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Maik Grunwald Olaf Dellwig Gerd Liebezeit Bernhard Schnetger Rainer Reuter Hans-Jürgen Brumsack 《Marine Chemistry》2007
In autumn 2002 a time-series station was installed in the tidal inlet between the Islands of Langeoog and Spiekeroog (Southern North Sea, NW Germany) to continuously measure physical, chemical, and meteorological parameters, even during extreme weather conditions (gale-force storms, drifting ice). Inside the pole of the station sensor tubes are installed in direction of the prevailing tidal currents. The tubes are equipped with hydrographic sensors (pressure, temperature, conductivity) and allow retrieval of water for nutrient analysis by automated instruments located inside the pole. Dissolved methane and the nutrients ammonia, nitrite, nitrate, phosphate, and silicate are measured at the station. 相似文献
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Gerd Rantitsch Reinhard F. Sachsenhofer Christian Hasenhüttl Barbara Russegger Thomas Rainer 《Tectonophysics》2005,411(1-4):57-72
Following Early Cretaceous nappe stacking, the Eastern Alps were affected by late-orogenic extension during the Late Cretaceous. In the eastern segment of this range, a Late Cretaceous detachment separates a very low- to low-grade metamorphic cover (Graz Paleozoic Nappe Complex, GPNC) above a low- to high-grade metamorphic basement. Synchronously, the Kainach Gosau Basin (KGB) collapsed and subsided on top of the section.Metamorphism of organic material within this section has been investigated using vitrinite reflectance data and Raman spectra of extracted carbonaceous material. In the southern part of the GPNC, vitrinite reflectance indicates a decrease in organic maturity towards the stratigraphic youngest unit. The remaining part of the GPNC is characterized by an aureole of elevated vitrinite reflectance values and Raman R2 ratios that parallels the margins of the GPNC. Vitrinite reflectance in the KGB shows a steep coalification gradient and increases significantly towards the western basin margin. The observed stratigraphic trend in the southern GPNC is a result of deep Paleozoic to Early Cretaceous burial. This maturity pattern was overprinted along the margins by advective heat and convective fluids during Late Cretaceous to Paleogene exhumation of basement rocks.During shearing, the fault zone was heated up to ca. 500 °C. This overprint is explained by a two-dimensional thermal model with a ramp-flat fault geometry and a slip rate of 1 to 1.5 cm/year during 5 Ma fault movement. The collapse basin above the detachment subsided in a thermal regime which was characterized by relaxing isotherms. 相似文献
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Partly flooded loose sand deposits are left back from lignite mining, particularly in east Germany. After flooding, gas inclusions in macropores enhance the pore pressure increase by total stress cycles without drainage, and this can cause the transition into a kind of suspension. Thus, natural and technical changes of surface loads triggered flow slides in chain reactions of sometimes catastrophic extent. Such collapsible deposits were and are stabilized by blast-induced liquefaction and densification. Successive collapse fronts in flooded grain skeletons are seismogeneous, and this appears as wavering in the near-field and leads to power-law spectra in the far-field. Apart from this evidence of mild fractality, the wild fractality of chain reactions eludes mathematical treatment. Therefore, uncommon methods of geotechnical design, operations and monitoring are required. 相似文献
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Measurement of meteorological quantities with fast-response sensors by means of the eddycorrelation technique allows calculation of turbulent transport without too severe demands with regard to stationarity and homogeneity. However, the measurement system causes frequency-dependent errors due to measuring height, averaging interval, sampling rate and mean wind speed. A correction method (Moore, 1986) was applied to measurements taken on a 130 m tower located at the German North Sea coast. The errors for 10-min averages, obtained at a height of 10 m were between 20 and 30%, mainly caused by the inertia of the sensors, increasing to between 30 and 60% at 130 m height due to a loss of low-frequency parts of the spectra because of the averaging interval. The corrections to the obtained data were validated by comparing the cospectra calculated from the data with the spectra used for the computation of the correction factors. 相似文献
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Gerd F. Tietz 《Chemical Geology》1987,60(1-4):163-176
Mineral composition was analysed within a saprolite profile from NE Nigeria. The determination of identifiable feldspar phases is only based on X-ray powder diffractograms. Representative K-feldspar fragments were selected for detailed SEM (scanning electron microscope) studies and EDX (energy-dispersive X-ray analysis) from the profile.
The analytical data indicate a significant contrast in weathering states between the lower and the upper profile section. This contrast reflects a different weathering history: the feldspars from the lower section exhibit weathering features that are characteristic for decomposition below the water table. When raised above the water table, another type of decomposition attacked only the feldspars within the upper section while those in the lower section still preserve the older weathering state. 相似文献
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Direct measurements of volume transports through Fram Strait 总被引:9,自引:1,他引:9
Eberhard Fahrbach Jens Meincke Svein Østerhus Gerd Rohardt Ursula Schauer Vigdis Tverberg Jennifer Verduin 《Polar research》2001,20(2):217-224
Heat and freshwater transports through Fram Strait are understood to have a significant influence on the hydrographic conditions in the Arctic Ocean and on water mass modifications in the Nordic seas. To determine these transports and their variability reliable estimates of the volume transport through the strait are required. Current meter moorings were deployed in Fram Strait from September 1997 to September 1999 in the framework of the EU MAST III Variability of Exchanges in the Northern Seas programme. The monthly mean velocity fields reveal marked velocity variations over seasonal and annual time scales, and the spatial structure of the northward flowing West Spitsbergen Current and the southward East Greenland Current with a maximum in spring and a minimum in summer. The volume transport obtained by averaging the monthly means over two years amounts to 9.5 ± 1.4 Sv to the north and 11.1 ± 1.7 Sv to the south (1 Sv = 106 m3 s−1 ). The West Spitsbergen Current has a strong barotropic and a weaker baroclinic component; in the East Greenland Current barotropic and baroclinic components are of similar magnitude. The net transport through the strait is 4.2 ± 2.3 Sv to the south. The obtained northward and southward transports are significantly larger than earlier estimates in the literature; however, within its range of uncertainty the balance obtained from a two year average is consistent with earlier estimates. 相似文献