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521.
Ralph Hinsch Charlotte M. Krawczyk Christoph Gaedicke Raul Giraudo Daniel Demuro 《Tectonophysics》2002,355(1-4)
In the area of the Bolivian Orocline, we examine the deformation pattern associated with the active development of a new thrust sheet. A dense grid of reprocessed 2-D seismic lines from hydrocarbon exploration industry is interpreted and a 3-D simplified structural and kinematic model is deduced. In the Boomerang Hills, onlapping Paleozoic and foredeep sediments are detached from the underlying S-dipping basement. They are thrust northeastwards by less than 2 km. Two zones can be differentiated along the Andean deformation front: (1) a W–E to NW–SE striking frontal segment of predominantly orthogonal shortening, comprising a thrust and anticline system; (2) a WSW–ENE striking lateral zone of oblique shortening within a complex system of thin-skinned strike–slip faults and minor folds. The deformation front always follows a pronounced edge in the topography of the top basement surface close to the boundary of the Paleozoic basin. The observed deformation pattern indicates intensified strain partitioning caused by the interaction of contraction direction and basement topography, which provides a near oblique ramp for the onlapping wedge of sediments. The SW–NE thrusting direction is divided into orthogonal and tangential components. These are accommodated by convergent and strike–slip structures, respectively, which sole into a common detachment horizon. The structural evolution of the new thrust sheet in the Bolivian Orocline is primarily controlled by the paleorelief of the Brazilian Shield because: (1) the shape of the basement affects the taper of the thrust wedge and localizes the deformation front and (2) small asperities in/close to the top of the basement promote fault localization. The coincidence of a relatively high basement position and a structural high of the Eastern Cordillera leads to the conclusion that the shape of the Brazilian Shield also controls the structural evolution of the pronounced eastern border of the Bolivian Orocline. 相似文献
522.
523.
524.
On the magnitude and apparent range of variation of the von Karman constant in the atmospheric surface layer 总被引:1,自引:1,他引:0
The half-century history of the experimental evaluation of the von Karman constant in the atmospheric surface layer is reviewed, an evidence indicating that this well-known scaling factor,k, is actually a weak variable that decreases with increasing Reynolds number is discussed. A combined average ofk=0.390 with a standard error of ±0.010 is found from two field studies, a result which indicates that there is only one chance in 40 that the true value of the scaling factor in the population from which the experimental sample was drawn could have been as large as the laboratory value of 0.40. Based on experimental and theoretical results given by others, it is suggested thatk varies from a maximum of 0.41 in light winds over open water and smooth land surfaces, to a minimum near 0.37 in stronger winds over forests and cities. This range is shown to imply that a working value ofk=0.39±1% is appropriate for flows over surfaces characterized by 0.7<z
0<8.7 cm, a roughness subrange which corresponds to a wide variety of terrain types from sparsely vegetated level plains to mixed croplands with occasional hedges and trees.sponsored in part by the Global Change Post Doctoral Program, Office of Health and Environmental Research, U. S. Department of Energy.Work sponsored by the National Science Foundation under Grant No. ATM-9019682. 相似文献
525.
TJ. Romke Bontekoe Christoph Winkler J. Gregory Stacy Peter D. Jackson 《Astrophysics and Space Science》1995,231(1-2):285-288
We are investigating the COBE DMR data at instances of known -ray bursts (GRBs) when any of the six DMR horn directions was coincident with the direction of a burst. The BATSE instrument on board GRO has detected 207 bursts during the eight-month period of overlap corresponding to the current release of COBE data. The odds of a GRB occurring within the DMR field of view are near one coincidence per year. Here we report on one such serendipitous observation in 1991, GRB 911226, for which a detailed analysis is currently in progress. 相似文献
526.
Christoph Winkler 《Experimental Astronomy》1995,6(4):71-76
INTEGRAL, the International Gamma-Ray Astrophysics Laboratory, to be launched in 2001, is the second medium-size scientific mission (M2) of the ESA long term programme Horizon 2000. INTEGRAL addresses the fine spectroscopy and accurate positioning of celestial gamma-ray sources in the energy range 10 keV to 10 MeV. The observational requirements will be met by a payload utilising coded mask imaging in combination with detector pixel arrays (Imaging) and cooled Germanium detectors (Spectroscopy). INTEGRAL is an ESA led mission in collaboration with Russia and USA. Most of the observing time will be made available to the general scientific community.This paper is largely based on the INTEGRAL Phase A study report (ESA SCI(93)1), written by the INTEGRAL Phase A Science Working Team: S. Bergeson-Willis, T.J.-L. Courvoisier, A.J. Dean, Ph. Durouchoux, B. McBreen, N. Eismont, N. Gehrels, J.E. Grindlay, W.A. Mahoney, J.L. Matteson, O. Pace, T.A. Prince, V. Schönfelder, G.K. Skinner, R. Sunyaev, B.N. Swanenburg, B.J. Teegarden, P. Ubertini, G. Vedrenne, G.E. Villa, S. Volonté, and C. Winkler. 相似文献
527.
Minitope coral islands represent one third of the islands located in the tropical Indo-Pacific. Subsistence farming and extensive agriculture dominate the traditional structure of income. As the lack of natural resources, infrastructure and capital restrict the developmental changes, the islands' natural environment has been utilized as economic potential. Planning and realization of land use systems introduced have, however, often been based on an insufficient data basis and have often inadequately considered the consequences of human impacts on the natural environment and its controlling factors. The result was environmental degradation and ecological destruction, affecting also the population's socioeconomic situation and in some cases rendering alternative land use impossible. Therefore, the long-term utilization of coral islands and, hence, the economic development of those countries require a specific development strategy. Based on the environmental and socioeconomic consequences of touristic utilization of coral islands in the Maldivian Archipelago, the model for a sustainable development strategy and its aims are derived, and the objectives, the conceptual structure, and the way of establishing them organizationally and administratively are presented. 相似文献
528.
Christoph Spötl 《International Journal of Earth Sciences》1992,81(2):309-321
Thin black dolomites occur within the evaporitic Alpine Haselgebirge Formation (Late Permian) of the central and eastern Northern Calcareous Alps, Austria. They have been compared with the southalpine Bellerophon Formation byTollmann (1964). Samples obtained from the gypsum-anhydrite deposit of Wienern am Grundlsee, Styria, are mostly unfossiliferous mudstones (dolomicrite and dolomicrospar) devoid of sedimentary structures. Only few samples contain a low-diversity ostracode fauna. Electron microprobe and X-ray diffraction analysis indicate well-ordered and near-stoichiometric dolomite (49.9±0.2 mol% CaCO3). The oxygen isotopic composition varies between –3.0 and –5.7 PDB. The 13C ratios fall into two distinct groups: –0.9 to +1.9, and –3.5 to –6.8 PDB. The carbon isotope data of the first group indicate a predominantly marine origin of the carbonates. The significantly depleted 13C ratios of the second group are probably due to freshwater influx into the basin and/or sulfate reduction. Sulfur and strontium isotope data from intercalated anhydrite and gypsum preclude an entirely non-marine origin of the brines. The light 18O ratios are probably due to early diagenetic sulfate reduction and/or dolomite recrystallization during moderate burial. A detailed interpretation of the depositional environment is rendered impossible because of the pervasive alpine tectonics. However, northalpine Bellerophon carbonates appear to be restricted to areas of major anhydrite deposition, and are absent in the halitedominated facies.
Zusammenfassung Im zentralen und östlichen Abschnitt der Nördlichen Kalkalpen Österreichs treten geringmächtige, bituminöse Dolomite im Verband der salinaren Alpinen Haselgebirge Formation (Oberperm) auf. Sie wurden vonTollmann (1964) mit der südalpinen Bellerophon Formation verglichen. Bei den untersuchten Proben von der Gips- und Anhydritlagerstätte Wienern am Grundlsee (Steiermark) handelt es sich fast durchwegs um fossilleere Mikrite und Mikrosparite, die keinerlei Sedimentstrukturen aufweisen. Nur sehr wenige Proben führen Ostrakoden. Nach Mikrosonden-Analysen und röntgendiffraktometrischen Untersuchungen bestehen diese mikrokristallinen Dolomite aus fast stöchiometrischen, gut geordneten Dolomit (49.9±0.2 Mol% CaCO3). Die Sauerstoffisotopenwerte schwanken von –3.0 bis –5.7 PDB und die 13C Verhältnisse fallen in zwei Gruppen: –0.9 bis +1.9, und –3.5 bis –6.8 PDB. Die Werte der ersten Gruppe indizieren eine im wesentlichen marine Bildung der Karbonate. Die deutlich leichteren 13C-Werte der zweiten Gruppe können durch Süßwassereinfluß während der Sedimentation und/oder durch Sulfatreduktion erklärt werden. Schwefel- und Strontium-Isotopenwerte, gemessen an Anhydriten und Gipsen im Verband mit den Dolomiten, schließen eine rein nicht-marine Herkunft der Salzlösungen aus. Die negativen 18O-Verhältnisse der Dolomite sind wahrscheinlich auf diagenetische Prozesse (Sulfatreduktion und/oder Umkristallisation) zurückzuführen. Die enorme alpidische Deformation dieser Evaporitserien gestattet es nicht, das ursprüngliche Ablagerungsmilieu der Karbonate zu rekonstruieren. Die nordalpinen Bellerophon Karbonate scheinen jedoch an Ablagerungsbereiche mit mächtiger Anhydritbildung gebunden zu sein, und fehlen primär in der Halit-dominierten Fazies.
Résumé En Autriche, dans les secteurs central et oriental des Alpes calcaires du nord, existent des dolomies bitumineuses de faible puissance en relation avec la formation évaporitique alpine de l'Haselgebirge (Permien supérieur).Tollmann (1964) les a comparées à la formation sud-alpine de Bellérophon. Des échantillons provenant des gisements de gypse et d'anhydrite de Wienern sur le Grundlsee (Styrie) montrent des mudstones (dolomicrites à dolomicrosparites) dépourvus de fossiles et de structures sédimentaires. Seuls quelques échantillons contiennent une faune à ostracodes peu diversifiée. Les examens à la microsonde et aux rayons X montrent une dolomite bien ordonnée et quasi-stoechiométrique (49,9±0,2% moléculaire de CaCo3). La composition isotopique de l'oxygène varie entre –3,0 et –5,7 PDB. Les rapports 13C se répartissent en deux groupes: –0,9 à +1,9 et –3,5 à –6,8 PDB. Ces données indiquent pour le premier groupe une origine surtout marine des carbonates. Les valeurs moins élevées des rapports du second groupe sont dues probablement à l'arrivée d'eau douce dans le bassin et/ou à une réduction des sulfates. Les valeurs isotopiques du soufre et du strontium, mesurées sur les gypses et anhydrites associés aux dolomies, excluent une origine entièrement continentale pour les saumures. Les faibles rapports 18O sont dûs probablement à une réduction diagénétique précoce des sulfates et/ou à la recristallisation de la dolomite pendant l'enfouissement. Une interprétation détaillée des conditions de dépôt est rendue impossible par l'ampleur de la déformation tectonique alpine. Il semble toutefois que des carbonates nord-alpins de type «Bellérophon» soient liés aux aires de forte sédimentation d'anhydrite et soient absents dans les faciès à halite dominante.
Haselgebirge ( ) . Tollmann (1964) . , Grundlsee, , , - . . - , - , (49.9–0,2 % 3). –3,0 –5,7% PDB, 13C : –0,9 –1,9% –3,5 –6,8% PDB. . / . , , , . 18 , , : / . . , , » « .相似文献
529.
Christoph Schnabel Valérie Olive Mariko Atarashi-Andoh Andrew Dougans Robert M. Ellam Stewart Freeman Colin Maden Martin Stocker Hans-Arno Synal Lukas Wacker Sheng Xu 《Applied Geochemistry》2007
This work constitutes the first survey of I isotope ratios for Scottish sea water including the first data for the west of Scotland. These data are of importance because of the proximity to the world’s second largest emission source of 129I to the sea, the Sellafield nuclear reprocessing plant, because of the increasing importance of the sea to land transfer of 129I and also as input data for dose estimates based on this pathway of 129I. 129I/127I ratios in SW Scotland reached 3 × 10−6 in 2004. No strong variation of I isotope ratios was found from 2003 to 2005 in Scottish sea waters. Iodine isotope ratios increased by about a factor of 6 from 1992 to 2003 in NE Scotland, in agreement with the increase of liquid 129I emissions from Sellafield over that time period. It is demonstrated that 129I/127I ratios agree better than 129I concentrations for samples from similar locations taken in very close temporal proximity, indicating that this ratio is more appropriate to interpret than the radionuclide concentration. 相似文献
530.
Hui Zhao D.J.Weidner Yun Liu 《矿物学报》2007,27(Z1):82-83
For the earth's lower mantle, a long-standing issue is whether it has a composition similar to that of the upper mantle represented by Ringwood's py-rolite model. Although a homogeneous mantle issupported by geophysical studies, and also used as an apriori assumption to estimate the composition of the bulk silicate earth (BSE) or primitive mantle( PM), it is inconsistent with a number of geochemi-cal observations. 相似文献