bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ostracods from the late Frasnian of the Neuville railway section (Dinant Synclinorium, Belgium) : relation to the Kellwasser Event
Authors: Casier Jean-Georges 
Published: June 2005

Abstract
Ostracods from the upper part of the Valisettes Formation (Frasnian), from the Matagne Formation (Idem) and from the base of the Senzeille Formation (Famennian) exposed in the Neuville railway section (southern side of the Philippeville Massif within the Dinant Synclinorium) have been studied in order to advance the knowledge of the late Devonian mass extinction. The ostracod assemblage present in the upper part of the Valisettes Formation belongs to the Eifelian ecotype, and is dominated by filter-feeding metacopid ostracods indicative of an hypoxic trend related to an increase in the water depth. The overlying Matagne Formation is characterised by opportunistic species belonging to the myodocopid ecotype indicative of more severe hypoxic water conditions. The ostracod assemblage recognised in the base of the Matagne Formation is comparable to the assemblage found in the Upper Kellwasser Horizon of the Schmidt quarry parastratotype (Kellerwald, Germany), and the sartenaeri, splendens and sigmoidale Zones of the biozonation on entomozoid ostracods are also recognised. The splendens Zone – sigmoidale Zone transition which corresponds to an important change in the entomozoid fauna in relation to the late Devonian mass extinction must be fixed definitively into the late Frasnian. Only Palaeophilomedes neuvillensis Casier, 1988, and Ovatoquasillites avesnellensis (Lethiers, 1973) survived the extinction in the Neuville railway section. P. neuvillensis is perhaps the sole true nekto-planktonic myodocopid present in the section, and the pre-adapted Lazarus species O. avesnellensis is known to have lived in very shallow marine and semi-restricted environments. We can conclude that the surface waters and the shallow marine environments were probably not disturbed during the late Devonian mass extinction. A figure, summarises the succession of events at the Frasnian – Famennian transition on the southern border of the Philippeville Massif.
Paleoenvironmental evolution of the Guercif basin (south Rifain corridor, northern morocco). Implications for the Messinian salinity crisis
Authors: Dayja Driss , Bignot Gérard 
Published: June 2005

Abstract
Foraminiferal biostratigraphic and paleoenvironmental results from the MDS1 borehole of the Guercif basin reveal the detailed history of its paleogeographic evolution during the late Neogene.
Four biostratigraphic events are recognised based on the study of planktonic foraminifera. In addition to the placement of the Tortonian-Messinian boundary at 798 m depth, they also allow correlation of the MSD1 borehole with other late Miocene sections in the Mediterranean area.
The diversity of benthic foraminifera is significant in the studied borehole. 111 species assigned to 55 genera, were identified.
Three successive assemblages of benthic foraminifera were recognised, each one conveying a different paleoenvironmental information. They thus recorded a number of fundamental changes in the environmental and water mass characteristics of the Guercif basin.
Following the oldest upper Tortonian transgressive marine deposits found at the bottom of the borehole, marls accumulated at lower epibathyal to upper mesobathyal depths (~400 to ~800 m). They recorded sea-floor dysoxia and associated stratification of the water column for the time interval between ~7.5 and ~7.3 Ma. During the latest Tortonian-early Messinian the basin experienced a rapid shallowing, first from the previously bathyal environments to deep neritic (~100 to ~200 m), and to shallow neritic afterwards (0 to ~30 m). The total absence of any foraminifera in the conglomerates situated at the top of the study borehole suggests that these sediments were deposited in subaerial environments. At this time the connection between the Atlantic Ocean and the Mediterranean Sea through the South Rifain Corridor was stopped. This local event contributed to the establishment of the particular conditions of the Messinian salinity crisis.
The very high alluvial formation of early Pleistocene age in the Creuse River Valley at Eguzon (Indre) : cryoturbation patterns, prehistoric occupation sites and absolute dating
Authors: Despriée Jackie , Gageonnet Robert 
Published: June 2005

Abstract
Around twenty prehistoric sites of the very early Palaeolithic were discovered on the northern edge of the Massif Central, in the Creuse Valley between Crozant and the Paris Basin, and on the Aigurande crystalline plateau that borders it. Concentrated more particularly around Eguzon, the sites are all closely linked to fluviatile formations, whose study, despite difficult exploration conditions, revealed many remnants of alluvial deposits. Those of the very high formation, some up to 15 m thick, were the best preserved.
The most significant site, at “Pont-de-Lavaud”, is in a thin bed of gravel made up mainly of quartz pebbles and debris with small, interbedded sand lenses. Tilted 6 to 7° in a small depression in the weathered foliated crystalline basement, the bed is at mid-slope of an interfluve between the Creuse River and one of its small tributaries. Excavation done between 1983 and 1995 uncovered many prehistoric artefacts carved out of quartz in the upper part of the sediment and, below this, various cryoturbation patterns (sorted circles, polygons, inclusions in the alluvium of alterite from the bedrock) and scattered, less abundant artefacts of the same type. Due to the outstanding state of conservation of these findings, they could be studied in a particularly detailed manner and, when coupled with the study of the alluvial formations, enabled us to :
– place them at the base of the very high terrace, located 90–110 m above the river’s present-day low water level – attribute the unusual position of the outcrop to the tilting of a block of bedrock by new displacement of an old fault, thus confirming the role of recent tectonics in the regional morphology ;
Absolute age dating by Electron Spin Resonance (ESR) of the best conserved outcrops of the very high alluvial formation gave an age of 1 to 1.2 million years, thus placing them at the end of the early Pleistocene. However, dating of alluvial remains near the site and of the site itself, gave ages between 0,9 and 1 million years. Differences are attributed to the role that greater erosion and pedogenic weathering might have played. Therefore, the “Pont-de-Lavaud” occupation sites are among the oldest presently known in Europe.
Diversity of radiolarian families through time
Authors: De Wever Patrick , O’dogherty Luis , Caridroit Martial , Dumitrica Paulian , Guex Jean , Nigrini Catherine , Caulet Jean-Pierre 
Published: June 2005

Abstract
The examination of radiolarian biodiversity at the family level through Phanerozoic time reveals some general trends known in other groups of organisms, especially among plankton, while some other trends seem to be quite peculiar. The Permian /Triassic crisis that is one of the most important in the evolution of marine organisms, is marked in radiolarian assemblages by the extinction of two orders (Albaillellaria and Latentifistularia) towards the end of the Permian, and mostly by the tremendous diversification of Spumellaria and Nassellaria in the early-mid Triassic. Radiolarian diversity increased from Cambrian to Jurassic, remained quite stable during the Cretaceous and has decreased slightly since then.
Syn-folding remagnetization events in the French-Belgium Variscan thrust front as markers of the fold-and-thrust belt kinematics
Authors: Szaniawski Rafal , Lewandowski Marek , Mansy Jean-Louis , Averbuch Olivier , Lacquement Frederic 
Published: June 2005

Abstract
New paleomagnetic studies have been carried out within the Ardennes segment of the N France - S Belgium Variscan fold-and-thrust belt to set constraints on the fold-thrust belt kinematics and reveal the casual relationships between vertical-axis rotations and major strike deviated zones localised along the general trend of the belt. Magnetite-bearing Devonian and Carboniferous limestones yielded two characteristic, secondary components of the natural remanent magnetization : a low temperature component recorded most probably during the late stages of folding and a high temperature component, acquired during incipient stages of deformation. Both post- and synfolding magnetizations were identified in the Lower Devonian hematite bearing sandstones. Ages of magnetization, inferred from the analysis of characteristic remanence inclinations compared to the reference curves for the stable parts of the Old Red Sandstones Continent (ORC), suggest the previous remagnetization event to be due to the burial of sedimentary rocks under the thick molassic foreland basin of Namurian-Westphalian age and the second to the final out-of-sequence activation of the thrust front in Stephanian times. Irrespective of the age of the magnetizations, orientations of paleomagnetic directions are dominantly governed by second-order structural trends. Clockwise rotations are observed in relatively narrow zones featuring deviated orientations of fold axes, other sites show paleomagnetic directions akin to those known from the ORC. We interpret this feature as a result of local transpressive deformations and related rotations, which occurred at lateral borders of propagating thrust-sheets. The latter deformation zones are suggested to be controlled by deep-seated discontinuities inherited from the Devonian Rheno-hercynian basin development. The Ardennes thrust belt was thus not rotated as a whole unit with respect to the ORC after the Namurian, preserving the initial orientation of the continental margin.
Ontogeny and covariation in the Toarcian genus Osperleioceras (Ammonoidea)
Authors: Morard Alain , Guex Jean 
Published: June 2005

Abstract
Starting from embryonic (protoconch-ammonitella) and early juvenile shells, which are indistinguishable at the species level, growth curves of Osperleioceras from the Reynesi Subzone (Upper Toarcian) of the Causses Basin (Aveyron, France) show a continuous radiating range of correlated variation in dimensional and ornamental characters, such as involution, whorl compression, rib strength and rib density. This covariation pattern can be observed among single-horizon assemblages, as well as during individual ontogenetic development.
The existence of a continuous intergradational series of shells, ranging from stout coarsely ribbed to smooth suboxycone morphologies, rules out functional or ecological selectivity to explain this non-random variability pattern. The complex interdependence of shape and sculpture can be simulated by a model in which sculpture intensity depends on mantle curvature [Guex, 1999].
The expression of covariation in subadult specimens since the base of Upper Toarcian reveals a rise in variability, concomitant with a size decrease, both contemporaneous with environmental instability. It developed in successive bursts from a fairly long low variability period spanning the whole Middle Toarcian.
Successive shearing tectonics during the Hercynian collisional evolution of the southwestern French Massif Central
Authors: Duguet Manuel , Faure Michel 
Published: June 2005

Abstract
In the French Massif Central, the Devonian-Carboniferous tectonic evolution of the Rouergue-Albigeois area is characterized by three phases of low-angle ductile shearing. The first event D1, which occurred probably in the Lower Devonian, is responsible for the south-westward thrusting of the high metamorphic Lévézou nappe which belongs to the Upper Gneiss Unit above the Lower Gneiss Unit overlying itself the Para-autochthonous Unit, (locally called the St-Serninsur-Rance nappe). In the late Devonian-early Carboniferous, this stack of nappes is reworked by a second event, D2, characterized by a top-to-the-NW shearing of the Para-autochthonous Unit upon the Lower Gneiss Unit developed under medium pressure/medium temperature metamorphism. The contact between the Lower Gneiss Unit and the Para-autochthonous Unit is a top-to-the NW low-angle fault that progressively evolues into a dextral strike-slip fault from west to east. The D2 event is followed by a top-to-the south D3 thrusting dated around 330–340 Ma. The main feature of the D3 compressional stage is the emplacement of the whole stack of nappes previously structured by D1 and D2 events upon the Albigeois series. The D3 event produced south-verging recumbent folds in the Albigeois, Mont-de-Lacaune and Montagne Noire. The significance of the D2 event either as thrusting or normal faulting is discussed.
A tectonic inversion by steps during the Cenozoic : the Dover Strait
Authors: Van Vliet-Lanoë Brigitte , Mansy Jean-Louis , Henriet Jean-Pierre , Laurent Michel , Vidier Jean-Pierre 
Published: June 2005

Abstract
The Boulonnais is a dome incised by a former marine gulf inset into a zone of tectonic inversion from the Middle Eocene, which was already partly excavated at least at the Upper Eocene. New sedimentological and paleopedological data obtained within the Boulonnais, completed with old seismic profiles, allow a better understanding of the inversion process which developed step by step. The initial breaching probably took place in the late Eocene. The Dover Strait was probably opened during the Lutetian, a part of the Oligocene and the late Neogene. Oligocene and Pliocene faunal assemblages are identical on both sides of the Strait. It was closed again for tectonic and eustatic reasons in the early Quaternary and reopen subsequently just before the Last Interglacial. The opening is related to the evolution of the Western Channel and of its paleovalley system. The inversion of the Variscan front accommodates most of the shortening induced by the Pyrenean Orogen on the western border of the European plate. The inversion of the Dover Strait region is almost synchronous with those of other basins of the Channel and North Sea areas. Tectonic, geomorphologic and climatic implications of this dynamic are discussed within the western European context.
Indication for counterclockwise declination deviation in the Cretaceous of the North Paris Basin
Authors: Márton Emó , Csontos László , Mansy Jean-Louis , Bergerat Françoise 
Published: June 2005

Abstract
Paleomagnetic sampling was carried out in Mesozoic exposures of Northwest France and Southeast Belgium. Cretaceous localities in Hainaut, Boulonnais and Normandie yielded statistically well defined paleomagnetic directions. These localities fall into two groups. Hainaut and Boulonnais are characterized by declinations suggesting 30° counterclockwise (CCW) angular deviation of declination with respect to the present North, while Normandie exhibits moderate (12°) clockwise (CW) angular deviation with respect to the present North. In Normandie, we also observed occasionally very weak signals of a CCW deviated component, which, however, could not be treated statistically. Fold test suggests that both groups of samples were remagnetized during deformation. The overall mean paleomagnetic declination of the first group is westernly, that of the second group practically coincides with post-Eocene European reference directions, From assessing structural inversion and relevant paleostress-directions in Normandie, remagnetization may be connected to tectonic inversion in late Eocene-Oligocene times.
While the statistically meaningful paleomagnetic result for the second group fit the synthetic stable European apparent polar wander path (APWP) at about 30 Ma, the overall mean paleomagnetic direction of the first group (based on 5 localities, representing 42 samples) defines a pole which is significantly offset from it, at any time following the deposition of the studied sediments. One explanation of this offset could be intraplate rotation on a small (Brabant Massif) scale. However, the angle of deviation in declination seems to be too large for a tectonic solution. Furthermore the data obtained from the Paleozoic do not show such declination deviation. It seems, therefore, that we need to increase considerably the direct stable European paleomagnetic database for the late Cretaceous-Tertiary, in order to further improve the late Cretaceous-Paleogene segment of the European APWP.
Fluid palaeo-circulation generated by the Pyrenean orogeny and its potential role in the formation of lead-zinc deposits in the Cévennes region: a modelling approach
Authors: Jost Anne , Violette Sophie , Macquar Jean-Claude , Dromart Gilles 
Published: June 2005

Abstract
Recent studies of the host rock palaeomagnetism of the lead-zinc deposits on the Cévennes margins pointed towards regional fluid circulation from the early to middle Eocene. The hypothesis has therefore been put forward that mineralising fluids might have migrated as a consequence of the Pyrenean uplift. Based on this assumption, a digital model was developed to describe this palaeo-circulation along two reconstituted cross-sections, in early Eocene times. One of them extends from the Gulf of Lion to the Les Malines deposits at the southern end of the Cévennes mountains; the other one connects the Montagne Noire to Les Malines in order to test the hypothesis of a more localised fluid circulation. The modelling of heat and fluid circulation along these cross-sections is constrained mainly by fluid-temperature data, derived from analyses of fluid inclusions. The maximum recorded temperatures are about 150°C. The METIS code (Ecole des Mines, Paris) was used to test the transport scenarios while prescribing hydrodynamic characteristics in the series that would allow fluid flow. Gravity-driven flow is initiated at a high point, either the Montagne Noire or the Pyrenees. Drainage occurs at depth. The permeable formations concerned are: Cambrian dolomite in the cross-section beginning in the Montagne Noire, and Triassic and Liassic carbonate or sandstone formations in the other one. The fluids converge at the deposit site through faults on the margins of the Cévennes horst. The highest temperatures reproduced by the digital simulations in a steady-state regime are in the order of 80°C at the deposit site for each pathway. A sensitivity test showed that higher temperatures, in the order of 150°C, could only be reached with a heat flux of 120 mW.m−2 and by optimising such parameters as permeability, aquifer geometry and thermal conductivity. However, such a parameter set does not seem geologically feasible. The modelling demonstrates that circulation must have occurred at greater depths in the case of gravity-driven fluid flow. The most probable explanation is that the fluid migrated in the deep crustal basement and that, during its ascent along the faults bordering the Cévennes heights, it mixed with basinal brines migrating through shallower aquifers.
Evidence of magmatic flow by 2-D image analysis of 3-D shape preferred orientation distributions
Authors: Launeau Patrick 
Published: June 2005

Abstract
The 3-D Shape Preferred Orientation (SPO) ellipsoid can be obtained by image analysis on a minimum of three perpendicular sections, when the 2-D measurements can be assimilated to ellipses. As numerous phenomenons can modify the SPO in magma (boundary condition effects, crystal interactions, joint migrations, etc.), the ellipsoid calculation is first tested on a set of digital models of simple shear flow. Those models, made of scattered shape ratio distribution, show that a suspension of crystals in a simple shear flow of the magma produces SPO parallel to the shear direction with an intensity given by the average shape ratio of the crystals, without any link with the amount of shear flow. This steady state SPO along the flow direction is particularly useful to study magma emplacement even if it is also shown that a critical shear rate γ between 4 and 8, for crystal shape ratio between 2 and 5 respectively, is sufficient to completely reorient a SPO. Therefore the SPO does not record magmatic strain as may do an enclave, which is an interface between two magmas with low viscosity contrast, that can record the whole strain of the magma by its passive deformation along the flow. An infinite strain is necessary here to parallelize the enclave on the shear flow direction. The application to a natural case (gabbronorite of the Bushveld, South Africa) shows that we must take care of the mineral chosen to describe a flow in a magma and that a careful classical study of the structures observed in thin sections is always required. To allow anyone to test the quality of the 2-D/3-D conversions, a web site is associated to this publication with a free access to all the image analysis and ellipsoid programs presented below.
Ammonites phylogenetic analysis: state of the art and new prospects
Authors: Rouget Isabelle , Neigeet Pascal , Dommergues Jean-Louis 
Published: June 2005

Abstract
Two main types of data are available to resolve phylogenies using fossils data: (1) stratigraphic ordering of taxa, and (2) morphological characters. In most phylogenetic studies dealing with ammonites, authors have given priority to the stratigraphic distribution of taxa. This practice is classically justified by the fact that the ammonite fossil record is frequently outstandingly good. In practice, the level of integration of stratigraphic and morphologic information in a single analysis depends on the confidence that authors have in the quality of data. Besides, many evolutionary concepts, which could differ over time and between authors (e.g. anagenesis, cladogenesis, iterative evolution), are added to these data to help infer phylogenetic relationships. As a result, phylogenetic hypotheses are based on eclectic methods which depend on the relative weight given to stratigraphic and morphologic information as well as on evolutionary concepts used. The validity of relationships proposed by previous authors is not dealt with in this paper. Instead, our goal is to draw attention to problems that these eclectic methods may cause, that is to say: (1) ammonites systematics is poorly formalised and (2) phylogenetic hypotheses as they are classically constructed are not rigorously testable. During the last 10 years, cladistic analysis has been applied to ammonites but is still unpopular among ammonitologists. However, studies have consistently shown that cladistics is not as unsuited a tool for ammonites phylogenetic reconstruction as is widely believed. Moreover, classical works open new questions about ammonite phylogeny and in particular, help to reappraise our view on the definition of morphological characters and their phylogenetic significance.
A new species of Hippopotamidae (Mammalia, Artiodactyla) from the Sagantole Formation, Middle Awash, Ethiopia
Authors: Boisserie Jean-Renaud 
Published: June 2005

Abstract
A new species of Hippopotamidae, Hexaprotodon dulu nov. sp., was discovered in the Middle Awash valley, Afar, Ethiopia. It was found in the Sagantole Formation, within volcaniclastic beds aged between 5.2 Ma and 4.9 Ma (40Ar/39Ar). It is therefore the oldest hippo species described as yet from Ethiopia. This hexaprotodont hippo exhibits a general morphology that is primitive, close in that respect to other Mio-Pliocene forms. However, its cranium and dentition display a distinctive association of measurements and features. This new species increases the hippo fossil record in East Africa. It also reinforces the hypothesis of hippo endemism in each African basin as early as the basal Pliocene.