Sampling strategy and climatic implications of tree-ring stable isotopes on the southeast Tibetan Plateau

We explore the potential of tree-ring cellulose δ¹⁸O and δ¹³C records for reconstructing climate variability in the southeast Tibetan Plateau. Our sampling strategy was designed to investigate intra and inter-tree variability, and the effects of the age of tree on δ¹⁸O variation. We show that intra-tree δ¹³C and δ¹⁸O variability is negligible, and inter-tree coherence is sufficient to build robust tree-ring δ¹⁸O or δ¹³C chronologies based on only four trees. There is no evidence of an age effect regarding δ¹⁸O, in contrast with tree-ring width. In our warm and moist sampling site, young tree δ¹³C is not clearly correlated with monthly mean meteorological data. Tree-ring δ¹⁸O appears significantly anti-correlated with summer precipitation amount, regional cloud cover, and relative humidity. Simulations conducted with the ORCHIDEE land surface model confirm the observed contribution of relative humidity to tree cellulose δ¹⁸O, and explain the weak correlation of δ¹³C with climate by the non-linear integration linked with photosynthesis. Altogether, the tree-ring cellulose δ¹⁸O is shown to be a promising proxy to reconstruct regional summer moisture variability prior to the instrumental period.     

Detailed gravity study of the offshore structure of Piton de la Fournaise volcano,Reunion Island

We present an interpretation of gravity data acquired in 1984 by the French R/V Jean Charcot on the submarine part of the eastern flank of Piton de la Fournaise volcano. We comment on the Bouguer anomaly map and give a quantitative interpretation of three gravity profiles. The main results are that a gravity high over Grand Brûlé, the lower subaerial part of the eastern flank, does not extend far offshore and that an anomalous topographic feature, discovered in 1982 on the submarine eastern flank, is characterized by a large negative anomaly. We propose three hypotheses to explain the origin of this anomaly, i. e., it marks the site of a new volcano, or it is a consequence of lateral volcanism from a volcano older than Piton de la Fournaise, or more probably, it represents a great landslide deposit.     

Flowage differentiation: Limitation of the “Bagnold effect” to the narrow intrusions

The Bagnold effect, the most important in the flowage differentiation, is practically inoperative in porphyritic rocks in the case of large dykes and pipes with a width or a diameter over 100 meters. For these large channels, the magmatic differentiation between the core and the walls is not related to the forced magmatic flow, but should be ascribed to other mechanisms: crystal settling, natural convection, synchronous injection of already differentiated materials.     

Seismic endoscopy: multi-offset multi-azimuth imaging around boreholes – data processing and experimental results

An acoustic method, called seismic endoscopy, able to perform 3D imaging around shallow-depth boreholes is presented. A probe, composed of an isotropic source and a directional receiver working in the 20–100 kHz frequency range, provides images of cylindrical volumes having radii of a few metres, with an accuracy of centimetres and 25° azimuthal directivity. In order to obtain clear images of the medium discontinuities, multi-offset and multi-azimuth data acquisition allows specific algorithms to be used to determine vertical directivity correction, azimuthal focusing and reflected wave enhancement by cancellation of the tube waves. The method is tested with data acquired in an acoustic tank and with synthetic data. Initial experimental results at a test site demonstrate the performance of the seismic endoscopy probe.     

Flexible Automatic Scheduling for Autonomous Telescopes: The MAJORDOME

We have developped a new method for the scheduling ofastronomical automatic telescopes, in the framework of theautonomous TAROT instrument. The MAJORDOME software canhandle a variety of observations, constrained, periodic,etc., and produces a timeline for the night, which may bemodified at any time to take into account the specificconditions of the night. The MAJORDOME can also handletarget of opportunity observations without delay.     

Essai sur la structure des domaines émergés autour de la Méditerranée occidentale

Résumé De travaux menés dans les zones littorales de l'Afrique du Nord et dans tout le S de l'Espagne, l'auteur tire une nouvelle définition des grands ensembles structuraux péri-méditerranéens. Ces ensembles sont, dans les Cordillères bétiques, du N au S: zones externes (Prébétique, Subbétiques, Pénibétiques), zones internes (Flyschs gaditans, Malaguides, Alpujarrides, Nevadides 1). Dans le Rif marocain, symétriquement, on rencontre du S au N: zones externes (Autochtone de l'Atlas, nappes prérifaines et intrarifaines), zones internes (Flyschs nord-rifains, Tétouanides 2), Ghomarides 3), Sebtides 4); la plupart de ces zones se poursuivent vers l'E, jusqu'en Tunisie et en Sicile.Le fait majeur, à souligner au départ, est la parfaite symétrie de la chaîne alpine de la Méditerranée occidentale: les nappes rifaines ne le cèdent pas en importance aux nappes bétiques. Les diverses unités des deux systèmes se raccordent de manière évidente par la courbure de Gibraltar. L'âge du paroxysme tectonique paraît entièrement compris entre Oligocène supérieur et Miocène supérieur, aucune preuve objective n'existant de nappes plus anciennes.La remise en place des divers ensembles structuraux dépend de l'hypothèse générale définie au départ. Il est d'abord fait allusion à l'interprétation classique, par charriages modérés, ne faisant pas appel à des modifications importantes dans l'emplacement des bassins sédimentaires, actuellement visibles en plan. Les objections à ce premier schéma paraissent déterminantes.Une deuxième interprétation, que l'auteur a déjà partiellement esquissée auparavant, sera envisagée: les unités externes (s'empilant sur elles-mêmes) et leurs socles s'enfonceraient sous les zones internes qui, par réaction, seraient poussées vers l'extérieur de la chaîne: chacune des nappes dépasserait la nappe plus basse, au cours de ce mouvement. Dans le cas de l'Espagne, avant les charriages, les domaines sédimentaires des zones internes se placeraient à l'inverse de la disposition actuelle, soit du N au S: Nevadides, Alpujarrides, Malaguides, Pénibétique et Flyschs gaditans (ultras). Du côté marocain, nous aurions de même du S au N: Sebtides, Ghomarides, Tétouanides, Flyschs nord-rifains (ultras). Cela obligerait, au total, à faire rapprocher l'un de l'autre, en profondeur, les bâtis de la Meseta ibérique et de l'Atlas marocain, d'environ 300 à 500 km, l'actuelle largeur de la mer d'Alboran (150 km) ne permettant pas de reloger les domaines de toutes les nappes. Un axe d'enfouissement serait à rechercher sous l'actuelle Méditerranée.Une troisième interprétation, proposée aujourd'hui par l'auteur, considère que la chaîne péri-méditerranéenne montre une cicatrice structurale fondamentale, qui séparerait domaines internes bétiques et rifains, d'une part, domaines bétiques et rifains plus externes, de l'autre. Cette cicatrice se couderait au niveau de Gibraltar. Les nappes internes seraient comme aspirées vers la cicatrice ainsi que, en sens inverse, les nappes externes. La reconstitution paléogéographique finale est fort satisfaisante et l'ampleur des rétrécissements sensiblement diminuée.La position du domaine des Flyschs kabyles, nord-rifains et gaditans, fait enfin l'objet d'un examen nouveau: sans rejeter l'origine ultra, déjà proposée, l'auteur envisage d'autres solutions, qui auraient l'avantage de mieux s'intégrer dans l'image proposée aujourd'hui.     

Simulation of the interaction of galactic cosmic‐ray protons with meteoroids: On the production of radionuclides in thick gabbro and iron targets irradiated isotropically with 1.6 GeV protons

Abstract— Thick spherical targets made of gabbro (R = 25 cm) and of steel (R = 10 cm) were irradiated isotropically with 1.6 GeV protons at the Saturne synchrotron at Laboratoire National Saturne (LNS)/CEN Saclay in order to simulate the interaction in space of galactic cosmic‐ray (GCR) protons with stony and iron meteoroids. Proton fluences of 1.32 × 10¹⁴ cm^?2 and 2.45 × 10¹⁴ cm^?2 were received by the gabbro and iron sphere, respectively, which corresponds to cosmic‐ray exposure ages of about 1.6 and 3.0 Ma. Both artificial meteoroids contained large numbers of high‐purity target foils of up to 28 elements at different depths. In these individual target foils, elementary production rates of radionuclides and rare gas isotopes were measured by x‐ and γ‐spectrometry, by low‐level counting, accelerator mass spectrometry (AMS), and by conventional rare gas mass spectrometry. Also samples of the gabbro itself were analyzed. Up to now, for each of the experiments, ～500 target‐product combinations were investigated of which the results for radionuclides are presented here. The experimental production rates show a wide range of depth profiles reflecting the differences between low‐, medium‐, and high‐energy products. The influence of the stony and iron matrices on the production of secondary particles and on particle transport, in general, and consequently on the production rates is clearly exhibited by the phenomenology of the production rates as well as by a detailed theoretical analysis. Theoretical production rates were calculated in an a priori way by folding depth‐dependent spectra of primary and secondary protons and secondary neutrons calculated by Monte Carlo techniques with the excitation functions of the underlying nuclear reactions. Discrepancies of up to a factor of 2 between the experimental and a priori calculated depth profiles are attributed to the poor quality of the mostly theoretical neutron excitation functions. Improved neutron excitation functions were obtained by least‐squares deconvolution techniques from experimental thick‐target production rates of up to five thick‐target experiments in which isotropic irradiations were performed. A posteriori calculations using the adjusted neutron cross sections describe the measured depth profiles of all these simulation experiments within 9%. The thus validated model calculations provide a basis for reliable physical model calculations of the production rates of cosmogenic nuclides in stony and iron meteorites as well as in lunar samples and terrestrial materials.     

A Note on Extension Variances in IR2

Matheron (1971) proposed an approximation of the extension variance in IR. We propose in this note an extension of this formula in IR ² , based on a MacLaurin formula. Its application is shown in an example, the estimation of the maximum depressional storage of a soil surface.