The (Basal) Choteč Event, first recognised in the 1980s in Czechia, is a globally widespread anoxic pulse associated with transgression and eutrophication just above the Emsian-Eifelian (Early-Middle Devonian) boundary (cycle 1c of the Johnson et al. [1985] Devonian eustatic sea-level curve). Despite being one of several anoxia-driven faunal turnovers during the Devonian, the Choteč Event remains poorly understood. The global reach, intensity, and duration of anoxia is not constrained and nor is it clear whether eutrophication had its “roots” in contemporary floral developments on land (as suggested for younger Devonian anoxic events).We present a geochemical (carbon isotopes; trace metals as proxies for redox and productivity; and major elements for the Chemical Index of Alteration [CIA] as a weathering proxy) and palynological study of the Cabonera section (León, Spain). This succession is part of an extensive Devonian sequence developed around isolated islands in the Armorican Terrane Assemblage that was located between the supercontinents Laurussia and Gondwana. Here, limestones of the Emsian-Eifelian Santa Lucia Formation are abruptly overlain by siltstones and shales belonging to the Eifelian Huergas Formation. This conodont- and brachiopod-constrained manifestation of the Choteč Event sees the onset of a gradual 4‰ negative δ13Ccarb excursion (CIE) consistent with records in other regions. The lower part of the Huergas Formation (Cabornera Bed) records a brief interval of anoxia (low Th/U, elevated V/Al and U/Al) at the same level that sees the onset of the negative CIE. This appears to have been accompanied by, or was perhaps driven by, greatly enhanced primary productivity, with enrichment factors (EFs) of Ba, and particularly Ni, Zn and P, all >>1. This brief burst of productivity and anoxia soon ended, with EFs falling

The end-Permian mass extinction (EPME) is the largest extinction event of the Phanerozoic, but the specific causal pathways, especially in the terrestrial realm, are unresolved. Malformed pollen and spores recovered from the EPME interval have been taken as indicators of extreme environmental stress in terrestrial ecosystems. However, whether they relate to volcanism-driven ozone-layer deterioration and enhanced ultraviolet-B (UV-B) flux, or volcanogenic toxic pollutants including mercury and acid rain, or some combination of the two, remains unclear. Here, we take advantage of a novel palynological proxy, which utilises the ability of land plants to adjust the concentration of protective UV-B-absorbing compounds (UACs) in the outer wall of their reproductive propagules in response to changes in ambient UV-B flux. We analysed UAC abundances in ca. 800 pollen grains from an independently-dated Permian-Triassic boundary section in southern Tibet, in order to infer changes in UV-B-radiation flux at the Earth’s surface during the EPME. Our data reveal an excursion in UACs that coincides with a spike in mercury concentration and a negative carbon-isotope excursion in the latest Permian deposits, suggesting a close temporal link between large-scale volcanic eruptions, global carbon- and mercury-cycle perturbations, and ozone-layer disruption. Because enhanced UV-B radiation can exacerbate the environmental deterioration induced by massive magmatism, ozone depletion is considered a compelling ecological driver for the terrestrial mass extinction.

The Late Devonian Mass Extinction is the least understood of the ‘Big 5’ extinctions in virtually every aspect: timing, effects and causes - and there is little knowledge of the coupling of events on land and in the ocean. At one extreme, the marine crisis is viewed as a rapid, cataclysmic event at the Frasnian/Famennian boundary (the “Kellwasser Event”) followed by another crisis 13 Myr later (the “Hangenberg Event”). Alternatively, these Late and end-Devonian extinctions are viewed as a cumulative series of minor events, drawn out over the entire Devonian. Our project aims to resolve these through study of the spectacular Devonian sedimentary succession in northern Spain that is both remarkably complete and laterally extensive, providing a transect across an entire Devonian marine shelf from deep marine to near terrestrial environments. We present initial results from Piedrasecha, north of Léon. We analysed 47 samples spanning the Frasnian Nocedo Formation, and the Famennian-Tournasian (Carboniferous) Fueyo, Ermita and Baleas Formations. Combined geochemical and palynological analyses reveal:1) δ13Corg values are stable around -26‰ through the Frasnian and Famennian prior to a 2‰ negative shift associated with the onset of black mudstones at the base of the Baleas Formation (latest Famennian). This is likely a muted expression of the Hangenberg Event negative δ13Corg excursion.2) Redox proxies (Th/U, Mo/Al, V/Al and U/Al) indicate bottom waters remained oxygenated until the latest Famennian, when weakly dysoxic (at worst) conditions developed. There is no obvious expression of Kellwasser Event anoxia in this offshore setting, and only a weak manifestation of Hangenberg oxygen restriction.3) An order of magnitude shift in productivity proxy values (Ba/Al, Ni/Al, Zn/Al and P/Al) in the latest Famennian suggests that the Hangenberg Event is associated with increased primary productivity.4) Mercury is enriched in the upper Frasnian Nocedo Formation where it withstands normalisation to TOC (Hg/TOC values reach 388 ppb/wt%, similar to those reported for the Upper Kellwasser Horizon elsewhere). This mercury might derive from large igneous province volcanism and is potentially a chemostratigraphic marker for the Kellwasser Event, though we require better stratigraphic control to evaluate this. Significant Hg enrichments (up to 160 ppb) in the latest Famennian Baleas Formation do not withstand normalisation, as TOC reaches 4.7 wt% at this level. The succession is thermally mature and since TOC drops with thermal maturity, Hg/TOC values might be elevated in comparison to original values.5) Palynomorph assemblages are dominated by simple spores and Geminospora. The latter derives from the Mid-Late Devonian forest tree Archaeopteris. This suggests a rather homogenous vegetation typical of Late Devonian settings where successive extinctions stripped out diversity from terrestrial floras. However, it may be that in this distal section we are sampling spores that have been winnowed during transport. Work on other sections will enable us to test this.We have sampled 14 further sections providing a complete Devonian succession and with >500 samples in preparation we hope to resolve whether the Late and end-Devonian crises were the result of cumulative stresses, or were indeed cataclysmic events.

Oceanic Anoxic Events (OAEs) are important geological events that may be analogues to future climate-driven deoxygenation of our oceans. Much of the global ocean experienced anoxic conditions during the Cenomanian-Turonian OAE (OAE2; -94 Ma), whereas the Western Interior Seaway (WIS) experienced oxygenation at this time. Here, organic geochemical and palynological data generated from Cenomanian-Turonian age sediments from five sites in the WIS are used to investigate changing redox and ecological conditions across differing palaeoenvironments and palaeolatitudes. Heterogeneity across the sites is apparent, but important relationships and trends among oceanographic variables are recognised: 1) Increasing total organic carbon (TOC) and CaCO3 percentages indicate the onset of a sea-level maximum towards the end of OAE2; 2) C28 sterane is shown to be a useful marker for prasinophyte abundance, and concurrent increases in this marker and overall sterane abundance indicate prasinophyte-driven increase in algal productivity in a stratified water column; and 3) sterane ratios can be a more reliable geochemical proxy than redox proxies for assessing the Benthic Oxic Zone. Our redox data do not always follow established trends for the WIS overall, particularly for proximal settings. We therefore surmise that local effects, such as nutrient-driven expansion of the oxygen minimum zone and/or sedimentation-driven anoxia just below the sediment-water interface, have overprinted regional trends.

In the Late Devonian to earliest Mississippian, Svalbard was affected by a short-lived episode of deformation named the Svalbardian Orogeny. This event resulted in intense folding and thrusting in Devonian sedimentary successions. Deformation stopped prior to the deposition of Carboniferous to Permian sedimentary strata of the Billefjorden and Gipsdalen groups, which lie unconformably over folded Devonian strata. Later on, presumed Svalbardian structures were reworked during Eurekan tectonism in the early Cenozoic and partly eroded. At present, records of Svalbardian deformation are only preserved in narrow N–S-trending belts in central, northern, western, and southern Spitsbergen. Despite extensive field studies, the timing of the Svalbardian Orogeny is poorly constrained and remains a matter of debate in places because of conflicting ages and because of the complex tectonic history of Svalbard. The present contribution aims at reviewing and discussing all available age constraints for Svalbardian tectonism, including notably palynological, paleontological, and geochronological evidence. This has great implications for the plate tectonic reconstructions of Arctic regions and for the tectonic history of Svalbard. Palynological and paleontological evidence suggest that the Mimerdalen Subgroup is upper Givetian to lower Frasnian (ca. 385–380 Ma) in age and that the Billefjorden Group is mid-Famennian to Upper Mississippian (ca. 365–325 Ma) in age, constraining the Svalbardian event in central and northern Spitsbergen to 383–365 Ma if it ever occurred. Palynological ages indicate that the Adriabukta Formation in southern Spitsbergen is Middle Mississippian and therefore cannot have been involved in the Svalbardian event, thus suggesting that all the deformation in southern Spitsbergen is early Cenozoic in age and that strain-partitioning processes had a major role in localizing deformation in weaker stratigraphic units. The few geochronological age constraints yielding Late Devonian–Mississippian ages in Svalbard may reflect either Svalbardian contraction or extensional processes and are therefore of no use to validate or invalidate the occurrence of the Svalbardian event. On the contrary, the contradicting lines of evidence used to support the occurrence of the Svalbardian event and new regional geophysical studies suggest that Svalbard was subjected to continuous extension from the late Silurian to early Permian times.

Miospores with spines that have bifurcate tips and an equatorial flange from the genus Ancyrospora were an important part of the Mid and Late Devonian spore flora. A number of the early species were described from the Arctic regions of both Canada (Nunavut) and the Timan, Russia. The history of the genus Ancyrospora is reviewed, rediagnosed and compared with Hystricosporites and Nikitinsporites two genera that also possess bifurcate tipped spines. Material from Arctic Canada and Russia was investigated to compare the Givetian and Frasnian species of Ancyrospora that were described in early publications by McGregor, Owens, and Naumova. The species Ancyrospora ampulla , A. melvillensis , A. simplex , A. incisa , A. arguta , A. laciniosa and A. polyacantha are illustrated and described using the same terminology including profiles of the bifurcate sculptural elements. Morphological lineages are recognised between the different species and the Ancyrospora melvillensis morphon defined. Comparative range charts are presented from both Arctic Canada and Russia. Many of the taxonomic issues in comparing Canadian and Russian Ancyrospora are resolved.

A comprehensive study of dispersed Early Carboniferous seeds has been carried out to test the possibilities of using chemosystematics for Paleozoic fossils. This has involved their morphology; the ultrastructure of ion thinned sections and their material. The results of analysis of the FTIR and EPR spectra indicate that the key structural unit of the substance is the phenyl propane structure. The presence of relict lignin ( p ‑coumaric type) was established by structural-chemical analysis using pyrolytic chromatomass-spectrometry. Lignins of this type are unknown in modern plants. The concentration of phenoxyl radicals is 2–3 orders of magnitude higher in the samples than in modern lignins.

Summary The Green River Formation of the western US represents a ∼15 million-year record of unusually large, productive Eocene lakes. The development of a particularly organic-rich (up to 43% total organic content) Mahogany oil shale (49.3 to 48.7 Ma) occurred at a key climate transition and during the decline of the Early Eocene Climatic Optimum (EECO). Hydrogen isotopic compositions (δ2H) of leaf wax (n-alkanes) and algal (phytane) lipids preserved in the Mahogany Zone are used to reconstruct precipitation and lake water δ2H, respectively. Algal lipid and leaf wax δ2H values exhibit a strong linear relationship (R2 = 0.8), suggesting that algae and higher plants are utilising the same hydrogen-bearing sources for biosynthesis (i.e. lake water δ2H). δ2H in n-alkanes and phytane become increasingly depleted upward through the Mahogany Zone, indicating increased precipitation during the demise of the EECO. Similarly, biomarker trends differ from those expected during a lacustrine drying-up cycle, revealing a continental-interior hydrological response to cooling. Results of algal lipid and leaf wax δ2H, with additional lipid and terrestrial biomarker profiles and petrographic data, allow hydrological change to be differentiated from broader ecosystem change during the EECO.

The Ballagan Formation of northern Britain provides an exceptional record of Early Mississippian ecosystems that developed as tetrapods emerged onto land. In this paper, we study two 500-metre sections of the formation near Berwick-upon-Tweed, which are characterised by abundant ferroan dolostone beds. Five lithofacies are identified: cemented siltstone and sandstone, homogeneous dolomicrite, mixed dolomite and siltstone, mixed calcite and dolomite, and dolomite with evaporite minerals. Cemented sediments have non-planar to planar subhedral dolomite crystals, up to 40 mu m in size, whereas other facies predominantly comprise dolomicrite or planar euhedral dolomite rhombs 15 mu m in size, with patches of larger rhombs indicating partial recrystallisation. The macro- and microfossil content of the dolostones is dominated by sarcopterygian (rhizodont) and actinopterygian fish, bivalves, Serpula, ostracods and Chondrites trace fossils; with rarer Spirorbis, chondrichthyans (Ageleodus, hybodonts and ?ctenacanths, xenacanths), non-gyracanth acanthodians, gastropods, eurypterids, brachiopods, plant debris, wood, lycopsid roots, charcoal, megaspores, phycosiphoniform burrows, Zoophycos? and Rhizocorallium. The oxygen and carbon isotope composition of dolomites range from -3.6% to -1.7% (for delta O-18) and -2.6% to +1.6% (for delta C-13) respectively indicating dolomite growth in mixed salinity waters. Frequent marine storm-surge events transported marine waters and animals into floodplain lakes, where evaporation, interstitial sulphate-reducing bacteria, iron reduction and methanogenesis allowed dolomite growth in the shallow sub-surface. Secondary pedogenic modification (by roots, brecciation, desiccation, and soil forming processes) is common and represents lake evaporation with, in some cases, saline marsh development. The dolostone facies are part of a complex environmental mosaic of sub-aerial dry floodplain, wet marshy floodplains, rivers, and lakes ranging in salinity from freshwater to hypersaline. Marine influence is strongest at the base of the formation and decreases over time, as the floodplain became drier, and forested areas became more established. Coastal lakes were an important habitat for animals recovering from the end-Devonian Hangenberg Crisis and may have acted as a pathway for euryhaline fishes, molluscs and arthropods to access freshwater environments.

The identification of taxonomic characters of spores in the different phylogenetic lineages of Paleozoic plants provides essential information that enables the reconstructions of the Earth's ancient plant communities and this should be taken into account in any paleoreconstruction (e.g., climatic, geographical, etc.). In this context, the introduction of new analytical instrumentation into paleopalynological studies and the development of new research methods are of particular importance. Therefore, in addition to the traditional methods of light, scanning electron and transmission microscopy, tomography, atomic force microscopy, as well as scanning electron microscopes (SEM) supplemented with new functionality are used to study paleopalynological objects. Chemosystematic methods, based on the biochemical characteristics of the evolutionary development of organisms, is being developed. These methods are enhanced by synthesizing the data from these chemical and physical research methods.

The rise of forests in the Mid and Late Devonian has attracted much attention as potential drivers of the Earth System.In this context it is important to understand what groups contribute to the first wetlands found at the Devonian palaeoequator.A time series of Devonian coals shows that the palaeoequatorial Mid and Late Devonian humic (vitrinite rich) coals are dominated by the lycopod microspore Cymbosporites and megaspore Verrucisporites that can be confidently associated as the spores from Protolepidodendropsis.This plant has successfully colonised and probably created the wetland coal environment by the ability to shallow root and hence anchor the trees above the anaerobic layer.The progymnosperm Archaeopteris is abundant from its spores in Devonian palaeoequatorial sediments but plays no role in these coal forming wetlands.More rigorous age dating shows that there is some evidence for a Tournaisian coal gap.

The morphology and ultrastructure of spores of the Devonian plant Kryshtofovichia africani Nikitin are examined. The structure of ultrathin exine megaspores of K. africani is established. The exine consists of two layers: granular ectexine and lamellate endexine. Microspores have a lamellate ultrastructure with a trend toward loosening and formation of the granular structure towards the ectexine outer part. Heterospory of K. africani is apparent in both morphological characters and sporoderm ultrastructure of micro- and megaspores.

The results of sporoderm studies for Paleozoic spores are obtained for the first time on a nanotomographic scanner. They are comparable to the results obtained on a scanning electron microscope (SEM) and transmitting electron microscope (TEM), verifying the interpretation of structures of the external and internal structure of the sporoderm for the objects studied. A nanotomographic scanner enables us to carry out complex studies of different sporoderm projections and to visualize the relationships and arrangement of its components without damaging the integrity of the object and losing unique Paleozoic material. Application of a nanotomographic scanner also reduces the time taken for object preparation for examination on a SEM or TEM. The nanosculpture of the exosporium of Devonian Kryshtofovichia africani Nikitin megaspores is revealed to show its two-layer structure, with the thicknesses and locations of the layers established.

Despite successful production from Carboniferous and Permian reservoirs in the Southern North Sea and onshore Netherlands and Germany, Paleozoic hydrocarbon plays across parts of NW Europe remain relatively under-explored onshore and offshore. This volume brings together new and previously unpublished knowledge about the Paleozoic plays of NW Europe. Improvements in seismic data quality and availability tied to previously unpublished well datasets form the basis for improved understanding of local to regional structural interpretations, depositional environments and basin history. New interpretations move significantly away from generalized basin development models, with improved definition of structural traps and source rock basins feeding to better constrained, locally variable burial, uplift, maturation and migration models. Particularly notable are the significant mapped extents and thickness of Paleozoic source, reservoir and seal rocks. Areas previously dismissed as regional highs and platforms are dissected by Paleozoic basins with evidence for mature source rocks into basin centres. Numerous potential Paleozoic plays or play elements result within thick organic-rich and variably mature successions. Outside or below existing Jurassic and Southern North Sea to onshore Netherlands and German Permian-Carboniferous plays, Paleozoic plays in frontier areas offer significant additional exploration opportunities.

Abstract A major stratigraphical problem in the offshore Paleozoic of the Inner Moray Firth is the identification of the top of the Devonian Old Red Sandstone Group beneath the lithologically similar Permian Rotliegend Group. Wireline log criteria for a revised Old Red Group to Permian boundary are given for the Inner Moray Firth. Section lines drawn using these criteria and flattened on the overlying Triassic Smith Bank or Permian Kupferschiefer formations show a relatively thin development of Rotliegend with two depocentres. The underlying Devonian when flattened on the Eday Marl shows a systematic subcrop pattern. There is currently no exposed onshore Old Red to Rotliegend boundary, but the possibility remains that a Permian section is present in the ‘Upper Old Red Sandstone’ of Tarbat in Easter Ross. An exposed Permian–Devonian boundary is present in East Greenland and provides an analogue for the Inner Moray Firth.

ABSTRACT An earliest Famennian (Late Devonian) record of tentaculitoids (an extinct ‘class’ of small calcareous conical shells) preserved as palynomorphs is documented from Sosnogorsk in the Komi Republic of Russia. These were preserved in considerable abundance in a near-shore shallow lagoon subjected to marine flooding with euxinia. Four forms of nowakiid tentaculitoids plus related aberrant forms are documented. They represent evidence for survival of the nowakiids into the earliest Famennian and hence post-date the Frasnian–Famennian mass extinction. It is hypothesised that the Frasnian and younger occurrence of tentaculitoids as palynomorphs may relate to a changing balance of carbonate and organic matter in their shells driven by the environmental conditions of the Frasnian–Famennian mass extinction.