부산대학교 도서관

The sedimentary and paleontological record study of the terrestrial end-Carboniferous, Permian and Triassic from the Catalan Pyrenees allowed to characterize its paleoenvironmental and paleoclimatic evolution and their influence on the terrestrial ecosystems during the Paleozoic–Mesozoic transition. This transition, featured by several climatic changes and mass extinctions, has been analyzed in a multidisciplinary study. Diverse fieldworks have resulted in the discovery of up to ten new fossil localities, mainly bearing tetrapod ichnites (here especially emphasized), but also bearing bone remains, invertebrate trace fossils and plants. Until the present work, few fossil footprint sites were known from these ages in the Catalan Pyrenees. The detailed stratigraphic columns and cartography allowed to establish the spatio-temporal succession of fossil sites and of the corresponding geological units (depositional units defined in previous works). The coupled study of ichnites and facies contribute to carry out paleoenvironmental analyses. The study of the fossil record implied the establishment of different biozonations, which have been complemented with paleomagnetic, cyclostratigraphic, mineralogical and elemental analyses. The late Carboniferous has been documented by the Grey Unit plant assemblage, indicating a Stephanian C age. The sedimentological and paleosol data point to a humid climate with short dry periods. The Carboniferous–Permian transition (Transition Unit) is featured by increases in seasonality and aridity. The lack of chronological markers in the studied outcrop precludes to clarify the age of the unit. The early Permian constitutes the beginning of the red-bed successions. Paleosols developed in the Lower Red Unit volcanosedimentary deposits and the absence of coal denote climate aridification and strong seasonality. Sporadic relatively humid intervals, depicted by meandering fluvial systems and deposits derived from unconfined runoff water, yield a tetrapod ichnoassemblage characteristic of the Artinskian and composed of: Batrachichnus salamandroides, Limnopus isp., cf. Amphisauropus, cf. Ichniotherium, Dromopus isp., cf. Varanopus, Hyloidichnus isp., Dimetropus leisnerianus and three types of Characichnos (swimming trace fossils). Arthropod trace fossils (especially Rusophycus and Acripes) are also common. The middle Permian record denotes humid climatic conditions and seasonality. Few fossil remains have been reported from the lower Upper Red Unit distal alluvial system. The presence of a vertebra assigned to the caseid group suggests an early Wordian age and, together with tetrapod ichnites documented in previous works, a faunal replacement is confirmed. The late Permian is characterized by a semi-arid climate, as indicated by the sedimentological, mineralogical and elemental data of the upper Upper Red Unit. Deposits of the playa-lake or ephemeral lacustrine system show orbital forcing during sedimentation. The documented tetrapod ichnoassemblage marks a replacement of the middle Permian faunas, possibly linked to an extinction. The Early and Middle Triassic is recorded by the fluvial system (from braided to meandering rivers and floodplains) of the Buntsandstein facies unit, which yields a tetrapod ichnoassemblage composed of: Prorotodactylus mesaxonichnus (erected as a new ichnospecies), cf. Rotodactylus, Rhynchosauroides cf. schochardti, undetermined Rhynchosauroides and chirotheriids, an undetermined Morphotype A and two types of Characichnos associated to the new ichnospecies and to chirotheriids. This fossil record is complemented with the presence of two recovered archosauromorph teeth and is indicative of the terrestrial ecosystems recovery after the end-Permian mass extinction, being archosauromorphs a relevant group. The continuous record throughout the Carboniferous–Permian and Permian–Triassic transitions (so far unknown from southwestern Europe), as well as the unsuspected fossil richness, make the Catalan Pyrenees a reference region worldwide to untangle some of the most drastic changes of Earth history.