A new decapod crustacean assemblage from the lower Aptian of La Cova del Vidre (Baix Ebre, province of Tarragona, Catalonia)

During fieldwork in a small outcrop of the lower Aptian Margas de Forcall Formation at La Cova del Vidre, hitherto known as the type locality of the anomuran Pagurus avellanedai, new decapod crustacean material has been recovered. In this newly recovered lot, two undescribed species of brachyuran have been recognised; there are here described as Rathbunopon tarraconensis n. sp. and Pithonoton Iluismariaorum n. sp. In addition, numerous remains of the anomuran P. avellanedai, enable an improvement of the original description of this taxon, and an analysis of associated ammonites from La Cova del Vidre has resulted in precise age calibration for the first time. (C) 2018 Elsevier Ltd. All rights reserved

Lower Cretaceous (Hauterivian-Albian) ammonite biostratigraphy in the Maestrat Basin (E Spain)

A review of the stratigraphic distribution of ammonoid species in the Lower Cretaceous (Hauterivian-Albian) of the Maestrat Basin (E Spain) was carried out. The specimens were mainly collected in the field by us and are stored in university or museum collections. Speci­mens from private collections and figured in the literature were also studied. We recognized 73 species that are distributed, in accordance with the latest version of the standard Mediterranean ammonite zonation for the Lower Cretaceous, in 14 ammonite zones: Acanthodiscus radiatus, Crioceratites loryi, Lyticoceras nodosoplicatum (Lower Hauterivian); Pseudothurmannia ohmi (Upper Hauterivian); Imerites giraudi (Upper Barremian); Deshayesites oglanlensis, Deshayesites forbesi, Deshayesites deshayesi, Dufrenoyia furcata (Lower Aptian); Epicheloniceras martini, Parahoplites melchioris, Acanthohoplites nolani (Upper Aptian); Leymeriella tardefurcata and Douvilleiceras mammillatum (Lower Albian). The recognition of these biozones allows a precise age calibration of the Maestrat Basin’s lithostatigraphic units that contain ammonoids as well as an associated indirect age calibration of the formations without ammonoids. Consequently, this report provides an updated, comprehensive and precise biostratigraphic framework, which aims to become a reference for the analysis of the Lower Cretaceous strata of the Maestrat Basin. The results are also relevant for the analysis of coeval ammonite-bearing sedimentary successions found in other Tethyan basins.En este trabajo se ha realizado una revisión detallada de la distribución estratigráfica de las especies de ammonoideos del Cretácico infe­rior de la Cuenca del Maestrazgo (Este de España). Los ejemplares recolectados, principalmente por los autores, han sido depositados en co­lecciones universitarias y museísticas. Además hemos estudiado los ejemplares de colecciones privadas y figurados en la literatura. Hemos reconocido 73 especies que se distribuyen, siguiendo la última versión de la biozonación de ammonites mediterránea estándar del Cretácico inferior, en 14 zonas de ammonoideos: Acanthodiscus radiatus, Crioceratites loryi, Lyticoceras nodosoplicatum (Hauteriviense inferior); Pseudothurmannia ohmi (Hauteriviense superior); Imerites giraudi (Barremiense superior); Deshayesites oglanlensis, Deshayesites forbesi, Deshayesites deshayesi, Dufrenoyia furcata (Aptiense inferior); Epicheloniceras martini, Parahoplites melchioris, Acanthohoplites nolani (Aptiense superior); Leymeriella tardefurcata y Douvilleiceras mammillatum (Albiense inferior). El reconocimiento de estas biozonas permite precisar la edad de las unidades litoestratigráficas que contienen ammonites y también una calibración indirecta de las formaciones que no contienen ammonites. En consecuencia este trabajo proporciona un marco bioestratigráfico actualizado, exhaustivo y preciso que pretende ser una referencia para el análisis estratigráfico del Cretácico inferior de la Cuenca del Maestrazgo. Los resultados obtenidos son también relevantes para el análisis de las sucesiones sedimentarias coetáneas con ammonites existentes en otras cuencas de Tetis

Deep incision in an Aptian carbonate succession indicates major sea-level fall in the Cretaceous

Long-term relative sea-level cycles (0 5 to 6 Myr) have yet to be fully understood for the Cretaceous. During the Aptian, in the northern Maestrat Basin (Eastern Iberian Peninsula), fault-controlled subsidence created depositional space, but eustasy governed changes in depositional trends. Relative sea-level history was reconstructed by sequence stratigraphic analysis. Two forced regressive stages of relative sea-level were recognized within three depositional sequences. The first stage is late Early Aptian age (intra Dufrenoyia furcata Zone) and is characterized by foreshore to upper shoreface sedimentary wedges, which occur detached from a highstand carbonate platform, and were deposited above basin marls. The amplitude of relative sea-level drop was in the order of tens of metres, with a duration of 2 km wide and cut 115 m down into the underlying Aptian succession. With the subsequent transgression, the incision was back-filled with peritidal to shallow subtidal deposits. The changes in depositional trends, lithofacies evolution and geometric relation of the stratigraphic units characterized are similar to those observed in coeval rocks within the Maestrat Basin, as well as in other correlative basins elsewhere. The pace and magnitude of the two relative sea-level drops identified fall within the glacio-eustatic domain. In the Maestrat Basin, terrestrial palynological studies provide evidence that the late Early and Late Aptian climate was cooler than the earliest part of the Early Aptian and the Albian Stage, which were characterized by warmer environmental conditions. The outcrops documented here are significant because they preserve the results of Aptian long-term sea-level trends that are often only recognizable on larger scales (i.e. seismic) such as for the Arabian Plate

Estratigrafia mesozoica i nous cefalòpodes de l'Aptià del Vendrell, sud-oest del massís del Garraf (Catalunya)

En aquest treball es mostra l'estratigrafia del Mesozoic de l'extrem sud-oest del massís del Garraf i es dóna a conèixer per primera vegada una associació de cefalòpodes procedents de l'Aptià (Cretaci inferior) de l'entorn del municipi del Vendrell. El Mesozoic que aflora a l'est del Vendrell esta format per roques fonamentalment carbonàtiques del Kimmeridgià-Berriasià a les que se li superposen de forma discordant els dipòsits del Barremià i l'Aptià. En l'Aptià del Vendrell s'identifiquen uns ammonits i nautiloïdeus trobats a la part baixa de la unitat Margues de Vallcarca (Salas & Moreno, 2008) i se'n realitza una anàlisi biostratigràfica. També s'analitza l'estratigrafia deis materials del Cretaci inferior (Barremià superior-Aptià superior) d'aquest sector de la conca de Salou-Garraf mitjan<;:ant una correlació amb la conca veïna del Maestral. Entre els cefalòpodes estudiats destaca la presencia de l'ammonit Pseudosaynella bicurvata (Michelin, 1838), ja que és la primera vegada que aquesta espècie se cita al massís del Garraf, i un exemplar ben conservat del nautiloïdeu Heminautilus lallierianus (d'Orbigny, 1841), el segon exemplar conegut d'aquesta espècie al Garraf. Des d'un punt de vista biostratigrafic, els cefalòpodes aptians estudiats constitueixen un dels registres més antics coneguts per a la unitat Margues de Vallcarca, essent atribuïble a les biozones Deshayesites forbesi i Deshayesites deshayesi (Aptià inferior). La correlació efectuada entre les unitats litostratigràfiques del Barremià superior i l'Aptià de les conques veïnes de Salou-Garraf i del Maestrat permet assignar al Barremià terminal la part basal de la unitat Margues de Vallcarca, quan c1assicament aquesta unitat de la conca de Salou-Garraf havia estat atribuïda íntegrament a l'Aptià.The current work shows the Mesozoic stratigraphy of the southwestern part of the Garraf Massif and reports for the first time an Aptian (Lower Cretaceous) cephalopod assemblage from the surroundings of the town of el Vendrell. The Mesozoic out craps to the east of el Vendrell primarily consist of carbonate rocks of Kimmeridgian-Berriasian age, which are uncorformably overlain by Barremian and Aptian deposits. In the Aptian of el Vendrell, we identify ammonoids and nautiloids that were collected in the lower part of the Vallcarca Marls Unit (Salas & Moreno, 2008), and we carry out a biostratigraphic analysis. We also analyze the stratigraphy of the Cretaceous materials (upper Barremian to upper Aptian) of this area of the Salou-Garraf Basin and establish a correlation with the neighboring Maestrat Basin. Among the cephalopods studied, the presence of the ammonite Pseudosaynella bicurvata (Michelin, 1838) is remarkable because it is the first time that this species is quoted in the Garraf Massif. In addition, we report a well-preserved specimen of the nautiloid Heminautilus lallierianus (d'Orbigny, 1841), which is the second specimen of this species known in the Garraf area. Fram a biostratigraphic point of view, the Aptian cephalopods studied herein are some of the oldest known records of the Vallcarca Marls Unit being attributed to the Deshayesites forbesi and Deshayesites deshayesi biozones (lower Aptian). The correlation between the upper barremian and Aptian lithostatigraphic units among the neighboring basins Salou-Garraf and Maestrat allows us to ascribe for the first time the basal part of the Vallcarca Marls Unit to the uppermost Barremian. This latter lithostatigraphic unit of Salou-Garraf Basin has been classically attribued to the Aptian

The Upper Aptian to Lower Albian syn-rift carbonate succession of the southern Maestrat Basin (Spain): Facies architecture and fault-controlled stratabound dolostones

Syn-rift shallow-marine carbonates of Late Aptian to Early Albian age in the southern Maestrat Basin (E Spain) register the thickest Aptian sedimentary record of the basin, and one of the most complete carbonate successions of this age reported in the northern Tethyan margin. The host limestones (Benassal Formation) are partially replaced by dolostones providing a new case study of fault-controlled hydrothermal dolomitization. The syn-rift sediments filled a graben controlled by normal basement faults. The Benassal Fm was deposited in a carbonate ramp with scarce siliciclastic input. The lithofacies are mainly characterized by the presence of orbitolinid foraminifera, corals and rudist bivalves fauna. The succession is stacked in three transgressive–regressive sequences (T–R) bounded by surfaces with sequence stratigraphic significance. The third sequence, which is reported for the first time in the basin, is formed by fully marine lithofacies of Albian age and represents the marine equivalent to the continental deposits of the Escucha Fm in the rest of the basin.The dolomitization of the host rock is spatially associated with the basement faults, and thus is fault-controlled. The dolostone forms seismic-scale stratabound tabular geobodies that extend several kilometres away from the fault zones, mostly in the hanging wall blocks, and host Mississippi Valley Type (MVT) deposits. The dolostones preferentially replaced middle to inner ramp grain-dominated facies from the third T–R sequences consisting of bioclastic packestones and peloidal grainstones. Field and petrology data indicate that the replacement took place after early calcite cementation and compaction, most likely during the Late Cretaceous post-rift stage of the basin. The dolostone registers the typical hydrothermal paragenesis constituted by the host limestone replacement, dolomite cementation and sulfide MVT mineralization. The Aptian succession studied provides a stratigraphic framework that can be used for oil exploration in age-equivalent rocks, especially in the València Trough, offshore Spain. Moreover, this new case study constitutes a world class outcrop analogue for similar partially stratabound, dolomitized limestone reservoirs worldwide

Ammonite taxonomy and biostratigraphy for the upper Aptian-lower Albian (Lower Cretaceous) of Cerro Chino, Chihuahua State, northeast Mexico

In this paper we study the ammonoid taxonomy and biostratigraphy from the upper Aptian to the lower Albian of the Cerro Chino area, with an emphasis on an accurate taxonomic characterization of the American endemic forms Kazanskyella, Quitmanites, Immunitoceras and Huastecoceras. These genera are important because they are characteristic of the unique ammonite fauna of the Central Atlantic province. In a critical taxonomic study of these endemic forms, we review numerous holotypes and other specimens that are currently housed in several collections in the United States and Mexico. Based on our analysis, we propose a local zonation from the upper Aptian to the lower Albian, with three ammonoid zones (Kazanskyella minima, Hypacanthoplites sp. and Douvilleiceras sp.), based on the Cerro Chino sections. This newly proposed zonation constitutes a step forward in the development of the standard Central Atlantic province ammonoid zonation, particularly because biostratigraphic data for this province during this time span are very scarce. In general, the uppermost Aptian ammonoid record worldwide is scarce and/or condensed, and so the fauna preserved at this location is significant, making the contribution here even more important. In this work, we are not able to pin down the position of the Aptian/Albian boundary based solely on the ammonoids from these sections. (c) 2017 Elsevier Ltd. All rights reserved