S isotopes on gypsum of the Oncala Group: evidence for marine influence in Berriasian carbonate-evaporite deposits of the Cameros Basin (La Rioja-Soria)

Comunicación presentada al IX Congreso Geológico de España, Huelva, septiembre 2016.[ES] Discriminar si el origen de las salmueras en las que precipitaron numerosas sucesiones evaporíticas era marino o continental puede resultar complicado usando exclusivamente criterios sedimentológicos si no contienen fósiles diagnósticos. Éste es el caso de los depósitos carbonático-evaporíticos laminados del Gr. Oncala (Berriasiense, cuenca de Cameros oriental), formados en extensos cuerpos de agua someros. En este trabajo se busca determinar el origen de la salmuera en la que se formaron estos sedimentos mediante el análisis de las composiciones del δ34S de los yesos preservados en la unidad. Los valores de δ34S de entre +18,5‰V-CDT y +21,8‰V-CDT (media de +20,5‰V-CDT) de los yesos del Gr. Oncala coinciden con la signatura isotópica de los sulfatos precipitados a partir de agua marina de edad berriasiense de acuerdo con las curvas globales más recientes (≈ +17 - +20‰V-CDT), lo que sugiere que la principal fuente de sulfato en estos cuerpos de agua procedía de aportes de agua marina, en lugar del reciclaje de evaporitas triásicas como se había propuesto anteriormente. El reconocimiento de influencia marina en estos cuerpos de agua permite clasificarlos como salinas costeras.[EN] Determining if the origin of the brine in which an evaporitic succession precipitated was marine or continental by analysing only sedimentological criteria may be difficult if it does not contain diagnostic fossils. This is the case of the laminated carbonate-evaporite deposits of the Oncala Gr (Berriasian, Cameros Basin), which were accumulated in shallow water bodies. The aim of this work is to interpret the origin of the brine in which these sediments were formed by analysing the δ34S compositions of the gypsum preserved in this unit. Gypsum δ34S values between +18,5‰V-CDT and +21,8‰V-CDT (mean value of +20,5‰V-CDT) in the Oncala Gr coincide with the isotopic signature of the sulphates precipitated in Berriasian seawater according to the most recent global curves (≈ +17 - +20‰V-CDT), which suggests that the main sulphate source in the water bodies was marine water, instead of the recycling of Triassic evaporites as previously interpreted. The recognition of marine influence in these water bodies allows us to classify them as coastal salinas.Este trabajo ha sido financiado por los proyectos de investigación CGL2011-22709 y CGL2014-52670-P.Peer reviewe

A coastal paradise for Aptian microbialites (Early Cretaceous, N Spain)

Peer Reviewe

The record of a marine transgression around the Jurassic-Cretaceous transition in the western Penyagolosa sub-basin (Teruel)

Comunicación presentada al IX Congreso Geológico de España, Huelva, septiembre 2016.[ES] La Fm. Villar del Arzobispo es una unidad mixta siliciclástico-carbonática que es considerada como la unidad que representa la culminación de la tendencia regresiva del Jurásico terminal-Cretácico basal en la parte suroriental de la Cuenca Ibérica. En el oeste de la sub-cuenca de Penyagolosa (Cuenca del Maestrazgo) esta unidad está formada, en su parte inferior, por una alternancia de carbonatos marinos, areniscas y lutitas y, en la parte media y superior, por lutitas y areniscas, principalmente, que alternan con calizas que se van haciendo progresivamente más abundantes hacia el techo de la unidad. Estas calizas son peloidales, bioclásticas y oolíticas y contienen abundantes fósiles marinos. La presencia de estas facies marinas demuestra la existencia de un periodo transgresivo durante la sedimentación de la parte superior de la unidad. El estudio micropaleontológico ha revelado la presencia de una asociación de foraminíferos dominada por Anchispirocyclina lusitanica y del alga dasycladal Zergabriella embergeri, que indican que el episodio transgresivo tuvo lugar durante el intervalo Titoniense superior-¿Berriasiense inferior?[EN] The Villar del Arzobispo Fm is a mixed siliciclastic-carbonate unit, which is considered as the unit that represents the culmination of the Late Jurassic-basal Cretaceous regressive trend in the southeastern Iberian Basin. In the western Penyagolosa sub-basin (Maestrazgo Basin) this unit is formed, in its lower part, by an alternation of marine limestone, sandstone and siliciclastic mudstone and, in the middle and upper part, by siliciclastic mudstone and sandstone alternating with limestone, which is progressively more abundant towards the uppermost part of the unit. This limestone is formed by peloids, bioclasts and ooids and contains abundant marine fossils. The presence of these marine facies demonstrates that a transgression took place during the sedimentation of the upper part of the unit. The micropaleontological study reveals the presence of a foraminifera association dominated by Anchispirocyclina lusitanica and the dasyclad algae Zergabriella embergeri, indicating that the transgressive episode took place during the Upper Tithonian-Lower Berriasian? interval.Este trabajo ha sido financiado por el proyecto CGL2014-52670-P y por una beca FPU.Peer reviewe

Revisiting the Late Jurassic-Early Cretaceous of the NW South Iberian Basin: new ages and sedimentary environments

The study of the Upper Jurassic-Lower Cretaceous deposits (Higueruelas, Villar del Arzobispo and Aldea de Cortés Formations) of the South Iberian Basin (NW Valencia, Spain) reveals new stratigraphic and sedimentological data, which have significant implications on the stratigraphic framework, depositional environments and age of these units. Moreover, these new data encourage revising the previously proposed stratigraphic correlations between the studied units and those deposited in adjacent areas of the Iberian Basin. The Higueruelas Fm was deposited in a mid-inner carbonate platform where oncolitic bars migrated by the action of storms and where oncoid production progressively decreased towards the uppermost part of the unit. The overlying Villar del Arzobispo Fm has been traditionally interpreted as an inner platform-lagoon evolving into a tidal-flat. Here it is interpreted as an inner-carbonate platform affected by storms, where oolitic shoals protected a lagoon, which had siliciclastic inputs from the continent. The Aldea de Cortés Fm has been previously interpreted as a lagoon surrounded by tidal-flats and fluvial-deltaic plains. Here it is reinterpreted as a coastal wetland where siliciclastic muddy deposits interacted with shallow fresh to marine water bodies, aeolian dunes and continental siliciclastic inputs. The contact between the Higueruelas and Villar del Arzobispo Fms, classically defined as gradual, is interpreted here as gradual and rapid, because the transition between both units comprises few meters. More importantly, the contact between the Villar del Arzobispo and Aldea de Cortés Fms, previously considered as unconformable, is here interpreted as gradual. The presence of Alveosepta in the Villar del Arzobispo Fm suggests that at least part of this unit is Kimmeridgian, unlike the previously assigned Late Tithonian-Middle Berriasian age. Consequently, the underlying Higueruelas Fm, previously considered Tithonian, should not be younger than Kimmeridgian. Accordingly, sedimentation of the Aldea de Cortés Fm, previously considered Valanginian-Hauterivian, probably started during the Tithonian and it may be considered part of the regressive trend of the Late Jurassic-Early Cretaceous cycle. This is consistent with the dinosaur faunas, typically Jurassic, described in the Villar del Arzobispo and Aldea de Cortés Fms

Influence of Keuper and late-variscan structure on the architecture of syn-extensional units of the northern margin of the Cameros Basin

Trabajo presentado en el IX Congreso Geológico de España, celebrado en Huelva (España), del 12 al 14 de septiembre de 2016[ES] Este trabajo aporta nuevos datos cartográficos y sedimentológicos para aclarar la controvertida evolución tectónica extensional de la Cuenca de Cameros (N de España). La geometría actual del borde norte de la cuenca representa la continuación de lineaciones tardivariscas NO-SE y SO-NE reconocidas en la Cuenca Vasco-Cantábrica, a lo largo de las cuales se produjo una importante tectónica salina sin-extensional. En la zona de estudio, la distribución irregular de los depósitos plásticos del Keuper es interpretada aquí como debida a una movilización sin-extensional. De este modo, la estructuración tardivarisca del basamento y las movilizaciones de Keuper, asociadas a ella, permiten explicar la arquitectura y distribución de las unidades sin-extensionales del relleno de la cuenca.[EN] This work provides new mapping and sedimentological data to shed light on the controversial extensionaltectonic evolution of the Cameros Basin (N Spain). The present-day geometry of the northern margin of the basin represents the continuation of NW-SE and SW-NE late-variscan lineaments of the Basque-Cantabrian Basin, along which important syn-extensional salt-tectonics occurred. In the study area, the irregular distribution of the Keuper plastic deposits is interpreted here as due to syn-extensional mobilization. Thus, the late-variscan basement structure and the Keuper mobilizations related to it, allow explaining the architecture and distribution of the syn-extensional units of the basin infillEste trabajo ha sido financiado por los proyectos de investigación CGL2011-22709 y CGL2014-52670-P, por el grupo de investigación UCM-CM 910429 y por una beca predoctoral FPU.Peer reviewe

Challenges to carbonate-evaporite peritidal facies models and cycles: Insights from Lower Cretaceous stromatolite-bearing deposits (Oncala Group, N Spain)

Peritidal carbonate-evaporite successions, since they are developed in the transition between continental and marine realms, provide essential keys for palaeobathymetric and palaeoclimatic interpretations. As a result, several facies models have been proposed to assist on the interpretation of ancient tidal flat deposits, and peritidal successions have been extensively used for cyclicity analyses. In this study, well-exposed, Lower Cretaceous peritidal deposits (Oncala Group, Cameros Basin, N Spain) are analysed and compared with the most commonly-used present-day analogues (from Shark Bay, the Arabian Gulf and the Bahamas) and with ancient peritidal successions, providing their palaeoenvironmental and palaeoclimatic interpretation, assessing the usefulness and limitations of the facies models, and evaluating the suitability of these deposits for analysis of decimetre to metre-scale cycles. The studied peritidal deposits consist of thinly-bedded to laminated dolostones, dolomitic stromatolites, stromatolite breccias, flat-pebble and edgewise breccias, and calcite and quartz pseudomorphs after anhydrite nodules. Abundant resemblances of the peritidal deposits of the Oncala Group with those of Shark Bay, including that they are largely composed of microbialites and intraclasts, makes the peritidal deposits of the Oncala Group one of the best fossil analogues of this present-day setting. However, the presence of anhydrite nodules indicates pervasive evaporite precipitation in the supratidal zone, which is a feature that does not occur in supratidal flats of Shark Bay, but is characteristic of arid sabkhas of the Arabian Gulf. Nevertheless, the fact that carbonate-evaporite tidal flats of the Oncala Group were laterally related with siliciclastic tidal flats with large freshwater input and broadly inhabited by dinosaurs, suggests that anhydrites precipitated under less arid climates than those of the Arabian Gulf nowadays, pointing to semiarid climatic conditions during deposition. Moreover, the fact that peritidal deposits with anhydrite nodules were exclusively formed in a low-subsidence area of the Cameros Basin suggests that the rate of accommodation space creation also played an important role in their development. Regarding the comparison with other fossil peritidal sediments, the studied deposits show more abundant similarities with Proterozoic and Cambrian successions, composed mainly of stromatolites, microbial laminites, and intraclasts, than with other Mesozoic peritidal deposits, in which bioclasts and burrowing are usually more abundant. This highlights the difficulties for assigning specific features to certain geological ages. Finally, peritidal facies of the Oncala Group may change laterally and vertically to any other facies, showing a patchy lateral distribution of facies and an unsystematic vertical stacking pattern. The sedimentary features of the stromatolite, breccia and thinly-bedded to laminated dolostone facies do not allow their assignment to a unique tidal zone. Moreover, sedimentary features indicative of subaerial exposure, such as anhydrite nodules formed in the capillary zone, occur within any of the carbonate facies and show limited lateral extent. This results in a succession that cannot be clearly subdivided into subsequent shallowing-upward cycles not even by using erosive surfaces or the anhydrite nodule layers as marker horizons of the upper part of the cycles, because their limited lateral extent prevents reliable correlations. Similar composite lateral and vertical facies relationships have been documented both in the present-day analogues and in ancient successions, which suggests that this kind of facies relationships may be common in peritidal successions and highlights the caution that must be taken when trying to perform cyclicity analysis on them

Between tides, winds and rivers: deciphering challenging sandstone bodies in a multifaceted coastal system (Late Jurassic-Early Cretaceous, south Iberian Basin, Spain)

MINECO/CGL2011-22709, MINCEO/CGL2014-52670-PPeer reviewe

Unveiling coastal aeolian facies in the Upper Jurassic record of eastern Iberia: new insights from the dinosaur fossil–bearing Villar del Arzobispo Fm (Teruel, E Spain)

Trabajo presentado en el 33rd International Meeting of Sedimentology y 16ème Congrès Français de Sédimentologie (2017), celebrado en Toulouse (Francia), del 10 al 12 de octubre de 2017The Upper Jurassic Villar del Arzobispo Fm is a mixed siliciclastic-carbonate succession that crops out in the Riodeva area (Teruel, eastern Spain) and preserves abundant dinosaur fossils. In this area, the succession has been interpreted as representing the preserved accumulation of an inner carbonate platform that evolved upwards into a predominantly siliciclastic fluvial system with minor marine carbonate incursions. However, preliminary studies performed in this area have revealed the presence of aeolian deposits intercalated with tidal, scarce alluvial and marine deposits, suggesting deposition in a coastal plain setting, rather than a fluvial system. In this work, we analyse the aeolian deposits of the Villar del Arzobispo Fm to reconstruct the depositional environments of the unit. For the first time, we describe the occurrence of dome-shaped aeolian dunes in the Mesozoic record of Iberia. The studied deposits are arranged in metre-thick sandstone beds (up to 10 m). Beds exhibit flat bases and tops, and a lateral continuity up to 300 m and occur interbedded with edaphized, reddish siliciclastic mudstone. Two facies associations are distinguished. The Aeolian dune facies association consists on fine-to medium-grained, well-to very well-sorted sandstone, which displays different types of large-scale cross-bedding. (1) Tangential cross-bedding is arranged in up to 2 m-thick sets, displaying tangential foresets (angles of 20-35°) and reactivation surfaces; internally, it is formed by mm-to cm-thick laminae that pinch out upwards and downwards. (2) Low-angle cross-bedding is arranged in sets up to 2.7 m-thick, displaying low-angle foresets (< 15°), laterally extensive bottomsets and reactivation surfaces; internally, it consists of mm-to cm-thick laterally continuous laminae. (3) Dome-shaped cross-bedding is arranged in up to 4 m-thick sets, consisting of convex-up, steeply dipping foresets (up to 35°) with preserved topsets. These features are typical of migrating aeolian dunes. Specifically, the tangential cross-bedding may result from the accumulation of grainflow packages on the lee side of dunes exceeding the angle of repose, whereas the low-angle cross-bedding may result from the accumulation of wind ripples in the dune plinths. Deposits displaying steeply dipping, convex-up foresets with preserved topsets are interpreted as dome-shaped dunes. The Interdune facies association comprises two facies. (1) Near-horizontally laminated sandstone with mm-to cm-thick layers of carbonaceous detritus occurring as drapes; these drapes commonly pass updip into the bottomsets and rarely the lower part of the foresets of aforementioned aeolian dune deposits. (2) Decimetrethick, fine-grained, climbing-rippled sandstone beds, interbedded with tangential cross-bedded sandstone. These facies suggest deposition in wet aeolian interdunes that were subjected to episodic aqueous floods. The fact that the studied deposits are interbedded with tidal and marine deposits, suggests that interdune flood events might have been caused by storms or spring tides in this coastal palaeoenvironment. Ephemeral flash flood events likely also occurred. Collectively, these facies relationships indicate that, during the Late Jurassic, coastal aeolian dunes developed in a coastal plain setting in eastern Iberia; this plain was also influenced by tides and affected by episodic alluvial depositionFunded by the Spanish project CGL2014-52670-P, Government of Aragón (FOCONTUR-E62) and a predoctoral scholarship (FPU13/02978).Peer reviewe

Revisiting the age and palaeoenvironments of the Upper Jurassic–Lower Cretaceous? dinosaur-bearing sedimentary record of eastern Spain: implications for Iberian palaeogeography

An integrated stratigraphic, palaeontological, palaeoenvironmental and palaeogeographical study of the traditionally considered Upper Jurassic–Lower Cretaceous dinosaur-bearing sedimentary record (DSR) of eastern Spain is accomplished for the first time. Several areas where dinosaur fossils are abundant (western Maestrazgo and South-Iberian basins) have been studied in detail. In all the areas, the DSR comprises a carbonate-dominated lower part (CLP), and an essentially siliciclastic upper part (SUP). Deposition occurred in a shallow-very shallow marine carbonate platform, laterally connected towards the N and W to coastal and alluvial environments. The overall upwards evolution is regressive with a transgresive episode at the uppermost part. The DSR includes deposits previously assigned, depending on the studied area, from the Kimmeridgian to the Barremian (locally even to the Aptian–Albian). However, ages obtained in this work from larger benthic foraminifera (LBF), demonstrate a Kimmeridgian–Tithonian age (locally Kimmeridgian-Early Berriasian?) for the DSR. These findings have important implications regarding the age of dinosaur fossils of these deposits, traditionally assigned to the Jurassic-Cretaceous transition, or even to the Early Cretaceous, erroneously, and have necessitated a deep litho- and chronostratigraphic revision of the units previously established in the studied areas: new data indicate that the DSR is correlatable with deposits of the Villar del Arzobispo Fm and that the usage of the Aldea de Cortés and El Collado Fms, traditionally assigned to the Early Cretaceous, should be avoided. New data also reveal that the DSR should be correlated with other Kimmeridgian–Tithonian dinosaur-bearing deposits of Iberia, such as those of the Cameros Basin, Asturias and Portugal, and have encouraged a revision of the Iberian palaeogeography at that time. In fact, ages obtained from LBF agree with data provided by the systematics of dinosaurs, since dinosaur faunas of eastern Spain are similar to those of the other Late Jurassic Iberian areas, especially to those of the Lusitanian Basin

Revisiting the age and palaeoenvironments of the Upper Jurassic–Lower Cretaceous? dinosaur-bearing sedimentary record of eastern Spain: implications for Iberian palaeogeography

An integrated stratigraphic, palaeontological, palaeoenvironmental and palaeogeographical study of the traditionally considered Upper Jurassic–Lower Cretaceous dinosaur-bearing sedimentary record (DSR) of eastern Spain is accomplished for the first time. Several areas where dinosaur fossils are abundant (western Maestrazgo and South-Iberian basins) have been studied in detail. In all the areas, the DSR comprises a carbonate-dominated lower part (CLP), and an essentially siliciclastic upper part (SUP). Deposition occurred in a shallow-very shallow marine carbonate platform, laterally connected towards the N and W to coastal and alluvial environments. The overall upwards evolution is regressive with a transgresive episode at the uppermost part. The DSR includes deposits previously assigned, depending on the studied area, from the Kimmeridgian to the Barremian (locally even to the Aptian–Albian). However, ages obtained in this work from larger benthic foraminifera (LBF), demonstrate a Kimmeridgian–Tithonian age (locally Kimmeridgian-Early Berriasian?) for the DSR. These findings have important implications regarding the age of dinosaur fossils of these deposits, traditionally assigned to the Jurassic-Cretaceous transition, or even to the Early Cretaceous, erroneously, and have necessitated a deep litho- and chronostratigraphic revision of the units previously established in the studied areas: new data indicate that the DSR is correlatable with deposits of the Villar del Arzobispo Fm and that the usage of the Aldea de Cortés and El Collado Fms, traditionally assigned to the Early Cretaceous, should be avoided. New data also reveal that the DSR should be correlated with other Kimmeridgian–Tithonian dinosaur-bearing deposits of Iberia, such as those of the Cameros Basin, Asturias and Portugal, and have encouraged a revision of the Iberian palaeogeography at that time. In fact, ages obtained from LBF agree with data provided by the systematics of dinosaurs, since dinosaur faunas of eastern Spain are similar to those of the other Late Jurassic Iberian areas, especially to those of the Lusitanian Basin.En este trabajo se realiza por primera vez un estudio multidisciplinar (estratigráfico, paleontológico, paleoambiental y paleogeográfico) del registro sedimentario del este de España que contiene abundantes fósiles de dinosaurio (DSR) y que tradicionalmente se ha asignado al Jurásico Superior-Cretácico Inferior. En concreto se han estudiado en detalle varias áreas de la Cuenca Suribérica y del oeste de la Cuenca del Maestrazgo en las que los fósiles de dinosaurio son más abundantes. En todas las áreas que se han estudiado, el DSR está formado por una parte inferior (CLP), esencialmente carbonática, y por una parte superior (SUP), esencialmente siliciclástica, que se depositaron en una plataforma carbonática somera o muy somera, que estaba conectada lateralmente, hacia el norte y oeste, con ambientes costeros y aluviales. La evolución de estos sistemas a lo largo del tiempo fue, en general, regresiva, aunque se ha podido registrar en ambas cuencas un episodio transgresivo en la parte más alta del registro estudiado. Respecto a la edad, el DSR se ha asignado previamente a edades comprendidas entre el Kimmeridgiense y el Barremiense (o incluso localmente al Aptiense-Albiense). Sin embargo, las edades obtenidas en este trabajo a partir de macroforaminíferos bentónicos (LBF) demuestran que el DSR tiene una edad Kimmeridgiense–Titoniense y, localmente, Kimmeridgiense–Berriasiense Inferior?. Estos nuevos hallazgos tienen implicaciones importantes en cuanto a la edad de los fósiles de dinosaurio que contienen los depósitos estudiados, que tradicionalmente se han asignado, erróneamente, al tránsito Jurásico-Cretácico o incluso al Cretácico Inferior, y hacen necesaria la realización de una revisión litoestratigráfica y cronoestratigráfica de las unidades previamente establecidas, y definidas, en las áreas de estudio: los nuevos datos indican que el DSR es equivalente a los depósitos de la Formación Villar del Arzobispo, por lo que se debe evitar el uso de las Formaciones Aldea de Cortés y El Collado, que tradicionalmente se han asignado al Cretácico Inferior. Los nuevos datos también revelan que los depósitos del DSR se deberían correlacionar con los depósitos de edad Kimmeridgiense-Titoniense de otras cuencas de Iberia como las de Cameros, Asturias o Lusitánica que también contienen abundantes fósiles de dinosaurio, y esto ha hecho necesario revisar la paleogeografía de Iberia para el Jurásico Superior. De hecho, las edades obtenidas a partir de los LBF concuerdan con los datos procedentes de la sistemática de los dinosaurios, ya que las faunas de dinosaurios del este de España son similares a las de otras cuencas del Jurásico Superior de Iberia, y especialmente a las de la Cuenca LusitánicaMinisterio de Economía y Competitividad (MINECO)Universidad Complutense de MadridGobierno de AragónInstituto Aragonés de FomentoMinisterio de EducaciónDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu