Community assembly in the Late Devonian Wutong Flora: Diversity patterns and multi-scale ecological drivers

Post-Collisional Ni Cu Mineralization in the late Devonian Binggounan Intrusion, North Qimantage (East Kunlun Orogenic Belt): Geochronological, Geochemical, and Petrogenetic Constraints

The nature and timing of Mid-Devonian–Visean plutonic activity in the Variscan Bohemian Massif (BM) and the Central Western Carpathians (CWC) differed profoundly. In the BM, most of this period was marked by vigorous arc-related magmatism that ceased only at ~340 Ma by the collision and the ensuing slab break-off. The oceanic subduction passed to deep continental underthrusting, and relamination of felsic metaigneous material of Saxothuringian origin, soon thereafter transformed into (U)HP–HT granulites. The Visean activity in the BM was characterized by an emplacement of voluminous (ultra-)potassic plutons and countless dykes of matching chemistry, but practically no syn- to early post-collisional S-type granitoids. In the BM, the bulk of S-type magmas was produced in Serpukhovian or younger. In the CWC, the evolution started later but was considerably faster; the classic magmatic arc seems not to be preserved here. Subduction, evidenced by Frasnian back-arc mafic magmatism and anatexis, was terminated by collision and early (Late Devonian) slab break-off. The attendant heat pulse produced dioritic rocks, and then a Tournaisian late-collisional flare-up of the I- and immature (biotite-bearing) S-type granitoids. The mature (muscovite-bearing) Visean S-type granites were already post-collisional. In the CWC, the (ultra-)potassic magmatic rocks are conspicuously missing, as are the (U)HP–HT granulites. This reflects a too early slab break-off and/or inappropriate composition of the downgoing continental slab. The contrasting Mid-Devonian to Visean magmatic histories clearly reflect distinct paleogeographic positions of the BM vs. CWC crustal segments, probably along the two unconnected sutures in the widely separated branches of the Variscan orogenic collage.

ABSTRACT The intracontinental deformation is an essential element of the tectonic evolution of the Central Asian Orogenic Belt (CAOB) during the Late Mesozoic. Located along the Mid‐southern CAOB, the Zhusileng–Hangwula tectonic belt connects the Beishan Orogenic Belt and the Solonker Suture. However, the chronological constraints of Mesozoic history on this region remain unclear. Here, we presented field observations, geochemical characteristics and low‐temperature thermochronometry (apatite fission track, AFT) results from the Chaheilingashun area (northwestern Zhusileng–Hangwula tectonic belt) to constrain the regional tectonic history. The whole‐rock geochemical data indicate that the Middle Devonian Chaheilingashun monzogranite pluton is a (high‐K) calc‐alkaline S‐type granitoid. This pluton most likely formed in a postcollisional setting during the Middle–Late Devonian. New AFT data and thermal history modelling of the Chaheilingashun pluton suggest that the region experienced rapid cooling and exhumation events (135–133 Ma). The regional Mid–Late Jurassic contractional deformation (termed phase B of Yanshanian deformation) could have lasted until the earliest Early Cretaceous. Following this shortening event, regional extension was widespread in the mid‐southern CAOB, as evidenced by rift‐related magmatism, metamorphic core complexes and widespread concurrence of extensional basins. Therefore, we suggest that the Early Cretaceous tectonic transition (from contraction to extension) could have occurred at 133 Ma in the Zhusileng–Hangwula tectonic belt. In addition, this transition could have resulted from multiple factors related to the far‐field effects of oceanic plate subduction.

This study combines structural mapping, petrographic analysis, and U-Pb zircon geochronology of low-grade metamorphic rocks from the Iberian Pyrite Belt (IPB), located in the westernmost domains of the South Portuguese Zone (SPZ). At Ilha do Pessegueiro beach, the Cercal volcanic-sedimentary complex (VSC) rocks, assigned to the Late Devonian in previous studies, exhibit a dominant S 1 slaty cleavage overprinted by S 2 crenulation cleavage. This ductile deformation has been attributed to contractional tectonics. However, new structural data indicate that older ductile structures formed in relation to a low-grade extensional shear zone (D 1 -E) and were tectonically transported to the east-southeast. The new age of the Cercal VSC felsic metatuffs (ca. 364-363 Ma) is consistent with VSC ages from other areas of the IPB, enabling us to bracket the D 1 -E deformation event between the Tournaisian and the Bashkirian. After the D 1 syn-convergent extension, a subsequent contractional deformation event (D 2 -C), resulting from the latest events of the Gondwana-Laurussia oblique convergence, caused inversion of the Carboniferous synorogenic basins and the formation of a thrust-and-fold belt. Recent data for the late Devonian-early Carboniferous geology of the IPB appear to support a correlation between the SPZ and the Meguma terrane.

Abstract The Lilliput Effect, wherein assemblages decrease in mean individual body size after mass extinctions, has not been documented at a wide geographic scale in any of the Late Devonian mass extinction pulses in invertebrate taxa. Based on a dataset of 800 scolecodonts (polychaete jaw elements) from the literature, museum collections, and newly presented data from the Appalachian Basin, we find that scolecodont size distribution per temporal bin decreases across the Frasnian/Famennian Kellwasser Events from a median length of 500 μm before the Kellwasser Events to a median length of 196 μm during the Kellwasser Events. The majority of the small scolecodonts documented during the extinction interval are newly measured specimens from the Kellwasser Events of the Appalachian Basin, although this size change is not unique to the Appalachian Basin. We interpret the reduction in body size as a hypoxia-driven occurrence of the Lilliput Effect because of the susceptibility of benthic invertebrates to hypoxia and the association of this extinction event with hypoxia. While previous studies have shown that polychaete community biomass decreases in response to oxygen stress, our study provides fossil evidence of individual size reduction, plausibly due to oxygen stress.

This publication presents results from a large cross-border Paleozoic study of the five-country area in the Southern-Central North Sea. A synchronization of the Devono-Carboniferous stratigraphy across the study area is established and includes seven stratigraphic units ranging from Devonian to Carboniferous that are correlated across the five national sectors of the North Sea. A new Tournaisian to Namurian tectonostratigraphic framework is proposed based on the integration of offshore wells, outcrop and seismic data, as well as legacy and new palynological information. Two main offshore palaeotopographic highs, the Mid North Sea High and the newly defined Central North Sea High, affected sediment pathways, stacking pattern, distribution and preservation of Late Devonian to Namurian depositional systems. Several extensive cross-border Paleozoic faults controlled the position and evolution of palaeo-basins and -highs. A SW–NE-oriented, curved, left-lateral, transtensional strike-slip fault set extends from the UK to the Norwegian sector. A NW–SE right-lateral fault set, which includes the Coffee Soil Fault System, accommodated fault block rotation and the formation of NW–SE-oriented pull-apart basins. These two newly defined fault sets were active during the Late Devonian to Early Carboniferous in response to NW–SE crustal shortening associated with lateral crustal extrusion towards the WSW.

The Mid-Paleozoic marks the transition from the low diversity oceans of the Cambrian to a Devonian world with established terrestrial ecosystems and a substantially higher diversity of marine benthos, especially in the pelagic realm. Key events were the dramatic radiation termed the Great Ordovician Biodiversification Event (GOBE) and the nekton revolution of the Devonian. The interval also includes two mass extinction events (end-Ordovician and Late Devonian) with numerous minor biotic crises in the Silurian and Devonian but curiously not in the Ordovician. These remarkable changes are set against a proposed back drop of increasing atmospheric oxygen levels and ocean ventilation. However, reviewing current ideas shows little consensus regarding either the timing or magnitude of these changes with different approaches (geochemical proxies and modelling) often producing conflicting interpretations. Broadly, Mid-Paleozoic oceans are likely to have been less well oxygenated than the present day but notions that the marine biota was potentially more resilient to dysoxic than modern taxa is not supported by the frequent association of crises and oceanic anoxic events. There is a more agreement regarding temperature trends with the Ordovician marked by a long-term cooling trend, partially coincident with the GOBE, culminating with an intense, end-Ordovician glaciation.

Late Paleozoic tectonic evolution of Hegenshan–Nenjiang Ocean: Constraints from Late Devonian–Early Carboniferous igneous rocks in the Xing’an Accretionary Terrane

Carbonatites are rare mantle-derived igneous rocks often economically enriched in rare earth and high field strength elements and are crucial archives of mantle and crustal processes. Zircon U-Th-Pb geochronology provides a powerful means of constraining their magmatic and hydrothermal evolution, but interpretation is often hindered by discordant data arising from open-system behavior. Discordant data are often dismissed as meaningless, yet hydrothermally recrystallized zircon can in fact record the timing of fluid-rock interaction, offering a means to date important orogenic-related or economic deposit-forming hydrothermal events. Here, we show that integrated U-Th-Pb geochronology, textural observations, trace element analysis, and Pb isotope data from the Mount Grace carbonatite and associated carbonatites and syenites in the southeastern Canadian Cordillera resolve both magmatic and hydrothermal histories. Four samples from meta-carbonatite and meta-alkaline rocks in the Monashee complex and Selkirk allochthon in the southern Omineca belt were studied to clarify the magmatic ages through new zircon U-Th-Pb geochronology. Concordant U-Pb zircon ages of ca. 360 Ma from the pyroclastic Mount Grace carbonatite confirm a Late Devonian depositional age for protoliths of the Monashee cover gneiss. Ca. 360 Ma magmatic ages for all four carbonatite-syenite samples expand the record of Late Devonian−Early Mississippian alkaline magmatism in the Monashee complex and Selkirk allochthon. Hydrothermally altered zircon domains that correspond with convolute zoning in cathodoluminescence and elevated light rare earth element contents yield a Th-Pb age of ca. 163 Ma from the Mount Grace carbonatite and U-Pb weighted mean and upper intercept ages of ca. 130 Ma from the Three Valley Gap carbonatite and syenite in the Monashee Complex and the Trident Mountain syenite in the Selkirk allochthon. Our data identifies a Jurassic hydrothermal event that affected carbonatites in both the Monashee complex and Selkirk allochthon, argued by some authors to have been tectonically separated until the Upper Cretaceous−Paleocene. Mineral Pb isotopic analyses from the same four carbonatites and syenites and one sediment-hosted magnetite-rich ore deposit reveal a highly radiogenic linear trend inconsistent with traditional closed-system models, likely indicating mixing between radiogenic Pb derived from clastic sedimentary sources and Pb in the alkaline bodies. This, along with the robust Late Devonian zircon age of the underlying Mt. Grace carbonatite, calls into question the validity of the shale curve model age for the Cottonbelt Pb-Zn deposit and helps resolve a longstanding age conundrum. Our findings refine the timing of Late Devonian carbonatite-alkaline magmatism along the western Laurentian margin, reveal a previously unrecognized Jurassic hydrothermal event that affected both the Monashee complex and Selkirk allochthon during Cordilleran orogenesis, and address a decades-old age conundrum in the Monashee complex leading to determination of a ca. 360 Ma maximum depositional age of the Monashee complex. More broadly, this study underscores the potential of hydrothermal zircon to date fluid-mediated events in carbonate-rich systems, offering a new framework for interpreting isotopically disturbed datasets in mineralized terranes.

Pygocephalomorphs are fossil eumalacostracans with a shrimp to lobster-like morphology, known from the Late Devonian (Famennian) to the early Permian (Cisuralian; Artinskian). In the late Paleozoic, pygocephalamorphs formed an important component of marginal marine, brackish and freshwater communities. Several species, including species of Tealliocaris and Pygocephalus, have been described from the Carboniferous of Canada, in particular from the Pennsylvanian. A revision of Pygocephalus from the Carboniferous of Nova Scotia, Canada, is proposed based on original material described by Copeland and on undescribed material from the Joggins Fossil Cliffs UNESCO World Heritage Site. The presence of three taxa is confirmed: Pygocephalus cooperi, Pygocephalus cf. cooperi and Pygocephalus dubius. The pygocephalomorphs of Joggins Fossil Cliffs, and more generally Nova Scotia, were likely benthic walkers based on their leg morphology and the paleoichnological evidence. A comparison of the studied assemblages with previously known assemblages from the Mississippian of Canada shows a faunal turnover among these assemblages, which could reflect paleoenvironmental changes in Atlantic Canada during the Carboniferous and thus various ecological affinities among taxa. We also observed three types of microstructures on the shield of Pygocephalus dubius: canal-like pores, which are most probably organule canals, setal attachment site, and polygonal reticular ornamentation.

“Placoderm” and sarcopterygian fishes dominated Devonian waters. Following the end-Devonian crisis, actinopterygians rapidly became major contributors to vertebrate diversity. This transition constitutes the first major diversification event of actinopterygians. Here, we investigate the morphological diversification of Devonian and Carboniferous actinopterygians by quantifying disparity using two-dimensional (2D) geometric morphometrics, which estimates disparity from continuous data and brings geometric information related to the shape changes in several morphological features. In total, 13 landmarks and 203 semi-landmarks were digitized on the body shape reconstructions of 84 species, and 18 landmarks and 50 semi-landmarks were digitized on the reconstructions of the lateral view of the skulls of 86 species. When compared to variations in taxonomic diversity over time, the pattern of body shape variations is congruent, reaching a maximum during the Viséan, but the pattern of skull disparity is not entirely congruent, presenting a first increase during the Late Devonian. Changes in body shape are associated with locomotory properties, while changes in skull shape are associated with functional properties of the feeding apparatus. This pattern strongly suggests the diversification of actinopterygians to be driven by divergence in trophic strategies. This evolutionary radiation seems to be the result of an adaptive response to new ecological opportunities, triggered by big environmental changes in mid-Paleozoic oceans.

The study explores a novel proxy for reconstructing atmospheric CO2 concentrations during the Late Devonian–Mississippian, a key interval marked by the transition from a greenhouse to an icehouse climate and the onset of the Late Palaeozoic Ice Age. Traditional proxies for Palaeozoic CO2 levels, such as palaeosols and vascular plant and phytoplankton remains, are limited by scarcity, poor dating, or susceptibility to diagenetic alteration. To address these challenges, this work evaluates the decoupled carbon isotope composition of conodont elements and host carbonates. Based on integrated isotope analyses and comparison with compiled CO2 estimates, the study reveals a significant negative correlation between the decoupling of carbon isotope composition of conodont elements and host carbonates and atmospheric CO2 content. The results indicate taxon-specific trends, with Ozarkodinida and Prioniodinida exhibiting similar regression gradients but distinct intercepts, suggesting ecological or physiological influences on isotopic fractionation. The findings support the potential of the decoupling of carbon isotope composition of conodont elements and host carbonates as a potential proxy for atmospheric CO2, with implications for reconstructing spatial and temporal variations in Palaeozoic carbon cycles and climate dynamics.

Palynological analysis of the Bakken Formation in three wells drilled by Hess Corporation in Mountrail and Williams counties, North Dakota, USA, has shed new light on the potential role of palynology in understanding the chronostratigraphic relationships and deposition of oil-bearing strata in the Williston Basin. A detailed sampling program examining palynomorphs and particulate organic matter yielded variable assemblages of sphaeromorphs, acritarchs, miospores, and plant fragments. Broadly, the Lower Bakken and Upper Bakken members are dominated by organic-walled sphaeromorphs (of possibly algal affinity) with a low diversity suite of acritarchs. Particulate organic matter consists mainly of structureless organic matter, most likely of marine origin, although some may be terrestrial but highly degraded. The upper and lower members are marine deposits. Variability in the size of the sphaeromorphs suggests that differences in productivity, ocean chemistry, light, and temperature, may have occurred during deposition, as evidenced by results of isotope and biomarker studies. The Middle Bakken Member samples yielded a mixed assemblage of miospores and acritarchs with minor occurrences of sphaeromorphs. Land plant-derived particulate organic matter dominates the Middle Bakken Member which was deposited under nearshore marine conditions as corroborated by the consistent, although rare, occurrence of acritarchs. Age-diagnostic palynomorph taxa are rare, although the key latest Devonian miospore, Retispora lepidophyta, appears consistently in the Middle Bakken Member and last occurs near the top of the unit, where the Devonian–Mississippian boundary is placed. Distinct distribution patterns of acritarchs at the genus level may prove to be of chronostratigraphic value with species of Gorgonisphaeridium common in the Middle Bakken Member and species of Micrhystridium dominant in the Upper Bakken Member. Although there is broad similarity with other studies from North America, examination of more wells in the Williston Basin are needed to better understand these relationships.

Eifelian (Middle Devonian) to Early Frasnian (Late Devonian) conodonts and strata in the Spanish Central Pyrenees: Global correlations and effects of climatic fluctuations in the biota

Bivalve taxa are rare from the fossil assemblage in the Carboniferous Kubang Pasu Formation. This study reports the discovery of the pectinid bivalve Euchondria sp. from the Kubang Pasu Formation exposed at Bukit Tuntung, Pauh, in Perlis state, NW Peninsular Malaysia. A single left valve is preserved in light grey shale and associated with previously reported Early Carboniferous (Viséan) ammonoids and the bivalve Posidonia becheri. The morphology and anatomy of the specimen is described. The genus Euchondria ranges from the Late Devonian to Permian which is consistent with its association with the Kubang Pasu Formation fossil assemblage of Viséan age. The fossil assemblage at Bukit Tuntung, which is relatively sparse compared to equivalent strata in western Perlis and dominated by thin-shelled bivalves and nektonic ammonoids indicates a relatively deeper marine depositional setting, which is consistent with the presence of turbidites.

Greenalite in iron-rich Precambrian sedimentary rocks is widely regarded as a primary mineral that formed in ferrous iron-rich and anoxic conditions. However, primary greenalite has rarely been reported in Phanerozoic rocks, as Phanerozoic oceans are considered to have been more oxygenated and less favorable for greenalite precipitation. Here, we report the discovery of greenalite nanoparticles in the Late Devonian Xialei Mn deposit. Nanoscale (20−1000 nm) euhedral to anhedral greenalite particles occur as randomly oriented crystallites enclosed in microcrystalline quartz crystals within chert-rich Mn and Fe-Mn ores. Greenalite-bearing ores show negative δ30Si values (avg. −0.5‰) close to those of Precambrian iron formations and hydrothermal silica, suggesting a substantial hydrothermal contribution. These characteristics support the interpretation that the greenalite formed in a mixing zone near deep-water vents where Fe2+-rich and SiO2(aq)-rich hydrothermal fluids mixed with seawater to produce gradients in pH and temperature amenable to greenalite genesis. The greenalite nanoparticles then accumulated hundreds of kilometers from this formation zone, being found in continental shelf metalliferous ores formed beneath upwelling zones, as indicated by sedimentologic, stratigraphic, and paleogeographic constraints. The presence of these greenalite-bearing Mn and Fe-Mn deposits on distal shelves (below storm wave base) records a profound regional oxygen-stratified water column in South China, characterized by hydrothermal input and anoxic bottom waters. These conditions are reminiscent of Precambrian oceans. Thus, greenalite-bearing Mn deposits provide a new archive to track hydrothermal metal fluxes and anoxia in Phanerozoic basins, with potential implications for other Phanerozoic hydrothermal chert and metal deposits.

Fibonacci spiral phyllotaxis is overwhelmingly the most common leaf arrangement among plants, both today and in the fossil record. Spiral phyllotaxis appeared as early as the Late Devonian, some 380 million years ago. This mathematical property has been rigorously studied in living conifer species; however, the phyllotaxis of fossil conifer seed cones remains under-studied, including that of the Middle Jurassic seed cones of Araucaria mirabilis. Twenty-one A. mirabilis seed cones from the Bosques Petrificados de Jaramillo National Park, Argentina, were analyzed for their morphometrics, phyllotaxis, and seediness. For each cone, the number of seeds in the cone, as well as the number of clockwise and counterclockwise parastichies, was counted on the well-preserved cone surface. Micro-CT was used to non-destructively observe the internal arrangement of the seeds in the cone. Then, Avizo was used to visualize one clockwise and one counterclockwise parastichy from each cone to determine the number of seeds in the spiral and the angle of rotation of the spiral. Here, we show that clockwise ontogenetic chirality and greater axis length and width positively correlate to greater seediness in A. mirabilis seed cones. Cones with clockwise ontogenetic chirality have moderately tighter spirals (p-value < 0.05, r = 0.2) with more seeds in them (p-value < 0.05, r = 0.3). Similarly, a taller axis is associated with a greater circumference (p-value < 0.01, r = 0.6), which, in turn, correlates with more bract/scale complexes (p-value < 0.05, r = 0.05). The most common phyllotaxis is 13,21 (64%) with 360° spirals (48%) and clockwise ontogenetic chirality (66%). Visualizing internal morphometrics and seed arrangements show which characteristics contribute to optimal seed packing. Thus, micro-CT imaging, in addition to traditional methods, enables a deeper study of conifer cone morphology and construction.

Ray-finned fish are the most speciose vertebrate group today, but the dynamics of their early diversification are contentious. Their fossil record suggests a first radiation in the Carboniferous following the Late Devonian mass extinction events. Conversely, recent phylogenetic hypotheses imply a radiation originating in the Late Devonian but lack the taxonomic breadth required to robustly test this. This necessitates phylogeny-free inference of actinopterygian diversification rates from fossil occurrences, itself challenging owing to complex systematics, incomplete occurrence databases and severe spatiotemporal sampling biases. Here, we analyse a comprehensive dataset of Palaeozoic actinopterygian genera and species using approaches that accommodate spatial and temporal sampling variation. We detect elevated actinopterygian diversification in the Late Devonian, with substantially greater lineage survival across the Hangenberg extinction event than indicated by the raw fossil record. Surprisingly, we detect no positive shifts in origination across the event, refuting previous hypotheses of explosive actinopterygian radiation in its wake. Instead, cryptic survival of diversified lineages appears responsible for the robust signal of increased diversity across different geographical scales in the Carboniferous. Nonetheless, these trends are overwhelmingly driven by low palaeolatitude Euramerican fossil assemblages, highlighting the ongoing spatial limitations of the actinopterygian fossil record.

Major morphological adaptations characterized the early evolutionary history of sarcopterygians during the Devonian (419-359Ma) and the Carboniferous (359-299Ma), punctuated by environmental changes and biodiversity crises. Here we present geometric morphometrics analyses of early sarcopterygian morphology to explore the impact of environmental and phylogenetic constraints on their morphology. Three analyses were performed by digitizing 2D landmarks and semi-landmarks on palaeontological reconstructions of the body shape, cheek, and skull roof. Major changes in shape seem associated with geological and biological changes from the Late Devonian and Early Carboniferous (Mississippian). An increase in shape diversity occurred during the Middle Devonian, when the first forests appeared, influencing freshwater and transitional environments, and when reef ecosystems were the most diversified. Skull roof and cheek disparity decrease during the end-Devonian mass extinction and recover during the Mid-Late Mississippian, with the reemergence of metazoan reefs and the rise of surviving groups such as actinistians. The skull roof disparity is associated primarily with shared ancestry and appears to be largely driven by the lack of an intracranial joint in dipnoans and tetrapods. The Devonian to Carboniferous environmental changes constitute a major turning point in early sarcopterygian history by having deeply impacted their morphological disparity.