Carboniferous Permian Transition Research Articles

Geochemical Constraints and Astronomical Forcing on Organic Matter Accumulation of Marine–Continental Transitional Shale Deposits in the Qinshui Basin during the Carboniferous–Permian Transition

Geochemical Constraints and Astronomical Forcing on Organic Matter Accumulation of Marine–Continental Transitional Shale Deposits in the Qinshui Basin during the Carboniferous–Permian Transition

Quantitative palaeogeographical reconstruction of the North China Block during the Carboniferous and Permian transition: Implications for coal accumulation and source rock development

The Carboniferous-Permian strata of the North China Block (NCB) contain significant economic reserves of coal and gas. In this paper, a comprehensive dataset comprising 401 stratigraphic sections encompassing the Carboniferous-Permian transition in the NCB is compiled from the OneStratigraphy and Geobiodiversity databases. We conducted quantitative analyses of this dataset using ArcGIS and GPlates software, and utilized an up to date plate motion model, to perform a dynamic palaeogeographical reconstruction. The spatio-temporal distribution of depositional facies were also analysed, including basement terranes, fluvio-lacustrine settings, swamps, shorelines, tidal flats, and carbonate platforms. Our reconstructions reveal that the NCB was flanked by basement areas of the Yinshan-Yanshan landmass in the north and the Qinling-Dabie landmass in the south. Peat (coal) deposition occurred across a range of terrestrial to coastal environments, including fluvio-lacustrine settings, deltas, shorelines and tidal flats. Carbonaceous and organic-rich clastic rocks also developed in these areas while organic-rich carbonate rocks were primarily deposited in carbonate platform. The conditions conducive to peat (coal) formation were intricately connected to eustatic fluctuations, which resulted in frequent transgressions and regressions. The sea-level fluctuations during the Pennsylvanian might be, in part, a response to both the waxing and waning of continental ice sheets and tectonic process in the northern margin of the NCB. In contrast, sea-level changes during the early Permian were probably controlled by the tectonic process only. This paper provides a state-of-the-art review of palaeogeographical evolution of the NCB during the Carboniferous and Permian transition, in response to eustatic and palaeoclimate change, and sheds light on resource accumulation based on quantitative analyses.

U–Pb age constraints on the Carboniferous–Permian transition in continental basins of eastern equatorial Pangaea (France): implications for the depositional history and correlations across the late Variscan Belt

Intramontane late Carboniferous–Permian basins of western Europe developed during the latest orogenic stages of the Variscan Mountain Belt in eastern Pangaea, at equatorial palaeolatitudes. Their stratigraphic framework is mainly based on continental subdivisions (e.g. Stephanian and Autunian continental stages), which can be contentious owing to biostratigraphic biases, resulting in long-distance diachronous subdivisions. To provide precise inter-basinal and global correlations to the internationally recognized chronostratigraphic marine stages, this study reports new U–Pb geochronology from the Aumance and Decize–La Machine basins, located in the northern French Massif Central. Zircon grains extracted from three volcanic ash-fall layers give weighted mean 206 Pb/ 238 U ages of 299.11 ± 0.35, 298.73 ± 0.36 and 298.59 ± 0.35 Ma (2 σ total propagated uncertainty) by the chemical abrasion isotope dilution thermal ionization mass spectrometry method, coinciding with the Carboniferous–Permian transition (Gzhelian and Asselian stages). These ages imply that the northern Massif Central basins developed synchronously in relatively short periods of time (<10 myr), reflecting substantial sedimentation rates. Finally, the new chronology of infilling of these basins confirms that they were connected during the late Carboniferous and early Permian periods, improving the knowledge on the late orogenic Variscan geodynamic setting in this area. Supplementary material: Operating conditions and complete analytical results are available at https://doi.org/10.6084/m9.figshare.c.6805228

Metamorphic Remnants of the Variscan Orogeny across the Alps and Their Tectonic Significance

Lithospheric slices preserving pre-Alpine metamorphic imprints are widely described in the Alps. The Variscan parageneses recorded in continental, oceanic, and mantle rocks suggest a heterogeneous metamorphic evolution across the Alpine domains. In this contribution, we collect quantitative metamorphic imprints and ages of samples that document Variscan tectonometamorphic evolution from 420 to 290 Ma. Based on age distribution and metamorphic imprint, three main stages can be identified for the Variscan evolution of the Alpine region: Devonian (early Variscan), late Devonian–late Carboniferous (middle Variscan), and late Carboniferous–early Permian (late Variscan). The dominant metamorphic imprint during Devonian times was recorded under eclogite and HP granulite facies conditions in the Helvetic–Dauphinois–Provençal, Penninic, and eastern Austroalpine domains and under Ep-amphibolite facies conditions in the Southalpine domain. These metamorphic conditions correspond to a mean Franciscan-type metamorphic field gradient. During the late Devonian–late Carboniferous period, in the Helvetic–Dauphinois–Provençal and central Austroalpine domains, the dominant metamorphic imprint developed under eclogite and HP granulite facies conditions with a Franciscan field gradient. Amphibolite facies conditions dominated in the Penninic and Southalpine domains and corresponded to a Barrovian-type metamorphic field gradient. At the Carboniferous–Permian transition, the metamorphic imprints mainly developed under amphibolite-LP granulite facies conditions in all domains of the Alps, corresponding to a mean metamorphic field gradient at the transition between Barrovian and Abukuma (Buchan) types. This distribution of the metamorphic imprints suggests a pre-Alpine burial of oceanic and continental crust underneath a continental upper plate, in a scenario of single or multiple oceanic subductions preceding the continental collision. Both scenarios are discussed and revised considering the consistency of collected data and a comparison with numerical models. Finally, the distribution of Devonian to Triassic geothermal gradients agrees with a sequence of events that starts with subduction, continues with continental collision, and ends with the continental thinning announcing the Jurassic oceanization.

Carboniferous-Permian high-resolution conodont biostratigraphy and paleoclimate change in North China

The Carboniferous-Permian transition is a critical period for the Late Paleozoic Ice Age that evolved from an acme to the subsequent demise with the initiation of long-term drying in low latitudes. During this time interval, extensive epicontinental deposition occurred in North China in the eastern tropical Tethyan region, and archived important information of climate and sea-level changes. Though several high-precision zircon UPb ages have been reported, they have some conflicts with previously defined biostratigraphic correlations, especially for the Taiyuan Formation. Lack of high-resolution conodont biostratigraphy has impeded the correlation with other well-studied Pangean records. In this study, five conodont zones were established for the successions of the Taiyuan Formation in southern North China. They are Streptognathodus wabaunsensis, S. isolatus, S. sigmoidalis, S. constrictus and S. fusus biozones in ascending order, constraining a late Gzhelian to late Asselian age for the Taiyuan Formation in southern North China, which is consistent with published high-precision zircon UPb ages. The Unitary Association (UA) analysis was used to reconcile the conodont biostratigraphy of the Taiyuan Formation in North China, and was combined with previously published high-precision UPb ages to construct a new chronostratigraphic framework for the Carboniferous-Permian strata across North China. It explicitly indicates an earlier initiation of climate aridification in the northern part than in the southern part of North China possibly due to northward drift and/or increased atmospheric pCO2 and associated global warming.

Estimating the Drivers of Diversification of Stoneflies Through Time and the Limits of Their Fossil Record

AbstractDeciphering the timing of lineage diversification and extinction has greatly benefited in the last decade from methodological developments in fossil-based analyses. If these advances are increasingly used to study the past dynamics of vertebrates, other taxa such as insects remain relatively neglected. Our understanding of how insect clades waxed and waned or of the impact of major paleoenvironmental changes during their periods of diversification and extinction (mass extinction) are rarely investigated. Here, we compile and analyze the fossil record of Plecoptera (1,742 vetted occurrences) to investigate their genus-level diversification and diversity dynamics using a Bayesian process-based model that incorporates temporal preservation biases. We found that the Permian-Triassic mass extinction has drastically impacted Plecoptera, while the Cretaceous Terrestrial Revolution corresponds with a turnover of plecopteran fauna. We also unveiled three major gaps in the plecopteran fossil record: the Carboniferous-Permian transition, the late Early Cretaceous, and the late Cenomanian to Bartonian, which will need to be further investigated. Based on the life history of extant Plecoptera, we investigate the correlations between their past dynamic and a series of biotic (Red Queen hypothesis) and abiotic (Court Jester hypothesis) factors. These analyses highlight the major role of continental fragmentation in the evolutionary history of stoneflies, which is in line with phylogeny-based biogeographic analyses showing how vicariance drove their diversification. Our study advocates analyzing the fossil record with caution, while attempting to unveil the diversification and extinction periods plus the likely triggers of these past dynamics of diversification.

Reconsidering Carboniferous–Permian continental paleoenvironments in eastern equatorial Pangea: facies and sequence stratigraphy investigations in the Autun Basin (France)

The late Carboniferous–early Permian represents a key period in the Phanerozoic history, given the major global geodynamic and climate modifications. The aim of this work is to better understand the context and characteristics of the sedimentation recorded in the continental environments of eastern equatorial Pangea at this time, through the example of the Autun Basin (northeastern Massif Central, France). The Autun Basin contains the historical stratotype of the Autunian continental stage, and its stratigraphy was recently improved by accurate numerical ages. This basin formed in an extensional tectonic context during the latest stages of the Variscan orogeny, and it is essential to study its paleoenvironmental evolution to provide new insights into the sedimentary evolution of contemporaneous surrounding basins. Using field and subsurface data, we propose a refined sedimentological model for the Autun Basin, relying on updated facies interpretations, organic matter content fluctuations, and sequence stratigraphy concepts and correlations. The continental environments of the lower sedimentary succession of the Autun Basin, previously considered to be fluvial and lacustrine, are herein re-interpreted as mainly lacustrine, comprising fine-grained organic matter-rich deposits, and supplied by coarser-grained deltaic siliciclastic sediments, without preservation of strict fluvial sedimentation. The determination of the sequence stratigraphy cycles, strengthened by the quantification of the organic matter content, and reflected by the temporal succession of progradational and retrogradational trends, is used to determine new correlations between several sections, as well as to reconstruct the paleoenvironment evolution at the Carboniferous–Permian transition. This study provides evidence that the sedimentation area of the Autun Basin at the time of its filling was much larger than the preserved basin area, and suggests connections with contemporaneous neighboring French basins, pointing to a large sedimentary system in the northeastern Massif Central area rather than narrow and isolated basins.

Syntectonic magmatism and reactivation of collisional structures during late-Variscan shearing (SW Sardinia, Italy)

The Arbus igneous complex (SW Sardinia, Italy) represents a good example of a short time lived post-collisional composite pluton emplaced at shallow crustal level in the external zone of the Variscan chain. The pluton almost consists of granodiorite and leucogranite rock-suites emplaced at 304 ± 1 Ma within a main NW trending thrust separating the metamorphic wedge from the fold and thrust belt foreland. The pluton emplaced into a dilatational step over connecting two NW–SE dextral shear zones which belongs to a regional network of post-collisional strike-slip structures marking the transition from collision to post-collisional extension. The microstructure observed for quartz and K-feldspar confirms the lack of significant post-emplacement deformation, indicating only limited high-temperature sub-solidus recrystallization. Anisotropy of magnetic susceptivity data and field-structural analysis have been carried out to reconstruct the geometry of the pluton and the trajectories of magmatic flow in relation to regional deformation structures. Overall, the magmatic and the magnetic fabrics are broadly discordant with the metamorphic foliation of the country rocks, defining an EW trending elliptical asymmetric sill rooted in the SW quadrant. The reconstructed architecture combined to petrologic observation indicates that accretion of the pluton involved injection of multiple dykes through a sub-vertical feeder zone, combined to lateral flow of the roof controlled by inherited collisional structure. The duration of magmatic activity and the cooling history of the contact metamorphic aureole have been evaluated through a suite of 2D thermal models. All these observations, together with the available geochronological constraints are suggestive of very rapid construction of the pluton. The proposed emplacement model is fully consistent with the regional phase of strike-slip tectonics and widespread magmatism accommodating the large rotation of the Corsica-Sardinia block during the Carboniferous-Permian transition.

Pre-existing lithospheric weak zone and its impact on continental rifting – The Mid-Polish Trough, Central European Basin System

The large portion of Central and NW Europe was subjected to widespread continental rifting since the Carboniferous-Permian transition. This process led to nucleation of several large depocentres, coalescing from the late Permian onwards into the extensive Central European Basin System (CEBS), that grew and evolved until the regional-scale Late Cretaceous inversion. Development of deep grabens from Germany to the Netherlands and the North Sea was connected with volcanism and crustal thinning. The exception makes the Mid-Polish Trough (MPT), trending NW-SE across Poland along the Teisseyre-Tornquist Zone (TTZ) at the margin of the East European Craton (EEC). The MPT is underlain by relatively thick lithosphere and its formation was not associated with volcanic activity in the direct neighbourhood. To investigate this anomaly, we compiled grids for key horizons defining the crustal architecture, separately for NW European and Polish sectors of the CEBS. Seismic reflection and well data were used to build the base Permian grid, whereas deep seismic refraction and reflection data along with constrained gravity inversion were employed to construct the top basement and Moho grids. Based on a dense net of seismic refraction profiles, the additional top Ediacaran grid was created solely for the Polish part of the CEBS. Our data show distinct crystalline crust thinning SW of the TTZ (β factor = 3.68) expressed in both shallowing of Moho and deepening of the crystalline basement. We interpret this feature as a fossilised crustal neck inherited after an Ediacaran rifting preceding the break-up of Rodinia. The early Permian rifting moderately contributed to the crustal thinning (β factor = 1.4), overprinting the primary rifted margin geometry. The 8 km deep MPT developed in front of a pre-existing crustal neck that obstructed further propagation of extensional deformation. Lithospheric mantle beneath a rift axis was probably too strong to accommodate extension but the thinner lithosphere farther west was weak enough to be stretched. Therefore, the location of the pre-existing weakness zone relative to a change in lithosphere thickness may localise a rift graben and shift the magmatism away from the surface expression of the rift. Thus, our study demonstrates that fossil crustal architecture was a key factor controlling the amount, distribution, and style of continental rifting.

Palaeoenvironmental reconstitutions at the Carboniferous–Permian transition south of the Paris Basin, France: implications on the stratigraphic evolution and basin geometry

The late Carboniferous-to-Permian coal-bearing Decize-La Machine Basin, and more specifically the Lucenay-les-Aix area, located south of the Paris Basin, has been investigated to reassess the palaeoenvironmental evolution and the basin architecture. The detailed sedimentological study has been carried out based on core data and digitised old mining data, i.e., seismic profiles and well-logs. An interpretation of well-logs without core data is proposed, based on a palaeoenvironmental interpretation from cores and their respective well-log data, and three depositional environments have been defined: an alluvial plain, an alluvial-fan, and deltaic and lacustrine environments. Correlations between wells have been performed using markers identified in seismic profiles, paired with sequence stratigraphic interpretations from well-log and core data. An evolution in seven major progradational–retrogradational stratigraphic cycles is proposed based on the evolution of the depositional environment observed at the basin scale, leading to a reconstruction of palaeogeographic maps at the Carboniferous–Permian transition. This new viewpoint shows that through time, the deposits, proximal at the base of the succession with coal preservation, become more lacustrine with the delta prograding into the basin. In consequence, the basin evolution shows a general retrogradational trend with increasing lacustrine deposits at the top of the succession eroded by the Permian–Triassic unconformity. Therefore, the current borders of the basin in the Lucenay-les-Aix area are not representative of those at the time of the sedimentary filling, and thus, this area could be part of a larger one, perhaps encompassing all north-eastern French Massif Central late Carboniferous-to-Permian basins.

Paleozoic-Mesozoic tectono-sedimentary evolution and magmatism of the Egersund Basin area, Norwegian central North Sea

This study focuses on the tectonic evolution of the greater Egersund Basin in the Norwegian central North Sea, with special emphasis on Late Paleozoic extensional tectonics following Caledonian collapse and the Variscan Orogeny, and the impact of the basement structural grain on this evolution. The Caledonian collapse likely resulted in development/rejuvenation of the deepest E-W trending structures/depocenters by Late Devonian time. Thus, a late Devonian-?early Carboniferous age can be assigned to the initial extension, which was associated with the development of an E-W striking basin system, to be overprinted by N–S extensional structures of similar age. A phase of regional magmatism at the Carboniferous-Permian transition (≈300 Ma) may be associated with a large igneous province centred on the Skagerrak area. Faulting during late Carboniferous-early Permian was minor within the study area as reflected by uniform sedimentary thicknesses of the uppermost Carboniferous and lower Permian sequences. Major normal faults, mainly trending N–S, were active during a late Permian-Early Triassic rift phase affecting large parts of the central and northern North Sea area. A later phase of extension was initiated in late Middle Jurassic time and the Egersund Basin proper formed during the Late Jurassic-Early Cretaceous. The depocenters that developed during this phase was influenced by the deep Late Paleozoic (sub-salt) structural grain, including strike-slip movements along the Sorgenfrei-Tornquist Zone. Later events include mild inversion along the northern flank of the Egersund Basin, possibly as a Late Cretaceous response to far-field Alpine compression, and Cenozoic regional tilting.

The origin of tetrapod herbivory: effects on local plant diversity.

The origin of herbivory in the Carboniferous was a landmark event in the evolution of terrestrial ecosystems, increasing ecological diversity in animals but also giving them greater influence on the evolution of land plants. We evaluate the effect of early vertebrate herbivory on plant evolution by comparing local species richness of plant palaeofloras with that of vertebrate herbivores and herbivore body size. Vertebrate herbivores became diverse and achieved a much greater range of body sizes across the Carboniferous-Permian transition interval. This coincides with an abrupt reduction in local plant richness that persists throughout the Permian. Time-series regression analysis supports a negative relationship of plant richness with herbivore richness but a positive relationship of plant richness with minimum herbivore body size. This is consistent with studies of present-day ecosystems in which increased diversity of smaller, more selective herbivores places greater predation pressures on plants, while a prevalence of larger bodied, less selective herbivores reduces the dominance of a few highly tolerant plant species, thereby promoting greater local richness. The diversification of herbivores across the Carboniferous-Permian boundary, along with the appearance of smaller, more selective herbivores like bolosaurid parareptiles, constrained plant diversity throughout the Permian. These findings demonstrate that the establishment of widespread vertebrate herbivory has structured plant communities since the late Palaeozoic, as expected from examination of modern ecosystems, and illustrates the potential for fossil datasets in testing palaeoecological hypotheses.

Provenance and paleogeography of the Southern Paraná Basin: Geochemistry and U[sbnd]Pb zircon geochronology of the Carboniferous-Permian transition

The Carboniferous-Permian transition of the intracratonic Paraná Basin (S Brazil) includes important evidence of the climate change, tectonics, and paleogeographic configuration of SW Gondwana. During this period, the Late Paleozoic Ice Age (LPIA) was in its final phase in the Paraná Basin, producing a temperate-tropical climate through the transition to the Permian. UPb laser ablation ICP-MS detrital zircon dates and whole-rock geochemistry of rocks from the upper Itararé Group (Carboniferous) and the lowermost Rio Bonito Formation (Early Permian) in the southern Paraná Basin are determined to characterize the sedimentary-dispersal patterns of the source area and glacial paleoflow. Geochemistry proxies suggest that the studied units experienced different degrees of weathering, with the Itararé Group's units forming in an arid environment. The overlying Rio Bonito Formation's units were deposited under hotter and more humid climate conditions. The Late Carboniferous to Early Permian units showed similar zircon-age distribution patterns, with a Neoproterozoic main peak from the Uruguayan Sul-Riograndese Shield. A lack of Mesoproterozoic sources in the studied samples indicates that this area of the Paraná Basin probably did not receive sediments from the African side during the Late Carboniferous as previously described. This result suggests a more complex system in which ice caps and small ice sheets dominated the glacial environment during the Late Carboniferous in this segment of SW Gondwana.

Correction to: Fusulinoids from the Carboniferous–Permian transition beds from the Abadeh Region (Sanandaj–Sirjan Zone, Iran)

The original version of this article unfortunately contained a mistake. Some labels are missing in the figure 3. The corrected figure is included in the next page.

Edaphosauridae (Synapsida, Eupelycosauria) from Europe and their relationship to North American representatives

A recent discovery from the Carboniferous–Permian transition of the southwest German Saar–Nahe Basin has revealed a medium-sized edaphosaurid skeleton. It is described as Remigiomontanus robustus gen. et sp. nov. Apart from a largely complete dorsal column, showing the typical hyper-elongated spines with lateral tuberculation, few other elements are preserved. Although lacking certain autapomorphies, the unique character combination of this new form strongly suggests an intermediate position between Ianthasaurus and Edaphosaurus. This study presents a revision of the complete European material of Edaphosauridae, counting the newly named genus Bohemiclavulus (type species Naosaurus mirabilis Fritsch, 1895), and a confirmation that Edaphosaurus credneri is an indeterminate juvenile of this most derived genus. Further fragments include a second young juvenile from the Dohlen Basin, east Germany, the lost spine set of Ramodondron from Boskovice Basin, Czech Republic, and a poorly preserved specimen from Autun, France, for which its hitherto parareptilian classification is debated. A renewed dataset is used to carry out a phylogenetic analysis. Exhaustive comparisons allow for a deeper understanding of back sail characters, which on the other hand hamper a phylogenetic resolution for both European and North American taxa. Previously reconstructed faunal provinces of edaphosaurid distribution are not evident from the present knowledge.

Bivalves of Northeast Asia at the Carboniferous–Permian Transition

Bivalves of Northeast Asia at the Carboniferous–Permian Transition

Carboniferous-Permian climate change constrained early land vertebrate radiations.

The Carboniferous-Permian transition (CPT) was Earth's last pre-Quaternary icehouse-greenhouse transition, recording major shifts in late Palaeozoic climate regimes and increased continental seasonality over approximately 40 Myr. Its parallels to Quaternary climate change have inspired recent investigations into the impacts of purported rainforest collapse on palaeotropical vertebrate diversity, but little is known about how the protracted spatial dynamics of this transition impacted the emergence of modern tetrapod lineages. Here, we apply ecological ordinance analyses on a dataset of 286 CPT fossil vertebrate localities binned across four physiographic regions forming a palaeoequatorial transect. Our results clarify the spatiotemporal expansion of land-living vertebrates, demonstrating that the reduction of tropical wetlands accommodated emerging dryland-adapted amniote faunas from a western Pangaean epicentre. We call this west-east lag the 'Vaughn-Olson model': CPT climatic transitions were regionally diachronous with delayed proliferation of amniote-dominated dryland assemblages in the east. By combining our ecological analyses with a phylogenetic approach, we demonstrate that this pattern also applies to some co-occurring total-group amphibians, suggesting that there was pervasive selection for such dryland adaptations across the crown tetrapod tree, in contrast with stem tetrapods and 'fishes'.

40Ar/39Ar chronological constraints on syn- and post-Variscan biotite porphyroblasts from the Iberian Chains, NE Spain

We perform a multidisciplinary study of biotite porphyroblasts and veinlet infills hosted in Cambrian strata of the hanging walls from the NW-SE-trending Datos, Jarque and Daroca thrusts (Iberian Chains). Stratigraphic and microstructural crosscutting features indicate that a biotite isograd runs parallel to the southeastern transects of the three thrusts. The metamorphic grade reached in the southeastern edge of the Iberian Chains is clearly distinct from both the Cadomian epizonal metamorphism, exclusively recorded in the Ediacaran–basal Cambrian Paracuellos Group, and the Variscan anchizone metamorphism recorded throughout Cambrian–Devonian strata. During post–Variscan negative inversion tectonics, renewed K-metasomatism along the same thrusts led to crystallisation of geochemically similar biotites in parallel fissures and veins. 40Ar/39Ar ages are (i) latest Westphalian–to–Guadalupian (285.82 ± 23.75 Ma) for metamorphic biotite porphyroblasts affected by diffusion loss of Ar, including the Carboniferous–Permian transition within error; and (ii) Early Triassic (246.87 ± 5.36 Ma) for biotite occlusion in post–Variscan veinlets. The Iberian Chains represent the southeastern prolongation of the Cantabrian and West Asturian-Leonese zones. The latter displays a uniform eastward decrease in metamorphic grade, whereas the Iberian Chains exhibits a heterogeneous distribution of low-grade metamorphic conditions (chlorite zone). The local presence of the biotite isograd is linked to the higher tectonic gradients associated with the Daroca, Jarque and Datos thrusts, quite similar to the metamorphic isogrades recognized both in the northeastern edge of the Demanda Massif and the Novellana-Pola de Allande-Degana Belt of the West Asturian-Leonese Zone. This distribution allows the identification of a broad NW-SE belt of biotite-in isograd-related synkinematic metamorphism, following the western contact of the Narcea Antiform, the Anguiano Thrust and the southeastern edges of the Daroca, Jarque and Datos Thrusts in the Iberian Chains. Based on Variscan structural style and metamorphic grades, the Datos Thrust links with the contact that separates the Cantabrian and West Asturian-Leonese zones of the Iberian Massif.

Aridification across the Carboniferous–Permian transition in central equatorial Pangea: The Catalan Pyrenean succession (NE Iberian Peninsula)

The Carboniferous–Permian terrestrial successions record a global climatic shift from icehouse to hothouse conditions. Our multidisciplinary study documents an aridification trend throughout the ~1000m thick composite terrestrial succession of the western Catalan Pyrenees (NE Iberian Peninsula), representing this time period. The detailed stratigraphic framework integrates sedimentology, paleopedology, biochronology (plant fossils and tetrapod footprints) and geochronology (paleomagnetism). Additional absolute age correlation is also carried out. The new and reviewed data show that the late Carboniferous wet environments (with short drought periods) progressively changed to a strong seasonal semi-arid and arid climate (with short humid periods) through the early Permian. This paleoclimatic trend supports the previously suggested aridification of the Pangean pan-tropical belt, and supports the hypothesis of the influence of the recurrent climatic fluctuations in Central Pangea, being tentatively correlated to the Southern Gondwanan glaciation-deglaciation periods. Therefore, the Carboniferous–Permian terrestrial succession from the Catalan Pyrenees emerges as a continuous record that can help to constrain late Paleozoic paleoenvironmental events.

Palynology of the Bajo de Veliz Formation, central-western Argentina: Implications for Carboniferous–Permian transition biostratigraphy

The Bajo de Veliz Formation (Paganzo Basin, Argentina) is one of the key upper Paleozoic successions characterizing the Carboniferous-Permian transition in westernmost Gondwana. A rich paleoflora with the first records of glossopterid leaves suggests an earliest Cisuralian age for the Pallero Member of the unit, although associated insects have been assigned to late Pennsylvanian groups. In this paper we present a new palynological analysis of the fossiliferous section with the goal of to correlate with coeval palynofloras from the region. The palynological assemblages, referred to the Pakhapites fusus–Vittatina subsaccata (FS) Biozone are characterized by Vittatina, Protophaloxypinus, Hamiapollenites, Pakhapites and Weylandites pollen (in proportions less than ten percent) together with the presence of the Converrucosisporites confluens Morphon. They have similar composition to those described for the Carboniferous-Permian stratotype and correlate with several associations from western Argentina and the Protohaploxypinus goraiensis Subzone of Brazil and Cristatisporites inconstans-Vittatina saccata Biozone of Uruguay. Available radiometric ages allow us to consider the probable beginning of the FS Biozone in the Gzhelian as well as the appearance of the glossopterids.