Registro de Carcharocles megalodon en el sector oriental de la Cuenca del Guadalquivir (Mioceno superior, Sur de España)

Tortonian diatomites of the San Felix Quarry (Porcuna), in the Eastern Guadalquivir Basin, have given isolated marine vertebrate remains that include a large shark tooth (123.96 mm from apex to the baseline of the root). The large size of the crown height (92.2 mm), the triangular shape, the broad serrated crown, the convex lingual face and flat labial face, and the robust, thick angled root determine that this specimen corresponds to Carcharocles megalodon. The symmetry with low slant shows it to be an upper anterior tooth. The total length estimated from the tooth crown height is calculated by means of different methods, and comparison is made with Carcharodon carcharias. The final inferred total length of around 11 m classifies this specimen in the upper size range of the known C. megalodon specimens. The palaeogeography of the Guadalquivir Basin close to the North Betic Strait, which connected the Atlantic Ocean to the Mediterranean Sea, favoured the interaction of the cold nutrient-rich Atlantic waters with warmer Mediterranean waters. The presence of diatomites indicates potential upwelling currents in this context, as well as high productivity favouring the presence of large vertebrates such as mysticetid whales, pinnipeds and small sharks (Isurus). These large vertebrates recorded in the Eastern Guadalquivir Basin were potential prey of C. megalodon.Las diatomitas tortonienses de la antigua Cantera de San Félix (Porcuna, Jaén), en el sector oriental de la Cuenca del Guadalquivir, han proporcionado restos aislados de vertebrados marinos entre los que destaca un gran diente de tiburón (123.96 mm desde el ápice hasta la línea basal de la raiz). La altura de la corona (92.2 mm), su forma triangular con bordes aserrados, la presencia de una cara lingual convexa y una labial plana, conjuntamente con la raíz angulosa y robusta, permiten determinar que este diente perteneció a un ejemplar de Carcharocles megalodon. La alta simetría de la pieza, su tamaño y su relación longitud/anchura de la corona permiten afrimar que se trata de un diente superior anterior. La longitud total estimada para este tiburón, es calculada a partir de diferentes métodos basados principalmente en la comparación con el tiburón blanco Carcharodon carcharias. La longitud total inferida finalmente para este ejemplar ronda los 11 m, lo que permite incluir este ejemplar dentro del rango de los ejemplares de C. megalodon de gran tamaño. La paleogeografía de la Cuenca del Guadalquivir próxima al Estrecho Nordbético que conectaba el Océano Atlántico con el Mar Mediterráneo, favoreció la interacción de aguas atlánticas frías y ricas en nutrientes con las aguas más cálidas del Mediterráneo. La presencia de diatomitas indica la actividad potencial de corrientes de upwelling en este contexto, así como la alta productividad que suele favorecer a grandes cetáceos y pinnípedos. Estos mamíferos marinos, registrados en el sector oriental d la Cuenca del Guadalquivir fueron potenciales presas de pequeños tiburones como Isurus el gran C. megalodon

On the microstructure, growth pattern and original porosity of belemnite rostra: insights from calcitic Jurassic belemnites

[EN] Calcitic belemnite rostra are usually employed to perform paleoenvironmental studies based on geochemical data. However, several questions, such as their original porosity and microstructure, remain open, despite they are essential to make accurate interpretations based on geochemical analyses. This paper revisits and enlightens some of these questions. Petrographic data demonstrate that calcite crystals of the rostrum solidum of belemnites grow from spherulites that successively develop along the apical line, resulting in a “regular spherulithic prismatic” microstructure. Radially arranged calcite crystals emerge and diverge from the spherulites: towards the apex, crystals grow until a new spherulite is formed; towards the external walls of the rostrum, the crystals become progressively bigger and prismatic. Adjacent crystals slightly vary in their c-axis orientation, resulting in undulose extinction. Concentric growth layering develops at different scales and is superimposed and traversed by a radial pattern, which results in the micro-fibrous texture that is observed in the calcite crystals in the rostra. Petrographic data demonstrate that single calcite crystals in the rostra have a composite nature, which strongly suggests that the belemnite rostra were originally porous. Single crystals consistently comprise two distinct zones or sectors in optical continuity: 1) the inner zone is fluorescent, has relatively low optical relief under transmitted light (TL) microscopy, a dark-grey color under backscatter electron microscopy (BSEM), a commonly triangular shape, a “patchy” appearance and relatively high Mg and Na contents; 2) the outer sector is non-fluorescent, has relatively high optical relief under TL, a light-grey color under BSEM and low Mg and Na contents. The inner and fluorescent sectors are interpreted to have formed first as a product of biologically controlled mineralization during belemnite skeletal growth and the non-fluorescent outer sectors as overgrowths of the former, filling the intra- and inter-crystalline porosity. This question has important implications for making paleoenvironmental and/or paleoclimatic interpretations based on geochemical analyses of belemnite rostra. Finally, the petrographic features of composite calcite crystals in the rostra also suggest the non-classical crystallization of belemnite rostra, as previously suggested by other authors.[ES] Los análisis geoquímicos obtenidos en rostros de los belemnites se utilizan habitualmente para llevar a cabo estudios paleoambientales. Sin embargo, hay cuestiones esenciales, como la porosidad y la microestructura original de los belemnites, que están todavía en discusión y que hay que tener en cuenta si se quieren realizar interpretaciones geoquímicas adecuadas. Los datos petrográficos obtenidos en este trabajo demuestran que los cristales de calcita del rostrum solidum de los belemnites crecen a partir de esferulitos que sucesivamente se desarrollan a lo largo de la línea apical, dando lugar a una microestructura “esferulítica prismática regular”. Los cristales de calcita surgen y divergen radialmente desde los esferulitos: hacia el apex, hasta que se forma un nuevo esferulito y hacia los bordes externos del rostro donde los cristales se van haciendo progresivamente mayores y prismáticos. La ligera variación de la orientación del eje-c de los cristales adyacentes explica la extinción ondulante. Al patrón radial, que da lugar a la textura micro-fibrosa de southlos cristales de calcita del rostro, se le superpone un bandeado de crecimiento concéntrico. Los datos petrográficos también indican que los rostros de los belemnites eran originalmente porosos como lo demuestra la naturaleza compuesta de los cristales de calcita que están formados sistemáticamente por dos zonas distintas que están en continuidad óptica: 1) la zona interna es fluorescente, tiene relieve óptico bajo, en microscopia de luz transmitida (TL), color gris oscuro en microscopia electrónica con electrones retrodispersados (BSEM), morfología triangular y contenidos en Mg y Na relativamente altos; 2) la zona exterior no es fluorescente, tiene relieve óptico alto (TL), color gris claro (BSEM), y contenidos en Mg y Na relativamente bajos. La zona fluorescente interior se formó primero, durante el crecimiento de los belemnites y la zona no fluorescente precipitó como un cemento rellenando la porosidad intra- e intercristalina. Las características petrográficas de los cristales de calcita también sugieren que la cristalización no clásica del esqueleto de los belemnites, como han sugerido algunos autores previamente.This research was carried out with the financial support of the projects CGL2011-22709, CGL2014-52670-P and RYC- 2009-04316 (Ramón y Cajal Program, Ministerio de Ciencia e Innovación), and by the “Sedimentary Basin Analysis” and “Paleoclimatology and Global Change” research groups of the Complutense University of Madrid.Peer reviewe

Palaeoenvironmental turnover across the Cenomanian-Turonian transition in Oued Bahloul, Tunisia: Foraminifera and geochemical proxies

The integrated analysis of foraminiferal assemblages, geochemical proxies, and stable isotopes in the Oued Bahloul section (Tunisia) allowed us to reconstruct the environmental turnover across the Cenomanian–Turonian boundary. An increase in palaeoproductivity proxies (P/Ti, U/Al, Sr/Al) and in d13C values, and a decrease in foraminiferal diversity and d18O values mark the beginning of the Oceanic Anoxic Event 2 (OAE2) at the Rotalipora cushmani and Whiteinella archaeocretacea biozones boundary. Eutrophic conditions at the seafloor and in the water column are evidenced by high proportions of buliminids and the replacement of planktic oligotrophic specialist Rotalipora by eutrophic opportunist Hedbergella. The enrichment in organic matter and redox sensitive elements, together with the abundance of low-oxygen tolerant benthic foraminifera, indicate dysoxic conditions in the deep-water column and at the seafloor (higher Uaut than Moaut). Among planktic foraminifera, deep- and intermediate-dwellers disappear (Rotalipora and Globigerinelloides), and surface-dwellers proliferate (Hedbergella). The persistency of the poorly oxygenated conditions during the W. archaeocretacea Biozone locally produced euxinic conditions where MoEF and Moaut reach high values, diversity presents minimum values, and benthic foraminifera temporarily disappear. The maximum percentage of heterohelicids indicates a stratified water column with a well-developed oxygen minimum zone. Improved oxygen conditions returned in the upper part of the W. archaeocretacea Biozone and Helvetoglobotruncana helvetica Biozone, with a slow recovery of foraminiferal assemblages, decrease in eutrophic genera (Heterohelix) and increase in mesotrophic genera (Whiteinella). A gradual increase in d18O values suggests decreased temperatures in surface waters. The OAE2 has been attributed to global temperature changes and palaeoceanographic reorganization. The poor mixing of surface and deep waters and enhanced primary productivity related to global warming – associated with increasing continental weathering and nutrient runoff – may have favored the eutrophication of the ocean and the expansion of the oxygen minimum zone

Lower/Middle Ordovician (Arenigian) shallow-marine trace fossils of the Pochico Formation, southern Spain: palaeoenvironmental and palaeogeographic implications at the Gondwanan and peri-Gondwanan realm

Nineteen ichnospecies belonging to thirteen ichnogenera (Archaeonassa, Catenichnus, Cochlichnus, Cruziana, Didymaulichnus, ?Diplichnites, Gordia, Lingulichnus, Lockeia, cf. Monocraterion, Planolites, Ptychoplasma, and Rusophycus) occur in the Pochico Formation (Arenigian) in the Aldeaquemada section, Sierra Morena, southern Spain, just above the Armorican Quartzite. They belong to the archetypal Cruziana ichnofacies, indicating a lower shoreface-upper offshore zone. The low degree of sediment reworking may be due to a high rate of sedimentation. The trace fossil assemblage, rich in large Cruziana, is typical of the Armorican Quartzite that developed on the margins of Gondwana and peri-Gondwanan microcontinents. The distribution of ichnofauna during the Early Ordovician was partly palaeogeographically controlled, although ichnological data from the literature point to paths of migration between Gondwana, Baltica and Laurentia. Differences between the ichnofauna of Gondwana and Baltica could be conditioned by facies (clastics in Gondwana and carbonates in Baltica) causing a taphonomic filter, because Cruziana requires diversified clastic deposits for preservation. The ichnofauna would also be influenced by trophic group amensalism between filter feeding and deposit feeding fauna, the former prevailing in Baltica and the latter in Gondwana.Se presenta el análisis sedimentológico/icnológico de los materiales de la Formación Pochico (Arenigian) de la sección de Aldeaquemada, Sierra Morena, Sur de España, provincia de Jaén, justo por encima la Cuarcita Armoricana. Se han reconocido diecinueve icnoespecies pertenecientes a trece icnogéneros (Archaeonassa, Catenichnus, Cochlichnus, Cruziana, Didymaulichnus, ?Diplichnites, Gordia, Lingulichnus, Lockeia, cf. Monocraterion, Planolites, Ptychoplasma, y Rusophycus). Las características icnológicas junto con los rasgos sedimentológicos permiten asignarlas a las icnofacies arquetípicas de Cruziana, comunes de las zonas de shoreface inferior a offshore superior. El grado de bioturbación relativamente bajo puede estar relacionado con una alta tasa de depósito. La asociación registrada, dominada por grandes Cruziana, es típica de la Cuarcita Armoricana desarrollada en los márgenes de Gondwana y peri-Gondwana. La distribucción de icnofósiles del Ordovícico temprano posee, en gran medida, un control paleogeográfico, aunque datos icnológicos procedentes de la literatura indican la existencia de migraciones entre Gondwana, Baltica y Laurentia. Las diferencias entre las asociaciones de Gondwana y Báltica pueden estar asociadas a las diferentes facies, con el dominio de materiales clásticos en Gondwana y de carbonatados en Báltica, causando un filtro tafonómico ya que el potencial de conservación de Cruziana es mucho mayor en las facies clásticas heterolíticas. A estos factores habría que añadir las estrategias de alimentación asociadas, diferenciando entre filtradores y aquellos que se alimentan de las partículas existentes en el sedimento, los primeros podrían verse favorecidos en Báltica y los segundos en Gondwana.Research by R.-T. was supported by Projects CGL2008-03007, and CGL2012-33281 (Secretaría de Estado de I+D+I, Spain), Project RNM-3715 and Research Group RNM-178 (Junta de Andalucía)

Foraminiferal assemblages as palaeoenvironmental bioindicators in Late Jurassic epicontinental platforms: relation with trophic conditions

Foraminiferal assemblages from the neritic environment reveal the palaeoecological impact of nutrient types in relation to shore distance and sedimentary setting. Comparatively proximal siliciclastic settings from the Boreal Domain (Brora section, Eastern Scotland) were dominated by inner−shelf primary production in the water column or in sea bottom, while in relatively seawards mixed carbonate−siliciclastic settings from the Western Tethys (Prebetic, Southern Spain), nutrients mainly derived from the inner−shelf source. In both settings, benthic foraminiferal assemblages increased in diversity and proportion of epifauna from eutrophic to oligotrophic conditions. The proximal setting example (Brora Brick Clay Mb.) corresponds to Callovian offshore shelf deposits with a high primary productivity, bottom accumulation of organic matter, and a reduced sedimentation rate for siliciclastics. Eutrophic conditions favoured some infaunal foraminifera. Lately, inner shelf to shoreface transition areas (Fascally Siltstone Mb.), show higher sedimentation rates and turbidity, reducing euphotic−zone range depths and primary production, and then deposits with a lower organic matter content (high−mesotrophic conditions). This determined less agglutinated infaunal foraminifera content and increasing calcitic and aragonitic epifauna, and calcitic opportunists (i.e., Lenticulina). The comparatively distal setting of the Oxfordian example (Prebetic) corresponds to: (i) outer−shelf areas with lower nutrient input (relative oligotrophy) and organic matter accumulation on comparatively firmer substrates (lumpy lithofacies group) showing dominance of calcitic epifaunal foraminifera, and (ii) mid−shelf areas with a higher sedimentation rate and nutrient influx (low−mesotrophic conditions) favouring potentially deep infaunal foraminifers in comparatively unconsolidated and nutrient−rich substrates controlled by instable redox boundary (marl−limestone rhythmite lithofacies).This research was carried out with the financial support of projects CGL2005−06636−C0201 and CGL2005−01316/BTE, and University of Oslo, Norway−Statoil cooperation. M.R. holds a Juan de la Cierva grant from the Ministry of Science and Technology of Spain

Dataset of characteristic remanent magnetization and magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform)

This data article describes data of magnetic stratigraphy and anisotropy of isothermal remanent magnetization (AIRM) from "Magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform) reveal changes in the monsoon system" [1]. Acquisition of isothermal magnetization on pilot samples and anisotropy of isothermal remanent magnetization are reported as raw data; magnetostratigraphic data are reported as characteristic magnetization (ChRM).info:eu-repo/semantics/publishedVersio

Palaeoenvironment of Eocene prodelta in Spitsbergen recorded by the trace fossil Phycosiphon incertum

Ichnological, sedimentological and geochemical analyses were conducted on the Eocene Frysjaodden Formation in order to interpret palaeoenvironment prodelta sediments in the Central Basin of Spitsbergen. Phycosiphon incertum is the exclusive ichnotaxon showing differences in size, distribution, abundance and density, and relation to laminated/bioturbated intervals. Large P. incertum mainly occur dispersed, isolated and randomly distributed throughout the weakly laminated/non-laminated intervals. Small P. incertum occur occasionally in patches of several burrows within laminated intervals or as densely packed burrows in thin horizons in laminated intervals or constituting fully bioturbated intervals that are several centimetres thick. Ichnological changes are mainly controlled by oxygenation, although the availability of benthic food cannot be discarded. Changes in oxygenation and rate of sedimentation can be correlated with the registered variations in the Bouma sequence of the distal turbiditic beds within prodeltal shelf sediments.Funding for this research was provided by Project CGL2012-33281 (Secretaría de Estado de Investigación, Desarrollo e Innovación, Spain), Project RYC-2009-04316 (Ramón y Cajal Programme) and Projects RNM-3715 and RNM-7408 and Research Group RNM-178 (Junta de Andalucía). The authors benefited from a bilateral agreement between the universities of Granada and Oslo, supported by the University of Granada