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81.
Terra Nova, 22, 390–395, 2010 Abstract We present the results of coupled analogue and numerical models that provide new insights into the relationships between volcanoes and thrusts. The effects of both upper‐crustal magma chambers and the load of volcanoes on the geometry of thrust systems were investigated. Analogue modelling points to a strong influence exerted by a magma chamber on thrust geometry, which, as suggested by the numerical models used to rationalize these results, is related to the stress redistribution around the weak heterogeneity. The low‐viscosity body below a volcanic edifice localizes compressional deformation and causes a curvature of the thrusts towards the magma chamber, opposite to the direction of tectonic transport. In these conditions, the volcanic load has a negligible effect on the structural geometry. These results are in contrast with those of previous studies, where intrusions or the load of major volcanoes generated a curvature of the thrusts away from volcanic edifices in the direction of tectonic transport. 相似文献
82.
83.
84.
Doz. Dr. Edith Kristan-Tollmann Prof. Dr. Alexander Tollmann 《International Journal of Earth Sciences》1982,71(3):987-1019
Zusammenfassung Es wird zunächst ein kurzer Überblick über die stratigraphische und fazielle Entwicklung der Trias im Gesamtraum der Tethys zwischen Betischer Kordillere in Spanien und Timor gegeben. Hierbei zeigt sich, daß im Westabschnitt, besonders im mediterranen Raum, eine mio- und aristogeosynklinale und nur untergeordnet eugeosynklinale Entwicklung der Trias vorliegt, in Ostasien (Himalaya, China) auch eugeosynklinal entwickelte Trias vermehrt auftritt. Die europäische Entwicklung der Tethystrias ist durch ihre vielfältige Individualisierung von der asiatischen Trias, die in ihrem Oberteil weiträumig durch eine detritische Fazies beherrscht ist, unterschieden, was besonders auf den Einfluß der indosinischen Faltung in Ostasien zurückgeht. Nord- und Südast der Tethys aber deshalb und auf Grund eines verschiedenartigen Erbes als Paläo- und Neotethys zu bezeichnen, geht zu weit, da die Einheit der gesamten Tethys hierdurch begrifflich zerrissen werden würde.Besonders hervorzuheben ist die Tatsache, daß zahlreiche typische Triasschichtglieder in verschiedenen Abschnitten des Gesamtraumes der Tethys auftreten, nach Litho- und Biofazies und Altersstellung eindeutig als gleichartig identifiziert werden können und demnach im gesamten Raum mit gleichen Namen belegt werden sollen. Das gilt besonders für Reichenhaller Rauhwacke, Gutensteiner Kalk, Reiflinger Kalk, Wettersteinkalk, Hallstätter Kalk, Dachsteinkalk, Kössener Schichten, Rhätoliaskalk — um nur einige Glieder zu nennen, die vom gesamten Raum vom mediterranen Gebiet bis über China hinaus, und zwar z. T. bis Timor — und im Falle des Hallstätter Kalkes bis Südamerika -, verfolgt werden können. Die Ursache liegt im gleichen Schicksal der Kontinentrandgebiete, teils durch Eustatik, teils durch die Mobilität des Schelfs, teils durch die gleichartigen Gesteinsbildner in Fauna und Flora bewirkt.Die Gemeinsamkeit von entscheidenden Faunenelementen über den gesamten Raum der Tethys hin ist ein nächstes, besonders ins Auge stechendes Merkmal. Sie bezieht sich nicht nur auf planktonische und pelagische Elemente, sondern auch auf vagil-benthonische, ja sessile Organismen und umfaßt überraschend viele Arten der Makro- und Mikrofauna, darunter viele Leitfossilien. Zahlreiche Formen sind bisher unter verschiedenen Lokalnamen beschrieben worden, deren Nachuntersuchung nun die Gleichartigkeit über den gesamten Raum der Tethys bestätigt hat. Natürlich bezieht sich diese Feststellung nur auf einen Teil der Fauna, daneben erscheinen auch an Faunenprovinzen gebundene Elemente.Schließlich werden Überlegungen über die Herkunft der Tethysfauna angestellt. Als Heimat eines wesentlichen überregional verbreiteten Anteils wird der ostpazifische Raum am amerikanischen Kontinentalrand, besonders der Raum von Britisch-Kolumbien abgeleitet. Als Gründe sprechen dafür: 1. Reichliche Beteiligung von Tethyselementen an der Fauna dieser ostpazifischen Provinz, 2. Fehlen eines Meeresweges quer durch (Mittel-) Amerika nach Osten zur Tethys in der Zeit der Trias, 3. Rekonstruktion eines Paläowind- und Meeresströmungssystems auf Grund der Triaspaläogeographie und aktualistischer Prinzipien, das eine Drift von Osten nach Westen durch Pazifik und Tethys bewirkt haben muß, 4. Die Möglichkeit dieser Wanderung von Faunenelementen über den Pazifik auch für vagiles und sessiles Benthos mit Hilfe von Larvenstadien und in pseudoplanktonischer Form auf Tang und Treibholz. Abgesehen von diesem über den gesamten tropischen bis tropennahen Raum von Pazifik und Tethys verbreiteten Anteil kommt naturgemäß noch ein autochthoner Anteil der Fauna hinzu, der sich in den einzelnen Faunenprovinzen jeweils autonom entwickelt hat — besonders begünstigt im asiatischen Teil der Tethys. Schließlich liegt nach der Verbreitung bestimmter Arten und Artgruppen noch die Möglichkeit der Wanderung eurasiatischer Formen in höheren Breiten mit den ostgerichteten Gegenströmungen von Tethys und Pazifik nahe.
Arbeit im Rahmen des Int. Geol. Correl. Programme, Projekt 73/I/4, Triassic of the Tethys Realm, durchgeführt. 相似文献
The development of the Triassic within the Tethys realm and the origin of its fauna
Summary This paper gives at first a survey about the stratigraphy and facies of the Triassic within the Tethys realm between Betic Cordillera in Spain and Timor in Indonesia. This review shows that the western part of the Tethys in the Mediterranean region comprises a mio-, (eu-)and aristogeosynclinal facies of the Triassic and prooves that the eugeosynclinal facies is more significant for the central- and eastasiatic part of the Tethys realm.The European development is characterized by an extreme individualisation of faciestypes and a hight specification of Triassic formations, whilst the Asiatic region is dominated by an extensive spreading of immense masses of detritus in the Upper Triassic — particularly in the northern branch of Tethys -, in dependence on the Indosinic orogenesis at the end of the Middle Triassic. The distinction of a northern Paleotethys and a southern Neotethys during the Mesozoic era with regard to this event can't be sanctioned, respecting the integrity of the Tethys as a whole.The following chapter stresses the fact that many alpine formations are spreaded whole over the Tethys realm, identic in lithofacies, biofacies, fauna, flora and stratigraphic position, so that one must not hesitate denominating the same formations with the same name (Lugeon/Andrusov-principle). Those formations and members, identical all over the Tethys region, are e. g. Reichenhaller cellular dolomite, Gutenstein Wurstel-limestone, Reifling-, Wetterstein-, Hallstatt- and Dachstein-limestone, which can be observed from the Mediterranean region up to China and Timor — the Hallstatt limestone as fare as Southern America. The reason of this surprisingly fact is caused by the same conditions of the plate margins during the Triassic tectonic history, moreover by the same conditions for the formation of organogeneous limestone by time-specific organismes and in some cases also in eustatic movements of the sea level.The next fact shown in this paper is the result that a lot of characteristic alpin fauna elements are spreaded all over the Tethys area, from the Alps to Indonesia. This statement concerns not only planctonic and pseudoplanctonic taxa, but also many bentonic elements living in a vagil or sessil manner within the macro- and microfauna — comprisingly also many index-fossils. Hitherto a lot of those species have been described under local names. The revision of the fossil material, collected directly by the authors in many sectors of the Tethys has confirmed this result of widespread species whole over the Tethys ocean.Finally some reflections are made about the origin of the Tethys fauna. A part of the Tethys fauna which is common with the fauna of the Eastern Pacific region, is regarded as originally developed in Western America, particularly in the territory of British Columbia, and transported by the Pacific ocean currents westwards into the Tethys. A short connection between Eastern Pacific and Western Tethys by a Protoatlantic (Poseidon) did not existe in consequence of the existence of Pangea during the Triassic time. Therefore the communication of the identic faunistic elements of Eastern Pacific and Tethys must have be realized by transpacific way: New observations about the longevity of larval stages, also of recent benthic organisms and reflections about the Triassic paleocurrent system in the Panthalassa established on actualistic principles (Fig. 2) proove the feasibility of such a theory. By the counter-current in high latitudes the transport of Tethyal elements to eastern areas along the shore of America could be effected.
Résumé Cet article donne premièrement un résumé de la stratigraphie et du faciès du Trias de la région mesogéenne entre la Cordillère Bétique et Timor en Indonésie. Il apparaît ainsi qu'on trouve dans les régions méditerranéennes notamment un faciès mio- et aristogéosynclinal, tandis que le faciès eugéosynclinal est plus fréquent dans la partie centrale et orientale de la Téthys asiatique.La partie européenne de la Téthys est caractérisée par une individualisation extrême des types de faciès et des formations. Au contraire, le faciès de la région asiatique est dominé par des masses détritiques dans le Trias supérieur, comme conséquence de la phase orogénique indosinienne dans l'Asie orientale.Par la suite on démontre que bien des formations alpines sont répandues dans toute la région de la Téthys, identiques en lithofaciès, biofaciès, faunes, flores et dans leur position stratigraphique — en conséquence, il ne faut pas hésiter d'employer les mêmes désignations pour les mêmes formations dans tout le territoire en question. On retrouve par exemple les cargnieules de Reichenhall, les calcaires vermiculés de Gutenstein, les calcaires de Reifling, du Wetterstein, de Hallstatt et du Dachstein etc. à partir de la région méditerranéenne jusqu' en Chine et à Timor; d'autre part, les calcaires de Hallstatt se retrouvent jusqu' en Amérique méridionale. Ce fait étonnant tient à des conditions identiques valables pour les bords des plaques continentales pendant le Triassique, ainsi qu'à une formation identique des calcaires organogènes provoquée par l'existence simultanée des mêmes organismes et aussi par des oscillations eustatiques de l'océan.Un autre résultat que nous aimerions mentionner dans cet article est le fait qu' un nombre assez grand des éléments de la faune alpine est répandu dans tout le territoire de la Téthys. Cette constatation ne concerne pas seulement les éléments (pseudo-)planctoniques, mais aussi beaucoup d'organismes bentoniques (vagiles et sessiles) de la macroet microfaune. Jusqu' à présent, beaucoup de ces espèces sont décrites sous des noms locaux. La révision des suites des fossiles, collectionnées par les auteurs eux-mêmes dans les différents secteurs de la Téthys, a confirmé ce fait.Enfin des réflexions sont faites sur l'origine de la faune téthysienne. Une partie de cette faune de la Téthys, celle qui correspond à la faune de la région pacifique orientale, se serait développée d'abord en Amérique septentrionale, notamment en Colombie britannique, et aurait été transportée par le courant pacifique central vers l'ouest, dans la Téthys. Une communication directe, pendant le Trias, entre le Pacifique et la Téthys occidentale, par un Protoatlantique («Poseidon») n'existait pas du fait que la Pangéa était intacte. La migration des éléments faunistiques dans le Pacifique oriental et dans la Téthys n'était possible que le long de la route transpacifique. Des observations nouvelles sur la longue durée des stades larvales des organismes bentoniques ainsi que des réflexions concernant les paléocourants de la Panthalassa (Fig. 2) prouvent le bien-fondé de cette théorie. Par des contre-courants dans des latitudes supérieures, le transport des éléments faunistiques de la Téthys dans des régions arctiques et antarctiques de l'Amérique était possible.
, . , . . - , , ( ) — . , , . , , — — , . . . , , , , - , , . — — , , , , , , , , , , — . , , , . , . , , , , - . ; . , . . , . . - , , . : 1) - ; 2) ; 3) , ; 4) , . , , , , , — . , , - .
Arbeit im Rahmen des Int. Geol. Correl. Programme, Projekt 73/I/4, Triassic of the Tethys Realm, durchgeführt. 相似文献
85.
86.
David Alexander 《Environmental Geology》1992,20(3):165-179
Conceptual equations are presented for the net benefits, total risk, and total vulnerability associated with hazard zone occupation. It is shown that, as they are polycausal phenomena, landslides require a more sophisticated approach to this form of analysis than that employed for most other forms of hazard.Three examples of landsliding are examined. At Cuyocuyo, in the Peruvian Cordillera Oriental, slope instability is virtually inevitable, but human intervention may be disturbing some very fragile natural equilibria. At Calciano, in southern Italy, deforestation has resulted in a mudflow disaster, although man-made factors are not the only causes at work. Finally, in the Valle dell'Orco (also in southern Italy) demographic and agrarian change have aided the partial metamorphosis of the catchment into a large-scale mudflow complex (although the longer-term causes are natural, tectonic ones). These examples illustrate parts of the continuum that extends from dominant natural to dominant anthropogenic causes.Human intervention has played a key role in stimulating the natural antecedents of landslides occurring in the study areas. It is concluded that risk perception has not been wide enough to promote adequate risk mitigation, in part because of a failure properly to conceive of landslides as polycausal phenomena, in which man-made causes effectively cannot—and should not—be separated from natural ones. 相似文献
87.
Lewis M. Alexander 《GeoJournal》1992,26(4):503-509
Choke points are narrow international waterways where three characteristics are present. The waterway should be narrow and
capable of being closed off to both commercial and military snipping. There should be no readily available maritime route
to utilize in the event of closure. Finally, the choke point should be of considerable significance to at least several States.
This article identifies seven “primary” choke points which seem to satisfy these criteria.
These are Gibraltar, Bab el Mandeb, Hormuz, the Danish and Turkish Straits, and the Suez and Panama Canals. It also identifies
eleven “secondary” choke points, where at least one of the reouired characteristics is missing. The eleven include Dover,
Bering and Magellan Straits, as well as Malacca-Singapore and a number of others in the Western Pacific.
Turning to a consideration of the status of choke points in a Post-Cold War era, the article notes four basic assumptions:
(1) the intense military rivalry between the United States and the Soviet Union will be reduced in coming years; (2) for many
countries marine-related environmental concerns may be increasing considerably; (3) as the Cold War recedes, regional contests
and confrontations will grow more intense; and (4) the overall densities of water-borne traffic will undergo change as the
relative economic growth of regional centers changes. The article then considers the potential impact of these trends on the
future role of choke points. 相似文献
88.
A method is presented for constructing the coronal magnetic field from photospheric magnetograms and observed coronal loops. A set of magnetic field lines generated from magnetogram data is parameterized and then deformed by varying the parameterized values. The coronal flux tubes associated with this field are adjusted until the correlation between the field lines and the observed coronal loops is maximized. A mathematical formulation is described which ensures that (i) the normal component of the photospheric field remains unchanged, (ii) the field is given in the entire corona over an active region, (iii) the field remains divergence-free, and (iv) electric currents are introduced into the field. It is demonstrated that a parameterization of a potential field, comprising a radial stretching of the field, can provide a match for a simple bipolar active region, AR 7999, which crossed the central meridian on 1996 November 26. The result is a non-force-free magnetic field with the Lorentz force being of the order of 10–5.5 g cm s–2 resulting from an electric current density of 0.079 A m–2. Calculations show that the plasma beta becomes larger than unity at a relatively low height of 0.25 r supporting the non-force-free conclusion. The presence of such strong non-radial currents requires large transverse pressure gradients to maintain a magnetostatic atmosphere, required by the relatively persistent nature of the coronal structures observed in AR 7999. This scheme is an important tool in generating a magnetic field solution consistent with the coronal flux tube observations and the observed photospheric magnetic field. 相似文献
89.
Warmuth Alexander Hanslmeier Arnold Messerotti Mauro Cacciani Alessandro Moretti Pier Francesco Otruba Wolfgang 《Solar physics》2000,194(1):103-120
NOAA 8210 has been a region showing a remarkable level of activity well before solar maximum. Dominated by a large, rapidly rotating spot, it produced several intense flares during its disk passage at the end of April–beginning of May 1998. We examine the development of AR 8210 in H and white light (WL) and study the evolution of its complex magnetic topology. While the other principal flares are briefly reviewed, the great X1.1/3B flare of 2 May, which was observed at Kanzelhöhe Solar Observatory during a SOHO/UVCS ground support campaign, is studied in detail. This event has been documented in full-disk H and Na-D intensitygrams, Dopplergrams, and magnetograms, with a time cadence of one minute each. The flare was associated with a CME and produced significant geomagnetic effects. Furthermore, we point out the perspectives for our planned Flare Monitoring and Alerting System, since the two new instruments (Magneto-Optical Filter and Digital H camera), which made their first operational run with the campaign, are crucial components for this program. 相似文献
90.
Alexander Müller Dirk Flottmann Wolfgang Schulz Wolfram Seitz Walter H. Weber 《洁净——土壤、空气、水》2007,35(4):329-338
The development of instrumental analytics such as the LC-MS/MS has made it possible to quickly determine many component concentrations in a single chromatogram. However, the validation of such multi-methods needs new strategies for robustness and optimization. Statistical execution of analytical tests is one tool that can be utilized to meet this requirement. A Central Composite Design (CCD) was utilized for the validation of an LC-MS/MS multi-method for 84 analytes. The experimental design includes six design variables and two non-design variables (response variables). Concentration, ionization temperature, dwell time, gradient, flow (of eluent), and spraying/curtain gas (continuous design variables) were varied on five different levels; the whole design encompassed 91 runs. To investigate the robustness of a LC-MS/MS method both peak sensitivity and chromatographic separation had to be verified. Therefore, two non-design variables were necessary. The distribution of the peaks over analysis time was applied to describe the quality of the chromatographic separation. The sensitivity was described with the signal to noise ratio (S/N). The evaluation of the measured data was accomplished with the Analysis of Variance (ANOVA) and the Response Surface Methodology (RSM). Three main effects (concentration, ionization temperature, dwell time) and no significant interaction effect were found for the response variable “S/N”. The variables of concentration, ionization temperature, and dwell time had no significant effects for the response variable “S/N”. The ANOVA of the response variable chromatographic separation abandoned no significant effects as well. Therefore, robustness of the method can be guaranteed for all non significant design variables. 相似文献