Les corégones du lac de Neuchâtel: rendement de la pêche; âge et croissance des individus capturés par les pêcheurs professionnels

The fishery of twoCoregonus sp. of the Lake of Neuchâtel (Switzerland) were studied with statistics held since 1917. The younger age structure observed in 1978–80 due to eutrophication which enabled a faster growing of the fishes permits to explain the decrease in fish numbers as well as in weight of the catches.     

Les manifestations de l'eutrophisation des eaux dans un grand lac profond: le Léman (Suisse)

Contains a synthesis of the principal manifestations of accelerated eutrophication of the waters of Lake Geneva, based on a thorough study of the available publications and particularly on the reports of the ‘Commission internationale pour la protection du Léman contre la pollution’ [12]. The analysis of the present biological (flora and fauna) and physicochemical characteristics on the one hand, and the study of their evolution on the other, put the Lake of Geneva in the category of meso-eutrophic lakes.      

Note sur le genreChoricystis (Chlorophyceae)

This paper deals with the systematic position ofChoricystis. Its species and their synonyms are studied. Five species are considered to belong to the genera. The study has mainly been based on the original diagnosis and iconotypes. The author has also studied some samples ofCh. chodatii taken from damp soils of Argentina.     

Typologie et mode de mise en place des roches magmatiques dans les Pyrénées hercyniennes

Résumé L'évolution géodynamique hercynienne des Pyrénées se caractérise par une importante activité magmatique à l'origine de corps plutomques de taille, de composition et de niveaux de mise en place différents. A partir de ces caractéristiques nous avons pu établir une typologie qui nous a permis de distinguer deux types principaux de massifs: 1) les massifs de composition homogène, acides (massifs de type HA) ou basiques (massifs de type HB), localisés dans les grands ensembles métamorphiques régionaux et 2) les massifs de composition hétérogène, formés par l'association de roches basiques et de roches acides dont la répartition spatiale a permis de distinguer les massifs de type CA (roches acides au coeur du massif), les massifs de type CB (roches basiques au coer du massif) et les massifs de type CR (récurrences de lentilles de roches basiques dans un massif zoné de type CA ou CB), mis en place dans le Paléozoïque supérieur généralement loin des grands ensembles métamorphiques. Tous ces massifs se sont mis en place diapiriquement au cours du métamorphisme régional et de la déformation hercynienne majeure.

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One of the main characteristics of the Hercynian geodynamic evolution of the Pyrenees is an intense magmatic activity producing large plutonic bodies. They have different sizes, various compositions and distinct emplacement levels. From these characteristics, a typology for these massifs is defined. Two main types of massifs have been recognized: 1) massifs with an homogenous composition founded in large regional metamorphic areas, and 2) massifs with an heterogenous composition of acid and basic rocks, whose spatial disposition permits the recognition of three sub-types: a) the CA type where acid rocks are at the core of the massif; b) the CB type where basic rocks are at the core of the massif, and c) the CR type where numerous basic xenoliths are scattered within either a CA or a CB type massif. These heterogenous massifs generally occur within Upper Paleozoic rocks and usually far away from regional metamorphic areas. All of these massifs were emplaced diapirically during the regional metamorphism and the main Hercynian deformation.

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Zusammenfassung Ein wichtiges charakteristisches Merkmal der geodynamischen Entwicklung der Pyrenäen während der herzynischen Phase ist eine hohe magmatische Aktivität, auf die Plutone größerer Ausdehnung zurückgeführt werden. Größe, Mineralogie und Erstarrungstiefe der Plutone variieren. Anhand dieser Charakteristika können die Intrusivkörper in zwei Hauptgruppen differenziert werden. Die erste Gruppe (1) sind Plutone homogener Zusammensetzung in regionalmetamorph überprägten Gebieten. Die zweite sind heterogen zusammengesetzte Plutone (2) saurer und basischer Magmatite, deren räumliche Anordnung eine Untergliederung in drei Untergruppen ermöglicht:a) Bei dem CA-Typ befinden sich saure Gesteine im Kern; bei b), dem CB-Typ, liegen basische Gesteine im Kern vor und bei c), einem CR genannten Typ, sind zahlreiche basische Xenolithe entweder in dem CA-oder dem CB-Typ verstreut vorhanden. Diese heterogenen Plutone findet man allein in spätpaläozoischen Gesteinen und in der Regel weit entfernt von Gebieten, die metamorph beeinflußt wurden. Sämtliche Plutone haben eine Diapir-ähnliche Form und intrudierten zeitgleich mit der Regionalmetamorphose und der Hauptphase der herzynischen Deformation.

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Quantitative reconstruction of Late Cenozoic landscapes: a case study in the Sierra de Atapuerca (Burgos,Spain)

We have developed a method to reconstruct palaeorelief by means of detailed geomorphological and geological studies, geostatistical tools, GIS and a DEM. This method has been applied to the Sierra de Atapuerca (NE Duero Basin, Burgos, Spain), allowing us to model a three‐dimensional reconstruction of the relief evolution from the Middle Miocene to the present. The modelling procedure is based on geostatistical recovery of the palaeosurfaces characteristic of each geomorphological evolution stage, using polynomial regressions, trend surfaces and kriging. The modelling of morphology trends has been useful in establishing new geological and geomorphological relationships in the geodynamic evolution of this basin, such as uplift quantification, correlation of erosion surfaces and sedimentary units, and the evolution of fluvial base levels. The palaeosurface reconstruction together with an analysis of the slope retreat have allowed us to reconstruct the palaeoreliefs that define the Late Cenozoic landscape evolution of this area, where the Lower and Middle Pleistocene archaeopalaeontological sites of the Sierra de Atapuerca are located. Copyright © 2007 John Wiley & Sons, Ltd.     

Thrust Ramp Geometry and Spurious Rotations of Paleomagnetic Vectors

Interaction of deformation axes during pure translation of a hanging-wall over a footwall composed by frontal and oblique ramps is carefully evaluated together with the evolution of associated paleomagnetic vectors. Four different cases are distinguished on the basis of the deflection on the paleomagnetic vectors when the bedding correction is applied during the restoration process. Two cases (frontal and oblique ramp without mutual interaction) do not produce any deflection. But two cases in the transition zone between both ramps will undergo non-coaxial axis of tilting during progressive deformation. One of them will produce spurious rotation if the bedding correction is applied. These errors will affect the oroclinal bending diagram as well as the fold test producing an apparent oroclinality and an apparent syn-folding magnetization respectively. A well-known geometry and kinematics of the thrust system is needed to properly restore the beds (and vectors) and to avoid the spurious rotations and its collateral effects in paleomagnetic investigations. A paleomagnetic study in the Pyrenean External Sierras is shown as an example. Primary Eocene vectors underwent a clockwise rotation (40° about) during the emplacement of the South Pyrenean sole thrust, however the Rasal-Gabardiella system of oblique ramps display spurious rotations ranging from –8° up to 13° if the inappropriate bedding correction is performed.     

Eutrophisation du Léman indiquée par les communautés d'oligochètes: campagnes 1982–1985

Oligochaete communities (tubificid and lumbriculid worms) were studied between 1982 and 1985 in 23 areas of the mesoeutrophic Lake Geneva (Switzerland). Species numerically dominant in eutrophic lakes (mostlyPotamothrix hammoniensis), in mesotrophic lakes (mostlyP. vejdovskyi) and in oligotrophic lakes (mostlyStylodrilus heringiamus) constituted 52%, 36% et 12% of the worm communities, respectively (means across the 23 areas). The relative abundance of eutrophic species increased (15 to 94%) according to depth or to external organic inputs. In this case, the mean biomass (wet weight) of oligochaetes per area was higher than 15 g·m⁻² (up to 210 g). Mesotrophic species decreased (65 to 1%) along the same gradients of depth or of sedimentation. Oligotrophic species increased (0 to 31%) only in areas where the organic sedimentation was lessened by steep bottom slope and by currents. Thus, the structure of oligochaete communities reflected the patterns of sedimentation and the trophic state of Lake Geneva.