rb, Ba, Th, U, and K and depleted in Nb, Ta, Sr, P, and Ti, indicative of shoshonitic basalt. The Late Silurian tonalites have positive εNd(t) (+4.91 to +6.18) values and primarily originated from depleted mantle magmas metasomatized by subduction fluids, supplemented by a small amount of subducted sediments and crustal materials. The Middle Devonian volcanic rocks exhibit low SiO2, TiO2, and Na2O and high K2O, and MgO, enriched in Rb, K, and LREEs and depleted in Nb, Ta, Sr, and HREEs, characteristic of shoshonitic volcanic rocks. Their εNd(t) (+2.11 to +3.77) and εHf(t) (+5.90 to +11.73) values are positive. These characteristics indicate that the Middle Devonian volcanic rocks primarily originated from depleted mantle magmas metasomatized by subduction fluids, with the addition of crustal materials or subducted sediments during their formation. Based on regional geological data, it is believed that the study area underwent the following evolutionary stages during the Silurian–Devonian period: (1) active continental margin stage of southward subduction of the Paleo–Asian Ocean (PAO) (443–419 Ma); (2) arc-continent collision stage (419–405 Ma); (3) post-collision extension stage (404–375 Ma); (4) active continental margin stage, with the PAO plate subducting southward once again (375–360 Ma).