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We report the results of a multidisciplinary study of the early Permian (Artinskian–Kungurian) Sotres Formation of northern Spain integrating sedimentology, palaeosols, mineralogy, stable isotopes, palynology, ichnology and tectonics. This continental unit was deposited in the near-equatorial Peri-Tethyan Cantabrian Basin. Having developed in the middle of the Variscan fold belt, it is preserved within the present-day Cantabrian Mountains. Three subunits are recognised in the Sotres Formation based on tectono-stratigraphic and sedimentological data: a lower alluvial subunit, a middle carbonate lacustrine subunit, and an upper palustrine subunit. Multidisciplinary results reveal an upward change in climate from humid-subhumid conditions at the base of the formation (Artinskian) to semi-arid and arid conditions at the top of the formation (Kungurian), which may reflect global deglaciation near the end of the Late Paleozoic Ice Age and a probable northward migration of the Intertropical Convergence Zone. This general upward warming/drying climate trend was interrupted by a short-lived interval of monsoon conditions in mid-Kungurian times, which may have coincided with a pulse of global cooling. Our findings are in agreement with the climate trends reported for other central Pangaean basins. Rising CO2 levels may have been a driving factor for climate transition during this time interval. However, in our study area, which lies within the active central Variscan orogenic belt, tectonic conditions must have also played a role in driving climate change.

The present-day Cantabrian Mountains (North Spain) represent the western continuation of the Pyrenean-Cantabrian Orogen, which arose from a Cenozoic collision between the Iberian and Eurasian plates. The early Alpine sedimentary record of the Cantabrian basin is represented by the latest Carboniferous-Permian and Triassic rocks, mostly of continental origin. A lack of palaeontological data has led, until recently, to erroneous interpretations of the stratigraphic position of this sedimentary record. Within the framework of the Triassic sedimentary record in northern Spain, the precise age of six samples was determined and they were grouped into four palynological assemblages according to their taxonomic composition. The study of these assemblages includes a review of all the Triassic assemblages published to date as regards the Cantabrian Mountains, thereby optimising our Triassic palynostratigraphical knowledge of this area enabling comparisons with other Triassic assemblages of Central and SW Europe.

This study compares several geochemical factors (major and minor rare earth elements, Ti/Al ratios, and chemical index of alteration, CIA, values) in the Early Triassic Cañizar Formation (Fm) (Buntsandtein facies) of E Iberia with those of adjacent Middle Permian and Middle Triassic units (Alcotas and Eslida fms, respectively). According to significant differences detected, it seems that most geochemical perturbation occurred during the Early Triassic. Variations in Ti/Al ratios suggest changes in source areas between the studied units and even within the Cañizar Fm. These provenance changes correlate with successive tectonic pulses during the opening and development of the Iberian Basin, as they can be linked to major sedimentary surfaces and unconformities, as well as major sedimentological variations. Ti enrichment in the lower and middle part of the Cañizar Fm, together with high Sr and P concentrations, may be indicative of environmental alterations related to acid meteoric waters. Moreover, this acid alteration took place under arid conditions as reflected by CIA values, indicating that during the deposition of the Cañizar Fm, variable but predominantly physical weathering prevailed in contrast to the chemical weathering that took place when the Alcotas and Eslida formations were deposited. Our data along with the known fossil record of the study area indicate that during the Middle–Late Permian and Early Triassic, conditions in this tectonically active area changed from humid to arid-acid, hampering biotic recovery. Then, during late Early–Middle Triassic times, the return of more humid and less acid environments promoted biotic development. Geochemical markers emerged as useful tools complementary to sedimentological, paleontological, and tectonic data for unveiling paleoenvironmental events, especially in a setting of significant regional change.

Funds were provided by projects PGC2018-098272-B-100 and CGL2015-70970-P “FALPINO” (Spanish Ministry of Science, Innovation and Universities)., Lloret, J; Lopez-Gomez, J; Heredia, N; Martin-Gonzalez, F; De la Horra, R; Borruel-Abadia, V; Ronchi, A; Barrenechea, JF; Garcia-Sansegundo, J; Gale, C; Ubide, T; Gretter, N; Diez, JB; Juncal, M; Lago, M

The Late Carboniferous - early Permian was a time-interval of major geological and climatological changes, mostly due to the transition to greenhouse conditions from the maximum glacial coverage (Late Palaeozoic Ice Age or LPIA). This climatic change produced an increase of the extinction rates on land plants and a variation on the constitution and distribution of palaeofloras during this time. The restructuring of ecosystems during Late Pennsylvanian is interpreted as the "collapse of the rainforests". A replacement of hygrophytic (“Stephanian flora”) by mesophytic and meso-xerophytic flora (“Autunian flora”) that tolerate seasonally dry climate is described.In the Euramerican Province, the continental vegetation during the Pennsylvanian was a hygrophilous flora comprising pteridosperms, marattialean ferns, lycopsids, Calamites and Cordaites trees. At the Late Pennsylvanian-early Permian, the “Carboniferous hygrophilous flora” proliferated in the wet depressions (lowlands) and the mesophilic or even meso-xerophytic flora, grew on the heights (uplands) in the dewatered habitats. Later, this xerophytic flora will be dominant in the landscapes during the middle and late Permian.There are detailed palynostratigraphic studies that allow precise palynological datings for the Carboniferous period in the Euramerica Province. However, few palynological works have been published relative to the early Permian sedimentary record in this province. In a broad sense, these latter studies only differentiate the early Permian flora (“Autunian flora”) due to the presence of sporomorph taxa as Potonieisporites novicus and Vittatina costabilis, and the middle-late Permian (“Thuringian flora”) mainly characterised by Lueckisporites virkkiae and Nuskoisporites dulhuntyi. This lack of precision was probably due to the different sedimentation rates in the intramontane basins and the “border effect” (as a phytogeographic barrier) caused by the Variscan Belt.The number of works and the wrong use of non-chronostratigraphic terms like “Autunian” and “Thuringian”, making it necessary to re-calibrate the palynological assemblages in the Euramerica Province. A detailed biostratigraphic study allows us to show here, for the first time, a new palynostratigraphic chart derived from palynological studies from some of the best known low-latitude basins radiometrically dated (Pyrenees, Autun, Lodève, Collio and Tregiovo basins) and from basins with well-known internal lithostratigraphic correlation (e.g., the Cantabrian Mountains and the Iberian Ranges).Based on the results obtained here, the microflora evolution in the early-middle Permian has been described at low latitudes of the Euramerican Province. Furthermore, this study provides a solid base for stabilising the palynozones for the Permian in the southern domain of the Variscan Belt.

The late Carboniferous to early Permian interval was a time of major global changes on Earth. It encompassed the final consolidation of the Pangaea supercontinent and the subsequent development and infill of continental basins. This interval also witnessed a climate transition towards warmer conditions, including the substantial retreat of the extensive continental ice sheets developed during the Late Palaeozoic Ice Age (LPIA). The end of this climate transition represented an evolution form an icehouse to a greenhouse period at the early to middle Cisuralian, which in turn was a time of important tectonic changes in Pangaea. However, our understanding of this whole chain of processes still has many gaps and many of its features still generate debate, especially those concerning the origin and the end of this transition period. This study focuses the late Carboniferous to early Permian interval by means of a multidisciplinary study in the Pyrenean (P) and Basque-Cantabrian (BC) basins, that constitute a near equatorial complex extensional structure located in the middle of the late-Variscan fold belt. The present-day Pyrenean Ranges, extending E-W along almost 1000 Km, from the Mediterranean coast to the Basque-Cantabrian Cordillera, is the result of intense inversion of previous Permian to Cretaceous extensional to transtensional rift basins. In those basins, the time-interval has been traditionally studied in two separated structural units: Basque-Cantabrian Pyrenees and Aragonese-Catalan Pyrenees. However, this multidisciplinary study, proposes the existence of a lateral tectono-sedimentary connection for the entire basin. Nine late Carboniferous - early Permian sub-basins have been studied in the Basque-Cantabrian and Pyrenean domain. From west to east they are: Frieres, Sotres, Carmona, Anayet, Aragorn-Bearn, Castejón-Sas, Erill Castell, Gramós and Camprodón. Three lithological units, separated by unconformities and dated by means of pollen associations and radiometric data, represent the Permian record of these basins. They constitute three cycles of sedimentation of similar age (Gzhelian-Asselian, Asselian-Sakmarian, and Sakmarian-Kungurian) related to the same post-Variscan geodynamic stages of evolution affecting the whole Pyrenean and Basque-Cantabrian basins. The two younger cycles broadly coincide with other similar cycles defined in SE France and Sardinia, thus pointing to a common tectono-sedimentary evolution for the westernmost continental Peri-Tethys domain during this time-interval. In addition, the middle cycle (Asselian-Sakmarian) mostly represents a calc-alkaline volcano-sedimentary event in most of the sub-basins, related to a post-Variscan extensional phase. Detailed studies of paleosols, sedimentology, and mineralogy indicate a progressive evolution towards warmer conditions that were accelerated during the Artinskian, probably related to the end of the global icehouse period associated to the LPIA in the equatorial late-Variscan fold belt domain.

In recent years there is growing evidence of the importance of the Smithian-Spathian (Early Triassic) ecological crisis to explain the delayed recovery of life after the Permian-Triassic Boundary mass extinction. This study focuses on sedimentary continental rocks of middle Permian to Middle Triassic age from four different Peritethys basins in subequatorial latitudes. Similar distribution patterns of aluminum phosphate-sulfate (APS) minerals contents in these rocks in the four studied basins provide evidence of increased acidity during the Smithian-Spathian transition, coinciding with a lack of indicators of organic activity in the same interval. Thus, this period of high acidity on land, may have been one of the causes of this biological crisis. Based on the quantification of APS minerals in the studied sedimentary sequences, we propose that it was not until acidity in the environment diminished, that biotic recovery was possible. APS data may also be useful to interpret other past biotic crises.

This work focuses on the Olenekian-Anisian (Early-Middle Triassic) continental record of the Central-Eastern Pyrenean basin (NE Spain), a near-equator (10°-14°N) basin located in the western peri-Tethys margin, inside the Variscan fold-belt. Due to the mass mortality of the end-Permian and the subsequent Smithian-Spathian Boundary (SSB) crisis, the Early Triassic and its transition to the Middle Triassic was a time period with intermittent stages of environmental instability that affected fauna and flora intensely. Compared to other crisis, a remarkable feature is the longer time required to achive life recovery during this time-interval and the fact that continental environments have been less globally studied than their marine counterparts. Furthermore, in SW Europe there is almost no sedimentary continental record from the beginning of the Triassic. This multidisciplinary study, embracing sedimentology, mineralogy, palaeontology, palaeopedology and palaeogeography, of 10 complete and well dated Early-Middle Triassic field sections has allowed (1) the location and characterization of the oldest Mesozoic sedimentary record in the basin, which is of late Smithian age and overlies the late-middle Permian continental rocks and of (2) the Smithian-Spathian transition (SST), (3) the timing of life recovery during the late Spathian-Anisian, (4) the characterization of the first incursion of the Tethys sea into the basin, and (5) the comparison of the evolution of this basin with other basins of the same age in SW Europe. The SST coincides with hyper-arid climate conditions, evolving to semi-arid in the late Spathian and semi-arid to semi-humid in Anisian times. Poorly sorted breccias and conglomerate alluvial sheets with aeolian reworking dominate the SST, as a result of these environmental changes and tectonicsA broader comparison, based on stratigraphic studies by other authors, indicates less aridity in the basin studied compared to other SW Europe basins in the same period, maybe due to its greater proximity to the equator. Sedimentary characteristics changed during the late Spathian, when sandy braided fluvial systems developed and the first dispersed plants, pollen assemblages and paleosols appeared. Well-developed floodplains and associated paleosols and plants developed during the early Anisian, when more humid conditions prevailed. The occurrence of aluminium phosphate-sulphate (APS) minerals might be considered as evidence of environmental acidification during the Olenekian with an amelioration during the early Anisian, as described in neighboring basins, although in the Pyrenean basin this acidification was probably less intensive. The first incursion of the Tethys sea reached the Central-Eastern Pyrenean basin during the Anisian-Ladinian transition, about 3 My later than in neighbouring Southwestern Europe basins. General comparison with other Early-Middle Triassic continental records of Western Europe basins indicates contrasting trends of climate and sedimentary evolution, probably related to the still prevailing great paleorelief of the Variscan foldbelt, where part of the study basin could constitute an elevated area during some time-intervals, possibly related to the so-called Ebro High.

International audience; The Permian-Triassic rifting represents the first of the two Mesozoic rifting stages recorded in the Iberian Peninsula. Its first phases of development started during the Early Permian, and were linked to the beginning of the break-up of Pangea, the large, unique and rheologically unstable supercontinent that mainly resulted from the collision of Gondwana and Laurussia. This chapter analyzes this first rifting stage in Iberia in two separate phases, an initial or tectonic phase, and a later mature phase. This analysis focuses on the main Permian-Triassic basins of the Iberian Peninsula: the Pyrenean, Iberian, Catalan, Ebro and Betic basins, as well as the basins located in the present-day Balearic Islands. In order to achieve a better understanding of the analyses of these basins, a multidisciplinary approach has been carried out by 48 researchers, including studies of tectonics, sedimentology, magmatism, mineralogy, geochemistry and paleontology.

The Pyrenean-Cantabrian Orogen arose through the collision of the Iberian and Eurasian plates, mostly in Cenozoic times. This orogen comprises two main mountain ranges, the Pyrenees to the east, and the Cantabrian Mountains to the west. To date, the early Alpine tectono-sedimentary phases preserved in the Cantabrian Mountains, of Permian and Triassic age, have been considered independently from the same phases in neighbouring basins of SW Europe, and even from the eastern part of the same orogeny (the Pyrenean orogeny). In consequence, the beginning of the Alpine cycle in the Cantabrian Mountains has been interpreted within a specific geodynamic context, far from the general evolutionary phases of the western Peri-Tethys basins. Through detailed field work, including geological mapping, sedimentology, lithostratigraphy and petrology of volcanic rocks, and new palaeontological data, here we define several new lithostratigraphical formations and five new tectono-sedimentary cycles (TS I-V) for the initial phases of evolution of the Mesozoic Basque-Cantabrian Basin, interrupted by periods of tectonic stability. To complete this information, we include data from an onshore borehole (Villabona Mine) and two offshore boreholes constrained by 2D reflection seismic profiles acquired in the North Iberian continental platform. The main tectono-sedimentary cycles, related to the deposition of five major identified lithostratigraphic units, can be described as follows: TS I (late Gzelian-early Asselian), relating to the late Variscan deformation and preserved in a single outcrop in all the Cantabrian Mountains (San Tirso Formation). This formation is constituted by medium-distal alluvial fan deposits in which humid intervals predominate, forming some thin coal beds. TS II (Asselian-Sakmarian), a post-Variscan extensional phase with associated calc-alkaline magmatism, represented by profuse volcanic and volcanosedimentary intercalations in the early Permian sedimentary basins (Acebal Formation) and small plutons in surrounding areas. TS III (Kungurian), or reactivation of the post-Variscan extension leading to alluvial and lacustrine carbonate sedimentation in arid climate conditions, which do not change during the rest of the Permian and Triassic periods (Sotres Formation). A generalized karstification in the basin represents the end of Permian deposition, followed by an interruption in sedimentation longer than 30 Myr. The Permian tectono-sedimentary cycles (TS II and TS III) are contemporary with Variscan belt collapse and the basins are controlled by extensional reactivation of NE-SW and E-W Variscan structures, and NW-SE late Variscan structures. TS IV (late Anisian–middle Carnian), renewed sedimentation in more extensive basins, precursors of the great Mesozoic Basque-Cantabrian Basin. This cycle is represented by fluvial deposits (Cicera Formation, or Buntsandstein facies), which are interrupted by the first Mesozoic marine ingression (Rueda Formation, or Muschelkalk facies). TS V (Norian-Rhaetian), or shallow marine carbonate deposits (Transición Formation) related to increasingly compartmentalized sub-basins, controlled by normal faults. This final TS is broadly connected with different basins of the western Peri-Tethys domain. The identification of units TS I-V in the Cantabrian Mountains along with the volcanic character of TS II, all indicate the development of a common post-Variscan to early Alpine tectono-sedimentary evolution for the whole Pyrenean-Cantabrian realm., This work was funded by projects CGL2014-52699P and CGL2015-70970-P (Spanish Ministry of Economy and Competitiveness and FEDER Funds of the European Union), as well as projects: >Sistemas Sedimentarios y Variabilidad Climática> (642853) of the CSIC, Basin Analysis (910429), and Palaeoclimatology and Global Change (910198) of the Universidad Complutense de Madrid. The authors thank Luis Villa Iglesias and José Antonio Marín Barcaíztegui (MINERSA GROUP) for providing all the required borehole data from the Villabona Mine (Asturias) and for facilitating access to the mines for sampling. We thank both anonymous referees and Editor Andre Strasser for improving the final version with their comments, and A. Burton for reviewing the English.

We present a source-to-sink environmental magnetic study of a sediment core from Lake Sanabria (north-west Iberian Peninsula) and rocks of its catchment. The results indicate the occurrence of magnetite, and probably also pyrrhotite, in sediments accumulated between ca. 26 and 13 cal ka BP in a proglacial lake environment. These minerals also appear to dominate the magnetic assemblage of Palaeozoic rocks from the lake catchment. This indicates that sedimentation was then driven by the erosion of glacial flour, which suffered minimal chemical transformation due to a rapid and short routing to the lake. A sharp change in magnetic properties observed in the lake sediments between 13 and 12.6 cal ka BP reflects the rapid retreat of glaciers from the lake catchment. Sediments from the upper half of the studied sequence, accumulated after 12.6 cal ka BP in a lacustrine environment with strong fluvial influence, contain magnetite and smaller amounts of maghemite and greigite. We suggest that greigite grew authigenically under anoxic conditions caused by enhanced accumulation of organic matter into the lake. The occurrence of maghemite in these sediments suggests pedogenic activity in the then deglaciated lake catchment before the erosion and transportation of detrital material into the lake.

The Triassic record in the SE Iberian Ranges starts with two tecto-sedimentary units of continental origin in Buntsandstein facies: and Cañizar and Eslida Formations. The Eslida Formation always lies conformably on top of the Cañizar Formation and it grades upwards into overlying coastal mud flats, traditionally assigned to the Röt facies. In the past, accurate dating of the Eslida Formation was problematic because of its continental character, absence of datable fossil remains, and lithological similarities with Middle–Upper Permian rocks. Macroflora and fossilised vertebrate footprints in the Eslida Formation indicate an Anisian age (Middle Triassic). In this work, we date the Eslida Formation on the basis of a palynological assemblage. The precise dating of the Eslida Formation is essential in order to establish stratigraphical correlations with other units in the Iberian Ranges and to obtain palaeogeographical considerations on the rapid subsidence represented by the sedimentary record of this unit in the new NNE–SSE Middle Triassic rift developed in eastern Iberia., This research was supported by projects CGL2014-52699P (Spanish Ministry), CSIC Research Groups: Sistemas Sedimentarios y Variabilidad Climática (642853) and Procesos de Formación Mineral, and UCM-BSCH-GR58/08 Projects Análisis de Cuencas (910429) and Paleoclimas (910198).

In this paper, a method based on element mapping of randomly selected areas of thin sections on electron microprobe is proposed to quantify the relative contents of strontium-rich hydrated aluminium phosphate-sulphate (APS) minerals in siliciclastic continental sedimentary rocks. The main problems for these minerals to be quantified are related to their small size, low concentrations, and optical properties. By comparing the element maps obtained for the rocks in the study area of the Iberian Ranges (E Spain) with the results of whole rock analysis and with factors indicating the presence of life (bioturbation, palaeosols, and macro-plant remains), it has been possible to correlate relatively high levels of APS minerals in the first sedimentary record (Cañizar Formation) after the Permian–Triassic boundary, with the lack of living organisms. The APS are related to early diagenetic phases precipitated at low pH conditions and are therefore markers of formation in an acidic environment. Our findings suggest a long period of sustained acidic conditions followed by an environmental change linked with the recovery of life and with lower APS mineral contents. This change is detected at the top of the Cañizar Formation, at the end of the Spathian. The method proposed could be used as a tool to address the environmental changes that took place during the Permian–Triassic transition in continental environments., This work has been supported by projects: CGL2011-24048, CGL2014-52699P (Spanish Ministry), CSIC Research Groups ― Sistemas Sedimentarios y Variabilidad Climática (642853) and Procesos de Formación Mineral, and UCM-BSCH-GR58/08 Projects: Análisis de Cuencas (910429) and Paleoclimas (910198). V. Borruel-Abadía works with a predoctoral grant of the Spanish Ministry of Economy and Competitiveness. The manuscript was improved by constructive criticism of Prof. G. Pe-Piper and an anonymous reviewer.

Until recently the climate of the Early–Middle Triassic at low latitudes was broadly considered as generally temperate-warm with no major climate oscillations. This work examines the climate of this period through a detailed study of the sedimentary, plant, soil and mineral records of continental rocks (Buntsandstein facies) in eastern Iberian basins. Our findings indicate temporal climate variations for these near equator (10°–14°N) regions and unveil the significance of such variations in the southern Laurasian domain. The climate of Iberia's Early Triassic was mainly dominated by alternating brief (< 0.4 ma) arid and semi-arid climate periods, with two main arid periods documented at the end of the Smithian and middle Spathian. However, an initial short subhumid to semi-arid period was also observed in the late Spathian. Remarkably, this latter period appears just after an unconformity related to the tectonically induced Hardegsen Event in western Europe. It is also of interest that this short subhumid climate period is concurrent with the beginning of faunal and floral recovery in the basins examined. The Early Triassic ended again with a short very arid period. Although the beginning of the Anisian (Aegean) was represented by alternating arid and semi-arid to subhumid intervals, during the Bithynian and Pelsonian clearly wetter climates are recorded by the succession consisting of alternating semi-arid to semi-humid intervals. This general tendency was interrupted by three short but marked intervals, two humid intervals in the late Bithynian, and one arid period near the Bithynian/Pelsonian boundary. Iberia was crossed by prominent irregular highs separating marked corridors or isolated areas. This palaeogeography, prevailing since Variscan tectonics, clearly conditioned dominant climates and their geographical distribution. No clear climate belts developed in these conditions. However, isolated internal climate zones separated by elevated areas are identified. This palaeogeographic configuration and the low latitudinal position of Iberia determined central Iberia highs in the southernmost border of Laurasia, beyond which more humid conditions clearly extended towards the equator reaching the present-day Moroccan Meseta and Argana Basin.

The end of the Permian period is characterized by the largest mass extinction ever recorded in marine and terrestrial sedimentary rocks. The oldest plant macro-remains after the P–T boundary recorded in the Castilian Branch of the Iberian Range after this mass extinction belong to the Eslida Formation of Anisian age. These associations have been recovered at four localities and include sphenophytes (Equisetites, perhaps Neocalamites or Schizoneura), conifers (Volzia, Albertia, Pelourdea), lycophytes (Pleuromeia) and a possible seed fern (Peltaspermum). Facies associations and sedimentological analysis of the Eslida Formation have allowed for distinguishing four architectural elements: CH (channel deposits), LA (lateral accretion), CS (crevasse splay) and FF (overbank fines). The largest fossil remains are associated with CH and LA architectural elements and high-energy events, and they form part of the basal lag or reactivation surfaces. Smaller and well-preserved fragments are associated with the CS architectural elements. A sedimentologic, taphonomic and palaeoclimatic analysis reveals gradation from riparian hygrophytic vegetation to semi-arid xerophitic vegetation across the alluvial complexes and a progressive aridification through time. A comparison with other areas shows that this association is similar to coeval floras of Iberia and of the “Grès à Voltzia” Formation of northeastern France., This work has been supported by projects: CGL2011-24048 (Spanish Ministry), CSIC Research Groups “Sistemas Sedimentarios y Variabilidad Climática” (642853), and UCM-BSCH-GR58/08 Projects: Análisis de Cuencas (910429) and Paleoclimas (910198). V. Borruel-Abadía works with a predoctoral grant of the Spanish Ministry. EK acknowledges the Alexander von Humboldt-Stiftung (3.3-ITA/1141759STP) for financial support; the study of the material has been conducted within the framework of the project “The Permian–Triassic ecological crisis in the Dolomites: extinction and recovery dynamics in terrestrial ecosystems” funded by the Promotion of Educational Policies, University and Research Department of the Autonomous Province of Bolzano — South Tyrol.