259 research outputs found

    Josep Closas i Miralles (Barcelona 1900-1962)

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    Es presenta una breu nota biogràfica d'aquest geòleg, geògraf i excursionista, soci fundador de la Societat Catalana de Geografia, amb la bibliografia dels seus principals treballs científics.Se presenta una breve nota biográfica de este geólogo, geógrafo y excursionista, socio fundador de la Societat Catalana de Geografia, con la bibliografía de sus principales trabajos científicos.This piece is a brief biographical note of this geologist, geographer and hiker, founding partner of the Catalan Geographic Society, with the bibliography of its main scientific works

    Charophyte biostratigraphy of the upper Eocene-lower Oligocene of the Eastern Ebro Basin

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    The Eastern Ebro Basin constitutes a reference area for the study of Palaeogene charophyte biostratigraphy worldwide. A synthesis and an updated version of a number of previous biozonations is presented herein. Six charophyte zones (comprising biozones and superzones) are proposed for the Priabonian–Rupelian interval. Most of these biozones are partial range zones or assemblage zones. Interval zones have been avoided as far as possible. All these zones are defined on the basis of species of broad ecological requirements within the non-marine aquatic environments and with well-known biogeographic ranges, generally of European range. Additionally, they are supported by a number of associated species of more limited ecological requirements (e.g., brackish species) or biogeographic ranges. Calibration to the GPTS (Global Polarity Time Scale) is proposed on the basis of magnetostratigraphy. This biozonation can be largely used at the European scaleEl sector oriental de la Cuenca del Ebro constituye una zona de referencia mundial para el estudio de la bioestratigrafía de las carofitas paleógenas. En este trabajo se presenta una síntesis y una actualización de diversos trabajos anteriores. Se definen seis zonas de carofitas (comprendiendo biozonas y superzonas) para el intervalo Priaboniense–Rupeliense. La mayor parte de estas biozonas son de rango parcial o de asociación, y se han evitado, en lo posible, las biozonas de intervalo. Todas estas biozonas se basan en especies de amplios requerimientos ecológicos y de distribución biogeográfica bien conocida, generalmente de rango europeo. Además se acompañan con otras especies de requerimientos ecológicos más restringidos (por ejemplo salobres) o de rangos biogeográficos más limitados. Se propone una calibración con la escala de la polaridad global del tiempo geológico en base a la magnetoestratigrafía. Esta biozonación puede usarse a escala europea en casi su totalida

    Palaeogene Charophytes of the Balearic Islands (Spain)

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    Fossil charophytes were recorded in two different stratigraphic units from the non- marine Palaeogene of the Balearic Islands. In the Peguera Limestone Fm. of Mallorca the charophyte flora is characterised by two assemblages. The first contains Raskyella peckii subsp. meridionale, Harrisichara caeciliana and Maedleriella mangenoti, from the Bartonian and Lutetian; whilst the second is characterised by Harrisichara vasiformistuberculata and Nitellopsis (Tectochara) aemula, Middle Priabonian in age. The Cala Blanca Detrital Fm. has yielded Lychnothamnus stockmansii and Sphaerochara inconspicua in Menorca whilst in Mallorca it contains Lychnothamnus praelangeri, L. langeri and Sphaerochara hirmeri. This flora is Late Priabonian and Oligocene in age. These results suggest that the beginning of Paleogene non-marine deposition was diachronic in Mallorca. In terms of biogeography, the Eocene charophytes of Mallorca show affinity with North-African floras. The presence of the Eocene African subspecies Raskyella peckii meridionale in Mallorca enables the biogeographic boundary between this form and the European subspecies R. peckii peckii to be drawn at about 32º N latitude in the Iberian Plate

    New palaeobotanical data from Carboniferous Culm deposits constrain the age of the Variscan deformation in the eastern Pyrenees

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    The pre-Variscan rocks of the Pyrenees exhibit a polyphase deformation linked to the Variscan crustal shortening and a low-pressure–high-temperature metamorphism. However, there is scarce chronostratigraphic evidence of this Variscan deformation. In the Pyrenean low-grade metamorphic domains, maximum ages have been provided by the synorogenic Carboniferous Culm deposits. In medium- to high-grade metamorphic areas, the Variscan regional metamorphism or intrusive magmatic bodies constrain the age of the main Variscan deformation structures. However, these data usually provide a minimum age. Here, we present new palaeobotanical records that assign a Namurian age to the base of the Culm deposits of la Cerdanya in the eastern Pyrenees. This dating is based on the co-occurrence of the sphenopsids Archaeocalamites radiatus, Mesocalamites cistiiformis and the seed of Cardiocarpus sp. The plant remains were found in sandstone facies produced by high-density turbidity flows of a deep-sea fan system. The new biostratigraphic information constrains the age of the Carboniferous Culm succession in the eastern Pyrenees

    Foreword

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    Evolutionary history, biogeography, and extinction of the Cretaceous cheirolepidiaceous conifer, Frenelopsis

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    Frenelopsis Schenk (family Cheirolepidiaceae†) was among the most widespread conifer genera and a dominant element of wetland ecosystems in low to mid-palaeolatitudes in the the Northern Hemisphere. It was also one of the more important peat-forming shrubs and trees generating extensive deposits of Cretaceous lignite. The genus became extinct at the end of the Cretaceous. Studies of the presence/absence and diversity of Frenelopsis allow us to analyse its evolutionary history, biogeography, and the consider the possible causes of its extinction. During the Early Cretaceous, the genus diversified, triggered by the rise of short-lived species and the constraint of endemism. The maximum diversity and species richness were attained in Barremian and Aptian times while the maximum number of global occurrences is documented during the Albian. In the Late Cretaceous, Frenelopsis species richness declined and the genus became progressively more restricted to the Tethyan archipelago in the context of the rise to dominance of angiosperms. In the Maastrichtian, the last representatives of Frenelopsis survived in the coastal wetlands of Iberia as a relictual plant. In northeast Iberia (present-day Pyrenees) the last occurrences from this genus are early to middle Maastrichtian in age and show an intriguing contrast between the abundance of vegetative remains and the lack of Classopollis pollen grains. These data suggest that at the end of its lineage, the plant was reproducing only vegetatively and that male sterility may have contributed to extinction

    A review of the Late Jurassic-Early Cretaceous charophytes from the northern Aquitaine Basin in south-west France

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    Late Jurassic and Early Cretaceous charophyte assemblages from the northern part of the Aquitaine Basin in south-west France are reviewed here to understand their palaeoecological, palaeobiogeographical and biostratigraphic features. Three sites were studied: the Tithonian-lower Berriasian of Chassiron, and the Berriasian of Cherves-de-Cognac and Angeac-Charente. Abundant porocharaceans, less abundant clavatoraceans and scarce characeans recorded in Cherves-de-Cognac and Angeac-Charente indicate that brackish water environments were substituted by freshwater environments eastwards. The occurrence of Clavator grovesii var. grovesii and morphotypes intermediate with C. grovesii var. discordis in the same areas is significant from a biostratigraphic viewpoint, since these species belong to the Maillardii, Incrassatus and Nurrensis European charophyte biozones, representing the Berriasian. This observation refutes a previous dating of the Angeac-Charente site and highlights the absence of Hauterivian-Barremian records in northern Aquitaine, which is in contrast to the more complete Lower Cretaceous record in southern Aquitaine. These contrasting records could be due to differences in the available sedimentary space produced by the opening of the Bay of Biscay during the Barremian

    New palaeobotanical data from Carboniferous Culm deposits constrain the age of the Variscan deformation in the eastern Pyrenees

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    The pre-Variscan rocks of the Pyrenees exhibit a polyphase deformation linked to the Variscan crustal shortening and a low-pressure-high-temperature metamorphism. However, there is scarce chronostratigraphic evidence of this Variscan deformation. In the Pyrenean low-grade metamorphic domains, maximum ages have been provided by the synorogenic Carboniferous Culm deposits. In medium- to high-grade metamorphic areas, the Variscan regional metamorphism or intrusive magmatic bodies constrain the age of the main Variscan deformation structures. However, these data usually provide a minimum age. Here, we present new palaeobotanical records that assign a Namurian age to the base of the Culm deposits of la Cerdanya in the eastern Pyrenees. This dating is based on the co-occurrence of the sphenopsids Archaeocalamites radiatus, Mesocalamites cistiiformis and the seed of Cardiocarpus sp. The plant remains were found in sandstone facies produced by high-density turbidity flows of a deep-sea fan system. The new biostratigraphic information constrains the age of the Carboniferous Culm succession in the eastern Pyrenees
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