Isorthid AE (Brachiopoda) du dévonien inférieur du massif armoricain

Three species of Isorthidae are described in the Lower Devonian of the Armorican Massif. Two of them were hitherto badly known, being never adequately described nor figured: Isorthis (Protocortezorthis) miloni from the Gahard Formation (Gedinnian) and Isorthis (Protocortezorthis) trigeri from the Saint-Céneré Formation (Gedinnian-Siegenian). Isorthis oehlertiSolle, 1976 is considered as a synonym of Isorthis (Protocortezorthis) trigeri. The geographic distribution of these species allows to corroborate that until the top of the Lower Devonian (top of Le Faou Formation), two provinces with different faunal associations exist in the Armorican Massif.     

Corrélation de la biozonation des Charophytes avec celle des Foraminifères (Orbitolinidés dans le Valanginien inférieur du Bassin du Maestrat (Castellò, Espagne)

A correlation between the biozonations of orbitolinidsand charophytes is established in the Lower Valanginian from the Polacos Formation (Maestrat basin, Castelló, east of Spain). This correlation is based on the presence of the charophyte association: Perimneste micrandra-Perimneste ancora (rare), Globator trochiliscoides (primitive), Embergerella stellata, Flabellochara harrisii and Porocharaceae in the levels underlaying and overlaying the banks with the orbitolinid Valdanchella miliani. This charophyte assemblage is similar to the flora of the “Olba zone” from Grambast (1974), which was hypothetically attributed to the Hauterivian.According to our correlation, the olba flora was atleast already existing in the Lower Valanginian. Provisionally, the biostratigraphic boundary between the Berriasian and the Valanginian can be characterized in the continental domain of Tethys by the disappearance of Globator nurrensis and the first appearance of Embergerella stellata. Uncertainty still exists in the chronostratigraphy of the charophyte biozonation during the Middle Valanginian to Upper Hauterivan time interval.     

Foraminifères,Algues et Conodontes Bashkiriensdu Culm des Pyrénées béarnaises

Reworked benthic microfauna and microflora have been discovered in the Culm Carboniferous of the 〈Zone Primaire Axiale〉 (Western Pyrénées, Béarn).About fifty different species of Foraminifera have been identified, notably: Asteroarchaediscus, Neoarchaediscus, Eolasiodiscus, Eostaffella, Plectostaffella, Pseudostaffella.The associations as well as Algae and Conodontsfound with them indicate a Namurian C age (Lower Bashkirian G1, Zones 20–21).Paleogeographical consequences on a regional and Paleotethys scale are discussed.     

Découverte des sites du Paléolithique inférieur au Nord de l’Arménie

For a long time, the scientific community assumed that the Acheulean culture was expressed on the territory of the Armenian Plateau as well as in the neighboring regions of the Caucasus only by its late phase; therefore, it appeared in the second half of the Middle Pleistocene. In recent years, the Armenian-Russian mission has discovered and studied much older Acheulean industries sites, located in northern Armenia (the Lori intermountain Depression). These industries, represented by archaic type tools (large hand axes, picks, choppers, chisel-like tools, scrapers, points, etc.), are discovered in three deposits of origin of proluvial genesis. In the Karakhach site, this type of industry is deposited in the lower levels of volcanic tuff and below; the U/Pb study of this level of tuff proposes a series of dates, assigned to the time interval between 1.944 + 0.046 and 1.75 + 0.02 Ma. The paleomagnetic study demonstrated the inverse polarity on the tuff and the normal polarity of the underlying deposits; in correlation with other dating, this fact allows to attribute the Acheulean layers of the site of Karakhatch to the Lower Pleistocene, in particular to the Oldoway episode and to the Upper Matuyama time period. The estimated age and the techno-morphological characteristics of the tools indicate the Lower Acheulean period. The dating of the Muradovo site does not seem possible, however its very old industries and the archaeological layers, where they were discovered, find equivalents in the layered layer, surmounted by tuffs, of the Karakhatch site. The Kutran I site presented a paleosol sequence with similar Acheulean tools (hand axes, picks, choppers, etc.). Its oldest layer is older than 1.5 Ma, the upper layer is attributed to the early Middle Pleistocene; this fact means that it is possible to speak of the Lower Acheulean and of its transition to the Middle Acheulean period. The specific character and the age of the Lower Acheulean of Armenia admit that it could have formed independently of the Lower Acheulean of Africa, whose estimated age does not rise before 1.76 Ma. It should also be noted that on the neighboring territory of Georgia about the same time when appeared the Acheulean culture in Armenia, the Oldowan Dmanisi site already existed.     

Étude des Radiolaires d'un nodule phosphatédu Carbonifère inférieur de Bareilles,Hautes-Pyrénées,France

The discovery of well-preserved Radiolaria yielded into a single phosphatic nodule from Carboniferous lydites of Bareilles (Hautes-Pyrénées, France) allowed the identification of ten genera and nineteen species. Four of these species are new. The separation of the fauna from the phosphatic matrix has permitted it to be studied with the scanning electron microscope and to be correlated with faunas recently described by the same process. At least, seven species are identical with middle and upper Tournaisian phosphatic nodules from the Montagne Noire (Deflandre and Deflandre-Rigaud, 1944, Deflandre, 1973b) and from Istanbul, Turkey (Holdsworth, 1973), and eight others with Visean from the «Rheinische Schiefergebirge, West Germany (Won, 1983). The author questions the age of lydites from Hautes-Pyrénées, attributed to middle to upper Tournaisian (early Mississippian).     

Une association de Dasycladales (Algues vertes)du passage Albien-Cénomanien dans les Pyrénées et les Régions voisines (Chaînes Cantabriques,Provence)

Two Dasycladales (green Algae), Trinocladus tripolitanusRaineri, 1922 and? Dissocladella nov. sp. 1, are described from the Pyrenees, the Cantabrian Mountains and the Provence. In SW-Europe, the two species are found in the Upper Albian sensu lato (including the Vraconnian), in some cases along with the Vimport red Algae assemblage which does not persits beyond the Albian-Cenomanian boundary. In Libya, the type-locality of T. tripolitanus is however assigned to the Cenomanian/Turonian.     

Biostratigraphie des Miospores et des Chitinozoaires du Silurien supérieur et du Dévonien dans le bassin d'Illizi (S.E. du Sahara algérien)

Core samples from the Illizi basin yielded well preservedmiospores and Chitinozoa. The detailed study of the range of these microfossils allows accurate age assignment for upper Silurian and Devonian subsurface strata of the southeastern part of the algerian Sahara. On the other hand, these biostratigraphical data demonstrate the occurrence of important stratigraphical gaps related to recurrent emersions.     

La faune des bourdons (Hymenoptera: Apidae) du Parc National des Pyrénées occidentales et des zones adjacentes

Les bourdons constituent l’un des groupes de pollinisateurs les plus importants dans les écosystèmes montagnards. Cependant, la faune des bourdons du Parc National des Pyrénées occidentales (PNPO) est encore peu connue. Pendant trois ans, la faune des bourdons du Parc National des Pyrénées occidentales a fait l’objet d’une surveillance. Les inventaires effectués en juillet- août 2002, 2003 et 2005 ont permis l’observation de 5889 spécimens de bourdons de 29 espèces. Si l’on tient compte des observations des cinquante dernières années, la diversité spécifique du parc s’élève à 30 espèces de bourdons. Une telle diversité spécifique est remarquable et comparable à celle observée dans d’autres secteurs du massif pyrénéen. La faible différence entre les faunes du Parc et des réserves naturelles d’Eyne et de Nohèdes (Pyrénées-Orientales) rend compte du caractère exceptionnellement diversifié de la faune des bourdons du massif pyrénéen en général.     

Découverte d’une industrie du Paléolithique inférieur en bordure de la commune de Nice,au Vallon obscur à Saint-Isidore

An archaic lithic assemblage has just been brought to light in border of the municipality of Nice (Alpes-Maritimes, France), in secondary position in a geologic context of middle fluviatile terrace in left bank of the Var. Lithic artefacts collected gather some shaping products (worked or broken pebbles) and débitage products (cores, flakes, angular fragments), obtained on pebbles mainly in marly limestone, stemming from the local plio-Pleistocene conglomerate and the alluviums of the Var. This lithic production shows essentially the beginnings of chaînes opératoires, with the first phases of pebbles cortex removing. Flakes are very mainly cortical or semi-cortical, and cores reveal a weak technical investment, with a reduced enough number of removal negatives. The débitage of orthogonal type is the most frequent, and the bipolar technique on anvil is attested. Some rare flakes are retouched by notches or by abrupt continuous retouches. The sector where was brought to light this lithic industry, in sediments reshaped below a level of fluviatile terrace of the Var in 70 m of height, made us suggest a very ancient age for these vestiges, being able to go back up at the beginning of Middle Pleistocene, even of Lower Pleistocene, what is in agreement with the technical characteristics noticed on this lithic assemblage.     

Distribution paléoenvironnementale des huîtres dans le Messinien du bassin de Sorbas (Andalousie,SE Espagne)

Palaeoenvironmental distribution of Messinian oysters in the Sorbas Basin (Andalucia, SE Spain). According to their abundance in the Cainozoic deposits and their good preservation, the oysters constitute good indexes for the Neogene palaeoenvironmental reconstructions. So, in this paper, oysters are used to propose palaeoenvironmental reconstructions of the Sorbas Basin (Andalucia, SE Spain) during the Messinian, both before and during the deposit of evaporites. Four sections have been studied. The three first ones are located in the pre-evaporitic Messinian (La Mela, Cerro de Los Lobos and Cerro Mandras) and have provided four species of oysters: Neopycnodonte navicularis (Brocchi, 1814), Crassostrea gryphoides (Schlotheim, 1913), Ostrea lamellosa offreti Kilian, 1889, et Hyotissa hyotis (Linné, 1758). The sequential distribution of these species in the sections and the ecological affinities of Recent related species are used to propose a pattern of distribution of oysters during the Messinian in the western Mediterranean: (1) N. navicularis seems to be mainly a species of deep inner shelf and outer shelf (circalittoral sensu Néraudeau et al., 2001). (2) C. gryphoides et O. lamellosa offreti are distributed in the inner shelf (infralittoral sensu Néraudeau et al., 2001), mainly on fine substrates for C. gryphoides and mainly on coarse substrate for O. lamellosa offreti (3) H. hyotis is restricted to shallow inner shelf and near the coral reefs.The fourth section (Los Yesos) contains mainly evaporitic facies and has been interpreted with the palaeoenvironmental pattern of oysters distribution established with the previous study of pre-evaporitic series. This section comprises a serie of 75 metres of gypsum, but shows two intercalations of fossiliferous sands (at 10 and 30 metres from the base of the gypsum, respectively) in its lower midpart and a third fossiliferous intercalation of marls and limestones in its upper midpart (at 70 metres from the base of the gypsum). So, the section presents a cyclic succession of evaporitic deposits and non evaporitic facies with oysters. The three fossiliferous intercalations are interpreted as clear marine facies: (1)-the two first ones are closely similar (black sands with H. hyotis and N. navicularis) and characterize inner shelf; (2)-the marls and the fine limestones with N. navicularis of the third intercalation characterize outer shelf.     

Nouvelles données sur le Magdalénien inférieur de la Région Cantabrique : le Niveau F de la grotte de El Cierro (Ribadesella,Asturies, Espagne)

El Cierro Cave (Ribadesella, Asturias, Spain), located near the mouth of the River Sella, has yielded one of the most important Upper Palaeolithic sequences in northern Spain. To date, three major occupation periods at the cave have been identified and dated. The first was at the beginning of the Holocene (ca. 8500 BP; ca. 9000 cal BP); the second at the end of the Upper Palaeolithic, in the Younger Dryas (YD) or Greenland Stadial 1 (GS1) (ca. 11.200 BP; 12.700 cal BP) and the third during Greenland Stadial 2 (GS2) (ca. 16.300–15.500 BP; ca. 19.200–18.700 cal BP). This paper describes the stratigraphy documented in the excavations performed by F. Jordá Cerdá and A. Gómez-Fuentes between 1977 and 1979 and presents the first radiocarbon determinations for the first two occupation periods, together with the study of the archaeological materials found in Level F. This level, dated to 15.500 BP (ca. 18.700 cal BP) is characterised by specialised red deer hunting and the gathering of marine resources (winkles). Various artefacts made from animal raw materials have been documented; both finished products and items in the process of being manufactured, as well as portable art objects. The lithic assemblage, consisting mainly of local raw materials with a small proportion of allochthonous flint, is characterised by an abundance of small bladelet cores and backed bladelets. These archaeological remains and the radiocarbon date mean Level F can be attributed to the so-called “Cantabrian Lower Magdalenian”. This period has been documented archaeologically and dated to a similar time at other sites in the River Sella valley and in the rest of northern Spain.     

Etude du banc à nérinées à la limite «kimmeridgien-portlandien» dans le jura neuchâtelois méridional

A stastical analysis of the spatial orientation of gastropod shells in the Nerinea Bed shows that they are aligned parallel to the bedding plane (Fig. 6 A) but no preferential orientation of the direction of shells can be detected (Fig. 6 B). This fact and others exclude the possibility of an accumulation of shells by currents only: In some points the lower contact of the Nerinea Bed is gradational and even shells attacked by perforating algae or fungi are not abraded (Figs. 3, 4, 9). The matrix of the Nerinea Bed, a biopelsparite seems to favour the hypothesis that empty shells were concentrated by winnowing of the fine fraction, but the thickness of the accumulation prohibits a purely mecanical explanation of this kind. There can be no doubt that the Nerinea Bed reflects optimal ecological conditions which have led to a mass development. As it is very probable that Nerineids were sedentary organisms (Vogel 1968), it is tempting to explain the accumulation of shells by biologic factors only. Under optimal ecological conditions Nerineids perhaps lived in banks similar to oyster-beds or banks of Vermetids. Microfaunas and microfacies of the “Kimmeridgian” - “Portlandian” passage beds indicate a somewhat restricted environment thus confirming the conclusions ofHerm (1977) about Nerineids from the Upper Cretaceous Gosau-beds of the Eastern Alps. For local stratigraphy, the Nerinea Bed forms an ecostratigraphic marker-bed very useful in chronological correlations.     

Mise en évidence de la zone à Platynota (Kimméridgien inférieur) dans le Massif du Montejunto (Portugal); conséquences stratigraphiques et paléontologiques

The section has been logged on the southern slope of the Montejunto Mountain, near Cabanas de Torres (North of Tage River, Portugal). Typical ammonites of the Platynota zone with species-index Sutneria platynota (Reinecke) have been found in the lower part of the «Marnes d'Abadia formation. Orthosphinctes and Desmoides subzones of early Kimmeridgian are paleontologically well characterized. Unlike what is usually thought, the lower Kimmeridgian does occur. More fossiliferous beds of the «Marnocalcaires de Tojeira formation are coincident with Upper Oxfordian (Planula zone and Upper part of the Bimammatum zone). They yield Ardescia gr. enayi Atrops which appear earlier in Portugal than in South-eastern France.     

Suoidea du Miocène inférieur de Laugnac (Lot-et-Garonne, France)

The fossil vertebrate locality of Laugnac is the type locality of the Neogene mammalian zone MN2b. It has yielded many remains of Suoidea belonging to two different genera.Xenohyus venitor is characterized by its large size and especially its large central upper incisors, I1/ and I2/. It is quite difficult to know its phyletic relationships because the material is not abundant.Hyotherium cf.meisneri is more abundant with a quite good skull, pieces of skull, jaws and isolated teeth. It belongs to a peculiar lineage different from that ofH. major from Saint Gérand-le-Puy, France. It has some similarities withAureliachoerus aurelianensis from later geological levels (MN3-MN5).     

Découverte de Foraminifères planctoniques paléocènes dans les brèches,précédemment tenues pour aptiennes et d'origine diapirique,des Pyrénées basco-béarnaises

After the dating, by means of planktonic Foraminifera, of post-metamorphic marine breccias, Upper Danian–Lower Selandian in age, associated to hemipelagites and unconformably overlying the Cretaceous tectogenic axis of the Pyrenees from Roussillon to Bigorre, was it possible to extend westwards the breccia-filled Palaeocene ‘trough’ as far as the ‘Zone des Chaı̂nons béarnais’? This later unit, which belonged to the North-Iberian palaeomargin during Lower Cretaceous, was previously considered by several authors as characterized by an important halokinesis generating, during Aptian/?Albian, collapses of the Jurassic–Lower Cretaceous carbonate cover above dissolved salt domes and spectacular accumulations of breccias. In fact, we have everywhere identified Palaeocene planktonic microfauna within the matrix of these breccias (and within the associated hemipelagites), particularly of the reference ‘diapiric’ breccias of Etchebar, Lauriolle, Layens and Bosmendiette/Beloscare. Deposited into intra- ‘trough’ sub-marine canyons, after karstification and erosion of intermediate mountains with a steep topography previously induced by Uppermost Cretaceous compressions, the herein studied Palaeocene marine breccias should not be hereafter regarded as linked to any Lower Cretaceous diapirism on the North-Iberian palaeomargin. To cite this article: B. Peybernès et al., C. R. Palevol 1 (2002) 3–10.     

Dépression à long-terme des synapses excitatrices dans le cortex et l'hippocampe

The efficacy of excitatory synapses terminating on cortical and hippocampal pyramidal cells may be persistently depressed as well as potentiated. Homosynaptic long-term depression (LTD) seems to be triggered by an entry of calcium into a post-synaptic cell less than that needed to initiate long-term potentiation (LTP). Theoretical work predicted, and experimental studies confirmed, that moderate elevations of calcium initiate LTD via a cascade of biochemical interactions involving calcium-dependent phosphatases. Genetically modified animals confirmed the prediction of a sliding threshold that defines the limit between LTD and LTP. While mechanisms for the initiation of LTD are quite well established, it remains unclear whether pre- or postsynaptic mechanisms, or both, are involved in its maintenance. A role for LTD in processes of learning and forgetting in the adult animal remains to be firmly established. It seems probable, however, that a persistent reduction in synaptic weight is a basic process used in the establishment and refinement of neuronal circuirs during development.     

Découverte de charophytes et ostracodes de l’Yprésien inférieur dans les Monts des Ksour (Algérie) : biostratigraphie et paléoécologie

A stratigraphic, palaeontological and sedimentological study was carried out in the red beds cropping out on the left side of Oued Tafarahit, south-east of the Ksour Mountains (Algeria). The studied succession consists of a non-marine fining-upward detrital formation, including microconglomerate, sandstone and clay beds, which were previously attributed to the Cenozoic sensu lato, since no palaeontological evidence was available. Sedimentology suggests deposition in a fluvial environment. The clayey levels yielded the assemblage formed by the charophytes Peckichara atlasensis, Maedleriella cristellata, Nitellopsis (Tectochara) thaleri, Grovesichara sp., and Lamprothamnium papulosum and the ostracods Neocyprideis meguerchiensis, Herpetocypris? sp. and Cyprinotus? sp. This assemblage allows constraining the age of the detrital series from Oued Tafarahit to the Ypresian. Ostracods are typical of freshwater to euryhaline environments. The freshwater taxa (Herpetocypris? sp. and Cyprinotus? sp.) would indicate phases of desalinisation during periods of flood. However, the brackish water species (Neocyprideis meguerchiensis) is characteristic of saline phases related to low water table periods. Moreover the charophyte and ostracod assemblage confirms a close palaeobiogeographic relationship between North Africa and Southern Europe during the Lower Eocene.     

Les assemblages de diatomées des niveaux infra-gypseux du bassin messinien de Sorbas (Espagne)

In the Sorbas basin, the diatomites represent one of the main sedimentary components of the Messinian together with its two marginal carbonate platforms and the central gypsum deposits. Several vertical sections were taken in the infra-gypsum diatomites from successively more distal paleogeographic areas, ranging from the reef slopes (Cariatiz) to the basin (Los Yesos, Los Molinos). A total of 88 diatom species were determined: 50 centric and 38 pennate. Characteristic assemblages were defined for each category type, revealing ecological variations. In the three sections, plankton forms represent 90 % of the diatoms, with oceanic forms dominating the meroplanktonic and neritic. Nevertheless, some levels clearly indicate a coastal environment, attesting to the carbonate platform influence which progrades toward the basin. The diatom assemblages are relatively homogeneous throughout the three sections, indicating that, before gypsum deposition, the basin was still substantially open to the ocean, with waters sufficiently warm to allow coral reef development. Nevertheless, the basin might also have experienced episodes of colder Atlantic influences.     

Répartition stratigraphique et biozones des kystes de dinoflagellés au passage Jurassique moyen–Jurassique supérieur (Bathonien supérieur–Oxfordien inférieur) dans le Bassin de Guercif,Maroc nord-oriental

Despite the stratigraphical significance of dinoflagellate cysts as reliable markers for correlating and dating Jurassic–Cretaceous strata, investigations into this palynomorph group in the southern Tethyan Realm, specifically northwest Africa, are sparse and somewhat parochial. Most research on Jurassic dinoflagellate cysts is focussed on European depocentres in the Boreal and Sub-Boreal realms. This study is on biostratigraphical data from two petroleum boreholes (MSD1 and KDH1) drilled during 1985 in the Guercif Basin, northeast Morocco by ONAREP (Office National de Recherche et d’Exploitation Pétrolier), now ONHYM (Office National des Hydrocarbures et des Mines). These boreholes penetrated a thick siliciclastic succession, attributed to the Middle and Upper Jurassic, below Miocene marls. Over sixty dinoflagellate cyst taxa were identified. Four dinoflagellate cyst biozones, named GI to GIV, are established for the late Bathonian to early Oxfordian interval. These biozones are defined on the basis of the first appearance datum (FAD) and/or the last appearance datum (LAD) of some biomarker taxa which have wide geographical distributions. These are: Ctenidodinium combazii and Ctenidodinium sellwoodii for the GI Biozone (late Bathonian–early Callovian); Ctenidodinium continuum and Meiourogonyaulax caytonensis for the GII Biozone (middle Callovian); Gonyaulacysta centriconnata and Wanaea thysanota for the GIII Biozone (late Callovian–earliest Oxfordian); and Liesbergia liesbergensis and Systematophora penicillata for the GIV Biozone (early Oxfordian). These biozones are correlated to those already established for the respective intervals in other palaeogeographic regions, such as the Boreal, Sub-boreal and Tethyan realms.     

Les faunes d'ammonites du Carixien inférieur et moyen du gisement des Cottards (Cher)

The study of the traditional Cottard layer forthe first time allows the exact succession of lower and middle Carixian ammonites to be established.The most striking fact is the evolution of the Tropidoceras-Acanthopleuroceras lineage, a regular modification of the ribbing density and L¹ structure, an iterative variation of section and tuberculization.Precisions are given on Polymorphites and Beaniceras and three new species are described: Polymorphites evolutus, Beaniceras cottardiense, Acanthopleuroceras alisiense.