Permian

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 palaeontology.

The morphology of fossil footprints is the basis of vertebrate footprint ichnology. However, the processes acting
during and after trace fossil registration which are responsible for the final morphology have never been precisely
defined, resulting in a dearth of nomenclature. Therefore, we discuss the concepts of ichnotaphonomy,
ichnostratinomy, taphonomy, biostratinomy, registration and diagenesis and describe the processes acting on
footprint morphology. In order to evaluate the morphological quality of tetrapod footprints, we introduce the
concept of morphological preservation, which is related to the morphological quality of footprints (M-preservation,
acronym MP), and distinguish it from physical preservation (P-preservation, acronym PP), which
characterizes whether or not a track is eliminated by taphonomic and diagenetic processes. M-preservation
includes all the morphological features produced during and after track registration prior to its study, and may
be divided into substages (ichnostratinomic, registrational, taphonomic, stratinomic, diagenetic). Moreover, we
propose an updated numerical preservation scale for M-preservation. It ranges from 0.0 (worst preservation) to
3.0 (best preservation); intermediate values may be used and specific features may be indicated by letters. In
vertebrate footprint ichnotaxonomy, we regard the anatomy-consistent morphology and to a lesser extent the
trackway pattern as the only acceptable ichnotaxobases. Only footprints showing a good morphological preservation
(grade 2.0–3.0) are useful in ichnotaxonomy, whereas ichnotaxa based on poor morphological preservation
(grade 0.0–1.5) are considered ichnotaphotaxa (nomina dubia) characterized by extramorphologies. We
applied the preservation scale on examples from the Palaeozoic to the present time, including three ichnotaphotaxa
and 18 anatomy-consistent ichnotaxa/morphotypes attributed to several vertebrate footprint producers.
Results indicate the utility, feasibility and suitability of this method for the entire vertebrate footprint record in
any lithofacies, strongly recommending its use in future ichnotaxonomic studies.

Ronchi et al. (in press) comment on the stratigraphic, sedimentological, mineralogical and palaeontological analyses performed in the recently described Coll de Terrers Permian Triassic terrestrial succession from the Catalan Pyrenees by Mujal et al. (2017a). The comment debates our interpretation of a succession of red-beds as Permian (Upper Red Unit, URU). Instead, the comment infers that the analysed succession is part of the regional upper Buntsandstein facies unit (Triassic), debating the proposed stratigraphic scheme by using the tectonic evolution as the main argument. Here, we clarify and present more details on the interpretation published in Mujal et al. (2017a). Based on this clarification and taking into account the comment, we arrive to the conclusion that the interpretation and inferences presented in Mujal et al. (2017a) are sound and justified.

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.