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 calcalkaline 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).

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A new description and sampling campaign of the Sancerre-Couy core has been achieved to reconstruct the evolution of the depositional environments of the Permian and Triassic series and the palynological evolution of the Permian to Lower Jurassic series. High-resolution sequence stratigraphy of the Permian and Triassic series of the Paris Basin, based on well-log A c c e p t e d M a n u s c r i p t analysis, is used to determine seven progradational-retrogradational cycles in the Permian and twelve cycles in the Triassic. Out of the 54 samples collected from the Sancerre-Couy-1 core, only 23 were palynologically productive. Based on the taxonomic composition, four palynological assemblages are distinguished, three of which have been described in previous studies. These three classical palynological assemblages of the Sancerre-Couy-1 core are documented in detail for the first time in this present study. The description of the new assemblage and its correlation can be used to reassess the previously assigned ages: assemblage SC-1 is late Ladinian in age, SC-2 is of the Ladinian-Carnian transition, SC-3 is early Carnian in age, and SC-4 is of late Rhaetian age whereas it had previously been assigned a Hettangian age.

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The Middle Triassic (Ladinian) deposits of the Catalan Basin (Spain) are essentially represented by extensive marine carbonate platforms developed in a rift tectonic setting. During the Ladinian, a regional sea-level drop led to a significant paleogeographic reorganisation of the depocentres of eastern Iberia producing a relevant shift in the distribution of the sedimentary environments. To better calibrate the age of the correlative conformity and the associated depositional facies, a new palynological study was carried out in two localities in Tarragona province (Spain). The palynological assemblages suggest a Longobardian-Cordevolian age (Middle-Late Triassic transition) for the materials deposited below and above the correlative conformity. This study allows a refined biostratigraphic and sedimentary correlation between the carbonate sediments in the Catalan Basin and those in the Iberian Ranges and adjacent basins of the Tethys region.

<p>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.</p><p>In the Euramerican Province, the continental vegetation during the Pennsylvanian was a hygrophilous flora comprising pteridosperms, marattialean ferns, lycopsids, <em>Calamites</em> and <em>Cordaites</em> 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.</p><p>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 <em>Potonieisporites novicus</em> and <em>Vittatina costabilis</em>, and the middle-late Permian (“Thuringian flora”) mainly characterised by <em>Lueckisporites virkkiae</em> and<em> Nuskoisporites dulhuntyi</em>. 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.</p><p>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).</p><p>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.</p>