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51.
Bernard Peybernès Richard Ciszak Marie-José Fondecave-Wallez Pierre-Jean Combes Hubert Camus Michel Séranne 《Comptes Rendus Geoscience》2003,335(8):681-689
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
52.
Kenneth W.W. Sims Janne Blichert-Toft Philip R. Kyle Sylvain Pichat Pierre-Jean Gauthier Jurek Blusztajn Peter Kelly Lary Ball Graham Layne 《Journal of Volcanology and Geothermal Research》2008
We report new Nd, Hf, Sr, and high-precision Pb isotopic data for 44 lava and tephra samples from Erebus volcano. The samples cover the entire compositional range from basanite to phonolite and trachyte, and represent all three phases of the volcanic evolution from 1.3 Ma to the present. Isotopic analyses of 7 samples from Mt. Morning and the Dry Valley Drilling Project (DVDP) are given for comparison. The Erebus volcano samples have radiogenic 206Pb/204Pb, unradiogenic 87Sr/86Sr, and intermediate 143Nd/144Nd and 176Hf/177Hf, and lie along a mixing trajectory between the two end-member mantle components DMM and HIMU. The Erebus time series data show a marked distinction between the early-phase basanites and phonotephrites, whose Nd, Hf, Sr, and Pb isotope compositions are variable (particularly Pb), and the current ‘phase-three’ evolved phonolitic lavas and bombs, whose Nd, Hf, Sr, and Pb isotope compositions are essentially invariant. Magma mixing is inferred to play a fundamental role in establishing the isotopic and compositional uniformity in the evolved phase-three phonolites. In-situ analyses of Pb isotopes in melt inclusions hosted in an anorthoclase crystal from a 1984 Erebus phonolite bomb and in an olivine from a DVDP basanite are uniform and identical to the host lavas within analytical uncertainties. We suggest that, in both cases, the magma was well mixed at the time melt inclusions were incorporated into the different mineral phases. 相似文献
53.
S. García-Burillo F. Combes J. Graciá-Carpio A. Usero M. Guélin 《Astrophysics and Space Science》2008,313(1-3):261-265
High-resolution CO maps are an essential tool to search for observational evidence of AGN fueling in galaxy nuclei. While
their capabilities will be surpassed by ALMA, current mm-interferometers can already provide relevant information on scales
which are critical for the process of angular momentum transfer in fueling the AGN. In this context we present the latest
results issued from the NUclei of GAlaxies (NUGA) project, a high-resolution (0.5′′–1′′) CO survey of low luminosity AGNs conducted with the IRAM Plateau de Bure interferometer (PdBI). The use of more specific
molecular tracers of dense gas can probe the feedback influence of activity on the chemistry and energy balance in the interstellar
medium of nearby galaxies, a prerequisite to understanding how feedback operate at higher redshift galaxies. We discuss the
results obtained in an ongoing study devoted to probe the feedback of activity from nearby Seyferts to high-redshift QSO. 相似文献
54.
E. Xanthopoulos F. Combes T. Wiklind 《Monthly notices of the Royal Astronomical Society》2001,325(1):273-277
We have searched for molecular absorption lines at millimetre wavelengths in 11 gravitational lens systems discovered in the JVAS/CLASS surveys of flat spectrum radio sources. Spectra of only one source 1030+074 were obtained in the 3-, 2- and 1.3-mm bands at the frequencies corresponding to common molecular transitions of CO and HCO+ as continuum emission was not found in any of the other sources. We calculated upper limits to the column density in molecular absorption for 1030+074, using an excitation temperature of 15 K, to be N CO <6.3×1013 cm−2 and N HCO+ <1.3×1011 cm−2 , equivalent to hydrogen column density of the order N H <1018 cm−2 , assuming standard molecular abundances. We also present the best upper limits of the continuum at the lower frequency for the other 10 gravitational lenses. 相似文献
55.
Pierre-Jean Combes Bernard Peybernès Marie-José Fondecave-Wallez 《Eclogae Geologicae Helvetiae》2004,97(2):155-174
In the Eastern part of French Pyrenees, the Cucugnan area (Southern Corbières) corresponded during the early/Mid-Paleocene (Danian/Selandian) to a narrow transitional zone between the sea to the South (Pyrenean Paleocene Trough) and the continent (fluvio-palustrine and lacustrine Vitrollian deposits) to the North. To the South, in the North-Pyrenean Zone, the polygenic marine breccias and the associated Dano-Selandian Globigerinid-bearing hemipelagites have been preserved within successive paleokarsts superimposed onto the carbonate substratum (ante-Albian). Four paleosurfaces are recognized, principally filled by marine internal sediments with proximal and distal facies. To the North, in the Sub-Pyrenean Zone, a continental foreland basin is characterized by four formations of variegated Microcodium-bearing marls and channelized conglomerates, separated by erosional paleosurfaces underlining well-marked unconformities. An event correlation (chronodiagrams) between the marine realm to the South and the continental realm to the North is proposed, using the successive paleosurfaces and the lithological sequences (same number within the two realms). Our paleogeographic reconstruction shows, to the North, the Lake of Cucugnan and, to the South, a calcareous mountainous zone broken by the juxtaposition of deep paleocanyons (eroded in a continental context) later converted into rias submitted to marine oscillations. Several palinspastic transects are reconstructed: they show the polyphase control of the Frontal North-Pyrenean Overthrust on the Paleocene sedimentation and the importance of the successive intra-Vitrollian compressions/ transpressions (phase fini-crétacée auct.) inducing, within the two juxtaposed realms, emersions, erosions and karstic features which give a very contrasted paleogeography during a period characterized by plate convergence and creation of steep topographies.Manuscrit reçu le 25 septembre 2003 Révision acceptée le 4 mai 2004 相似文献