Rudist reef structure : Insights from orientation of hippuritids at l'Espà (Campanian, southern Pyrenees)

Altres ajuts: acords transformatius de la UABRudist were common Mesozoic reef builders, but rare examples exist to evaluate reef structure. The l'Espà locality (southern Pyrenees) is approached to study rudist reef structure by a quantitative assessment of the individuals' position (growing vs reworked) and its sedimentary context. This late Campanian reef is exposed along some 20 × 6 m outcrop. Builders are mainly Hippurites radiosus, although other rudists, such as Hippuritella lapeirousei, Hippuritella sp. and Mitrocaprina sp. are also present together with corals. The orientation of 325 specimens of mainly H. radiosus was plotted in stereographic and cartesian projections. Orientations and microfacies permit to differentiate 5 vertically stacked intervals (settings) along the outcrop: (1) Distal reef setting (reef-talus slope), with rudists reworked as large bunches of grouped specimens, with scarce erosion and preserving both valves articulated; (2) Halfway distal-proximal reef setting (close cluster reef), with abundant reworked, isolated, and flat-lying specimens. In this zone, endo-epibiont colonization on rudist shells is common, together with the presence of large (up to 1 m) branching and massive corals; (3) Proximal reef setting (frame/close cluster reef), where specimens are in life position; (4) A proximal back reef unit (spaced cluster reef) with few highly reworked specimens; (5) Distal back reef setting (very spaced cluster reef), with hardly any rudist fragments. This succession provides a reef tract model resembling that of most coral reefs and differs from smaller rudist reefs. The structure of the studied reef is well preserved as a result of high accommodation space related to thrust emplacement

Los fósiles : qué son y para qué sirven

Bajo el término fósil, se agrupan gran cantidad de evidencias materiales de la vida en el pasado. Generalmente, de los organismos fosilizados únicamente se conservan las partes duras, esqueléticas, por ser más resistentes a la destrucción. Pero además de los restos de organismos, también son fósiles las evidencias de la actividad orgánica, ya sean cuerpos materiales (huevos, polen, semillas, excrementos, .) o marcas como pisadas, pistas, madrigueras, etc,. Los fósiles nos permiten comprender la vida en el pasado (evolución de las especies, datación de los sedimentos que los contienen, estudios paleoclimáticos, etc.). Son varios los mecanismos que permiten que un organismo (o una de sus partes) fosilice.Under the term fossil we gather a large amount of material evidences of life in the past. Generally only the tough (skeletal) parts of the fossilized organisms are preserved because they are more resistant to destruction. Apart from organisms remains, the evidences of organic activity are also fossils, being material bodies (eggs, pollen, seeds, defecations) or marks such as footprints, tracks, nests etc,. Fossils allow us to understand life in the past (species evolution, datation of the sediments where are found, paleoclimatic studies .). Several mechanisms permit an organism (or its parts) to be fossilized

The Early Cretaceous coastal lake Konservat-Lagerstätte of La Pedrera de Meià (Southern Pyrenees)

A state of the art of the Barremian Konservat-Lagerstätte of la Pedrera de Meià site (Southern Pyrenees) is compiled here including the acquisition of new geological data. The relevance of this site, together with the nearby la Cabroa site, is due to its paleobiotic richness and the fact that 113 holotypes and paratypes of flora and fauna have already been defined. Since its discovery at the end of the 19th century and its exploitation as a lithographic limestone quarry, the site has been the object of paleontological interest by national and foreign research teams that are summarized here (including the catalogue of 224 publications). A survey of the existing type specimens in collections all over Europe is also provided, being France and Germany, the countries where more fossils are hosted other than Spain.The geological frame of this site is also reviewed, by revisiting unpublished geological mappings (mainly that of Krusat, 1966) and integrating it in a comprehensive map that includes 4 revisited outcrops of lithographic limestone which could be potential paleontological sites. Previous stratigraphic sections did allow the precise framing of paleontological data and findings, that now can be allocated in new stratigraphic sections accounting for 50m and that contain a minimum of 40.000 laminae, being a minimum estimation of the years represented in the la Pedrera de Meià site

A calibrated mammal scale for the Neogene of Western Europe. State of the art

A magnetobiostratigraphically calibrated mammal scale for the Neogene of Western Europe is presented in this paper. The Mammal Neogene MN units originally proposed by Mein [Report on activity RCMNS-Working groups] 1975 have been re-defined here on the basis of first appearances of selected small and large mammal taxa. The chronology of the lower boundaries of each unit had been established mostly after the significant magnetobiostratigraphic framework developed in the last decade in a number of Spanish basins: Ebro, Calatayud-Daroca, Vallès-Penedès, Teruel, Fortuna, Cabriel and Guadix-Baza. In the case of the early and middle Miocene particularly, MN 1, MN 2 and MN 3 , the authors have also taken into account the magnetobiostratigraphic framework developed in the North Alpine Foreland Basin. Some alternative correlations of the magnetostratigraphic data from this last basin are proposed in order to achieve a higher degree of consistence with the data from the Iberian basins. A quite well established magnetostratigraphic calibration of the MN boundaries can be proposed for most of the Neogene, from Middle Miocene to Late Pliocene. On the other hand, the chronological boundaries of the Early Miocene MN units are still poorly constrained due to: (1) scarcity of well-studied, continuous, thick magnetostratigraphic sections; (2) the difficulty in defining the boundaries of the MN zones for this time-span due to the relative homogeneity and persistence of the fossil rodent faunas and the absence of significant large mammal dispersal events. Some of the troubles which arise with the application of the MN units strengthen the need to take into account the palaeobiogeographical meaning of these units and their real suitability to date and correlate through extensive geographic areas

Paleoecosistemes del Permià i Triàsic continental de Mallorca (Illes Balears, Mediterrània occidental) : síntesi i prespectives futures

Altres ajuts: CERCA Programme/Generalitat de CatalunyaEl present article ofereix una revisió exhaustiva de tots els antecedents bibliogràfics sobre el permià i el triàsic de Mallorca en fàcies continentals, sintetitzant les dades més importants pel que fa a la geologia, paleontologia i datacions. Així, es destrien tres unitats litostratigràfiques del permià inferior-mitjà i quatre del triàsic inferior(?)-mitjà, amb un abundant registre fòssil que representa uns rics ecosistemes a la vorera de grans rius, situats a una paleolatitud equatorial amb un clima tropical. Aquesta publicació pretén servir de base per a futurs estudis sobre aquest tema, ressaltant la potencial gran importància del registre mallorquí en l'àmbit mundial per entendre com era la Terra fa més de 240 milions d'anys.The present paper offers an exhaustive review of all the previous works on the continental Permian and Triassic of Mallorca, synthesising all the relevant data regarding their geology, palaeontology and age attributions. This makes it possible to recognise three lithostratigraphic units forthe lower-middle Permian and four for the Lower(?)-Middle Triassic, with an abundant fossil record representing rich ecosystems on the banks of large rivers, located in an equatorial palaeolatitude and under a tropical climate. This work aims to serve as a basis for future studies to be built on, highlighting the potentially great international importance of the Mallorcan record to understand how the Earth looked like more than 240 million years ago

A captorhinid-dominated assemblage from the palaeoequatorial Permian of Menorca (Balearic Islands, western Mediterranean)

Altres ajuts: CERCA Programme/Generalitat de CatalunyaMoradisaurine captorhinid eureptiles were a successful group of high-fibre herbivores that lived in the arid low latitudes of Pangaea during the Permian. Here we describe a palaeoassemblage from the Permian of Menorca (Balearic Islands, western Mediterranean), consisting of ichnites of small captorhinomorph eureptiles, probably moradisaurines (Hyloidichnus), and parareptiles (cf. Erpetopus), and bones of two different taxa of moradisaurines. The smallest of the two is not diagnostic beyond Moradisaurinae incertae sedis. The largest one, on the other hand, shows characters that are not present in any other known species of moradisaurine (densely ornamented maxillar teeth), and it is therefore described as Balearosaurus bombardensis gen. et sp. nov. Other remains found in the same outcrop are identified as cf. Balearosaurus bombardensis gen. et sp. nov., as they could also belong to the newly described taxon. This species is sister to the moradisaurine from the lower Permian of the neighbouring island of Mallorca, and is also closely related to the North American genus Rothianiscus. This makes it possible to suggest the hypothesis that the Variscan mountains, which separated North America from southern Europe during the Permian, were not a very important palaeobiogeographical barrier to the dispersion of moradisaurines. In fact, mapping all moradisaurine occurrences known so far, it is shown that their distribution area encompassed both sides of the Variscan mountains, essentially being restricted to the arid belt of palaeoequatorial Pangaea, where they probably outcompeted other herbivorous clades until they died out in the late Permian

Ichnological evidence of Megalosaurid Dinosaurs crossing Middle Jurassic tidal flats

A new dinosaur tracksite in the Vale de Meios quarry (Serra de Aire Formation, Bathonian, Portugal) preserves more than 700 theropod tracks. They are organized in at least 80 unidirectional trackways arranged in a bimodal orientation pattern (W/NW and E/SE). Quantitative and qualitative comparisons reveal that the large tridactyl, elongated and asymmetric tracks resemble the typical Late JurassicEarly Cretaceous Megalosauripus ichnogenus in all morphometric parameters. Few of the numerous tracks are preserved as elite tracks while the rest are preserved as different gradients of modified true tracks according to water content, erosive factors, radial fractures and internal overtrack formations. Taphonomical determinations are consistent with paleoenvironmental observations that indicate an inter-tidal flat located at the margin of a coastal barrier. The Megalosauripus tracks represent the oldest occurrence of this ichnotaxon and are attributed to large megalosaurid dinosaurs. Their occurrence in Vale de Meios tidal flat represents the unique paleoethological evidence of megalosaurids moving towards the lagoon, most likley during the low tide periods with feeding purposes

Opaline chert nodules in maar lake sediments from Camp dels Ninots (La Selva Basin, NE Spain)

Chert nodule samples from three different well cores (CC, CP1 & CA) from the lacustrine infill of the Camp dels Ninot maar-diatreme (La Selva Basin) have been studied by means of X-ray diffraction, and optical and electron microscope technique. The chert nodules replace diatomites and carbonates layers, and varies in mineralogy between opal-A to opal-A/CT. The microtexture of the opal-A rich nodules is characterized by smooth microspheres of ~2μm in diameter that forms aggregates of amalgamated microspheres. Commonly, the nodules contain diatoms and their moulds when replacing diatomites, and dolomite or ankerite crystals and their moulds when replacing carbonates. The opal-A/CT rich nodules exhibit a microtexture consisting of microspheres of ~8μm in diameter that form aggregates with botryoidal and finger-like morphologies. Results indicate that the early diagenetic transformation of opal-A to opal-CT is not complete in the studied sediments.Peer Reviewe

Maar-diatreme infill features recorded in borehole imaging

Oriented borehole images recorded with an ultrasonic acoustic televiewer and continuous coring recovery has allowed the characterization of different facies and volcanic processes involved in the infill of a maar-diatreme volcano type. Maar-diatremes are associated with strong explosions throughout most of their development, focused along feeder dikes and generally attributed to magma-water interaction. In the case study of Camp dels Ninots maar-diatreme (Girona, Spain) we have recognized four facies types located in the center of the maar-diatreme: volcanic ash, phreatomagmatic breccia with lithics and juveniles, vesicular pyroclasts (scoria), massive basalt or welded pyroclastic fragments. Ultrasonic televiewer images allow to characterize the different volcanic facies, since they display a different degree of reflectivity and textures. Other features such as fracturing and grain size can be directly measured on the images.Projects 2014-100575 from Departament de Cultura de and SGR2014-901 from AGAUR (both from Generalitat de Catalunya) financed the drilling campaigns.Peer Reviewe