Exposure dating and reinterpretation of coarse debris accumulations (‘rock glaciers’) in the Cairngorm Mountains,Scotland     

Colin K. Ballantyne  Christoph Schnabel  Sheng Xu 《第四纪科学杂志》2009,24(1):19-31

Relict rock glaciers have considerable potential for contributing to palaeoclimatic reconstruction, but this potential is often undermined by lack of dating control and problems of interpretation. Here we reinvestigate and date four proposed ‘rock glaciers’ in the Cairngorm Mountains and show that the morphology of only one of these appears consistent with that of a true rock glacier produced by creep of underlying ice or ice‐rich sediment. All four features comprise rockslide or rock avalanche runout debris, and the possibility that all four represent unmodified runout accumulations cannot be discounted. Surface exposure dating of the four debris accumulations using cosmogenic ¹⁰Be produced uncertainty‐weighted mean ages of 15.4 ± 0.8 ka, 16.2 ± 1.0 ka, 12.1 ± 0.6 ka and 12.7 ± 0.8 ka. All four ages imply emplacement under cold stadial conditions, two prior to the Windermere Interstade of ca. 14.5–12.9 cal. ka BP and two during the Loch Lomond Stade of ca. 12.9–11.5 cal. ka BP. The above ages indicate that paraglacial rock‐slope failure on granite rockwalls occurred within a few millennia after deglaciation. The mean exposure ages obtained for runout debris at two sites – Strath Nethy (16.2 ± 1.0 ka) and Lairig Ghru (15.4 ± 0.8 ka) – are consistent with basal radiocarbon ages from Loch Etteridge, 22 km to the southwest (mean = 15.6 ± 0.3 cal. ka BP) and imply widespread deglaciation of the Cairngorms and adjacent valleys before 15 ka and possibly 16 ka. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

One hundred years of mountain hydrology in Switzerland by the WSL     

Christoph Hegg  Brian W. McArdell  Alexandre Badoux 《水文研究》2006,20(2):371-376

In 1903 the Swiss Federal Research Institute WSL started its first forest hydrology measurements with the aim to deliver a sound scientific basis for the implementation of new forest legislation introduced in Switzerland in 1876. This legislation was triggered by several large floods that occurred in Switzerland, for which a major cause was widely seen as the poor condition of forests at that time. Consequently, hydrologic research at WSL first focused on the influence of forests on floods. In the second half of the 20th century, other hydrological issues such as water quality, snow hydrology and sediment transport complemented the hydrologic research at WSL. Some recent results of this work are presented in three papers joining this introductory paper to mark the 100th anniversary of hydrologic research at WSL. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Radon variations in a Hungarian village     

E. Tóth  F. Deak  C. S. Gyurkócza  Z. S. Kasztovszky  R. Kuczi  G. Marx  B. Nagy  S. Oberstedt  L. Sajó-Bohus  C. S. Sükösd  G. Toth  N. Vajda 《Environmental Geology》1997,31(1-2):123-127

 A steady radon exhalation is assumed in most publications. In a village of North-East Hungary, however, high radon concentrations have been measured, differing strongly in neighbouring houses and varying in time, due to the interplay of geochemical phenomena. Received: 20 November 1995 · Accepted: 18 June 1996  相似文献   

Origin and early evolution of the planetary system     

D. Möhlmann 《Earth, Moon, and Planets》1985,33(2):201-214

It is shown by linear stability analysis that a preplanetary (presatellite) disk of dust and gas with Keplerian velocity field can become unstable due to the collective self-gravity of the disk. The radial distribution of rings, which may result from this instability, is derived. These rings later on can be the formation sites for planets around the Sun and for satellites around the planets. The derived orbits are shown to be in good agreement with that of the planets and the satellites (of Jupiter, Saturn, and Uranus). Predictions and conclusions seem to be possible for the existence of three yet unknown Uranian satellites, the origin of the early Moon and the possible radial extension of the planetary system.  相似文献   

Multiforced statistical assessments of greenhouse-gas-induced surface air temperature change 1890–1985     

Christian-D Schönwiese  Ursula Stähler 《Climate Dynamics》1991,6(1):23-33

Based on univariate correlation and coherence analyses and considering the physical basis of the relationships, a simple multiforced (multiple) statistical concept is used which correlates observational climatic time series simultaneously with volcanic, solar, ENSO, and the anthropogenic greenhouse gases forcing. This is appropriate to remove some natural climate noise in the observed data and to evaluate the components (signals) possibly due to the anthropogenic greenhouse gas forcing (CO₂, or equivalent CO₂ implying additional gases) during industrial time. In this paper, we apply this technique to 100 global box data time series 1890–1985, of the surface air temperature, using observed data from Hansen and Lebedeff. The results are presented in terms of latitudinal-seasonal and regional trends, where the observed trend patterns are compared with the hypothetical signals (statistical assessments) possibly due to anthropogenic greenhouse forcing. These latter signals can be amplified to enable a comparison with corresponding results from general circulation model (GCM) CO₂ doubling experiments. These observed-statistical assessments lead to results which are, at least qualitatively and in respect to the zonal mean temperatures, very similar to some GCM experiments indicating the maximum CO₂ doubling signals (statistical assessment > 12 K) in the arctic winter. However, these signals are moderate in the tropics and in the Southern Hemisphere (global average 2.8–4.4 K). As far as the industrial signals are concerned (observed period) these signals are somewhat larger (maximum 7 K, global average 0.5–0.9 K) than the observed trends (maximum 5 K, global average 0.5 K). Phase shifts of cause and effect may amplify these signals but are very uncertain.This paper was presented at the International Conference on Modelling of Global Climate Change and Variability, held in Hamburg 11–15 September 1989 under the auspices of the Meteorological Institute of the University of Hamburg and the Max Planck Institute for Meteorology. Guest Editor for these papers is Dr. L. Dümenil  相似文献   

Transfer factors of contamination between the German Bight and its tributary waters derived from measured tritium and Cs-137 activity concentrations     

Christoph Wedekind  Günter Främcke 《Ocean Dynamics》1991,44(2):59-75

Summary Evaluation of the results of radioactivity monitoring in the southern North Sea between 1977 and 1987 has shown that in the water of the German Bight three areas stand out due to their different ratios between salinity and concentration of dissolved Cs-137 and tritium. While salinity steadily increases with greater distance from the coast, the Cs-137 concentration above 34 PSU (Practical Salinity Unit) increases sharply and shows how far water from the western and central North Sea, contaminated by nuclear reprocessing in Sellafield (Irish Sea), reaches into the German Bight. In the 34 to 32.5 PSU range, the influence can be seen of water contaminated by tritium originating in the rivers Rhein, Maas and Schelde, precipitation and the nuclear reprocessing plant at La Hague (Channel). Below 32.5 PSU, the influence of the influx from the rivers Elbe, Weser and Ems becomes apparent. These rivers are less contaminated with tritium.Assuming that Cs-137 and tritium, like the salinity of sea water, behave conservatively and that the decay-time of these two isotopes is long compared with the time-scale of water exchange in the southern North Sea, the concentration values measured are used to calculate the structure of the water masses in the three areas of the German Bight mentioned above using the mixing principle. Evaporation is taken into account. Results show that beyond 34 PSU, about half the sea water originates in the western central North Sea while the other half comes from the Channel. Below 34 PSU, the first mentioned share amounts only to a few per cent. Results also show that fresh water from the Rhein delta and precipitation, increasing with a decrease in salinity from 34 to 32.5 PSU, accounts for a maximum of 5% each. The fresh water influx into the German Bight via the rivers Elbe, Weser and Ems amounts to app. 11% when the PSU value reaches 29. The calculated portions are the mean values for the observation period. The number of measurements available makes it impossible to distinguish more exactly between the temporal and spatial variability of the amounts of the individual components.The quantity of each calculated portion of sea water also represents the transfer factor of concentration between the nuclide concentration in the source (e. g. the Rhein) and the concentration in the German Bight. In addition, these factors are used to calculate the transfer factors of discharge using the annual drainage rates of the sources. Thus a radioactive discharge rate of 10¹⁵ Bq per year into the Rhein would produce a mean activity concentration of 0.34 Bq/l in the German Bight (at a salinity of 33.5 PSU). To verify the calculated transfer factors, tritium concentrations in the German Bight are derived from existing environmental tritium data and the results are compared with the values actually measured.

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Transferkaktoren zwischen der Deutschen Bucht und ihren Zuflüssen abgeleitet aus der Tritium- und Cs-137-Aktivitätskonzentration in den beteiligten Gewässern

Zusammenfassung Eine zusammenhängende Auswertung der Meßergebnisse der Radioaktivitätsüberwachung in der südlichen Nordsee über den Zeitraum 1977 bis 1987 hat gezeigt, daß im Wasser der Deutschen Bucht deutlich drei durch den Salzgehalt des Meerwassers und die Konzentration der gelösten Radionuklide charakterisierte Bereiche zu unterscheiden sind.Während der Salzgehalt mit wachsender Entfernung von der Küste stetig zunimmt, steigt die Cs-137-Konzentration oberhalb 34 PSU (Practical Salinity Unit) sprunghaft an und signalisiert die Grenze, bis zu der das durch die Kernbrennstoff-Wiederaufarbeitung in Sellafield (Irische See) kontaminierte Meerwasser der westlichen und mittleren Nordsee in die Deutsche Bucht vordringt. Im Bereich 34 bis 32,5 PSU ist das von Westen zugeführte, stärker Tritium-kontaminierte Wasser aus Rhein, Maas, Schelde und atmosphärischem Niederschlag zu erkennen, an das sich unterhalb 32,5 PSU der geringer mit Tritum kontaminierte Zufluß aus Elbe, Weser und Ems anschließt.Davon ausgehend, daß sich Cs-137 und Tritium wie der Salzgehalt im Meerwasser konservativ verhalten und daß weiterhin die Halbwertzeit des radioaktiven Zerfalls dieser beiden Nuklide lang ist gegenüber den Wasseraustauschzeiten im betrachteten Meeresgebiet, wurden die in der südlichen Nordsee gemessenen sowie aus der Literatur für den Süßwasserbereich entnommenen Konzentrationswerte dazu genutzt, um rechnerisch mit Hilfe des Mischungsgesetzes den Wassermassenaufbau in den drei genannten Salinitätsbereichen in der Deutschen Bucht quantitativ zu bestimmen. Es zeigte sich, daß oberhalb von 34 PSU das Meerwasser aus etwa gleichen Teilen aus der westlichen/mittleren Nordsee und dem Kanal stammt, während unterhalb dieser Salzgehaltsgrenze nur noch mit wenigen Prozentanteilen Wasser aus der mittleren Nordsee zu finden ist. Ferner ergab sich, daß das aus dem Rheinmündungsbiet bzw, aus dem atmosphärischen Niederschlag stammende Süßwasser — mit sinkendem Salzgehalt steigend — bei 32,5 PSU einen maximalen Anteil von jeweils 5% an Meerwasser hat. Der direkte Süßwasserzufluß aus Elbe, Weser und Ems beträgt in die Deutsche Bucht bei 29 PSU ca. 11%.Die berechneten Anteile sind Mittelwerte über den gesamten Beobachtungszeitraum; die Anzahl der Messungen läßt eine genauere Unterscheidung in zeitliche und räumliche Variabilität der Zusammensetzung nicht zu.Die Größe des jeweils bestimmten Anteils am Meerwasser stellt gleichzeitig den Transferfaktor der Konzentration zwischen der Nuklidkonzentration im Ursprungsgewässer (z. B. dem Rhein) und der sich daraus einstellenden Konzentration in der Deutschen Bucht dar. Ferner wurden die Transferfaktoren der Konzentration in Verbindung mit aus der Literatur entnommenen Größen der jährlichen Abflußmengen der Ursprungsgewässer genutzt, um auch die Transferfaktoren der jährlichen Einbringung zu ermitteln. So ergibt die jährliche Einbringung von 10¹⁵ Bq eines Nuklides z. B. in den Rhein bei 33,5 PSU in der Deutschen Bucht eine mittlere Konzentration von 0,34 Bq/l.Als Anwendungsbeispiel und zur Überprüfung der Richtigkeit der Transferfaktoren wird die Auswertung des Tritiumauslasses bei La Hague auf die Deutsche Bucht berechnet und mit den gemessenen Werten verglichen.

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African linkage of Precambrian Sri Lanka     

Prof. Dr. A. Kröner 《International Journal of Earth Sciences》1991,80(2):429-440

New age and isotopic data show that the high-grade basement rocks of Sri Lanka were not linked to the Archaean granulite domain of southern India but experienced their main structural and metamorphic development during the Pan-African event some 950 to 550 Ma ago. This occurred when West Gondwana and East Gondwana collided to form one of the longest collisional structures in the Supercontinent — the Mozambique belt that extends from Mozambique to Ethiopia and Sudan. A major tectonic boundary, interpreted as a thrust zone, divides the Highland/Southwestern Complex in the central part of Sri Lanka from the Vijayan Complex in the E and SE. The former is interpreted to represent the remnant of a once extensive passive margin extending west, in a Gondwana reconstruction, via Madagasgar to Tanzania and Mozambique. The Vijayan Complex may have been part of a separate continental margin plutonic assemblage, and its collision with the Highland/ Southwestern Complex marks the final amalgamation of East and West Gondwana into a supercontinent some 550 Ma ago. The Sri Lankan granulites cannot be correlated with the distinctly older granulites of the Eastern Ghats belt of India, and this suggests that Sri Lanka was situated close to the SE coast of Madagascar in a Gondwana reconstruction.

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Zusammenfassung Neue Isotopen- und Altersdaten aus dem metamorphen Grundgebirge von Sri Lanka zeigen, daß dieses Gebiet nicht, wie vielfach vermutet, Teil des archaischen Granulitkomplexes von Südindien war, sondern seine strukturelle und metamorphe Entwicklung während der panafrikanischen Orogenèse zwischen ca. 950 Ma und ca. 550 Ma hatte. Diese Orogenèse ist das Resultat der Kollision zwischen West-Gondwana (Afrika und Südamerika) und Ost-Gondwana (Südindien, Australien und Antarktis) und führte zur Bildung eines der längsten Kollisionsgürtel des Superkontinentes, dem Mosambik-Gürtel, der sich von Mosambik bis nach Äthiopien und in den Sudan erstreckt. Der West- und Zentralteil Sri Lankas mit den Wanni und Highland/Southwestern Komplexen wird vom Vijayan Komplex im Osten und Südosten durch eine Überschiebungszone getrennt, die möglicherweise eine Sutur darstellt. Die Gesteine im Westen und in den Highlands werden als der Rest eines ehemals weiträumigen passiven Kontinentalrandes interpretiert, zu dem wohl auch die lithologisch ähnlichen Abfolgen der hochmetamorphen Gebiete in Mosambik, Tansania und Madagaskar gehörten. Der Vijayan Komplex war wohl Teil der separaten plutonischen Suite eines aktiven Kontinentalrandes, und seine Kollision mit dem Highland/ Southwestern Komplex markiert das endgültige Verschweißen von West- und Ost-Gondwana zu einem Superkontinent vor ca. 550 Ma. Die Granulite Sri Lankas können nicht mit den deutlich älteren Granuliten des Gürtels der Eastern Ghats in Südost Indien korreliert werden sondern ähneln eher den hochgradigen Gesteinen in Südost Madagaskar. Damit ist die Lage Sri Lankas nahe Madagaskar in einer Gondwana Rekonstruktion wahrscheinlicher als nahe der Südostküste Indiens.

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Résumé De nouvelles données isotopiques et géochronologiques montrent que les roches métamorphiques du socle du Sri Lanka ne constituent pas, comme on l'a souvent cru, une partie du complexe granulitique archéen de l'Inde méridionale, mais qu'elles ont vécu leur propre histoire tectono-métamorphique au cours de l'orogenèse panafricaine, entre 950 et 550 Ma. Cette orogenèse est le résultat de la collision entre le Gondwana occidental (Afrique et Amérique du Sud) et le Gondwana oriental (Inde du sud, Australie et Antarctique) et constitue une des plus grandes chaînes de collision du Supercontinent: la chaîne du Mozambique, qui s'étend du Mozambique jusqu'au Soudan et en Ethiopie. Un contact tectonique majeur, interprété comme un charriage, sépare le »Highland/South-western Complex« (partie centrale du Sri Lanka) du »Vijayan Complex« (partie est et sud-est). Le premier de ces complexes est interprété comme un reste d'une ancienne marge passive de grande étendue, à laquelle appartenaient aussi les séries lithologiquement analogues du domaine très métamorphique du Mozambique, de Tanzanie et de Madagascar. Le «Vijagan Complex« a pu être une partie d'un ensemble plutonique séparé de marge active; sa collision avec le »Highland/Southwestern Complex« marque la réunion finale en un super-continent il y a quelque 550 Ma, des Gondwanas oriental et occidental. Les granulites du Sri Lanka ne peuvent pas être corrélées avec celles de la chaîne des Eastern Ghats (Inde du sud-est) qui sont nettement plus anciennes; elles se rapprochent plutôt des roches très métamorphiques du sud-est de Madagascar. On en déduit que la position du Sri Lanka, dans une reconstruction du Gondwana, devait être plus proche de Madagascar que de la côte sud de l'Inde.

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Fluid entrapment and reequilibration during subduction and exhumation: A case study from the high-grade Nestos shear zone, Central Rhodope, Greece     

Kurt Krenn  Christoph Bauer  Alexander Proyer  Evripidis Mposkos  Georg Hoinkes 《Lithos》2008,104(1-4):33-53

A fluid inclusion study on metamorphic minerals of successive growth stages was performed on highly deformed paragneisses from the Nestos Shear Zone at Xanthi (Central Rhodope), in which microdiamonds provide unequivocal evidence for ultrahigh-pressure (UHP) metamorphism. The correlation of fluid inclusion density isochores and fluid inclusion reequilibration textures with geothermobarometric data and the relative chronology of micro- and macro-scale deformation stages allow a better understanding of both the fluid and metamorphic evolution along the P–T–d path. Textural evidence for subduction towards the NE is recorded by the orientation of intragranular NE-oriented fluid inclusion planes and the presence of single, annular fluid inclusion decrepitation textures. These textures occur within quartz “foam” structures enclosed in an earlier generation of garnets with prolate geometries and rarely within recrystallized matrix quartz, and reequilibrated both in composition and density during later stages of exhumation. No fluid inclusions pertaining to the postulated ultrahigh-pressure stage for microdiamond-bearing garnet–kyanite–gneisses have yet been found. The prolate shape of garnets developed during the earliest stages of exhumation that is recorded structurally by (L  S) tectonites, which subsequently accommodated progressive ductile SW shearing and folding up to shallow crustal levels. The majority of matrix kyanite and a later generation of garnet were formed during SW-directed shear under plane-strain conditions. Fluid inclusions entrapped in quartz during this stage of deformation underwent density loss and transformed to almost pure CO₂ inclusions by preferential loss of H₂O. Those inclusions armoured within garnet retained their primary 3-phase H₂O–CO₂ compositions. Reequilibration of fluid inclusions in quartz aggregates is most likely the result of recrystallization along with stress-induced, preferential H₂O leakage along dislocations and planar lattice defects which results in the predominance of CO₂ inclusions with supercritical densities. Carbonic fluid inclusions from adjacent kyanite–corundum-bearing pegmatoids and, the presence of shear-plane-parallel fluid inclusion planes within late quartz boudin structures consisting of pure CO₂-fluid inclusions with negative crystal shapes, bear witness of the latest stage of deformation by NE-directed extensional shear.This study shows that the textures of early fluid inclusions that formed already during the prograde metamorphic path can be preserved and used to derive information about the kinematics of subduction that is difficult to obtain from other sources. The textures of early inclusions, together with later generations of unaltered primary and secondary inclusions in metamorphic index minerals that can be linked to specific deformation stages and even P–T conditions, are a welcome supplement for the reconstruction of a rather detailed P–T–d path.  相似文献   

Fluid and source magma evolution of the Questa porphyry Mo deposit,New Mexico,USA   总被引：14，自引：1，他引：13  

Leonhard M. Klemm  Thomas Pettke  Christoph A. Heinrich 《Mineralium Deposita》2008,43(5):533-552

Combined fluid inclusion microthermometry and microanalysis by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) are used to constrain the hydrothermal processes forming a typical Climax-type porphyry Mo deposit. Molybdenum mineralisation at Questa occurred in two superimposed hydrothermal stages, a magmatic-hydrothermal breccia and later stockwork veining. In both stages, texturally earliest fluids were single-phase, of low salinity (~7 wt.% NaCl_equiv.) and intermediate-density. Upon decompression to ~300 bar, they boiled off a vapour phase, leaving behind a residual brine (up to 45 wt.% NaCl_equiv) at temperatures of ~420°C. The highest average Mo concentrations in this hot brine were ~500 μg/g, exceeding the Mo content of the intermediate-density input fluid by about an order of magnitude and reflecting pre-concentration of Mo by fluid phase separation prior to MoS₂ deposition from the brine. Molybdenum concentrations in brine inclusions, then, decrease down to 5 μg/g, recording Mo precipitation in response to cooling of the saline liquid to ~360°C. Molybdenite precipitation from a dense, residual and probably sulphide-depleted brine is proposed to explain the tabular shape of the ore body and the absence of Cu-Fe sulphides in contrast to the more common Cu-Mo deposits related to porphyry stocks. Cesium and Rb concentrations in the single-phase fluids of the breccia range from 2 to 8 and from 40 to 65 μg/g, respectively. In the stockwork veins, Cs and Rb concentrations are significantly higher (45–90 and 110–230 μg/g, respectively). Because Cs and Rb are incompatible and hydrothermally non-reactive elements, the systematic increase in their concentration requires two distinct pulses of fluid exsolution from a progressively more fractionated magma. By contrast, major element and ore metal concentrations of these two fluid pulses remain essentially constant. Mass balance calculations using fluid chemical data from LA-ICPMS suggest that at least 25 km³ of melt and 7 Gt of deep input fluid were necessary to provide the amount of Mo contained in the stockwork vein stage alone. While the absolute amounts of fluid and melt are uncertain, the well-constrained element ratios in the fluids together with empirical fluid/melt partition coefficients derived from the inclusion analyses suggest a high water content of the source melt of ~10%. In line with other circumstantial evidence, these results suggest that initial fluid exsolution may have occurred at a confining pressure exceeding 5 kbar. The source of the molybdenum-mineralising fluids probably was a particularly large magma chamber that crystallised and fractionated in the lower crust or at mid-crustal level, well below the shallow intrusions immediately underlying Questa and other porphyry molybdenum deposits. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Geochemistry of late stage medium to high-K calc-alkaline and shoshonitic dykes in the Ulukişla Basin (Central Anatolia, Turkey): Petrogenesis and tectonic setting     

M. A. Kurt  M. Alpaslan  M. C. Göncüoǧlu  A. Temel 《Geochemistry International》2008,46(11):1145-1163

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