Reassessment of Prejanopterus curvirostris,a Basal Pterodactyloid Pterosaur from the Early Cretaceous of Spain     

Xabier PEREDA-SUBERBIOLA  Fabien KNOLL  José Ignacio RUIZ-OME?ACA  Julio COMPANY  Fidel TORCIDA FERNáNDEZ-BALDOR 《《地质学报》英文版》2012,86(6):1389-1401

Prejanopterus curvirostra, from the Early Cretaceous of La Rioja province, was the first pterosaur genus and species described from Spain. The material comprises disarticulated cranial and postcranial remains from several individuals. The fossil-bearing bed is assigned to the lacustrine Leza Formation (eastern Cameros Basin, NW margin of the Iberian Range). This unit is regarded as either Berriasian-Valanginian or Barremian-Aptian. Prejanopterus curvirostris (specific name emended) was originally diagnosed on the basis of several characters of which the most significant was a lateral curvature of the rostrum. Re-examination of the holotype (rostrum) and paratype (partial rostrum with teeth) indicates that there is no genuine sideways bend of the preserved premaxilla-maxilla segments, but a slight dorsal curvature. Prejanopterus is characterized by a unique combination of characters: an emended diagnosis is provided. In contrast with previous estimates, the wing span of Prejanopterus was probably not much (if ever) in excess of 2 m. A phylogenetic analysis suggests that Prejanopterus is a basal pterodactyloid positioned between Pterodactylus and Cycnorhamphus-Gallodactylus. Prejanopterus represents the first evidence of Pterodactylidae in the Early Cretaceous of the Iberian Peninsula.  相似文献   

Mg/Ca-paleothermometry in the western Mediterranean Sea on planktonic foraminifer species Globigerina bulloides: Constraints and implications     

Soumaya Boussetta  Nejib Kallel  Franck Bassinot  Laurent Labeyrie  Jean-Claude Duplessy  Nicolas Caillon  Fabien Dewilde  Hélène Rebaubier 《Comptes Rendus Geoscience》2012,344(5):267-276

We generated a high-resolution SST_Mg/Ca record for the surface-dwelling planktonic foraminifera Globigerina bulloides from the core MD99-2346 collected in the Gulf of Lion, and compared it to that obtained using modern analogue techniques applied to fossil foraminiferal assemblages (SST_MAT). The two temperature records display similar patterns during the last 28,000 years but the SST_Mg/Ca estimates are several degrees warmer (∼ +4 °C) than SST_MAT. The temperature shift between SST_Mg/Ca and SST_MAT remained relatively constant over time. This seems to exclude a bias on the Mg/Ca record associated with salinity or secondary Mg-rich calcite encrustation on the foraminiferal tests during early diagenesis. Therefore, anomalously high Mg/Ca suggests either: (1) the empirical equation for G. bulloides of Elderfield and Ganssen (2000) is incorrect; or (2) there is a specific Mediterranean genotypes of G. bulloides for which a specific Mg/Ca-temperature calibration is needed.  相似文献   

New palaeontological data from the organic-rich layers of the Bathonian of the Grands Causses (France)     

Fabien Knoll  Gilles Cuny  Pierre-Olivier Mojon  Raquel López-Antoñanzas 《Proceedings of the Geologists' Association. Geologists' Association》2014

The palaeontological content (charophytes and vertebrates) of organic-rich layers from the Middle Jurassic (Bathonian) of the Grands Causses at Mostuéjouls (Aveyron, France) has been examined. It is rich in gyrogonites of Porochara douzensis. The vertebrates of the lower layer include a single hybodontiform tooth, “semionotiform” teeth and scales, and one pycnodontiform tooth whereas the upper layer has yielded one hybodontiform tooth, a variety of actinopterygian remains (mostly Caturus sp. and indeterminate pycnodontiforms) and a few possible reptile remains. The variation in fauna between the two layers is ascribed to a different degree of marine influence.  相似文献   

Hydrous partial melting in the sheeted dike complex at fast spreading ridges: experimental and natural observations   总被引：5，自引：1，他引：4  

Lydéric France  Juergen Koepke  Benoit Ildefonse  Sarah B. Cichy  Fabien Deschamps 《Contributions to Mineralogy and Petrology》2010,160(5):683-704

In ophiolites and in present-day oceanic crust formed at fast spreading ridges, oceanic plagiogranites are commonly observed at, or close to the base of the sheeted dike complex. They can be produced either by differentiation of mafic melts, or by hydrous partial melting of the hydrothermally altered sheeted dikes. In addition, the hydrothermally altered base of the sheeted dike complex, which is often infiltrated by plagiogranitic veins, is usually recrystallized into granoblastic dikes that are commonly interpreted as a result of prograde granulitic metamorphism. To test the anatectic origin of oceanic plagiogranites, we performed melting experiments on a natural hydrothermally altered dike, under conditions that match those prevailing at the base of the sheeted dike complex. All generated melts are water saturated, transitional between tholeiitic and calc-alkaline, and match the compositions of oceanic plagiogranites observed close to the base of the sheeted dike complex. Newly crystallized clinopyroxene and plagioclase have compositions that are characteristic of the same minerals in granoblastic dikes. Published silicic melt compositions obtained in classical MORB fractionation experiments also broadly match the compositions of oceanic plagiogranites; however, the compositions of the coexisting experimental minerals significantly deviate from those of the granoblastic dikes. Our results demonstrate that hydrous partial melting is a likely common process in the root zone of the sheeted dike complex, starting at temperatures exceeding 850°C. The newly formed melt can either crystallize to form oceanic plagiogranites or may be recycled within the melt lens resulting in hybridized and contaminated MORB melts. It represents the main MORB crustal contamination process. The residue after the partial melting event is represented by the granoblastic dikes. Our results support a model with a dynamic melt lens that has the potential to trigger hydrous partial melting reactions in the previously hydrothermally altered sheeted dikes. A new thermometer using the Al content of clinopyroxene is also elaborated.  相似文献   

Exploring Geological and Topographical Controls on Low Flows with Hydrogeological Models     

Claire Carlier  Stefanie B. Wirth  Fabien Cochand  Daniel Hunkeler  Philip Brunner 《Ground water》2019,57(1):48-62

This study investigates how catchment properties influence low-flow dynamics. With 496 synthetic models composed of a bedrock and an alluvial aquifer, we systematically assess the impact of the hydraulic conductivity of both lithologies, of the hillslope and of the river slope on catchment dynamics. The physically based hydrogeological simulator HydroGeoSphere is employed, which allows obtaining a range of low-flow indicators. The hydraulic conductivity of the bedrock K_bedrock, a proxy for transmissivity, is the only catchment property exerting an overall control on low flows and explains 60% of the variance of Q95/Q50. The difference in dynamics of catchments with same K_bedrock depends on hillslope gradients and the alluvial aquifer properties. The buffering capacity of the bedrock is mainly related to K_bedrock and the hillslope gradient. We thus propose the dimensionless bedrock productivity index (BPI) that combines these characteristics with the mean net precipitation. For bedrock only models, the BPI explains 82% of the variance of the ratio of Q95 to mean net precipitation. The alluvial aquifer can significantly influence low flows when the bedrock productivity is limited. Although our synthetic catchment setup is simple, it is far more complex than the available analytical approaches or conceptual hydrological models. The direct application of the results to existing catchments requires nevertheless careful consideration of the local geological topographic and climatic conditions. This study provides quantitative insight into the complex interrelations between geology, topography and low-flow dynamics and challenges previous studies which neglect or oversimplify geological characteristics in the assessment of low flows.  相似文献