Analytic theory of Titan’s Schumann resonance: Constraints on ionospheric conductivity and buried water ocean     

Christian Béghin  Orélien Randriamboarison  Michel Hamelin  Erich Karkoschka  Christophe Sotin  Robert C. Whitten  Jean-Jacques Berthelier  Réjean Grard  Fernando Simões 《Icarus》2012,218(2):1028-1042

This study presents an approximate model for the atypical Schumann resonance in Titan’s atmosphere that accounts for the observations of electromagnetic waves and the measurements of atmospheric conductivity performed with the Huygens Atmospheric Structure and Permittivity, Wave and Altimetry (HASI–PWA) instrumentation during the descent of the Huygens Probe through Titan’s atmosphere in January 2005. After many years of thorough analyses of the collected data, several arguments enable us to claim that the Extremely Low Frequency (ELF) wave observed at around 36 Hz displays all the characteristics of the second harmonic of a Schumann resonance. On Earth, this phenomenon is well known to be triggered by lightning activity. Given the lack of evidence of any thunderstorm activity on Titan, we proposed in early works a model based on an alternative powering mechanism involving the electric current sheets induced in Titan’s ionosphere by the Saturn’s magnetospheric plasma flow. The present study is a further step in improving the initial model and corroborating our preliminary assessments. We first develop an analytic theory of the guided modes that appear to be the most suitable for sustaining Schumann resonances in Titan’s atmosphere. We then introduce the characteristics of the Huygens electric field measurements in the equations, in order to constrain the physical parameters of the resonating cavity. The latter is assumed to be made of different structures distributed between an upper boundary, presumably made of a succession of thin ionized layers of stratospheric aerosols spread up to 150 km and a lower quasi-perfect conductive surface hidden beneath the non-conductive ground. The inner reflecting boundary is proposed to be a buried water–ammonia ocean lying at a likely depth of 55–80 km below a dielectric icy crust. Such estimate is found to comply with models suggesting that the internal heat could be transferred upwards by thermal conduction of the crust, while convective processes cannot be ruled out.  相似文献   

Variations de l’âge des sédiments calcaires et « Culm » carbonifère dans la chaîne varisque du Sud de la France : migration de l’orogenèse varisque     

Jean-Jacques Delvolvé  Marie-France Perret 《Geodinamica Acta》2013,26(2):117-126

Résumé

Dans le Sud de la France et les Pyrénées espagnoles, les calcaires sous-jacents aux roches détritiques du Culm carbonifère ont fait l’objet d’une datation systématique par conodontes. Il en ressort que le dépôt de ces niveaux carbonates s’est poursuivi de plus en plus tardivement de l’Est vers l’Ouest : du Viséen inférieur (V3b) en Montagne Noire, au Namurien supérieur (G2) en Pays basque.

Les roches détritiques à caractère flyschoïde du Culm remanient, localement, des éléments de calcaire de plate-forme. La datation de ces éléments par foraminifères, algues, pseudo-algues et végétaux supérieurs montre qu’ils sont de plus en plus récents d’Est en Ouest : leur âge s’échelonne du Viséen 3bp-Namurien A en Montagne Noire, au Westphalien C (Kachirien) au Pays basque (Massif des Cinco-Villas).

Ces divers résultats montrent que les manifestations tectoniques, responsables des premiers épandages détritiques du Culm puis de la resédimentation des calcaires de plate-forme dans le bassin, ont commencé de plus en plus tardivement de la Montagne Noire au Pays basque.

Dans sa branche Sud, l’orogenèse varisque, si l’on s’en tient à la position actuelle de ses segments observables, a migré progressivement du Nord vers le Sud, en Montagne Noire et dans le Massif de Mouthoumet, puis vers l’Ouest, des Pyrénées centrales aux Pyrénées orientales.  相似文献   

Weathering of a Quaternary glass-rich basalt in Bakrit,Middle Atlas Mountains,Morocco. Comparison with a glass-poor basalt     

Lhoucine Karrat  Alain Perruchot  Jean-Jacques Macaire 《Geodinamica Acta》2013,26(5):205-215

Abstract

We compared the disintegration processes and mineralogic and chemical evolution pathways of two Quaternary basalts at Bakrit and Ifrane, weathered in the same physiographic and hydrologic conditions, but differing in texture according to the quantity of glass present. At Bakrit, quite abundant glass favoured the formation of a microfissure network throughout the rock and its disintegration without any distinct weathering front. As a result, basaltic sand with polymineral grains and a clayey-silty matrix were produced. At Ifrane, weathering of a glass-poor basalt produced only a clayey-silty saprolite. In glass-rich basalts, secondary minerals formed in microfissures and were 2/1 clay-mineral rich. In glass-poor basalts, secondary minerals formed mainly within primary minerals and were 1/1 clay-mineral rich. Because glass could be easily dissolved, it protected the minerals of close chemical composition, especially the plagioclases. The order of basalt-mineral weathering (olivine, labrador, augite, Fe-Ti oxides) was modified when glass was abundant (glass, olivine, augite, labrador, Fe-Ti oxides). © Elsevier, Paris  相似文献   

Log-uniform distribution of gold deposits along major Archean fault zones     

Olivier Rabeau  Jean-Jacques Royer  Michel Jébrak  Alain Cheilletz 《Mineralium Deposita》2013,48(7):817-824

The location of potentially unrecognized gold deposits in the close vicinity of the Cadillac–Larder Lake Fault Zone in the Archean Abitibi Subprovince (Canada) is predicted by applying a stochastic approach to the distribution of known gold deposits. The methodology uses the distances between neighboring orogenic gold deposits along the fault trace. The cumulative distribution of the curvilinear inter-distances along the fault zone, are adequately represented by a log-uniform model. The average inter-distance is 1.95 km, and an upper inter-distance of 5.6 km is observed. The same distribution pattern appears along the Destor–Porcupine Fault Zone (Abitibi). This log-uniform distribution shows that the spatial distribution of gold deposits is regionally controlled by the major crustal shear zone. Lithologies and structures only seem to exert a local influence at the deposit scale. The log-uniform spacing could be interpreted as the result of the crustal failure locations induced by hydraulic overpressure along mechanically independent segments on the main fault.  相似文献   

Delineating spring recharge areas in a fractured sandstone aquifer (Luxembourg) based on pesticide mass balance     

J. Farlin  L. Drouet  T. Gallé  D. Pittois  M. Bayerle  C. Braun  P. Maloszewski  J. Vanderborght  M. Elsner  A. Kies 《Hydrogeology Journal》2013,21(4):799-812

A simple method to delineate the recharge areas of a series of springs draining a fractured aquifer is presented. Instead of solving the flow and transport equations, the delineation is reformulated as a mass balance problem assigning arable land in proportion to the pesticide mass discharged annually in a spring at minimum total transport cost. The approach was applied to the Luxembourg Sandstone, a fractured-rock aquifer supplying half of the drinking water for Luxembourg, using the herbicide atrazine. Predictions of the recharge areas were most robust in situations of strong competition by neighbouring springs while the catchment boundaries for isolated springs were extremely sensitive to the parameter controlling flow direction. Validation using a different pesticide showed the best agreement with the simplest model used, whereas using historical crop-rotation data and spatially distributed soil-leaching data did not improve predictions. The whole approach presents the advantage of integrating objectively information on land use and pesticide concentration in spring water into the delineation of groundwater recharge zones in a fractured-rock aquifer.  相似文献   

On the limits of using combined U-series/ESR method to date fossil teeth from two Early Pleistocene archaeological sites of the Orce area (Guadix-Baza basin,Spain)     

Mathieu Duval  Christophe Falguères  Jean-Jacques Bahain  Rainer Grün  Qingfeng Shao  Maxime Aubert  Jean-Michel Dolo  Jordi Agustí  Bienvenido Martínez-Navarro  Paul Palmqvist  Isidro Toro-Moyano 《Quaternary Research》2012,77(3):482-491

The combined U-series/electron spin resonance (ESR) dating method was applied to nine teeth from two Early Pleistocene archaeological sites located in the Orce area (Guadix-Baza Basin, Southern Spain): Fuente Nueva-3 (FN-3) and Barranco León (BL). The combination of biostratigraphy and magnetostratigraphy places both sites between the Olduvai and Jaramillo subchrons (1.78–1.07 Ma).Our results highlight the difficulty of dating such old sites and point out the limits of the combined U-series/ESR dating method based on the US model. We identified several sources of uncertainties that may lead to inaccurate age estimates. Seven samples could not be dated because the dental tissues had (²³⁰Th/²³⁴U) activity ratios higher than equilibrium, indicating that uranium had probably leached from these tissues. It was however possible to calculate numerical estimates for two of the teeth, both from FN-3. One yielded a Middle Pleistocene age that seems to be strongly underestimated; the other provided an age of 1.19 ± 0.21 Ma, in agreement with data obtained from independent methods. The latter result gives encouragement that there are samples that can be used for routine dating of old sites.  相似文献   

Erratum to: Nanoscale zero-valent iron flakes for groundwater treatment     

R. Köber  H. Hollert  G. Hornbruch  M. Jekel  A. Kamptner  N. Klaas  H. Maes  K.-M. Mangold  E. Martac  A. Matheis  H. Paar  A. Schäffer  H. Schell  A. Schiwy  K. R. Schmidt  T. J. Strutz  S. Thümmler  A. Tiehm  J. Braun 《Environmental Earth Sciences》2016,75(6):532

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Lower and Middle Pleistocene human settlements recorded in fluvial deposits of the middle Loire River Basin,Centre Region,France     

Jackie Despriée  Pierre Voinchet  Hélène Tissoux  Jean-Jacques Bahain  Christophe Falguères  Gilles Courcimault  Jean Dépont  Marie-Hélène Moncel  Sophie Robin  Marta Arzarello  Robert Sala  Laurent Marquer  Erwan Messager  Simon Puaud  Salah Abdessadok 《Quaternary Science Reviews》2011,30(11-12):1474-1485

This paper records the findings from c. 80 prehistoric sites that have been discovered in the alluvial deposits of the rivers Creuse, Cher, and Loir, tributaries of the middle Loire River, over the period since 1981. These deposits comprise river terrace aggradations formed during successive glacial–interglacial cycles which have recorded climate and environment during Quaternary time. The systematic dating of these river deposits by Electron Spin Resonance (ESR) applied to optically bleached sedimentary quartz has resulted in the establishment of a chronological framework for the evolution of these rivers during Lower and Middle Pleistocene (between 1.7 Ma and 130 ka). Evidence for Early Palaeolithic (Mode 1) industries with an in situ context (workshops, soils) in the highest aggradations indicates that Hominins were present in the study area, near the geographical centre of France (47°N), around 1.1 Ma. Examination of the sites indicates that Human occupations were located along valley bottom sites during temperate episodes. Subsequently, after a gap of several hundred thousand years industries with handaxes appear in the Middle Loire Basin in the interval between 700 and 600 ka, and then continuously from 400 ka. These two phases of settlement produced industrial assemblages with clear differences in their responses to the supplies of raw materials and in the modes of making flakes.  相似文献   

The use of GPS for marine positioning in Germany—requirements,experience, and concepts     

Wolfgang Lechner  Gunther Braun  Harry Wirth 《Marine Geodesy》2013,36(3-4):233-241

Abstract

While beginning to establish a German Civil GPS Information and Observation Service in 1990, the actual and (near) future GPS market in Germany was analyzed. In addition, the feasibility of using GPS for water authority tasks has been studied during past years. Typical capabilities in this area are real‐time positioning for hydrographic surveying (kinematic application) and precise transfer of levels to tide gauges and verification at offshore positions.

The article describes the user interests, the requirements, some of the test campaigns, and the derived concepts for future applications.  相似文献   

Regolith mass balance inferred from combined mineralogical, geochemical and geophysical studies: Mule Hole gneissic watershed, South India   总被引：3，自引：0，他引：3  

Jean-Jacques Braun  Marc Descloitres  Jean Riotte  Simon Fleury  Jean-Loup Boeglin  Eva Lacarce  M. Sekhar  M.S. Mohan Kumar  S. Subramanian  Bernard Dupré 《Geochimica et cosmochimica acta》2009,73(4):935-24

The aim of this study is to propose a method to assess the long-term chemical weathering mass balance for a regolith developed on a heterogeneous silicate substratum at the small experimental watershed scale by adopting a combined approach of geophysics, geochemistry and mineralogy. We initiated in 2003 a study of the steep climatic gradient and associated geomorphologic features of the edge of the rifted continental passive margin of the Karnataka Plateau, Peninsular India. In the transition sub-humid zone of this climatic gradient we have studied the pristine forested small watershed of Mule Hole (4.3 km²) mainly developed on gneissic substratum. Mineralogical, geochemical and geophysical investigations were carried out (i) in characteristic red soil profiles and (ii) in boreholes up to 60 m deep in order to take into account the effect of the weathering mantle roots. In addition, 12 Electrical Resistivity Tomography profiles (ERT), with an investigation depth of 30 m, were generated at the watershed scale to spatially characterize the information gathered in boreholes and soil profiles. The location of the ERT profiles is based on a previous electromagnetic survey, with an investigation depth of about 6 m. The soil cover thickness was inferred from the electromagnetic survey combined with a geological/pedological survey.Taking into account the parent rock heterogeneity, the degree of weathering of each of the regolith samples has been defined using both the mineralogical composition and the geochemical indices (Loss on Ignition, Weathering Index of Parker, Chemical Index of Alteration). Comparing these indices with electrical resistivity logs, it has been found that a value of 400 Ohm m delineates clearly the parent rocks and the weathered materials. Then the 12 inverted ERT profiles were constrained with this value after verifying the uncertainty due to the inversion procedure. Synthetic models based on the field data were used for this purpose. The estimated average regolith thickness at the watershed scale is 17.2 m, including 15.2 m of saprolite and 2 m of soil cover.Finally, using these estimations of the thicknesses, the long-term mass balance is calculated for the average gneiss-derived saprolite and red soil. In the saprolite, the open-system mass-transport function τ indicates that all the major elements except Ca are depleted. The chlorite and biotite crystals, the chief sources for Mg (95%), Fe (84%), Mn (86%) and K (57%, biotite only), are the first to undergo weathering and the oligoclase crystals are relatively intact within the saprolite with a loss of only 18%. The Ca accumulation can be attributed to the precipitation of CaCO₃ from the percolating solution due to the current and/or the paleoclimatic conditions. Overall, the most important losses occur for Si, Mg and Na with −286 × 10⁶ mol/ha (62% of the total mass loss), −67 × 10⁶ mol/ha (15% of the total mass loss) and −39 × 10⁶ mol/ha (9% of the total mass loss), respectively. Al, Fe and K account for 7%, 4% and 3% of the total mass loss, respectively. In the red soil profiles, the open-system mass-transport functions point out that all major elements except Mn are depleted. Most of the oligoclase crystals have broken down with a loss of 90%. The most important losses occur for Si, Na and Mg with −55 × 10⁶ mol/ha (47% of the total mass loss), −22 × 10⁶ mol/ha (19% of the total mass loss) and −16 × 10⁶ mol/ha (14% of the total mass loss), respectively. Ca, Al, K and Fe account for 8%, 6%, 4% and 2% of the total mass loss, respectively.Overall these findings confirm the immaturity of the saprolite at the watershed scale. The soil profiles are more evolved than saprolite but still contain primary minerals that can further undergo weathering and hence consume atmospheric CO₂.  相似文献