ESR/U-series chronology of the Lower Palaeolithic palaeoanthropological site of Visogliano, Trieste, Italy     

Christophe Falgures  Jean-Jacques Bahain  Carlo Tozzi  Giovanni Boschian  Jean-Michel Dolo  Norbert Mercier  Hlne Valladas  Yuji Yokoyama 《Quaternary Geochronology》2008,3(4):390-398

The Visogliano shelter, in north-eastern Italy, is an important Middle Pleistocene occupation site where human remains were found together with an archaic lithic industry, including choppers, chopping tools and a few protobifaces. It is of utmost importance to try to document this period, when a second wave of settlement colonised Western Europe, carrying new flaking techniques and tools.Combined ESR/U-series analyses, integrated with biostratigraphical and environmental data, define a chronological frame for the layers from which the artefacts were unearthed. The lower levels, including human remains, can be dated to the 350–500 kyr time span, in agreement with micromammal and stratigraphical studies.These data make Visogliano one of the oldest palaeoanthropological sites in Italy, where human remains are directly associated with protobifaces, choppers and chopping tools. In Western Europe, Visogliano is contemporaneous to the G soil of the Arago Cave, France, with which it shares several similarities in faunal assemblages and radiometric data, and which contains human remains also. These data make Visogliano as one of the oldest sites in Europe where the Acheulian culture is observed.  相似文献   

Development of a Field Preconcentration/Elution Unit for Routine Determination of Dissolved Metal Concentrations by ICP-OES in Marine Waters: Application for Monitoring of the New Caledonia Lagoon     

Benjamin M. Moreton  Jean-Michel Fernandez  Mathieu B.D. Dolbecq 《Geostandards and Geoanalytical Research》2009,33(2):205-218

An iminodiacetate chelating resin was optimised for the rapid determination of Co, Cu, Fe, Mn and Ni in seawater. Using inexpensive, high-capacity, reusable cartridges allowed high flow rates of up to 25 ml min⁻¹. High preconcentration factors, of up to 500, were obtained in order to analyse samples using an ICP-OES. The requirement for a buffer was eliminated due to the high tolerance of the ICP-OES to interfering matrix elements, thereby further reducing the potential for contamination. Quantification limits in seawater were: Co = 6 ng l⁻¹, Cu = 8 ng l⁻¹, Fe = 6 ng l⁻¹, Mn = 5 ng l⁻¹ and Ni = 6 ng l⁻¹. The method was verified by the analysis of near shore seawater (CASS-4) and open ocean seawater (NASS-5) reference materials. In order to satisfy the high sampling demands using the iminodiacetate cartridges, a portable off-line preconcentration unit was developed for routine analysis. The multi-channel preconcentration unit, was capable of treating up to eight samples simultaneously with concentrating times as little as 30 minutes. The technique was also used to determine dissolved metals in fresh and interstitial waters. The technique has been successfully used in a number of environmental studies and impact assessments to evaluate the effects of mining on the New Caledonian lagoon.  相似文献   

Absolute seafloor vertical positioning using combined pressure gauge and kinematic GPS data   总被引：1，自引：0，他引：1  

Valérie Ballu  Marie-Noelle Bouin  Stéphane Calmant  Eric Folcher  Jean-Michel Bore  Jérome Ammann  Olivier Pot  Michel Diament  Bernard Pelletier 《Journal of Geodesy》2010,84(1):65-77

Knowledge of the position and motion of points on the seafloor can be critically important in both fundamental research (for example, global geodesy and plate tectonics) and for more practical applications such as seismic risk evaluation, off-shore construction and pipeline monitoring. In the Vanuatu subduction zone, for example, measuring deformation underwater could provide valuable information for modeling deformation and understanding the seismic cycle. We report a shallow water experiment in Vanuatu to measure the relative and absolute depth of seafloor points. The experiment differs from previous efforts mainly in that it uses the height of the sea surface determined by kinematic GPS, allowing us to locate the points in a global reference frame. The ITRF2005 ellipsoidal height of a seafloor benchmark was determined with a 1-sigma uncertainty of 0.7–2.1 cm. The estimated ellipsoidal height differs only by a few tenths of a centimeter between measurements made in 2004 and another set made in 2006. These results are encouraging and open new perspectives for vertical underwater deformation monitoring in shallow water areas. Sea-surface GPS measurements can also help to reduce the uncertainty in depth difference determination for relative measurements.  相似文献   

Quantifying FES2004 S<Subscript>2</Subscript> tidal model from multiple space-geodesy techniques,GPS and GRACE,over North West Australia     

Stavros A. Melachroinos  Jean-Michel Lemoine  Paul Tregoning  Richard Biancale 《Journal of Geodesy》2009,83(10):915-923

Unmodeled sub-daily ocean S₂ tide signals that alias into lower frequencies have been detected in the analysis of gravity recovery and climate experiment (GRACE) space gravity fields of GRGS. The most significant global S₂ aliased signal occurs off the northwest coast of Australia in a shallow continental shelf zone, a region with high tidal amplitudes at a period of 161 days. The GRACE S₂ aliased equivalent water height grids are convolved with Green’s functions to produce GRACE aliased tidal loading (GATL) vertical displacements. The analysis of hourly global positioning system (GPS) vertical coordinate estimates at permanent sites in the region confirms the presence of spectral power at the S₂ frequency when the same ocean tide model (FES2004) was used. Thus, deficiencies in the FES2004 ocean tide model are detected both directly and indirectly by the two independent space geodetic techniques. Through simulation, the admittance (ratio of amplitude of spurious long-wavelength output signal in the GRACE time-series to amplitude of unmodeled periodic signals) of the GRACE unmodeled S₂ tidal signals, aliased to a 161-day period, is found to have a global average close to 100%, although with substantial spatial variation. Comparing GATL with unmodeled S₂ tidal sub-daily signals in the vertical GPS time-series in the region of Broome in NW Australia suggests an admittance of 110–130%.  相似文献   

Young (late Amazonian), near-surface, ground ice features near the equator, Athabasca Valles, Mars     

Devon M. Burr  Richard J. Soare  Jean-Michel Wan Bun Tseung 《Icarus》2005,178(1):56-73

A suite of four feature types in a ∼20 km² area near 10° N, 204° W in Athabasca Valles is interpreted to have resulted from near-surface ground ice. These features include mounds, conical forms with rimmed summit depressions, flatter irregularly-shaped forms with raised rims, and polygonal terrain. Based on morphology, size, and analogy to terrestrial ground ice forms, these Athabascan features are interpreted as pingos, collapsing pingos, pingo scars, and thermal contraction polygons, respectively. Thermal Infrared Mapping Spectrometer (THEMIS) data and geological features in the area are consistent with a sedimentary substrate underlying these features. These observations lead us to favor a ground ice interpretation, although we do not rule out volcanic and especially glaciofluvial hypotheses. The hypothesized ground ice that formed the mounds and rimmed features may have been emplaced via the deposition of saturated sediment during flooding; an alternative scenario invokes magmatically cycled groundwater. The ground ice implicit in the hypothesized thermal contraction polygons may have derived either from this flooding/ground water, or from atmospheric water vapor. The lack of obvious flood modification of the mounds and rimmed features indicates that they formed after the most recent flood inundated the area. Analogy with terrestrial pingos suggests that ground ice may be still extant within the positive relief mounds. As the water that flooded down Athabasca Valles emerged via a volcanotectonic fissure from a deep aquifer, any extant pingo ice may contain evidence of a deep subsurface biosphere.  相似文献   

Sea ice–ocean coupling using a rescaled vertical coordinate z     

Jean-Michel Campin  John Marshall  David Ferreira   《Ocean Modelling》2008,24(1-2):1-14

Realistic representation of sea ice in ocean models involves the use of a non-linear free-surface, a real freshwater flux and observance of requisite conservation laws. We show here that these properties can be achieved in practice through use of a rescaled vertical coordinate “z^*” in z-coordinate models that allows one to follow undulations in the free-surface under sea ice loading. In particular, the adoption of “z^*” avoids the difficult issue of vanishing levels under thick ice.Details of the implementation within MITgcm are provided. A high resolution global ocean sea ice simulation illustrates the robustness of the z^* formulation and reveals a source of oceanic variability associated with sea ice dynamics and ice-loading effects. The use of the z^* coordinate allows one to achieve perfect conservation of fresh water, heat and salt, as shown in extended integration of coupled ocean sea ice atmospheric model.  相似文献   

Classical and Mg ii-selected damped Lyman α absorbers: impact on Ω_H i at z < 1.7     

Céline Péroux †  Jean-Michel Deharveng  Vincent Le Brun  Stefano Cristiani 《Monthly notices of the Royal Astronomical Society》2004,352(4):1291-1301

  相似文献   

Improved GRACE science results after adjustment of geometric biases in the Level-1B K-band ranging data   总被引：3，自引：1，他引：2  

Martin Horwath  Jean-Michel Lemoine  Richard Biancale  Stéphane Bourgogne 《Journal of Geodesy》2011,85(1):23-38

The GRACE (Gravity Recovery and Climate Experiment) satellite mission relies on the inter-satellite K-band microwave ranging (KBR) observations. We investigate systematic errors that are present in the Level-1B KBR data, namely in the geometric correction. This correction converts the original ranging observation (between the two KBR antennas phase centers) into an observation between the two satellites’ centers of mass. It is computed from data on the precise alignment between both satellites, that is, between the lines joining the center of mass and the antenna phase center of either satellite. The Level-1B data used to determine this alignment exhibit constant biases as large as 1–2 mrad in terms of pitch and yaw alignment angles. These biases induce non-constant errors in the Level-1B geometric correction. While the precise origin of the biases remains to be identified, we are able to estimate and reduce them in a re-calibration approach. This significantly improves time-variable gravity field solutions based on the CNES/GRGS processing strategy. Empirical assessments indicate that the systematic KBR data errors have previously induced gravity field errors on the level of 6–11 times the so-called GRACE baseline error level. The zonal coefficients (from degree 14) are particularly affected. The re-calibration reduces their rms errors by about 50%. As examples for geophysical inferences, the improvement enhances agreement between mass variations observed by GRACE and in-situ ocean bottom pressure observations. The improvement also importantly affects estimates of inter-annual mass variations of the Antarctic ice sheet.  相似文献   

The significance of stretching lineations in terms of progressive deformation and finite strain     

Benoit Ildefonse  Jean-Michel Caron 《Geodinamica Acta》2013,26(3):161-170

Abstract

For a given increment of deformation, stretching lineations can be defined either by old grains or by new grains.

Progressive strain accumulated in a matrix causes reorientation of old grains. The velocity field acting within a grain depends on the degree of non-coaxiality of the progressive strain in the matrix, and on the competence contrast between grain and matrix (e.g. Lister & Williams, 1983). Deformed populations of old grains do not systematically track the principal directions of finite stretch; this depends on the mechanical behavior of the grains. On the other hand, these populations may be good markers of finite strain magnitude, provided that the initial distribution is known.

In contrast, the statistical shape orientation distribution of population of new grains cannot be related in a simple way to the finite strain magnitude, but their preferred orientation is considered to be the best indicator of the principal directions of finite stretch.

An example is considered from the schistes lustrés near Kenestrelle (Val Chisone, Western Alps), where the observed mineral lineation is attributed to a late E-W stretching event in the alpine orogenic history.  相似文献   

Bilan,fonctionnement et protection du système karstique de la Fontaine de Vaucluse (sud-est de la France)     

Bernard Blavoux  Jacques Mudry  Jean-Michel Puig 《Geodinamica Acta》2013,26(3):153-172

Résumén

L’aquifère karstique de la célèbre Fontaine de Vaucluse a fait l’objet de nouvelles investigations hydrogéologiqurs dont les résultats portent sur la définition et le fonctionnement du système.

Les données géologiques (lithologie, structure) nous ont permis la délimitation d’un impluvium de 1115 km² dont l’altitude moyenne. 870 m, est confirmée par les traceurs naturels physico-chimiques et isotopiques.

Le bilan hydrique, faute d’un réseau météorologique représentatif, a été calculé à partir d’un modèle climatique par tranches d’altitude, qui utilise les gradients pluviométriques et thermiques régionaux. On montre alors que les 3/4 des pluies efficaces proviennent des zones situées au-dessus de l’altitude moyenne de l’impluvium.

Les études hydrodynamiques et physico-chimiques nous ont permis de démontrer la faible inertie du système malgré sa taille, donc sa bonne karstification, ce qui confirme à l’échelle de l’ensemble les observations spéléologiques ponctuelles du plateau et de l’émergence.

Malgré leur faible apport au débit total, les précipitations estivales marquent la chimie de l’émergence et interrompent ainsi la phase de tarissement.

La contribution de l’eau des réserves au débit est prépondérante : respectivement les 3/4 et les 2/3 des volumes annuels écoulés en 1981 et 1982.

Compte tenu de l’absence de sols et de terrains poreux de couverture, ainsi que du développement de la karstification, la vulnérabilité du système est grande. Aussi une attention particulière doit-elle être portée à l’aménagement de la zone montagnarde de l’impluvium dont le rôle est prépondérant dans l’alimentation du système.  相似文献