Sedimentology and cyclostratigraphy of the Barahona Formation (Lower Jurassic) in the Aragonese Branch of the Iberian Range

A detailed bed-by-bed sedimentological and cyclostratigraphic characterization of the Barahona Formation has been carried out in two representative outcrops in the Aragonese Branch of the Iberian Range, in order to characterize the sedimentary environment and evaluate the factors controlling the sedimentation during the upper Pliensbachian in the Iberian Basin. Facies range from proximal mid-ramp bioclastic packstones, distal mid-ramp bioclastic wackestones and mudstones, to proximal outer-ramp marly limestones and marls. Sequence analysis indicates the presence of twelve metre-thick high-order sequences, grouped in four longer-term sequences, which have been interpreted in terms of relative sea-level variations controlled by climatic changes in the bands of short- and longterm eccentricity cycles. At the longer scale, the studied unit records the regressive episode of the late Pliensbachian, and probably the initial deepening of the Toarcian cycleSe realiza la caracterización sedimentológica y cicloestratigráfica capa a capa de la Formación Barahona en dos afloramientos representativos de la Rama Aragonesa de la Cordillera Ibérica, con objeto de proponer un modelo de sedimentación y evaluar los factores que controlaron la sedimentación durante el Pliensbaquiense superior en la Cuenca Ibérica. Las facies representan una rampa carbonatada dominada por tormentas, desde rampa media proximal (packstones bioclásticos) y media distal (wackestones y mudstones bioclásticos) a rampa externa proximal (margocalizas y margas). El análisis secuencial constata la presencia de doce secuencias de alto orden de potencia métrica, agrupadas en cuatro secuencias de mayor duración temporal. Las secuencias se atribuyen a variaciones relativas del nivel del mar inducidas por cambios climáticos asociados a ciclos orbitales de excentricidad de corto y largo término.A mayor escala, la Fm. Barahona registra el evento regresivo del Pliensbaquiense superior y, en su parte terminal, probablemente el inicio de la profundización del ciclo toarciens

Carbon and oxygen stable isotope record of upper Kimmeridgian shallow-marine ramp carbonates (Iberian Basin, NE Spain): the imprint of different burial and tectonic histories

Bulk carbon and oxygen stable isotopes of ancient shallow-marine carbonates can record the effects of multiple palaeoenvironmental factors, but also the imprint of several post-depositional processes, which may alter the original marine isotopic composition. In this study, carbon and oxygen stable isotope analyses were performed on bulk carbonate, bivalve calcitic-shell (Trichites) and calcite vein samples from two stratigraphic sections (Tosos and Fuendetodos, present-day distance 15km), representing proximal inner- and distal mid-ramp environments, respectively, of the uppermost Kimmeridgian ramp facies deposited in the northern Iberian Basin (NE Spain). These successions underwent different diagenetic pathways that altered the primary marine isotopic composition in each section in different ways. Different burial histories, tectonic uplift and a variable exposure to meteoric diagenesis from the end of the Kimmeridgian to the Cenozoic (following Alpine tectonic uplift) are reflected in the different alteration patterns of the carbon and oxygen stable isotope signatures. A significant deviation to lower values in both δ13O and δ18O is recorded in those carbonates mostly exposed to meteoric diagenesis (distal mid-ramp Fuendetodos section), because of post-depositional tectonic uplift (telogenesis). On the other hand, the deposits mainly affected by burial diagenesis (proximal inner-ramp Tosos section) only record low δ18O with respect to expected values for pristine Kimmeridgian marine carbonates. The different burial and tectonic uplift histories of these deposits in each sector, due to their different tectonic evolution in this part of the basin, resulted in a variable degree of diagenetic resetting. However, in spite of the different diagenetic resetting reported of the carbon and oxygen stable isotope signatures in each section, these carbonates show similar cement types in termsof fabrics and cathodoluminescence properties. The diagenetic resetting reported for these carbonates prevents the use of the δ13O and δ18O records for addressing palaeoenvironmental interpretations, but instead highlights useful features regarding the variable diagenetic overprint of the studied shallow-marine carbonate successions concerning their specific post-depositional history

Carbon and oxygen stable isotope record of upper Kimmeridgian shallow-marine ramp carbonates (Iberian Basin, NE Spain): the imprint of different burial and tectonic histories

Bulk carbon and oxygen stable isotopes of ancient shallow-marine carbonates can record the effects of multiple palaeoenvironmental factors, but also the imprint of several post-depositional processes, which may alter the original marine isotopic composition. In this study, carbon and oxygen stable isotope analyses were performed on bulk carbonate, bivalve calcitic-shell (Trichites) and calcite vein samples from two stratigraphic sections (Tosos and Fuendetodos, present-day distance 15km), representing proximal inner- and distal mid-ramp environments, respectively, of the uppermost Kimmeridgian ramp facies deposited in the northern Iberian Basin (NE Spain). These successions underwent different diagenetic pathways that altered the primary marine isotopic composition in each section in different ways. Different burial histories, tectonic uplift and a variable exposure to meteoric diagenesis from the end of the Kimmeridgian to the Cenozoic (following Alpine tectonic uplift) are reflected in the different alteration patterns of the carbon and oxygen stable isotope signatures. A significant deviation to lower values in both δ13O and δ18O is recorded in those carbonates mostly exposed to meteoric diagenesis (distal mid-ramp Fuendetodos section), because of post-depositional tectonic uplift (telogenesis). On the other hand, the deposits mainly affected by burial diagenesis (proximal inner-ramp Tosos section) only record low δ18O with respect to expected values for pristine Kimmeridgian marine carbonates. The different burial and tectonic uplift histories of these deposits in each sector, due to their different tectonic evolution in this part of the basin, resulted in a variable degree of diagenetic resetting. However, in spite of the different diagenetic resetting reported of the carbon and oxygen stable isotope signatures in each section, these carbonates show similar cement types in termsof fabrics and cathodoluminescence properties. The diagenetic resetting reported for these carbonates prevents the use of the δ13O and δ18O records for addressing palaeoenvironmental interpretations, but instead highlights useful features regarding the variable diagenetic overprint of the studied shallow-marine carbonate successions concerning their specific post-depositional history

From platform to basin to swell: orbital control on sedimentary sequences in the Oxfordian, Spain

Climatic, oceanographic and ecological changes that control the formation and deposition of sediment in shallow and deep depositional environments commonly occur with periodicities of a few 10 000 years. Consequently, in order to interpret sedimentary sequences in the geological past, high time resolution is required. This is best obtained by cyclostratigraphy. Three sections have been studied in the Oxfordian of north-eastern Spain: one represents a shallow, siliciclastic-carbonate platform with repetitive subaerial exposures, one an intraplatform basin with sponge bioherms, and one a swell where iron ooids and glauconite formed. The platform section displays a well-defined stacking pattern of depositional sequences; the deeper-water sections are well dated by ammonites. The correlation between the three sections is a best-fit solution integrating biostratigraphy, sequence stratigraphy and cyclostratigraphy. It is concluded that the small-scale depositional sequences formed in tune with the 100-ka orbital eccentricity cycle. An additional factor was differential subsidence that ruled basin morphology

Caracterización y origen de estructuras tipo hummocky en sedimentos fangosos (Kimmeridgiense, Ricla)

Los afloramientos Kimmeridgienses de Ricla (Zaragoza) exponen a lo largo de unos 6 km de extensión las facies de la zona media de una rampa carbonatada. Las facies más distales son calizas fangosas que intercalan niveles arenoso-oolíticos, interpretados como depósitos de tormenta y, algunos de ellos, como depósitos de olas internas. En las calizas fangosas se observan también estructuras sedimentarias de origen incierto, de tipo hummocky (HCS) concentradas en determinados paquetes de capas, y cuyo análisis sedimentológico e interpretación constituyen el objeto del presente TFG

Evaluation of pinnacle reef distribution at shallow subsurface using integrated geophysical methods: a case study from the Upper Kimmerdigian (Spain)

The well exposed outcrops of the upper Kimmeridgian shallow-marine carbonates at Jabaloyas (Iberian Chain, NE Spain) permit the evaluation of geophysical methods for the identification of sedimentary facies. Direct measurement of magnetic susceptibility in facies and detailed grids of magnetometry, electromagnetic multifrequency and ground-penetrating radar (50e500 MHz antennas) have been performed in two study areas where the upper Kimmeridgian rocks are nearly horizontal. Magnetometry indicates negative anomalies in residual magnetic field and vertical magnetic gradient related to reef pinnacles and faults. Electromagnetic data reveal that positive anomalies of apparent conductivity correlate with non-reefal facies. The areal distribution of magnetometry and EM data does not permit the unequivocal identification of pinnacles and faults at the studied area. By contrast, ground penetrating radar profiles and maps of relative reflectivity in two way travel time slices are useful for the identifi- cation of faults (hyperbolic anomalies) and reefal and non-reefal facies (radar facies A and B, respec- tively). The integration of geophysical data, mainly ground penetrating radar, has permitted the 3D reconstruction of reef pinnacles and its tectonic framework

Sedimentología y cicloestratigrafía de las calizas de plataforma abierta de la Fm. Río Palomar (Pliensbachiense inferior; cuenca Ibérica)

Las calizas de la Fm. Río Palomar (Pliensbachiense inferior) en el afloramiento de Almonacid de la Cuba (Zaragoza) se depositaron en una plataforma carbonatada de tipo rampa, entre los dominios medio-distal (facies dominante de wackestone bioclástico) y externo-proximal (facies mudstone, margocalizas y margas), donde la génesis y acumulación de sedimento se debió a producción bentónica y pelágica y a la resedimentación producida por las tormentas desde dominios someros. La sedimentación estuvo controlada por cambios climáticos relacionados con ciclos de Milankovitch. Estos habrían originado cambios periódicos de la acomodación-sedimentación, manifestados en secuencias sedimentarias de diferente orden (bundles, sets de bundles y lotes de sets), así como del aporte de detritos (minerales magnéticos), como refleja la ciclicidad obtenida del análisis espectral de los datos de susceptibilidad magnética (ciclos de excentricidad larga, oblicuidad y precesión). Los lotes de sets y los bundles corresponderían a los ciclos de excentricidad larga y precesión, respectivamente. Sin embargo, los ciclos de oblicuidad no tienen expresión estratigráfica en secuencias, ni los sets de bundles asignables a ciclos de excentricidad corta tienen su equivalente en el registro de la susceptibilidad magnética. Estas diferencias pueden relacionarse con la variable impronta de los cambios climáticos en el continente vs. la plataforma marina

Sedimentología y cicloestratigrafía de las facies marinas de la Formación Barahona (Jurásico Inferior) en la Rama Aragonesa de la Cordillera Ibérica

Las facies marinas depositadas durante el Pliensbachiense en la Cuenca Ibérica registran un ciclo transgresivo-regresivo que culmina en el Pliensbachiense Superior con una regresión a escala regional europea, que en esta cuenca está representada por las calizas bioclásticas de la Fm. Barahona. En el presente Trabajo Fin de Máster se realiza la caracterización sedimentológica y cicloestratigráfica capa a capa de esta unidad en dos afloramientos representativos de la Rama Aragonesa de la Cordillera Ibérica (Obón y San Pedro), con objeto de proponer un modelo de sedimentación y evaluar los factores que controlaron la sedimentación durante el Pliensbachiense Superior. Se han reconocido 5 facies, correspondientes a distintos ambientes dentro de la cuenca. El modelo propuesto establece un área fuente de producción de carbonato y de generación del sedimento bioclástico en una hipotética zona de rampa interna altamente energética, sometida a la acción del oleaje de buen tiempo, y una zona más profunda correspondiente con los dominios medio y externo proximal, en la cual se producía la resedimentación de la fracción bioclástica fina, y de fangos carbonatados y detríticos. Mediante el análisis secuencial, se ha constatado la presencia de 12 secuencias de alto orden de potencia métrica, agrupadas en 4 secuencias de largo término, de evolución de facies profundizante y/o somerizante. Su génesis estuvo controlada por cambios climáticos asociados a la variación de los parámetros orbitales de excentricidad de corto y largo término, respectivamente, que producirían variaciones en el nivel del mar relativo y, por tanto, variaciones de producción del sedimento en las zonas someras y de su resedimentación hacia las zonas distales. Las conclusiones obtenidas han sido comparadas y puestas en contexto con el marco regresivo y de clima frío propuesto previamente por otros autores para este intervalo de tiempo en otras cuencas de sedimentación próximas