Oeuvres patriotiques de Voltaire, Catherine la Grande et le Grand Frédéric, suivies des trois héroïnes de France [Jeanne d'Arc, Melle Philis de la Charce de la Tour-du-Pin et Jeanne Hachette]

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Magnetostratigraphy of the Miocene continental deposits of the Montes de Castejón (central Ebro basin, Spain): geochronological and paleoenvironmental implications

A detailed magnetostratigraphic study has been carried out in the early to middle Miocene distal alluvial and lacustrine sediments of the Montes de Castejón (central Ebro Basin). The study was based on the analysis of 196 magnetostratigraphic sites sampled along a stratigraphic interval of about 240 meters. Local magnetostratigraphy yielded a sequence of 12 magnetozones (6 normal and 6 reverse) which could be correlated with the Geomagnetic Polarity Time Scale (GPTS) interval C5Cr to C5AD (between 17 and 14.3 Ma.). The sampled sedimentary sequences include the boundary between two tectosedimentary units (TSU, T5 and T6) already defined in the Ebro Basin. The magnetostratigraphy of the Montes de Castejón allows to date the T5/T6 TSU boundary at 16.14 Ma, within chron C5Cn.1n. This magnetostratigraphy also allows us to analyse in detail as well as to discuss the variations in sedimentation rates through space and time between different lacustrine environments: Outer carbonate lacustrine fringes and distal alluvial plains (Montes de Castejón sections) show higher sedimentation rates than offshore lacustrine areas (San Caprasio section, 50 km east of Montes de Castejón).

Late Neogene lacustrine record and paleogeography in the Quillagua-Llamara basin, Central Andean fore-arc (Northern Chile)

The Cenozoic QuillaguaLlamara basin (northern Chile, Central Andes) is an asymmetrical, intramassif fore-arc basin with a relatively wide northern sector separated from a narrower southward extension by a basement threshold. The north- ern sector was characterised by a noticeable Oligocene?late Neogene alluvial-fan and lacustrine dominated deposition which resulted in sequences up to 900 m thick, whereas the southern sector was often a bypass zone with thinner fluvial and lacustrine sediment accumulation.

Flux and composition of settling particles across the continental margin of the Gulf of Lion: the role of dense shelf water cascading

Settling particles were collected using sediment traps deployed along three transects in the Lacaze-Duthiers and Cap de Creus canyons and the adjacent southern open slope from October 2005 to October 2006. The settling material was analyzed to obtain total mass fluxes and main constituent contents (organic matter, opal, calcium carbonate, and siliciclastics). Cascades of dense shelf water from the continental shelf edge to the lower continental slope occurred from January to March 2006. They were traced through strong negative near-bottom temperature anomalies and increased current speeds, and generated two intense pulses of mass fluxes in January and March 2006. This oceanographic phenomenon appeared as the major physical forcing of settling particles at almost all stations, and caused both high seasonal variability in mass fluxes and important qualitative changes in settling material. Fluxes during the dense shelf water cascading (DSWC) event ranged from 90.1 g m(-2) d(-1) at the middle Cap de Creus canyon (1000 m) to 3.2 g m(-2) d(-1) at the canyon mouth (1900 m). Fractions of organic matter, opal and calcium carbonate components increased seaward, thus diminishing the siliciclastic fraction. Temporal variability of the major components was larger in the canyon mouth and open slope sites, due to the mixed impact of dense shelf water cascading processes and the pelagic biological production. Results indicate that the cascading event remobilized and homogenized large amounts of material down canyon and southwardly along the continental slope contributing to a better understanding of the off-shelf particle transport and the internal dynamics of DSWC events.

El margen continental sur-balear: un modelo deposicional reciente sobre un margen de tipo pasivo.

El estudio sedimentológico de testigos continuos de pistón, complementado con el análisis de perfiles de sísmica de reflexión del talud y ascenso continental sur-balear, ha permitido caracterizar tres grupos de sedimentos genéticamente relacionados. Los sedimentos gravitativos, volumétricamente los más abundantes, son los únicos presentes en la mayoría del talud continental. Entre éstos se incluyen las arenas de desbordamiento, las arenas limosas gravitativas, los lodos gravitativos y los lodos de talud. Estos sedimentos muestran una clara afinidad con las diferentes provincias deposicionales del margen y una gradación entre ellos hacia aguas profundas. Las turbiditas y las hemipelagitas están preferentemente en los sectores más distales del margen y asimismo gradan con los otros sedimentos gravitativos.

Nuevos datos sobre la biozonación del Burdigaliense continental de la cuenca del Vallès-Penedès

En esta nota preliminar se dan a conocer dos nuevos yacimientos de microvertebrados situados en la cuenca del Valles-Penedes. La asociación de Roedores sita ambas localidades (Can Mar Vell y Can Julia) en la MN-4, equivalente al Burdigaliense superior. Dicha asociación y las caracteristicas litológicas y sedimentológicas de la unidad litoestratigráfica que la contiene, indican la existencia de reas lacustres y palustres en torno a las que lacobertera vegetal alcanzaba un notable desarrollo. Estas zonas lacustres podan pasar lateralmente a reas distales y proximales de abanicos aluviales, en las que se desarrollaba una intensa sedimentación detrítica y predominaban las condiciones subaéreas.

Los sedimentos de la plataforma continental balear

El análisis sedimentológico de distintos sectores de la plataforma continental balear (Bahia de Campos, Sur de Menorca y Canal de Menorca) ha puesto de manifiesto la existencia de siete grupos de facies: A) algales, B) de bivalvos, C) de gasterpodos, D) bioclsticas, E) mixtas, F) de fragmentos liticos y G) cementadas (costras algales y calcarenitas). La distribución de estas facies sedimentarias guarda una estrecha relación con la profundidad, excepto en el Sur de Menorca, y con las comunidades bentónicas que se desarrollan en la plataforma continental. Las facies que recubren actualmente la plataforma balear se depositaron durante la fase del ascenso del nivel del mar de la transgresión Versiliense.

Emplacement of ultramafic rocks into the continental crust monitored by light and other trace elements: An example from the Geisspfad body (Swiss-Italian Alps)

In order to evaluate the influence of continental crustal rocks on trace element budgets of serpentinized peridotites incorporated into the continental crust, we have analyzed the chemical composition of whole rock samples and minerals of the Geisspfad ultramafic complex (Swiss-Italian Alps). This complex represents a relict oceanic succession composed of serpentinites, ophicarbonates and metabasic rocks, emplaced into crustal gneisses during Alpine collision. Following peak metamorphic amphibolite facies conditions, fluid flow modified some of the trace element contents of ophicarbonates and deformed serpentinites close to the contact with country rocks. The fluid originated from the surrounding continental crustal rocks as documented by the increase of Pb in the serpentinites, and by the strongly negative all) values (-112 parts per thousand) of some ultramafic rocks close to the contact with surrounding gneisses. Little or no modification of the fluid mobile elements Li, B or U was observed in the serpentinite. In-situ analysis of light elements of serpentinite minerals indicate redistribution of light elements coupled to changes of mineral modes towards the outer 100-150 m of the massif. In the centre of the massif, Li is preferentially concentrated in olivine, while Be and B are hosted by tremolite. In contrast, at the outer rim of the massif, Li and Be are preferentially incorporated into diopside, and B into antigorite. This redistribution of light elements among the different minerals is visible in the serpentinite, at a maximum distance of -100-150 m from the ophicarbonate-metabasite contact. Our results show that interaction of ultramafic rocks and crust-derived fluids can be easily detected by studies of Pb and partial derivative D in whole rocks. We argue that small ultramafic bodies potentially record an emplacement-related trace element signature, and that crustal light element values in ultramafic rocks are not necessarily derived from a subducting slab. (C) 2008 Elsevier B.V. All rights reserved.