Discovery of a double impact crater in Libya: the astrobleme of Arkenu     

Philippe Paillou  Ake Rosenqvist  Jean-Marie Malezieux  Bruno Reynard  Tom Farr  Essam Heggy 《Comptes Rendus Geoscience》2003,335(15):1059-1069

Using orbital imaging radar, we detected a double circular structure, located in the southeastern part of the Libyan Desert, which is partially hidden under sandy sediments. Fieldwork confirmed it to be an unknown double impact crater, each crater having a diameter of about 10 km, younger than 140 Ma. Sampling on the site enabled the observation of quantities of shatter cone structures and impact breccias containing planar fractures. To cite this article: P. Paillou et al., C. R. Geoscience 335 (2003).  相似文献   

Use of high water marks and eyewitness accounts to delineate flooded coastal areas: The case of Storm Johanna (10 March 2008) in Brittany,France     

Jean-Marie Cariolet 《Ocean & Coastal Management》2010,53(11):679-690

Mapping flooded coastal areas can be carried out using different methods and can promote a better understanding and management of coastal flood risks. The delineation of the coastal areas in western Brittany inundated during a storm that came through on 10 March 2008 was determined based on eyewitness accounts and physical marks noted in situ. Using this methodology, 25 sites were mapped, representing an overall flooded area of more than 30 ha. The delineation of the flooded areas was compared with the official French (PPR-SM) flood zones, revealing some discrepancies. Finally, two case studies illustrate how coastal flood mapping can be useful for validating hydrodynamic models.  相似文献   

Spectra of accretion discs around white dwarfs     

Irit Idan  Jean-Pierre Lasota  Jean-Marie Hameury  Giora Shaviv 《New Astronomy Reviews》2008,51(10-12):759

We present the spectra of accretion discs around white dwarfs calculated with an improved and updated version of Shaviv and Wehrse [Shaviv, G., Wehrse, R., 1991. A&A 251, 117] model. The new version includes line opacities and convective energy transport and can be used to calculate the spectra of hot discs in bright systems (nova-like variables or dwarf novae in outburst) as well as the spectra of cold accretion discs in quiescent dwarf novae.  相似文献   

Estimating turbidity and total suspended matter in the Adour River plume (South Bay of Biscay) using MODIS 250-m imagery     

Caroline Petus  Guillem Chust  Francis Gohin  David Doxaran  Jean-Marie Froidefond  Yolanda Sagarminaga 《Continental Shelf Research》2010

The Basque coastal waters (South Bay of Biscay) are directly influenced by the Adour River freshwater plume. The Adour outflow leads to important variations of suspended matter concentrations and turbidity, which in turn may affect biological productivity and water quality. This study aims at both developing specific algorithms and testing the efficiency of atmospherically corrected MODIS-Aqua 250-m surface reflectance product (MYD09) to map total suspended matter concentrations and turbidity within the Adour coastal region. First, regional empirical algorithms based on in-situ data were tested to retrieve the concentration of total suspended matter and turbidity from the remote sensing reflectance. Then, the respective sensitivity of MODIS surface reflectance bands 1 and 2 for water quality application was investigated as well as the quality of atmospheric corrections. Finally, selected algorithms were applied to the MYD09 product. The resulting 250-m resolution maps were then compared to 1000-m maps produced by IFREMER and comparisons between satellite measurements and in-situ sampling points were performed. Results show that MODIS-Aqua band 1 (620–670 nm) is appropriate for predicting turbidity and total suspended matter concentrations using polynomial regression models, whilst band 2 is unadapted. Comparison between total suspended matter concentration 250-m resolution maps and mineral suspended matter 1000-m maps (generated by IFREMER) produced consistent results. A high correlation was obtained between turbidity measured in-situ and turbidity retrieved from MODIS-Aqua satellite data.  相似文献   

Electron paramagnetic resonance study of iridium in forsterite     

J. M.?GaiteEmail author  H.?Rager 《Physics and Chemistry of Minerals》2003,30(10):628-630

Electron paramagnetic resonance of Ir²⁺ in forsterite is studied at Q-band frequency and room temperature. There are four equivalent spectra superimposed along the three crystallographic axes. The individual spectrum consists of four hyperfine lines of approximately equal intensity separated from each other by 42 G; one axis of the g tensor is near the c axis. Ir²⁺ is certainly substituted for Mg²⁺. Because of the fourfold degeneracy of the EPR spectrum, it may be suggested that iridium occurs at M₁. Taking into account that one eigenvector of the g tensor is nearly parallel to c, it seems also possible that the substitution takes place at the M₂ position. In this case, the lattice relaxation of the crystal structure around Ir²⁺ at M₂ must break the point symmetry m at M₂.  相似文献   

Observation of sections of oceanic crust and mantle cropping out on the southern wall of Kane FZ (N. Atlantic)     

Jean-Marie Auzende  Mathilde Cannat  Pascal Gente  Jean-Pierre Henriet  Thierry Juteau  Jeffrey Karson  Yves Lagabrielle  Catherine Mével  Maurice Tivey 《地学学报》1994,6(2):143-148

The objective of the 20 Nautile dives of the recent Kanaut cruise was to study the southern wall of the Kane Fracture Zone from its eastern intersection with the Mid-Atlantic Ridge (MAR) to 5 Myr in age. The geological mapping shows four successive massifs, wrench faulted and slightly tilted. The transform-facing walls of these massifs exhibit outcrops of fresh and serpentinized peridotites, gabbros and basalts. The entire crustal exposure is cataclased and metamorphosed to greenschist facies.  相似文献   

Nitrogen dynamics in Posidonia oceanica cuttings: implications for transplantation experiments     

Lepoint G  Vangeluwe D  Eisinger M  Paster M  van Treeck P  Bouquegneau JM  Gobert S 《Marine pollution bulletin》2004,48(5-6):465-470

A (15)N tracer study was performed during an experimental transplantation trial of natural Posidonia oceanica cuttings. The experiment was done in situ at 17 m depth in the Revellata Bay (Calvi, NW Corsica, France). Despite high survival rates of transplants (>90%) after one year, the weight and the N content of transplants are significantly lower than those of reference plants. In absence of roots, the transplants are not able to meet their N requirement, because leaf uptake is insufficient to replenish the N lost during the natural leaf decay. This could constitute a major cause of long-term failure for transplantation experiments or natural re-colonisation processes. The increase of the (15)N content in the roots shows that the plant re-allocates the nitrogen of one organ (i.e. leaves, rhizomes) to ensure the growth of another (i.e. roots).  相似文献   

Acoustic monitoring of gas emissions from the seafloor. Part II: a case study from the Sea of Marmara     

Gaye Bayrakci  Carla Scalabrin  Stéphanie Dupré  Isabelle Leblond  Jean-Baptiste Tary  Nadine Lanteri  Jean-Marie Augustin  Laurent Berger  Estelle Cros  André Ogor  Christos Tsabaris  Marc Lescanne  Louis Géli 《Marine Geophysical Researches》2014,35(3):211-229

A rotating, acoustic gas bubble detector, BOB (Bubble OBservatory) module was deployed during two surveys, conducted in 2009 and 2011 respectively, to study the temporal variations of gas emissions from the Marmara seafloor, along the North Anatolian Fault zone. The echosounder mounted on the instrument insonifies an angular sector of 7° during a given duration (of about 1 h). Then it rotates to the next, near-by angular sector and so forth. When the full angular domain is insonified, the “pan and tilt system” rotates back to its initial position, in order to start a new cycle (of about 1 day). The acoustic data reveal that gas emission is not a steady process, with observed temporal variations ranging between a few minutes and 24 h (from one cycle to the other). Echo-integration and inversion performed on the acoustic data as described in the companion paper of Leblond et al. (Mar Geophys Res, 2014), also indicate important variations in, respectively, the target strength and the volumetric flow rates of individual sources. However, the observed temporal variations may not be related to the properties of the gas source only, but reflect possible variations in sea-bottom currents, which could deviate the bubble train towards the neighboring sector. During the 2011 survey, a 4-component ocean bottom seismometer (OBS) was co-located at the seafloor, 59 m away from the BOB module. The acoustic data from our rotating, monitoring system support, but do not provide undisputable evidence to confirm, the hypothesis formulated by Tary et al. (2012), that the short-duration, non-seismic micro-events recorded by the OBS are likely produced by gas-related processes within the near seabed sediments. Hence, the use of a multibeam echosounder, or of several split beam echosounders should be preferred to rotating systems, for future experiments.  相似文献