28 research outputs found
Soir d'automne : valse lente : [pour piano] / par J. Châteauneuf ; [lith. de] H. V.
Titre uniforme : Châteauneuf, J. (18..-19.. ; compositeur). Compositeur. [Soir d'automne. Piano
Response of a low-subsiding intracratonic basin to long wavelength deformations: the Palaeocene–early Eocene period in the Paris Basin
The uppermost Cretaceous to early Palaeogene is a period of major
deformations of the western part of the Eurasian plate with prominent basin
inversions starting from the Coniacian onwards. These deformations occur in
a complex geodynamic setting within both the context of the Africa–Eurasia
convergence and the North Atlantic opening. While Mesozoic graben inversions
have been extensively studied, particularly in Eastern Europe and the North
Sea, more gentle deformations that affect thicker crust areas (intracratonic
basins and emerged lands) are not as well documented.
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The objective of this study is to constrain the exact timing, type, and
magnitude of the early Palaeogene deformations affecting the intracratonic
Paris Basin and to integrate them at the western European scale. Low-amplitude deformations are attempted through a high-resolution
reconstitution of its stratigraphic record based on well-dated outcrops and
well-dated wells, and a high number of well-logs that are correlated using
the “stacking pattern” sequence stratigraphic technique.
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Two orders of sequences are identified (third and fourth order) and
correlated throughout the basin. Basin geometric and palaeogeographic
reconstitutions are based on sediment thickness and facies analysis.
Two-dimensional accommodation space measurements were taken in order to
quantify the magnitude of the deformations.
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Three phases of deformation were recognized.
<br><br> 1. An intra-Maastrichtian–pre-Thanetian (59 Ma) deformation, with major
uplift and erosion of the Cretaceous strata with two sub-periods of
deformation: Maastrichtian–pre-middle-Danian and Upper Danian–pre-Thanetian long-wavelength deformations. This period of major deformation
is coeval with Upper Cretaceous/pre-Danian compressive deformations
linked to the Africa–Eurasia convergence in southern France and with
volcanic activity from the North Atlantic to Massif Central and the Rhenish
Shield during the Palaeocene.<br><br> 2. An early Ypresian (55.1–54.3 Ma) medium-wavelength deformation ( × 10 km), here reported to be a stress rearrangement related to the onset of the
North Atlantic opening.
<br><br> 3. An uppermost Ypresian (49.8 Ma) long-wavelength deformation ( × 100 km),
contemporaneous with flexural compressive deformations in the Aquitaine
Basin (Pyrenean deformation), and related to the Iberia–Eurasia convergence
Late Variscan (315 Ma) subduction or deceptive zircon REE patterns and U-Pb dates from migmatite-hosted eclogites? (Montagne Noire, France)
International audienceEclogites hosted in sillimanite-bearing migmatites in the Montagne Noire dome (French Massif Central) have an oceanic protolith and recorded a prograde P–T path from ~19.5 kbar, 700°C to the pressure peak at ~21 kbar, 750°C (pseudosection modelling), suggesting metamorphism in a subductional setting. Subsequent exhumation to low-pressure high-temperature (LP–HT) conditions (~6 kbar, 730°C) is constrained by the equilibration conditions of the embedding migmatite. In samples of a fresh and a retrogressed eclogite, all zircon crystals but one display similar REE patterns (no Eu anomaly, flat HREE), usually ascribed to crystallisation under eclogite-facies conditions. Yet, the U-Pb apparent ages of zircon crystals from both eclogites spread from c. 360 Ma to a dominant data cluster at c. 315 Ma. The c. 315-310 Ma zircon U-Pb dates obtained from the embedding migmatite are interpreted as the age of crystallisation of the partial melt during the LP–HT metamorphic stage. First-order geological evidence, in particular the sedimentary record, excludes the existence of a subduction zone in the region at this period. Unless calling upon a major reappraisal of the tectonics of the European Variscan orogen, this suggests an ambiguous relation between REE patterns and U-Pb dates in the zircon population. Various scenarios that could account for the observations are discussed. Confronting our data with the results of a previously published Sm-Nd dating of garnet, and regional considerations, we consider that 360 Ma is the best approximation of the minimum age of the eclogite-facies event. We hypothesise that the eclogites formed farther north and were transferred to their present location by lower-crustal flow. It is inferred that during the subsequent exhumation, eclogite-facies zircon grains recrystallised and underwent partial to total resetting of their U-Pb system, whereas the REE system remained mostly unmodified. These results caution against the use of REE patterns as the only criterion to associate a specific zircon age with HP metamorphism in eclogites occurring in migmatitic domes
Filamentation ''remote'' sensing of chemical and biological agents/pollutants using only one femtosecond laser source
International audienceAll matters in the path of filaments induced by an intense femtosecond laser pulse propagating in air could be fragmented and result in the emission of characteristic fluorescence spectra from the excited fragments. The fluorescence spectra exhibit specific signatures (fingerprints) that can be used for the identification of various substances including chemical and biological species. In this paper, we present an overview of the recent progress in our laboratory concerning the "remote" sensing of chemical and biological agents/pollutants in air using filamentation-induced nonlinear fluorescence techniques