Paleoenvironmental evolution of the Paratethys in the Slovenian Basin during the Late Paleogene     

Gerhard?SchmiedlEmail author  Maria?Scherbacher  Angela?A.?Bruch  Bogomir?Jelen  James?H.?Nebelsick  Christoph?Hemleben  Volker?Mosbrugger  Helena?Rifelj 《International Journal of Earth Sciences》2002,91(1):123-132

Several sections from the uppermost Eocene and Oligocene of northern Slovenia have been investigated with respect to sedimentary facies, foraminiferal assemblages, stable isotopes, carbonate microfacies, and palynology. The main objective was to reconstruct the paleoenvironmental history of the Paleogene Paratethys in this region of the eastern Alpine realm. The sediments exhibit a transgressive succession beginning with conglomerates, sandstones, and mudstones of fluvial and lacustrine origin followed by carbonates and muddy marls indicating marine conditions. The foraminiferal faunal changes from brackish to shallow marine to deeper marine assemblages and the distribution of the palynofloras corroborate the sedimentological results. Microfacies analysis of the limestones shows a wide variation of shallow water, generally mud-rich facies dominated by coralline algae, foraminifera, and corals. Microfaunas adapted to low-oxygen conditions indicate temporal sluggish bottom-water circulation which can be associated with high fresh-water fluxes. These results are discussed as reflecting both the global sea-level rise during the Early Oligocene and the regional tectonic and climatic evolution.  相似文献   

A Reanalysis and Reinterpretation of Geodetic and Geological Evidence of Glacial-Isostatic Adjustment in the Churchill Region, Hudson Bay     

Detlef Wolf  Volker Klemann  Johann Wünsch  Fei-peng Zhang 《Surveys in Geophysics》2006,27(1):19-61

We review the historical, geological, tide-gauge, GPS and gravimetric evidence advanced in favour of, or against, continuing land uplift around Hudson Bay, Canada. We also reanalyse the tide-gauge and GPS data for Churchill using longer time series than those available to previous investigators. The dependence of the mean rate of relative sea-level change obtained from the tide-gauge record on the length and mid-epoch of the observation interval considered is investigated by means of a newly developed linear-trend analysis diagram. For studying the shorter-period variability of the tide-gauge record, the wavelet transform is used. The mean rate of land uplift obtained from GPS is based on a new analysis using IGS solutions of GFZ. To include the post-glacial land uplift, sea-level indicators from the Churchill region representing the relative sea-level history during the past 8000 years are also used. Finally, the values of the four observables are jointly inverted in terms of mantle viscosity. The optimum values are ~3.2 × 10²⁰ Pa s and ~1.6 × 10²² Pa s for the upper- and lower-mantle viscosities, respectively.  相似文献   

Monitoring of atmospheric deposition in European forests and an overview on its implication on forest condition     

Richard Fischer  Volker Mues  Erwin Ulrich  Georg Becher  Martin Lorenz 《Applied Geochemistry》2007

Forest conditions in Europe have been monitored over 20 years jointly by the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and the European Union (EU). Maps for mean bulk SO₄, NO₃ and NH₄ deposition at around 400 intensive monitoring plots in the years 1999–2001, as well as time trends for the period 1996–2001, are presented. Mean bulk SO₄ deposition at 169 plots mostly located in central Europe decreased from 7.4 to 5.8 kgS ha⁻¹ a⁻¹. Mean NH₄ bulk deposition decreased from 6.2 to 5.3 kgN ha⁻¹ a⁻¹. Nitrate bulk deposition fluctuated around 5 kgN ha⁻¹ a⁻¹. On average, throughfall deposition was considerably higher than bulk deposition. Time trends for mean tree crown defoliation as an overall indicator for forest condition show a peak in the mid 1990s for most of the monitored main tree species and a recent increase for the years 2003 and 2004. Multivariate linear regression analyses show some significant relations between deposition and defoliation. These relations depend on the tree species and site characteristics. Effects of deposition are moderated by the influence of biotic stress factors such as insects and fungi and by abiotic stress factors, such as weather.  相似文献   

Younger Dryas to mid-Holocene environmental history of the lowlands of NW Transylvania, Romania   总被引：2，自引：1，他引：2  

Angelica Feurdean  Volker Mosbrugger  Bogdan P. Onac  Victor Polyak  Daniel Veres   《Quaternary Research》2007,68(3):364-378

Pollen, micro-charcoal and total carbon analyses on sediments from the Turbuta palaeolake, in the Transylvanian Basin of NW Romania, reveal Younger Dryas to mid-Holocene environmental changes. The chronostratigraphy relies on AMS ¹⁴C measurements on organic matter and U/Th TIMS datings of snail shells. Results indicate the presence of Pinus and Betula open woodlands with small populations of Picea, Ulmus, Alnus and Salix before 12,000 cal yr BP. A fairly abrupt replacement of Pinus and Betula by Ulmus-dominated woodlands at ca. 11,900 cal. yr BP likely represents competition effects of vegetation driven by climate warming at the onset of the Holocene. By 11,000 cal yr BP, the woodlands were increasingly diverse and dense with the expansion of Quercus, Fraxinus and Tilia, the establishment of Corylus and the decline of upland herbaceous and shrubs taxa. The marked expansion of Quercus accompanied by Tilia between 10,500 and 8000 cal yr BP could be the result of low effective moisture associated with both low elevation of the site and with regional change towards a drier climate. At 10,000 cal yr BP, Corylus spread across the region, and by 8000 cal yr BP it replaced Quercus as a dominant forest constituent, with only little representation of Picea abies. Carpinus became established around 5500 cal yr BP, but it was only a minor constituent in local woodlands until ca. 5000 cal yr BP. Results from this study also indicate that the woodlands in the lowlands of Turbuta were never closed.  相似文献   

The exceptional oder flood in summer 1997 — riverine mass and nutrient transport into the Pomeranian Bight     

Volker Mohrholz  Marianna Pastuszak  Stanisław Sitek  Klaus Nagel  Hans Ulrich Lass 《Ocean Dynamics》1998,50(2-3):129-144

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Estimates for the luminosity function of galaxies and its evolution     

Volker Springel  & Simon D. M. White 《Monthly notices of the Royal Astronomical Society》1998,298(1):143-152

A new method is presented to obtain a non-parametric maximum likelihood estimate of the luminosity function and the selection function of a flux-limited redshift survey. The method parametrizes the selection function as a series of stepwise power laws and allows possible evolution of the luminosity function. We also propose a new technique to estimate the rate of evolution of the luminosity function. This is based on a minimization of the observed large-scale power with respect to the evolutionary model. We use an ensemble of mock surveys extracted from an N -body simulation to verify the power of this method. We apply our estimators to the 1.2-Jy survey of IRAS galaxies. We find a far-infrared luminosity function in good agreement with previously published results and evidence for rather strong evolution. If the comoving number density of IRAS galaxies is assumed to scale ∝ (1 +  z ) ^P , we estimate P  = 4.3 ± 1.4.  相似文献   

Natural shock behavior of almandite in metamorphic rocks from the ries crater,Germany     

Volker Stähle 《Earth and Planetary Science Letters》1975,25(1):71-81

An extensive study of a big number of gneiss specimens with various shock features from the suevite allowed unravelling of the shock behavior of almandite garnets.Almandites in shocked metamorphic rocks show with increasing dynamic pressures strong irregular fracturing. differently oriented sets of planar fractures or elements, brown turbidity and nucleation of minute crystals of an unknown phase in solid garnets. At higher peak pressures garnet was found to break down to (1) orthopyroxene + spinel + glass, and to (2) spinel + glass due to fast shock-melting.Extensive quantitative electron microprobe studies of almandite garnets and their breakdown products were carried out. The breakdown products within the original grain boundaries of the garnets consist of an alumina-rich orthopyroxene (with up to 10 wt. % Al₂O₃), hercynite to pleonaste spinels and a silica and calcium-rich glass matrix. The chemical zonation of magnesium and manganese of the former garnets is inherited in the composition of the newly formed orthopyroxenes.Petrographic evidence and chemical composition suggest a fast breakdown of the almandite garnets after passing of shock waves at rapidly falling pressures and very high post-shock temperatures within the ejected gneissic rock material.  相似文献   

Relations between electrical conductivity and petrological parameters of the crust and upper mantle     

Volker Haak 《Surveys in Geophysics》1980,4(1-2):57-69

Laboratory data of the electrical conductivity of rocks and minerals pertinent to the deeper crust and upper mantle and summarized. They are discussed in the context of a theory to calculate effective conductivities of materials in the state of partial melt. Most published data have been obtained by too rapid measurements, i.e. without reaching an equilibrium state of the sample. Conductivity measurements on a material similar to the composition of pyrolite are not het known, their importance is outlined. A global conductivity distribution obtained by electromagnetic induction studies is represented by a few results covering oceanic and continental areas. Till today it seems to be a doubtful venture to deduce the temperature of the upper mantle or even the existence of a partial molten asthenosphere from a global conductivity distribution. On a more local scale the correlation of electrical conductivity with temperature and state of the material seems to be more realistic. This is tentatively shown by two petrological models of the Afar depression in Ethiopia and of the midoceanic rift.  相似文献   

Zur Frage der Geoelektrischen Blitzgefährdung     

Hon.-Doz. Dr. Volker Fritsch 《Pure and Applied Geophysics》1956,35(1):149-160

Zusammenfassung Der Verfasser untersucht das Problem, ob die Einschlagstelle des Blitzes auch durch die geoelektrische Bodenbeschaffenheit mitbestimmt ist. Zur Untersuchung dieser Frage wurden bisher Modellversuche, mathematische Berechnungen und Auswertungen der Statistik herangezogen. Der Verfasser kommt durch die Auswertung einer umfangreichen Blitzschlagstatistik, die für österreich angelegt wurde, zu dem Ergebnis, dass es ausgedehnte Gebiete gibt, die wegen ihrer besonderen geoelektrischen Bodenbeschaffenheit stark blitzgefährdet sind und dass auch begrenzte Zonen dieser Art, die sogenannten « Blitznester » existieren.

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Summary The author investigates the problem whether certain places of the ground are especially often struck by lightning and whether this effect is caused by the geoelectrical nature of the underground. By examining a great number of results obtained in Austria the author comes to the solution that the question of the existance of the so-called « lightning nests » must be answered in the affirmative.

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Aus einem Referat auf dem 4. Internationalen Blitzschutzkongress 1956 in Meran.  相似文献   

Synchronous uplift of the lower crust of the Ivrea Zone and of Southern Calabria and its possible consequences for the Hercynian orogeny in Southern Europe     

Volker Schenk 《Earth and Planetary Science Letters》1981

Along the border of the Adriatic microplate, pre-Alpine granulite-facies rocks from the deepest crust are outcropping at only two places: in the Ivrea Zone of the Southern Alps and in Southern Calabria. In these two areas the main features of the present crustal structures, i.e. overlapping of large continental crustal and upper mantle segments, are interpreted as resulting from their Hercynian geodynamic evolutions.The tilted, nearly complete crustal sections in both areas display very similar lithological sequences and experienced a common geological evolution, as deduced from petrological and radiometric dates. At the end of Hercynian time (～295 m.y.), the Ivrea body and the lower crustal rocks of Southern Calabria were contemporaneously sheared off from the upper mantle and uplifted into intermediate crustal levels, where they slowly cooled during Mesozoic time. The tectonic uplift was accompanied by granitoid plutonism and andesitic to rhyolitic volcanism, which continued after the Hercynian uplift.Considering the presently similar crustal structures and the Upper Carboniferous and Permian geological evolutions along the whole Adriatic plate boundary, the Ivrea Zone and Southern Calabria are used to resolve the pre-Alpine history of the boundary zone between the Adriatic and the Central European block: the uplift of the lower crustal/upper mantle flakes of the Adriatic block was due to flat overthrusting of these flakes on the continental crust of “Central Europe”. The material of the Central European crust underthrust (subducted) thereby melted during the re-equilibration of the geotherms which had been disturbed by the subduction process; this led to an extensive calc-alkaline plutonism and volcanism of crustal origin along the Adria boundary. In this boundary region, the overlying uppermost crustal levels (“Schiefergebirgsstockwerk”) were synchronously folded (“Asturian phase”) in response to the overlapping of the deeper crustal levels. Subsequently to the orogeny, the mountain chain was eroded and molasse basins developed on the overthrust Adriatic crustal segment during the Lower Permian.In this model, the granulite-facies flakes of the Ivrea Zone and of Southern Calabria are interpreted as pre-Hercynian lower crustal segments which were thrust into the middle crust during the Hercynian orogeny, thus giving rise to wave velocity inversions in the crust. Further, it is proposed that similar geodynamic processes have played a role in the genesis of the Conrad discontinuity which is present in many parts of the Hercynian fold belt. But only in the Ivrea Zone and in Southern Calabria the crustal discontinuities formed in Hercynian time were uplifted to the surface as a result of Alpine reactivation of the Adriatic boundary zone and due to their special positions in the bends of the Alpine-Apennine-Maghrebide mountain system.According to the present knowledge of the Carboniferous paleogeography and of the orogenic evolution on both sides of the Adria sufure zone, this fault zone was located within the European continent. Its role during the Hercynian orogeny is discussed envisaging two possibilities: an A-subduction zone or a subfluence zone (in the sense of Behr and Weber).  相似文献