Tectonique superposée de la zone de faille d’Arakapas (Massif de Troodos,Chypre)

Résumén

Une analyse tectonique du couloir faillé d’Arakapas est menée à partir de la mesure de plus de 3 000 plans striés relevés dans les formations ophiolitiques du Troodos et du Kellaki. Des mesures ont également été effectuées dans les formations du Crétacé terminal — Paléogène et du Néogène, afin de préciser l’âge des différents stades de la déformation. Elles ont été traitées par les méthodes des dièdres droits et du calcul du tenseur des contraintes. Il est montré que le couloir d’Arakapas a été le siège de plusieurs déformations successives. Au Néogène règne un régime en extension qui succède à un jeu décrochant dextre contemporain des compressions d’âge Crétacé terminal à Miocène. Un jeu décrochant antérieur peut-être mis en évidence. Il serait compatible avec le fonctionnement en faille transformante océanique proposé par divers auteurs.     

A continuum-based model on axial pile-head dynamic impedance in inhomogeneous soil

Acta Geotechnica - This paper presents a closed-form solution on the steady dynamic response of circular piles embedded in inhomogeneous soil. The soil is modeled as a viscoelastic continuum, and...     

Circumgranular bassanite in a gypsum crust from eastern Algeria – a potential palaeosurface indicator

Detrital sand grains are surrounded by thin bassanite coatings in the upper part of a coarse-crystalline gypsum crust from the Algerian Sahara. The bassanite developed by topotactic replacement of the surrounding gypsum in the absence of a liquid phase. Heating experiments using a gypsum crystal with sand inclusions produced similar patterns and textures. In one experiment, bassanite developed around quartz and carbonate grains but not along the sides of the heated gypsum crystal. This is the result of differences in heat capacity between gypsum, quartz and calcite. Bassanite formation in the crust from Algeria was not controlled by differences in thermal properties. Instead, the bassanite apparently formed under conditions of thermal equilibrium. The occurrence of bassanite as circumgranular coatings in the crust is interpreted as being related to the availability of submicroscopic space along the contact between the gypsum cement and the enclosed sand grains. The presence of coatings of this type, or derived relict features, is a potential criterion for the recognition of palaeosurfaces.     

Nouvelles données pétrographiques et structurales sur le magmatisme du Sud du bassin de Morondava (Sud-Ouest de Madagascar)

New petrological and geochemical data are presented on basic igneous rocks from the south of the Morondova basin located in the southwestern part of Madagascar. The structural setting is well defined and, with the aid of a schematic map, the spatial relationships between the magmatic centres and major faults can be deduced from seismic data. On the other hand, new petrographic and geochemical data enable the different types of basaltic magmatism manifested in this area to be distinguished. It appears that tholeiitic magmatism evolved towards transitional magmatism from the south to the north of the Morondava basin. This geochemical evolution of basaltic magmatism can be linked to the initiation of rifting between Madagascar and Africa along the Mozambique channel and the length of the Davie ridge associated with the opening of the Indian ocean. These observations, together with structural data and recently obtained geochronological data, contribute to a better understanding of the mechanism and evolution of Madagascan rifting.     

Considerations generales sur la distribution de l'uranium dans les roches granitoides

Using definite examples the authors show that it is possible to find, in a given granite, relations between uranium and the other elements, but these relations cannot be generalized. They cannot depend on the petrographical and mineralogical properties rather than on the chemical composition. One finds with the essential minerals some apparent relations but they are valid only for a given rock. The nature of a granite depends, mainly, on its formation and consequently on the original material from which it derived. The present data on radioactivity of granites cannot be generalized.     

Influence of Mediterranean sea-level changes on the Dacic Basin (Eastern Paratethys) during the late Neogene: the Mediterranean Lago Mare facies deciphered

A recently published scenario viewing the Messinian salinity crisis as two evaporitic steps rather than one has led to a search for new indices of the crisis in the Eastern Paratethys. Fluvial processes characterized the southwestern Dacic Basin (Southern Romania, i.e. the Carpathian foredeep) whereas brackish sediments were continuously deposited in its northern part. This is consistent with previously evidenced responses of the Black Sea to the Messinian salinity crisis. High sea‐level exchanges between the Mediterranean Sea and Eastern Paratethys are considered to have occurred just before and just after desiccation of the Mediterranean. This accounts for two successive Mediterranean nannoplankton‐dinocyst influxes into the Eastern Paratethys that, respectively, belong to zones NN 11 and NN 12. Meanwhile, two separate events that gave rise to Lago Mare facies (with Paratethyan Congeria, ostracods and/or dinoflagellate cysts) arose in the Mediterranean Basin in response to these high sea‐level exchanges and located 5.52 and 5.33 Ma (isotopic stages TG 11 and TG 5, respectively), i.e. just before and just after the almost complete desiccation of the Mediterranean). These Lago Mare facies formed independently of lakes with ostracods of the Cyprideis group that developed in the central basins during the final stages of desiccation. The gateway faciliting these water exchanges is not completely identified. A proto‐Bosphorus strait seems unlikely. A plausible alternative route extends from the northern part of the Thessaloniki region up to the Dacic Basin and through Macedonia and the Sofia Basin. The expression ‘Lago Mare’ is chronostratigraphically ambiguous and should be discontinued for this purpose, although it might remain useful as a palaeoenvironmental term.     

'Race' as a scientific and organizational construct: a critique

'Race' for many years has been a major construct of science and society. While its importance as such has not historically been particularly pronounced on a global scale, the emergence of its most forceful architects, the Anglophone countries, to pre-eminence since World War II has significantly extended its geographical range and added to its significance as an idea within commercialized culture as well as within social organization.In the present paper, 'race' is critically examined from the following angles: 1) its role in the behavioral and medical sciences; b) its historical origins and manifestations within the Anglophone countries, particularly the United States; and c) its emergence as a 'liberal' concept and operating principle since World War II. Questions of why and how 'race' arose and its continued use in science, society and culture drive both the trajectory and depth of this research. 'Race' is found to be a modern construct which arose as a consequence of colonialism and slavery, and was substantially constructed in its present form and substance by England and its off-spring societies, particularly the United States. 'Race' was not used as a term expressing a social idea until modern times, and had no basis in the primordial civilizations which greatly influenced modern Western societies (e.g., ancient Greece and Rome). Efforts undertaken by liberals – particularly in the United States – to 'humanize' the concept of 'race' since the 1960's have been largely unsuccessful. 'race' is viewed as inherently hierarchical, a fact which is evident from its historical and present role in science and society.