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Apatite is a ubiquitous accessory mineral found in most magmatic rocks and is often the only U-bearing mineral available to date mafic rocks because primary zircon and/or baddeleyite are not present. In this paper, U-Pb LA-ICP-MS dating of apatite was applied to seven different dike and sill samples of dolerite from the Variscan belt of Brittany (Armorican Massif, western France). These dolerites, which are characterized by a within-plate tholeiite geochemical signature, are organized in several dense swarms across the belt. Their geochemical compositions are homogeneous although they intrude a large geographical area subdivided into several domains each characterized by different tectonic-metamorphic settings. Their emplacement ages were so far poorly constrained due to the difficulty to date these mafic rocks using either the 40Ar/39Ar or the U-Pb methods on classical minerals like mica, plagioclase, or zircon. Although the closure temperature of apatite is lower than the emplacement temperature of the magma, physical models show that the time needed to solidify and cool these mafic dikes and sills below the apatite closure temperature is basically of the order of 100 years or less. Consequently, the U-Pb dates obtained on apatite can be interpreted as the emplacement ages for these mafic intrusions. Our results demonstrate that, in all cases, the apatite grains do carry enough radiogenic Pb to be dated by in situ U-Pb analyses and yield a 207Pb-corrected mean age of 363.4 ± 5.8 Ma. These results reveal the existence of a major and short-lived magmatic event in the Variscan belt of Brittany during the Devonian-Carboniferous transition, a feature further highlighted by field evidence. Beyond the geological implications of these results, U-Pb LA-ICP-MS dating of apatite appears to represent an ideal tool to date small size mafic intrusions.

A half-century has passed since the dawning of the plate tectonic revolution, and yet, with rare exception, palaeogeographic models of pre-Jurassic time are still constructed in a way more akin to Wegener's paradigm of continental drift. Historically, this was due to a series of problems – the near-complete absence of in situ oceanic lithosphere older than 200 Ma, a fragmentary history of the latitudinal drift of continents, unconstrained longitudes, unsettled geodynamic concepts and a lack of efficient plate modelling tools – which together precluded the construction of plate tectonic models. But over the course of the last five decades strategies have been developed to overcome these problems, and the first plate model for pre-Jurassic time was presented in 2002. Following on that pioneering work, but with a number of significant improvements (most notably longitude control), we here provide a recipe for the construction of full-plate models (including oceanic lithosphere) for pre-Jurassic time. In brief, our workflow begins with the erection of a traditional (or ‘Wegenerian’) continental rotation model, but then employs basic plate tectonic principles and continental geology to enable reconstruction of former plate boundaries, and thus the resurrection of lost oceanic lithosphere. Full-plate models can yield a range of testable predictions that can be used to critically evaluate them, but also novel information regarding long-term processes that we have few (or no) alternative means of investigating, thus providing exceptionally fertile ground for new exploration and discovery.

Constructing palaeogeographical maps is best achieved through the integration of data from hotspotting (since the Cretaceous), palaeomagnetism (including ocean-floor magnetic anomalies since the Jurassic), and the analysis of fossils and identification of their faunal and floral provinces; as well as a host of other geological information, not least the characters of the rocks themselves. Recently developed techniques now also allow us to determine more objectively the palaeolongitude of continents from the time of Pangaea onwards, which palaeomagnetism alone does not reveal. This together with new methods to estimate true polar wander have led to hybrid mantle plate motion frames that demonstrate that TUZO and JASON, two antipodal thermochemical piles in the deep mantle, have been stable for at least 300 Ma, and where deep plumes sourcing large igneous provinces and kimberlites are mostly derived from their margins. This remarkable observation has led to the plume generation zone reconstruction method which exploits the fundamental link between surface and deep mantle processes to allow determination of palaeolongitudes, unlocking a way forward in modelling absolute plate motions prior to the assembly of Pangaea. The plume generation zone method is a novel way to derive ‘absolute’ plate motions in a mantle reference frame before Pangaea, but the technique assumes that the margins of TUZO and JASON did not move much and that Earth was a degree-2 planet, as today.

The Ordovician to Middle Devonian Prague Basin, Bohemian Massif, represents the shallowest crust of the Variscan orogen corresponding to c. 1–4 km palaeodepth. The basin was inverted and multiply deformed during the Late Devonian to early Carboniferous Variscan orogeny, and its structural inventory provides an intriguing record of complex geodynamic processes that led to growth and collapse of a Tibetan-type orogenic plateau. The northeastern part of the Prague Basin is a simple syncline cross-cut by reverse/thrust faults and represents a doubly vergent compressional fan accommodating c. 10–19 % ~NW–SE shortening, only minor syncline axis-parallel extension and significant crustal thickening. The compressional structures were locally overprinted by vertical shortening, kinematically compatible with ductile normal shear zones that exhumed deep crust in the orogen's interior at c. 346–337 Ma. On a larger scale, the deformation history of the Prague Syncline is consistent with building significant palaeoelevation during Variscan plate convergence. Based on a synthesis of finite deformation parameters observed across the upper crust in the centre of the Bohemian Massif, we argue for a differentiated within-plateau palaeotopography consisting of domains of local thickening alternating with topographic depressions over lateral extrusion zones. The plateau growth, involving such complex three-dimensional internal deformations, was terminated by its collapse driven by multiple interlinked processes including gravity, voluminous magma emplacement and thermal softening in the hinterland, and far-field plate-boundary forces resulting from the relative dextral motion of Gondwana and Laurussia.

Fossil plant localities are potential geosites, but related information is limited for some paleofloristic domains. Four geosites representing Visean (Mississippian, Carboniferous) plant-bearing deposits are reported from two areas of the Moscow Basin (central eastern Laurussia). These are the Mountainous Msta area in the northwestern segment of this basin and the Tula Region in its southern segment. The localities were examined in the field and characterized with criteria related to geoheritage properties (e.g., geoheritage types, physical view, accessibility, vulnerability, and research importance). One of these localities has already been established as a geosite (official status of protected area) and three other localities are proposed as geosites in this work (two of them are situated in the planned protected area). It is established that all considered geosites represent notable assemblages of Visean plants, with some exhibiting unique preservation and interesting sedimentary features, such as the “Tula pipes”. Essentially, the localities are small natural outcrops and abandoned quarries with perfect accessibility. They have potential for future research projects, as well as for geological education and tourism. Presently, their vulnerability is only potential, but it can increase due to touristic exploitation in the nearest future; thus, this property requires special attention. More generally, these geosites are important sources of the knowledge of the Early Carboniferous equatorial vegetation in eastern Laurussia.

The complicated nomenclatural history of the extinct genus Cyclostigma Haught., established for arborescent trunks of presumably ancient isoetopsids (Isoetophyta: Cyclostigmatales), is reviewed and corrected with newly found bibliographic and historical data. The fossil name Cyclostigma , an illegitimate later homonym of two extant angiosperm genera, Cyclostigma Hochst. ex Endl. (Apocynaceae) nec Cyclostigma Klotzsch (Euphorbiaceae), was recently conserved and listed in App. III of ICN since the XVIII IBC in 2011. The fossil generic name Cyclostigma , associated with three species epithets and a distinct fossil family name Cyclostigmataceae (\"Cyclostigmeae\"), was invalidly published by Haughton in his series of works of 1859 and 1860 (reprinted several times), the genus lacking a description. Haughton's family name based on his \"Cyclostigma\" and the species published in this genus were also not validly published. However, the generic name Cyclostigma was validly published in a little-known publication by Haughton in 1859, not by Heer in 1871, as generally accepted in modern systematic palaeobotany, or Baily in 1861. In course of thorough nomenclatural analysis it has been shown that three fossil species names, which fell into oblivion still in the early works in the 19th century, Sigillaria dichotoma Haught. 1855, Lepidodendron griffithii Brongn. 1857 and L. minutum Haught. 1855 (non Sauveur) have priority over Cyclostigma kiltorkense Haught. 1859. Since C. kiltorkense has entered solidly into systematic palaeobotany and served as an index marker in historical geology, its retention through conservation is proposed. The nomenclature of the name Cyclostigmataceae is corrected as to be first validly published by Haughton in 1860.

The complicated nomenclatural history of the extinct fossil-genera Acitheca and Strephopteris (fertile foliage) and Polymorphopteris (sterile foliage), established for fossil ferns (Marattiopsida), is reviewed and corrected with new bibliographic and historical data. Strephopteris as a generic name established for fertile foliage of Acitheca-type has priority, but due to the long and widespread use of Acitheca it was recently proposed to reject it in favour of the established name Acitheca. Since Acitheca as a fossil-genus was established for distinctive fertile foliage, but its currently accepted type, A. polymorpha (≡ Pecopteris polymorpha), was founded on sterile foliage, it is proposed to reject this type and return to the earlier concept of Sterzel who thought that Acitheca was typified by the fossil-species Scolecopteris conspicua, based on fertile foliage. This procedure requires official conservation of the type. Correction of the type allows continuing the current use of another fossil-genus, Polymorphopteris, which was inadvertently validated on the same type as Acitheca. The legitimization of the fossil-genus Polymorphopteris, based on sterile foliage only, will stabilize the current established systematics of fossil marattiopsid remains, for which no fertile organs are known. Since Scolecopteris conspicua, when established as a fertile counterpart of sterile foliage known as Pecopteris polymorpha, originally included two unrelated archetypes of fertile foliage, known as compressions and petrifactions, the typification of the fossil-species by fossil specimens known as compressions allows continued use of Acitheca as a distinct fossil-genus for fertile foliage as compressions. The petrifactions formerly attributed to A. polymorpha from younger sediments (Lower Permian) of France are re-considered as a distinct fossilspecies, Scolecopteris renaultii sp. nov. The formerly not validly published fossil-genus Bifariusotheca for Acitheca-like fossils from the Permian of China is validated. Kamatheca is validated for the aberrant Angaridan fossil-species, Acitheca gigantea. Nine not validly published fossil-species of Polymorphopteris are validated to follow modern circumscription of the fossil-genus: Polymorphopteris cistii comb. nov., P. gothanii comb. nov., P. integra comb. nov., P. magdalenae sp. nov., P. multifurcata comb. nov., P. oblongifolia comb. nov., P. pseudobucklandii comb. nov., P. pseudointegra comb. nov., and P. wagneri sp. nov. Callipteridium subelegans and Scolecopteris conspicua are neotypified; Acitheca isomorpha and Pecopteris cistii are lectotypified. As an addition to Taxonomic literature II records, the precise dates of publication of the taxonomic works of Germar's Versteinerungen (1844–1853) and Schimper & Schenk's Palaeophytologie (1879–1890) are established for the first time.

The Pulo do Lobo Zone, which crops out immediately north of the allochthonous South Portuguese Zone in southern Iberia, is classically interpreted as a polydeformed accretionary complex developed along the southern margin of the Gondwanan parautochthon (Ossa-Morena Zone), during the late Palaeozoic closure of the Rheic Ocean. This closure was a major event during the amalgamation of Pangaea. U-Pb laser ablation inductively coupled mass spectrometry dating of detrital zircons from late Palaeozoic Devono-Carboniferous clastic units in the South Portuguese Zone and Pulo do Lobo Zone yield contrasting age populations and attest to the exotic nature of both zones. Detrital zircons from the South Portuguese Zone display populations typical of detritus derived from either Gondwana (Ossa-Morena Zone), or peri-Gondwanan terranes. In contrast, rocks from the Pulo do Lobo Zone contain populations consistent with derivation from Baltica, Laurentia or recycled early Silurian deposits along the Laurentian margin. An example of one such deposit is the Southern Uplands terrane of the British Caledonides. Taken together, these data can be reconciled by a model involving tectonic transport of a crustal fragment that was laterally equivalent to the Southern Uplands terrane between the allochthonous South Portuguese Zone and Gondwana as a result of an early Devonian collision between an Iberian indenter with Laurussia.

In this paper we formulate answers to three important questions related to Givetian carbonate records and their use for reconstructing million-year-scale past palaeoenvironmental changes. First, we provide detailed illustrations of the fascinating diversity that shaped a significant shallow reefal platform during early to late Givetian time in the Rhenohercynian Ocean; secondly we improve the sedimentological model of the extensive Givetian carbonate platform in the Dinant Basin; and thirdly we evaluate the application of magnetic susceptibility as a tool for long-term trend correlations and palaeoenvironmental reconstructions. These goals are reached by making a sedimentological, geophysical and geochemical study of the La Thure section. Through the early–late Givetian interval we discerned 18 microfacies ranging from a homoclinal ramp to a discontinuously rimmed shelf and then a drowning shelf. The comparison of these sedimentological results with those published for the south of the Dinant Syncline allowed us to provide an up to date model of the vertical and lateral environmental development of one of the largest Givetian carbonate platforms in Europe. This comparison also increased the knowledge on the distribution of facies belts in the Dinant Basin and allowed us to highlight the Taghanic Event. Palaeoredox proxies reveal a substantial change in the oxygenation level, from oxygen-depleted to more oxic conditions, between middle and late Givetian time. We demonstrated the relationship between variation in magnetic susceptibility values and proxies for siliciclastic input (such as Si, Al). The La Thure section is considered a key section for the understanding of internal shelf settings bordering Laurussia's southeastern margin.

It is usually considered that after the extinction of the Devonian tree Archaeopteris, no new arborescent lignophytes were established before the late Tournaisian. A reassessment of this pattern is presented here based on a three-fold approach: a re-evaluation of the taxic diversity of Tournaisian lignophyte trees based on descriptions of new plants from palaeotropical latitudes, a study of the patterns of phenotypic changes occurring among early lignophytes using a principal coordinate analysis and a phylogenetic analysis of the affinities of the arborescent taxa. The best supported results indicate that a substantial taxonomic and phenotypic diversity of arborescent lignophytes was already established in the first part of the Tournaisian, including some taxa that persisted until the Serpukhovian. Two genera may have originated in the Late Devonian and crossed the Devonian-Carboniferous boundary. Fewer originations and a decrease in phenotypic diversity occurred in the Viséan. The phenotypic distinctiveness of tree stems compared with those of other growth forms in the lignophytes is assessed. We propose a scenario in which the presence of lignophyte trees is continuous across the Devonian-Carboniferous boundary, with arborescent taxa distinct from Archaeopteris already present in the latest Devonian, possibly in upland floras, and diversifying significantly soon after the Devonian-Carboniferous boundary.