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1.
The Pyreneo-Languedocian submarine sediment body, located in the western sector of the Gulf of Lions, is an example of a fan-like depositional system essentially controlled by salt tectonics. The area was subjected to a combined effect of overburden subsidence into the evacuated salt layer and a significant distal salt thickening, due to preferential basinward salt migration. This mode of salt migration impacted the Quaternary sea-bottom morphology by creating a large midslope topographic low, providing space accommodation for the Pyreneo-Languedocian fan. At gulf scale, the fan is a unique feature because unchannelized sedimentary environment in the area occurs at slope level, thus in minor water depth in relation to all other deep-water sedimentary systems offshore Gulf of Lions. To cite this article: A.T. dos Reis et al., C. R. Geoscience 336 (2004).  相似文献   

2.
The BATHYMAY marine survey was carried out in January 2004 around the French volcanic island of Mayotte, onboard the research vessel Marion Dufresne 2. Multibeam bathymetry revealed for the first time the morphology of the whole outer slope. Preliminary interpretations show broad canyons that deeply incise the slope, numerous volcanoes and huge landslides. Large submarine plateaus are also highlighted, bounded by steep cliffs and active normal faults. A model for Mayotte is suggested, in which eruptive activity, sometimes influenced by normal faulting, was concentrated along a N140° regional line (the Comoros archipelago axis), with landslide activity concentrated on the northeastern and southwestern flanks of this line. To cite this article: J.-C. Audru et al., C. R. Geoscience 338 (2006).  相似文献   

3.
In the La Serre horst of the Alpine foreland, the pre-Triassic La Serre median fault zone separates a Late Devonian–Early Carboniferous granite from an ignimbrite of unknown age and from Permian deposits. Motion along this fault zone took place first in ductile conditions and then evolved in brittle conditions. Both ductile and brittle shear criteria indicate a top-NE normal-dextral displacement. Similar motions are reported along faults bounding Late Palaeozoic intramontane coal basins located in the Massif Central and correspond to a widespread NE–SW Late to Post-Orogenic extension that affected the Variscan basement during Late Carboniferous to Early Permian times. To cite this article: G. Coromina, O. Fabbri, C. R. Geoscience 336 (2004).  相似文献   

4.
The so-called ‘Porphyro??des’ Unit of South Brittany is located below units marked by an early HP–LT event (blueschists from the Île de Groix) and above units marked by Upper Carboniferous HT metamorphism. P–T estimates in the Porphyro??des (at Belle-Île-en-Mer), using the phengite–chlorite thermobarometer, indicate pressures around 8 kbar and temperatures of 350–400 °C. These new estimates suggest that the early tectonic history of the ‘Porphyro??des’ should be linked to that of the overlying Blueschists, and imply a much larger areal extension of the HP–LT domain in this part of the Hercynian Belt. To cite this article: F. Le Hébel et al., C. R. Geoscience 334 (2002) 205–211.  相似文献   

5.
In the Grands Causses, incised valleys, lapies, fissures and sinkholes inherited from successive polyphase karstifications were filled by Palaeocene marine sediments overall assigned to the P1c–P3 interval (Upper Danian–Lower Selandian). These sediments are distributed into three detritic facies, generated by extensional tectonics controlling karstic and erosional processes. Upper Cretaceous marine fossils known within these facies are interpreted as reworked from hypothetically pellicular deposits. The probable palaeogeographic connection with the Pyrenean Palaeocene ‘Breccia trough’ supposes the presence of a SE–NW ‘ria’ running across the continental areas of Lower Languedoc and draining towards the northwest the marine waters of the Palaeocene transgression as far as the Rodez region. To cite this article: B. Peybernès et al., C. R. Geoscience 335 (2003).  相似文献   

6.
By us considered as Albo-Aptian in age and generated through halokinetic processes, the Bosmendiette breccias have been recently interpreted as Selandian (Palaeocene) globigerine-bearing sediments deposited in sub-marine canyons within a deep trough crossing the Pyrenees, from the Mediterranean Sea to the Atlantic Ocean. These breccias are really azoic in their lower part and contain a scarce microfauna including radolarians and benthic foraminifera at the top of the formation. They are unconformably covered by the Urgo-Aptian limestones and marls and indicate, under opening marine conditions, Lower Cretaceous collapse movements and northward sliding of the Jurassic slumped cover, related to the growth of the Béloscare–Apoura diapir. To cite this article: J. Canérot et al., C. R. Geoscience 336 (2004).  相似文献   

7.
In the Mejez El Bab–Testour area (northern Tunisia), the Early Eocene extension induced block tilting and salt tectonics of the Triassic evaporites. Tectonic events and halokinesis have determined the organization of Ypresian sediments. Diapiric structures have been generated during Cretaceous along the east–west, north–south and NE–SW major faults and emphasised during Lower Eocene. In this region, the Ypresian deposits constitute a filling sequence and show several thickness and facies variations. They correspond to a Nummulitic and Globigerina mixed facies characterizing a platform-basin transition zone. To cite this article: H. El Ouardi, C. R. Geoscience 334 (2002) 141–146.  相似文献   

8.
The structural analysis and the 3D modelling of Stephanian granites of the Pelvoux Massif characterize an emplacement along sinistral NW–SE- and dextral NE–SW-trending shear zones in the Pelvoux and in the Aiguilles Rouges–Mont Blanc Massifs, respectively. This Carboniferous shear system is consistent with a north–south extension direction known in the whole Variscan belt at this time. To cite this article: P. Strzerzynski et al., C. R. Geoscience 337 (2005).  相似文献   

9.
The explanation normally given for the tectonics of Sainte-Victoire Mountain, a dozen kilometres east of Aix-en-Provence, to the north of the limestone Provence, is incorrect. To the east, the morphology of the Sainte-Victoire is subdued, whereas to the west, before the mountain breaks savagely, the morphology is that of a young mountain as appears in Alpine landscapes. This unusual aspect in the region and the large subvertical faults with vertically striated surfaces that mark the massif to the south and to the west, induce the idea of strong vertical uplifts and caste doubt on the tectonic interpretation given in 1962 by Corroy et al. According to those authors, the Sainte-Victoire is a unit of Jurassic and Cretaceous formations overthrusting 1800 m to the south conglomerates of the Late Cretaceous or Palaeocene. New observations about the conglomerate transgression over the Jurassic and Cretaceous beds, and about the faults around and on the massif do not give evidence of an overthrusting but, on the contrary, induce the idea of a uplift, perhaps still active, in the form of a ‘piano key’ inclined to the northeast. To cite this article: J. Ricour et al., C. R. Geoscience 337 (2005).  相似文献   

10.
The autochthonous magnesian carbonates and the gypsum depicted in the Holocene deposits from the ‘Marais de Sarliève’ (Limagne, France) result from an alkaline, magnesian and sulphated composition of waters. This is also recorded by the composition of algal micro- and macrophytes. This may be explained by the dissolved fluxes from the Oligocene catchment and from a restriction. During the historical period, the lake evolved towards a lesser restriction. To cite this article: J.-G. Bréhéret et al., C. R. Geoscience 335 (2003).  相似文献   

11.
In volcanic areas, the quality of the geological data at the various scales is of paramount importance for the estimation of aquifer potentialities and thus for groundwater exploitation. Geological and hydrogeological investigation (synthesis of existing data, field geological observations, reconstruction of the infra-volcanic morphology, stream gauging, field hydrogeology, etc.) have been performed on the 450-km2 Aubrac basaltic plateau (Massif Central, France). These results allow us to specify the hydrological structure and functioning of this volcanic plateau that were quite unknown before. It is mainly constituted by the piling up of lava flows resting on a plutonic and metamorphic substratum. This volcanic unit constitutes an aquifer of regional importance whose groundwater resources are currently underexploited. These results allow us to delineate zones and strategies for priority hydrogeological prospecting. To cite this article: P.-Y. Bourlier et al., C. R. Geoscience 337 (2005).  相似文献   

12.
Remnants of rhyolite lava-dome and of alkaline microgranite extrusions emerge, as inselbergs, in the alluvial plain, south of Lake Chad. The peralkaline, arfvedsonite- and acmite-bearing rhyolites are determined as pantellerites. They can be related to a tectonomagmatic stage, dated of the Late Cretaceous, of the western central Africa rift system. They may constitute the NNE extension of a N50° to 30° elongated succession of small alkaline complexes, from the Gulf of Guinea to the North-Cameroon, which initiated the magmatic activity of the Cameroon Line. To cite this article: J.-P. Vicat et al., C. R. Geoscience 334 (2002) 885–891.  相似文献   

13.
To the south of Les Sables-d'Olonne (Vendée, France), the Early Liassic (Hettangian) sedimentation locally begins with continental clastics (including the dinosaur footprint-bearing beds of Le Veillon) prior to the deposition of shallow marine carbonates. Subsurface data (water borehole and geophysical line) indicate frequent variations in thickness of the clastics, related to fault block pattern. Simultaneously, numerous sedimentary dyke swarms developed within the metamorphic basement. These tectonic features resulted from an Early Liassic NNE–SSW-trending extension of the basement. Mineralized zones (silicification and metal-bearing mineralization) are related to hydrothermal circulations, contemporaneous (at least in part) with the Early Liassic extension. These different events may be related to the early stage of evolution (Triassic–Liassic) of the Biscay rift. To cite this article: C. Montenat et al., C. R. Geoscience 338 (2006).  相似文献   

14.
Camptonites have been discovered at Mount Cameroon. They contain phenocrysts of olivine + clinopyroxene + plagioclase ± kaersutite ± bi and ocelli of nepheline or analcite and carbonates. 87Sr/86Sri values are similar to those of the basalts of Mount Cameroon (≈0.7033). The camptonites are interpreted as resulting from fractional crystallization of a basaltic magma generated by a low degree of melting of an infra-lithospheric metasomatized mantle tapped by huge lithospheric cracks. To cite this article: I. Ngounouno et al., C. R. Geoscience 338 (2006).  相似文献   

15.
Avicennia pollen grains have been discovered in marine facies from the Middle Miocene deltaic series of Châteauredon (southeastern France). Based on the local stratigraphy, an age between 15.8 and 16.5 Ma is proposed for these grains. The age and the transgressive context of the Avicennia bearing-levels are in agreement with the maximum extension of the mangrove known in the western Mediterranean during interval N8–NN4 pro parte, in relation with the Langhian highstand. This mangrove occurrence at 42°N latitude during Middle Miocene is a more northern witness of the mangrove sites known in Languedoc and Provence areas. It also implies a lower climatic gradient than today. To cite this article: J.-J. Châteauneuf et al., C. R. Geoscience 338 (2006).  相似文献   

16.
The Upper Oligocene–Miocene deposits of the foreland Austral Basin of Tierra del Fuego represent the youngest foredeep fill, developed in front of the adjacent fold and thrust belt. They consist of superbly exposed, sub-horizontal clastic successions of more than 600 m of sedimentary thickness. The study of 11 sections by means of facies analysis and sequence stratigraphic criteria enabled the identification of five depositional sequences (SI–SV), bounded by unconformities (dI-dV) involving hiatuses of different magnitudes. The basal sequence (SI) includes two members: A, mudstone dominated, deposited by cohesive flows; and B, glauconite-rich, sandstone dominated, deposited by episodic turbidity currents. The remaining sequences (SII–SV) are composed of complex arrangements of fine conglomerates, coarse- to fine-grained sandstones, and mudstones that were deposited mainly by hyperpycnal flows. The basal unconformities of the SI to SIV involve minor hiatuses, while that of the SV is a major order unconformity. Two types of clinofom geometries are recognized in the foredeep sequences. Type a clinoforms present a wedge shaped geometry and characterize the foredeep infill during the compressional tectonic regime. Regarding this clinoform type, SI is situated closer to the orogen and shows variations in the bedding dip with development of internal unconformities. SII to SIV are situated towards the foreland and are characterized by subhorizontal conformable beds of large lateral extension. Type b clinoforms, with sigmoidal geometry, show a clear northeast progradation related to a progressive foredeep fill under tectonic quiescence. This clinoform type characterizes the deposits in SV. The recognition of hyperpycnites and different types of clinoform geometries in these sequences incorporates new concepts in reservoir prospects, which are critical for the evaluation of the petroleum system in the Austral Basin.  相似文献   

17.
Interpretation of the recent high-resolution survey, CANADOU 2000, in the Bay of Douarnenez (Finistère, France) allowed us to restore the morphology of the substratum and the sedimentary filling of the bay. The Brioverian and Palaeozoic substratum reveals a well-defined network of incised valleys as results of successive emergence stages of the Bay during the Quaternary. Valleys join in a westward-widened mean valley, called Ys Valley. The present-day sedimentary fill of the bay of Douarnenez appears mainly controlled by the Holocene rise and the consecutive highstand. It comprises fluvial and estuarine deposits filling up incised valleys and marine sedimentation extending out of the incised valleys. To cite this article: G. Jouet et al., C. R. Geoscience 335 (2003).To cite this article: G. Jouet et al., C. R. Geoscience 335 (2003).  相似文献   

18.
The work of searching, recovering and quality control of ancient sea-level measurements at Brest is presented. This work enables us to complete a study carried out by Cartwright in 1972, which showed a decrease in the tidal M2 semi-diurnal amplitude of 1% per century. After including these ancient data, as well as the last four decades of observations in the analysis, our results show an increase of the amplitude of M2 after 1960 and a decrease before 1880, suggesting a long-period oscillation rather than a steady secular trend. To cite this article: N. Pouvreau et al., C. R. Geoscience 338 (2006).  相似文献   

19.
Flow properties of turbidity currents in Bute Inlet, British Columbia   总被引：1，自引：0，他引：1  
Bute Inlet, a fiord along the southwestern coast of British Columbia, Canada, includes a sea-floor sedimentation system 70 km in length which resembles those developed on some large submarine fans. Turbidity currents originate at the head of the flord on the submerged delta fronts of the Homathko and Southgate rivers. They move downslope for about 30 km within a single large incised channel, spill onto a depositional area termed the channel lobe complex, and finally spread out over a low-relief distal splay area that passes 55 km downslope into a flat basin floor. During the present study, turbidity currents in Bute Inlet were studied using sea-floor morphology, bottom sediment distribution, and in-situ instrument packages. The mean velocities of the most recent flows, estimated from surface sediment grain size, has varied between 100–120 cm s–1 in the incised channel, 20–50 cms–1 in the channel lobe complex, and < 5 cm s–1 on the basin floor. Velocities based on channel morphology are poorly constrained but are in the range of 160-425 cm s–1 in the upper part of the incised channel and 66 cm s–1 in the lower channel. Calculated flow densities range from 1.049 to 1.028g cm–3. Turbidity flows monitored in 1986 using submerged instrument packages exceeded 32 m in thickness in the upper part of the incised channel, where the maximum measured velocity was 330 cm s–1. At the head of the channel lobe complex the maximum velocity had declined to 75 cm s–1. The density of the monitored flows is estimated at 1.025-1.03g cm–3. The cored sediments and channel morphology yield estimates of mean flow velocities that are generally greater than those measured by the in-situ instrument packages and estimated from modern surface sediments. The former suggest past flow velocities up to 500 cm s–1 in the incised channel, about 20 cm s–1 in spillover deposits along the lower part of the incised channel, and 100-140 cm s–1 in the distal splay. The contrast between the velocities of modern and past flows suggests that past flows may have been considerably larger and more energetic than those presently occurring in Bute Inlet. The size properties of sediments in the monitored turbidity flows suggest a strong vertical size gradient in the suspended load during transport. The surface and cored sediments fine downslope from the channel lobe complex to distal splay area. Distinctive sedimentary sequences are recognized in cores from the spillover lobes, channel lobe complex, distal splay, and basin floor depositional areas. Many individual turbidites grade downslope from massive Ta divisions in the channel lobe complex and probably in the incised channel to Ta divisions overlain by slurried divisions on the distal splay and largely slurried beds on the basin floor. These facies suggest that individual currents commonly evolve from largely cohesionless suspensions in the incised channel and channel lobe complex to dilute cohesive slurries downslope on the distal splay and basin floor. Many flows in Bute Inlet fail to develop a traction state of sedimentation and the resulting turbidites lack well-developed Tb. Tc, and Td divisions.  相似文献   

20.
The Kimmeridgian Stage is represented in the cliffs of the Dorset-type area and those in Normandy by richly fossiliferous marine mudstones and limestones. Taken together, these coastal exposures provide the only complete composite outcrop through this part of the Jurassic in the Sub-boreal Faunal Province. Detailed correlations between the two successions are presented here: these enable the Normandy-coast sections to be more accurately placed than previously within in their regional chronostratigraphical context. The Normandy succession is more completely exposed than that in Dorset, and is situated midway between Dorset and the Sub-Tethyan succession of the Berry region. It therefore offers a better prospect than any English section for inter-province correlation at this stratigraphical level. To cite this article: R. Gallois, C. R. Geoscience 337 (2005).  相似文献   

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