ABSTRACT Pteriomorph bivalves constituted an important and diverse group within Silurian–Devonian marine palaeocommunities of southwestern Gondwana. However, their systematic, taphonomic and palaeoecological aspects remain poorly studied. The genus Actinopteria Hall, 1884, exhibits a wide stratigraphic and palaeobiogeographic distribution throughout the Malvinoxhosan Bioregion, ranging from the Ludlow to the early Givetian. This study presents a systematic revision and a taphonomic analysis of Actinopteria from the Lower Devonian of the Paraná Basin, southern Brazil, based on specimens from the Ponta Grossa Formation. Specimens were analysed using detailed shell morphometric parameters, taphonomic signatures, facies analysis and ichnological data. Systematic analysis confirms the diagnostic features of Actinopteria langei Petri, 1967, significantly expanding its known morphological variability. In addition, a new species, Actinopteria grahni sp. nov. is described based on distinctive shell proportions, auricle development and ornamentation patterns. Taphonomic signatures of Actinopteria and associated fauna indicate an allochthonous taphocoenosis resulting from transport and deposited in a transitional offshore setting still influenced by storm waves. Morphofunctional traits, integrated with sedimentological and taphonomic evidence, support the interpretation of an endobyssate mode of life adapted to proximal marine environments. http://urn:lsid:zoobank.org:act:FDC4A26F-5973-478A-B0CC-D4C2A4A8B840

Lower Devonian (ca. 418–407 Ma) volcanic rocks of the Dalhousie Group of the Gander Zone from the northern mainland Appalachians of northern New Brunswick are part of an overstep unit (the Middle Paleozoic Matapedia cover sequence) deposited across the accreted vestiges of the early Paleozoic Iapetus Ocean (proto-Atlantic Ocean). These shallow marine to subaerial mainly bimodal volcanic rocks were deposited in a post-collisional extensional setting. The felsic melts were generated by anhydrous melting of associated basalts in the lower continental crust with melting initiated by heat from rising underplated mafic magma. The ɛ Nd (t) values of rhyolites are positive (+ 3.45 – + 4.7) and similar to those of associated basalts (+3.9 - + 4.2). Likewise, their depleted model mantle ages ranging from ∼610 to ∼770 Ma are similar to those of basalts (∼700–790 Ma) and interpreted to represent enrichment ages associated with ancient Neoproterozoic subduction. The origin of the volcanic rocks of the Dalhousie Group is probably related to post-Salinic relaxation, extension, and breakoff of the Acadian Seaway slab and marks the transition to the Acadian orogenic cycle.

ABSTRACT The terebratulid brachiopod Septotyhys is documented for the first time in the Lower Devonian of the Precordillera basin. The material comes from the uppermost part of the los Espejos Formation (reddish-purple interval) of well constrained early Lochkovian age. This is not only the earliest record of the genus Septothyris but also is one of the oldest records of the Order Terebratulida worldwide. The early Lochkovian brachiopod fauna of the Precordillera developed during the short time interval that mediates between the extinction that decimated the Silurian Afro-South American fauna and the first appearance of the typical Devonian Malvinoxhosan fauna. The brachiopod assemblage containing Septothyris sulcata sp. nov. consists of genera and species that evolved from local Silurian ancestors, as well as taxa introduced in the Precordillera basin from low-latitude temperate oceans. It seems likely that the faunal turnover at the Silurian/Devonian transition was linked to the significant environmental change from a storm-dominated platform to restricted quiet marine waters that took place in the Precordillera basin at that time.

Shale gas, a clean energy source with large reserves and wide distribution, is gaining global attention. The Nanpanjiang Basin, in the southern part of Yangtze Block, is a strategic area for marine shale-gas exploration, with the Tian'e region as a key target. Field investigations and previous studies have confirmed the distribution of Lower Devonian Tangding shale in the Nanpanjiang Basin. This study, using organic geochemistry, X-ray diffraction and scanning electron microscopy, analysed the geochemical characteristics of source rocks, shale reservoir properties, gas content and preservation conditions. The Tangding shale is 100–250 m thick, with burial depths of 2100–4200 m. The total organic carbon (TOC) values of the shales exceed 2.0 wt%, comprising mainly kerogen types Type II 1 –II 2 and high- to over-mature organic matter, indicating excellent source-rock potential. The shales contain a high percentage of brittle minerals, with well-developed pore spaces and adsorption capacities, suggesting a good shale-gas reservoir. A relatively high clay mineral content, along with strong compaction and cementation, enhances the shale's self-sealing capacity, ensuring good preservation conditions for shale gas. The gas content is relatively high, indicating significant shale-gas accumulation. Multi-episode tectonic movements have significantly influenced shale-gas preservation. Compared with typical shale-gas accumulation conditions in other basins, the Tangding shales in the Tian'e area offer favourable conditions for shale-gas accumulation, making the northwestern part of the Tian'e area an important target zone for shale-gas exploration in the Nanpanjiang Basin.

The Lower Devonian Lilydale Limestone (Pragian) contains diverse invertebrate fossil faunas including Ostracoda. This contribution provides a taxonomic reassessment of these previously studied ostracod specimens. Twenty ostracod taxa are redescribed and illustrated Evlanella? sp.; Primitiella? sp.; Paraparchites uniumbonata; Paraparchites? sp.; Beyrichiopsis sp.; Bairdiocypris subtrigonalis; Bairdiocypris cf. subtrigonalis; Bairdiocypris sp. 1; Bairdiocypris sp. 2; Bairdiocypris sp. 3; Bairdiocypris sp. 4; Bairdiocypris? sp. 5; Microcheilinella s.l. lilydalensis; Microcheilinella s.l. semicultrata; Bairdia s.l. flexuosa; Bairdiacypris? halli; Bairdiacypris? sp.; Ampuloides? sp.; Gen. indet. 1; Gen. indet. 2; Gen. indet. 3. The problematic identity of some taxa relates to the internal mould state of preservation for all examined specimens. Tamara T.A. Camilleri* [tamara.camilleri@deakin.edu.au], Deakin University, School of Life and Environmental Sciences (Melbourne Campus), Victoria 3125, Australia. Museums Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia; Elizabeth A. Weldon [l.weldon@deakin.edu.au], Deakin University, School of Life and Environmental Sciences (Melbourne Campus), Victoria 3125, Australia. Museums Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia; Mark T. Warne [mark.warne@deakin.edu.au], Deakin University, School of Life and Environmental Sciences (Melbourne Campus), Victoria 3125, Australia. Museums Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia; Rolf Schmidt [RSchmid@museum.vic.gov.au], Museums Victoria, GPO Box 666, Melbourne, Victoria 3001, Australia.

In the Neufchâteau–Eifel Synclinorium (southern Belgium), remnants of the spoil heap of the disused and now flooded underground Sainte-Barbe Quarry (Warmifontaine) yielded an invertebrate Pragian assemblage occurring in the dark monotonous slates of the La Roche Formation (Martelange Member). This locality is considered as a new Belgian Konservat-Lagerstätte (fossil conservation deposit) due to the presence of both biomineralised and soft-bodied organisms. Two specimens from the Sainte-Barbe Quarry Biota are described and assigned to two distinct classes of extinct echinoderms. The first one corresponds to an almost complete, flattened and distorted dendrocystitid solutan, which is tentatively identified as Dehmicystis? sp., based on similarities with D. globulus from the Hunsrück Slate (Emsian) of Germany. The second echinoderm specimen is a well-preserved, flattened, fully articulated and almost complete mitrate stylophoran, morphologically close to Mitrocystites? styloideus-like peltocystidans from the Lower and Middle Devonian of Germany. Taphonomic attributes of the two echinoderms from Warmifontaine (e.g. both fully articulated; mitrate with its aulacophore preserved in feeding position) suggest they were probably killed and entombed by obrution deposits in an otherwise quiet and deep setting. Other echinoderms (asteroids, crinoids, blastoids, cyclocystoids, ophiuroids) reported from the Lower Devonian of Belgium are also briefly discussed and illustrated (e.g. holotypes).

Two Devonian asteropygine trilobite specimens exhibiting rare cases of encrustation are recorded. An almost fully articulated exoskeleton of Rhenops australocustos from the lower Emsian in Luxembourg carries hederelloid colonies on its cephalon and thorax. The colonies are interpreted to have attached syn vivo (i.e. to the living trilobite) and the relation with their host was likely commensal. A cephalon of Philonyx philonyx from the upper Emsian in Germany exhibits five putative morphotype encrusters identified as hederelloids, auloporid corals, cornulitids, bryozoans and foraminifers. This is the first documented evidence of a foraminifer on a trilobite host. This cephalon is either a moult or a carcass.

Research subject. The material composition, formation conditions, and age of amphibolites of the Central zone of metamorphism (CZM) of the Rai-Iz massif. Materials and methods. Microprobe studies of minerals were conducted using a Cameca-SX100 microanalyzer; the content of petrogenic elements was determined by an X-ray multichannel spectrometer CPM-35; the REE content was determined by a mass spectrometer with inductively coupled plasma NexION 300S in the Collective Use Center “Geoanalitik”, Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences. 40 Ar/ 39 Ar dating was carried out at the Institute of Geology and Mineralogy of the Siberian Branch of the Russian Academy of Sciences according to A.V. Travin’s method. Results. The petrography and geochemistry of the amphibolites of the CZM Rai-Iz massif were studied; the parameters of their metamorphism were established, and the age of 40 Ar/ 39 Ar was determined. Two types of amphibolites were identified: garnet amphibolites, epidote-garnet amphibolites, and clinopyroxene-amphibole and amphibole-phlogopite-garnet rocks. The main minerals were found to be amphibole and garnet. Amphibole corresponds to edenite, pargasite, and ferropargasite. In some amphibole samples, chemical zonation was established, manifested in the depletion of the marginal parts of Al 2 O 3 and FeO grains relative to the central ones, while the MgO content increased from the center to the edge. Garnets from garnet and epidote-garnet amphibolites exhibited an almandine-grossular composition with pyrope (3–16 %) and spessartine (3–13 %) components; in amphibole-phlogopite-garnet rocks, garnet demonstrated an almandine–pyrope composition. In the pomegranate, the following chemical zonation was established: the FeO content increases from the center to the edge of the grains, while the MnO content decreases. The age of amphibolites determined by the 40 Ar/ 39 Ar method (405.2 ± 5.4 Ma) corresponds to the Lower Devonian. The averaged formation parameters of amphibole-bearing rocks correspond to P = 6–13 kbar, T = 430–860° C, and to the boundary of amphibolite and greenschist facies and the boundary of amphibolite and granulite facies. REE spectra in the studied rocks, normalized relative to chondrite, showed the predominance of heavy lanthanides over light ones. The character of REE distribution is close to N-MORB basalts. Conclusion. The studied rocks formed at the boundary of the early and middle Devonian. Their formation was associated with regional metamorphism in the conditions of the onset of collision.

New taxa of spiriferids of the subfamily Howellellinae are described from the Lower Devonian deposits of North-East Eurasia: Howellella (Howellella) septentrionalis Baranov and Nikolaev, sp. nov. H. (Howellella) nelyudimica Baranov and Nikolaev, sp. nov., and the subfamily Callispiriferinae Johnson, 1994—Dubatolovispirifer Baranov and Nikolaev, gen. nov. with the type species D. ribbed Nikolaev et Baranov, sp. nov.

Lower Devonian crinoid pluricolumnals from Morocco are severely infested by sclerobionts: Evidence for a parasitic outbreak on the shelf of northern Gondwana

New palynological data and paleoenvironmental implications for the Lower Devonian and Lower Cretaceous successions in the Rio do Peixe Basin, Brazil: Sedimentary organic matter analyses

ABSTRACT Antarctaspids, a basal subgroup within the Arthrodira, display a mosaic of arthrodire and petalichthyid features. However, their morphology has remained poorly understood due to the paucity of well-preserved specimens. Here, we describe a new antarctaspid arthrodire, Panjiangosteus eurycephala gen. et sp. nov., from the Posongchong Formation (Pragian, Lower Devonian) of Wenshan Prefecture, Yunnan, China. Using X-ray computed tomography, we reveal previously undocumented anatomical details of antarctaspids, including the neck joint and the dorsal surface of the neurocranium. In addition to diagnostic antarctaspid characters, Panjiangosteus also exhibits some features characteristic of more derived arthrodires, notably the convergence of middle and posterior pit-lines onto the central plate and the subdivision of the posterior pit-line into two discrete segments. Crucially, Panjiangosteus is characterized by its broad skull roof and the vertical sliding neck joints reminiscent of petalichthyids. Phylogenetic analysis recovered antarctaspids as a paraphyletic grade at the base of Arthrodira, with Panjiangosteus placed more derived than the other antarctaspids. These findings refine our knowledge of antarctaspid cranial morphology, shed new light on character transitions in early arthrodire evolution, and support a close relationship between petalichthyids and arthrodires.https://zoobank.org/urn:lsid:zoobank.org:pub:F07656F3-1537-48DD-8133-D67B44B9FE31

The Posongchong Flora is an important window for understanding early vascular plant evolution. During a recent investigation of the Feigucun Section in the Bainiuchang area, Southeastern Yunnan, the author’s team discovered a large number of plant fossils from the Posongchong Formation of the Pragian Stage, Lower Devonian Series. Among the fossils collected in this investigation, there are six morphologically distinct drepanophycalean fossils, characterized by irregular dichotomous branching forming clustered stems, with the surface of the stems densely covered with spirally arranged falcate leaves. After comparing with coeval plant fossil records, it was found that the above characteristics are consistent with the generic characteristics of Hueberia fossils found in the Posongchong flora, indicating that these specimens should be assigned to the genus Hueberia. The team compared the newly discovered Hueberia fossils with the previously described Hueberia zhichangensis. The comparison revealed that the Hueberia specimens collected in the Bainiuchang area have thicker stems, longer intervals between successive branchings, and certain differences in leaf morphology from Hueberia zhichangensis. Therefore, the team considers that there are significant differences between it and Hueberia zhichangensis in morphology, geographical distribution, and other aspects, and there is sufficient reason to erect a new species, Hueberia bainiuchangensis sp. nov. The discovery of this species enriches our understanding of the species diversity of the genus Hueberia, expands the geographical distribution range of the Posongchong Flora, further corroborates that the Southeastern Yunnan region had extremely high biodiversity during the Pragian Age of the Early Devonian, and provides new clues for the study of Early Devonian plant evolution.

Symbiotic (mutualistic) relationships are hypothesized for species of the tabulate coral genus Cladochonus McCoy, 1847 associated with trepostome and cryptostome bryozoans in the Devonian. The species Cladochonus isaacmariai n. sp. from the Birdsong Shale (Lower Devonian, middle Lochkovian) of Tennessee, USA, was an obligatory symbiont of the trepostome bryozoan Nakremella symbiotica n. gen. n. sp. Cladochonus sp. A and Cladochonus sp. B from the Givetian (Middle Devonian) of Sauerland, Germany, are intergrown with the cryptostome species Intrapora variabilis Ernst, 2008. This interrelation is interpreted to be obligatory for the coral and facultative for the bryozoan. The coral symbionts benefitted from the bryozoans due to the enhanced mechanical stabilisation and enhanced feeding, while the bryozoans benefitted from the provision of a substrate, access to the higher tiering (arborescent growth), and receiving protection from the corals.

Impact of Depositional Facies and Diagenetic Alterations on Reservoir Quality Tidal Sandstones: Insights from the Lower Devonian Tadrart Formation, the Central Ghadamis Basin, NW Libya

New eurypterids from the Lower Devonian Nagaoling Formation of Guangxi, South China

The Tungurahua Volcano Geopark (GVT), is located in the center of the Ecuadorian Andes, and comprises an area of 2,397 km2 . The name-giving Tungurahua Volcano, which is one of the most active volcanoes in Ecuador, is only one of many other volcanic complexes to be part of the GVT. All these volcanic edifices are the result of the subduction of the oceanic Nazca plate below the South American continental plate, along the active continental margin. A novel sustainability model of geoparks has been applied to the GVT, of which methods consisted of revising secondary information from documents and interviews with experts and primary data collected and validated during field trips performed in two stages, where twenty Geosites were defined. Furthermore, we structured a scientific committee of seven Universities, two NGOs and other stakeholders. Additional elements of our management and assessment included to describe the evolutionary history of this particular area since the Lower Devonian, and, to elaborate a monitoring and conservation plan that includes the placement of signage, interpretive scripts and tourist mapping. The key has been the joint work and strategic alliances based on local development axes such as geoeducation, geoconservation and geotourism focused on the Sustainable Development Goals. To present a novel sustainability model for geoparks, applied in a case study in Ecuador. Review of information and guide questionnaires that directed the interviews with experts of other geoparks. Validation of obtained data in the field. Inventories of sites where geotourism were performed. A novel sustainability model of geoparks has been applied by the described methods. A scientific committee was structured. A description of the evolutionary history of the study area is given. A monitoring and conservation plan was elaborated and presented. We reached a joint work, focused on the SDG´s. Generation of economic income, creation of strategic alliances and protection of the given heritage; Networking with Global Geoparks; recognition and conservation of geological heritage within the SDG´s. Especially the consolidation of global collaboration networks, the professionalization of staff, and the acquisition of sustainable resources are aspirations that, for the present times, may not allow to be achieved in the short or medium term due to budgetary and management constraints.

Horizontal wells combined with multi-stage hydraulic fracturing represent the most effective approach for extracting resources from tight reservoirs. Hydraulic fracturing involves injecting formulated fluids at high pressure to fracture the formation, thereby enhancing permeability and facilitating hydrocarbon flow. Proppant is introduced to maintain the flow pathways open. In horizontal wells, performing multiple fracturing stages is critical to achieve economically viable production. However, unforeseen challenges can arise, leading to suboptimal outcomes. This case study explores a hydraulic fracturing project of a tight reservoir in Algeria, located at a depth exceeding 4,200 m, with formation pressure around 7,000 psi and temperature reaching 150 °C. In 2018, significant challenges were encountered during fracture initiation in three horizontal wells. Extremely high breakdown pressures, combined with severe wellbore damage, resulted in only one stage being successfully completed following heavy intervention efforts. This study details the encountered challenges, their root causes, and the taken remediation actions, highlighting the importance of 1D geomechanical model to optimize fracture placement. It illustrates how real-time analysis of multiple injection tests guided decisions on using innovative perforation techniques and specific acid stimulation treatments. This study underscores the uniqueness of each tight reservoir, requiring specific design from well orientation selection to hydraulic fracturing execution. The combination of stress complexities, high pressure and temperature conditions, drilling orientation and wellbore damage was analysed to improve the reservoir characterization. These insights help mitigate risks and enhance the success rates of hydraulic fracturing in this reservoirs, emphasizing the need for tailored approaches in such projects.

ABSTRACT The facies and ichnofacies of the ‘Siliciclastiques de l’Oued Koufane’ Formation (Emsian) in the Ben Zireg basin (SW, Algeria) indicate a distal position of shallow marine infilling (lower Member) represented by mud-dominated facies fed by episodic distal tempestites. The sand-rich episodes are bioturbated by the trace fossils related to the Cruziana ichnofacies after each storm event. The presence of Chondrites-Zoophycos ichnoassemblage as in Jaidet Formation of the Moroccan Jebilet suggests a narrow environmental resemblance (in the lower Member) but differentiation seems to operate when the Ben Zireg area evolved to regressive tidal rhythmites (upper Member). Thus, directly to the north of Ben Zireg, the hypothetical emerged ‘ridge’ (Western Saharan Atlas, Algeria) could exist in continuity to the Moroccan Tamlelt ridge in the western zone. This ridge must be narrow because the Tiffrit area localised northward developed a deep-sea fan system as a result of the Gondwanian slope on the eastern side of the Rheic Ocean.

A new trackway produced by crawling fishes, which includes imprints of the trunk, snout, tail, body drag traces, and pectoral fins, was discovered in the Lower Devonian (middle-upper Emsian) marginal marine deposits in the Holy Cross Mountains, Poland. The snout imprints are represented by a low-angle variant of the already described Osculichnus tarnowskae, which has generally been interpreted as a hunting trace of fishes. However, in this case, it is considered an imprint of a fish's snout, used for anchoring in the sediment during the locomotion of at least partially emerged fish. This compound trackway provides the first evidence of the previously unknown life behaviour and locomotion abilities of dipnoan fishes in the early stage of their evolution and documents a testing land mobility skills of vertebrates, predating by about 10million years fully terrestrial tetrapods locomotion traces. Similar trackways are produced by extant lungfish during terrestrial locomotion. The trackway co-occurs with a new resting trace produced by a dipnoan fish supporting itself with one or two pairs of fins on the bottom.