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391.
Jens E. Danielsen Esben Auken Flemming Jrgensen Verner Sndergaard Kurt I. Srensen 《Journal of Applied Geophysics》2003,53(4):181
The transient electromagnetic (TEM) method has been used extensively for hydrogeophysical exploration in Denmark for the past decade. Innovative instrumentation combined with multi-dimensional modelling and interpretational insights based on experience gained through numerous case studies have proven to be a successful strategy. In the case study reported here, the combination revealed an unknown and unexpected buried valley complex. Drill hole data were in good agreement with estimates of both the bearings and depths of valleys defined by the TEM surveys. The Pulled Array Transient Electromagnetic (PATEM) system was built to provide high data density for increased lateral resolution. A High moment Transient Electromagnetic (HiTEM) system was developed for delineation of aquifers to depths up to 300 m. Because both of these systems provide high data density, data quality can be assessed as part of the interpretational strategy. When acquiring TEM measurements in areas as densely populated as the Danish countryside, precautions must be taken to minimize coupling between the TEM system and man-made conductors. Modelling the slope of the flanks of buried valleys has challenged the adequacy of the one-dimensional (1-D) assumption for inversion of TEM data. The study shows that for a valley structure in a low-resistive layer, the 1-D assumption is sufficient to track the presence of rather steep slopes. For a valley structure in a high-resistive layer, however, the insensitivity of the TEM method to resistors makes it difficult to determine a slope with a 1-D inversion, and only the overall structure is defined. 相似文献
392.
Eric E. Hiatt Kurt Kyser Robert W. Dalrymple 《Journal of Geochemical Exploration》2003,80(2-3):221-240
The Thelon Basin, Nunavut, Canada, is host to unconformity-type uranium mineralisation and has the potential to host other economic deposits. The Thelon Formation (ca. 1750 Ma) is composed of thick (meters to tens of meters), poorly sorted, trough cross-bedded conglomerate and coarse-grained lithic arenite beds, and to a lesser extent, well-sorted, medium- to coarse-grained quartz arenite beds. Relatively rare, 1–12 cm thick, clay-rich siltstones to fine-grained sandstone layers punctuate the coarser lithofacies. Based on regional analysis of drill cores and outcrops, multiple unconformity-bounded sequences are defined in this fluvial-dominated sedimentary succession. Stratigraphic correlations are based on detailed lithofacies analysis, distinct changes in fining-upward cycle thickness, and intraformational surfaces (unconformities, transgressive surfaces, and paleosols).Diagenetic and paragenetic relationships vary systematically with sedimentology and stratigraphy of the Thelon and provide a framework for understanding the evolution of fluid-flow systems in the context of basin hydrostratigraphy. Stratigraphic units with well-sorted textures, which lacked clay and unstable framework grains, originally were aquifers (depositional aquifers) during early basin evolution. However, pervasive, early quartz cementation radically reduced the porosity and permeability of these units, occluding pore throats and transforming them into aquitards. Proximal fluvial and alluvial fan lithofacies that contained detrital, mechanically infiltrated, and diagenetic clay minerals and/or unstable detrital grains originally had low permeabilities and only experienced minor quartz cementation. In the deep burial setting (2–7 km), these units retained sufficient permeability to allow diagenetic fluid flow (diagenetic aquifers) as suggested by feldspar dissolution, quartz dissolution, and formation and recrystallization of illite and other diagenetic reactions. Tracing potential diagenetic aquifer and aquitard units across the study area allowed development of a hydrostratigraphic model. In this model, diagenetic aquifers onlap onto, and focused basinal fluids into basement rocks to the east in the Thelon Basin (in the vicinity of the Kiggavik uranium deposit). 相似文献
393.
JuliaBoike OlafIppisch 《冰川冻土》2002,24(5):538-543
Mud boils, classified as non-sorted circles, are a common patterned ground phenomenon of permafrost areas. They typically consist of a bare circle center of cryoturbated soil and are surrounded by vegetation on more stable soil. The objectives are to examine differences in seasonal hydrologic and thermal dynamic across this gradient of cryoturbation, i.e. the region below the organic border and the mud center. We installed instruments in a mud boil at a site close to Ny-@lesund, Spitsbergen, in September 1998. The bare soil circle center ranges about 1 m in diameter and is surrounded by a vegetated border consisting of a mixture of low vascular plants, mosses and lichens. Fine soil (>95% clay and silt) in the lower part of the profile is overlain by coarser grained material (silt and sand). The grain size distribution also suggests an upwelling of fine material in the center of the circle. Temperature and moisture sensors were installed over a vertical 1 m×1 m profile and hourly data recording started in September 1998. Surface irregularities, as well as variations of grain size and moisture, create a non-uniform thermal and hydrologic dynamic. We qualitatively analyze this dynamic with respect to the mud boils physical stability. 相似文献
394.
Balancing lateral orogenic float of the Eastern Alps 总被引:2,自引:0,他引:2
Hans-Gert Linzer Kurt Decker Herwig Peresson Rudi Dell'Mour Wolfgang Frisch 《Tectonophysics》2002,354(3-4)
Oligocene to Miocene post-collisional shortening between the Adriatic and European plates was compensated by frontal thrusting onto the Molasse foreland basin and by contemporaneous lateral wedging of the Austroalpine upper plate. Balancing of the upper plate shortening by horizontal retrodeformation of lateral escaping and extruding wedges of the Austroalpine lid enables an evaluation of the total post-collisional deformation of the hangingwall plate. Quantification of the north–south shortening and east–west extension of the upper plate is derived from displacement data of major faults that dissect the Austroalpine wedges. Indentation of the South Alpine unit corresponds to 64 km north–south shortening and a minimum of 120 km of east–west extension. Lateral wedging affected the Eastern Alps east of the Giudicarie fault. West of the Giudicarie fault, north–south shortening was compensated by 50 to 80 km of backthrusting in the Lombardian thrust system of the Southern Alps. The main structures that bound the escaping wedges to the north are the Inntal fault system (ca. 50 km sinistral offset), the Königsee–Lammertal–Traunsee (KLT) fault (10 km) and the Salzach–Ennstal–Mariazell–Puchberg (SEMP) fault system (60 km). These faults, as well as a number of minor faults with displacements less than 10 km, root in the basal detachment of the Alps. The thin-skinned nature of lateral escape-related structures north of the SEMP line is documented by industry reflection seismic lines crossing the Northern Calcareous Alps (NCA) and the frontal thrust of the Eastern Alps. Complex triangle zones with passive roof backthrusts of Middle Miocene Molasse sediments formed in front of the laterally escaping wedges of the northern Eastern Alps. The aim of this paper is a semiquantitative reconstruction of the upper plate of the Eastern Alps. Most of the data is published elsewhere. 相似文献
395.
Minimal and maximal models of Late Pleistocene Glaciation on the Tibetan Plateau are considered. The large ice sheet models indicate that disintegration of the ice sheet could have contributed up to 7 mm/yr of present vertical uplift and 2 mm/yr of horizontal extension. The former value can account for more than 50% of the observed uplift in central Tibet. The peak free-air gravity anomaly arising from the deglaciation would be around −5.4 mGal. In contrast, the smaller ice sheet models do not contribute significantly to the signals of present uplift and gravity anomalies. Modern geodetic measurements therefore have the potential to constrain the Late Pleistocene glaciation of the Tibetan Plateau. Assuming a large ice sheet over the Tibetan Plateau, the disintegration can contribute up to 6 m of eustatic sea-level rise. 相似文献
396.
397.
Impact of accounting for coloured noise in radar altimetry data on a regional quasi-geoid model 总被引:1,自引:1,他引:0
We study the impact of an accurate computation and incorporation of coloured noise in radar altimeter data when computing a regional quasi-geoid model using least-squares techniques. Our test area comprises the Southern North Sea including the Netherlands, Belgium, and parts of France, Germany, and the UK. We perform the study by modelling the disturbing potential with spherical radial base functions. To that end, we use the traditional remove-compute-restore procedure with a recent GRACE/GOCE static gravity field model. Apart from radar altimeter data, we use terrestrial, airborne, and shipboard gravity data. Radar altimeter sea surface heights are corrected for the instantaneous dynamic topography and used in the form of along-track quasi-geoid height differences. Noise in these data are estimated using repeat-track and post-fit residual analysis techniques and then modelled as an auto regressive moving average process. Quasi-geoid models are computed with and without taking the modelled coloured noise into account. The difference between them is used as a measure of the impact of coloured noise in radar altimeter along-track quasi-geoid height differences on the estimated quasi-geoid model. The impact strongly depends on the availability of shipboard gravity data. If no such data are available, the impact may attain values exceeding 10 centimetres in particular areas. In case shipboard gravity data are used, the impact is reduced, though it still attains values of several centimetres. We use geometric quasi-geoid heights from GPS/levelling data at height markers as control data to analyse the quality of the quasi-geoid models. The quasi-geoid model computed using a model of the coloured noise in radar altimeter along-track quasi-geoid height differences shows in some areas a significant improvement over a model that assumes white noise in these data. However, the interpretation in other areas remains a challenge due to the limited quality of the control data. 相似文献
398.
Late Cretaceous exhumation history of an extensional extruding wedge (Graz Paleozoic Nappe Complex, Austria) 总被引:1,自引:1,他引:0
Krenn Kurt Fritz Harald Mogessie Aberra Schaflechner Johannes 《International Journal of Earth Sciences》2008,97(6):1331-1352
Late Cretaceous structures within the eastern Graz Paleozoic Nappe Complex define an extruding wedge with north-eastward directed
thrusting in eastern portions and strike-slip shear along the margins. Stacking structures are overprinted by south-westward
directed extension with low-grade metamorphic rocks in the hangingwall and high-grade basement rocks in the footwall. Pressure–temperature
and structural data are obtained from successively opening quartz veins that record various stages of progressive deformation
and metamorphism. Fluid inclusion data and related structures show that during extension isothermal decompression from ca.
550°C and 8 kbar down to ca. 450°C and 2 kbar was related to exhumation of rocks from deep crustal levels. The data point
to a high geothermal gradient and explain condensed paleo-isotherms due to ductile normal faulting in the eastern areas of
the Graz Paleozoic Nappe Complex. The investigated Late Cretaceous structural elements suggest that the Graz Paleozoic Nappe
Complex decoupled from the surrounding basement units and operated as a large-scale extension–extrusion corridor that evolved
prior to Miocene extrusion tectonics in the Eastern Alps. 相似文献
399.
Johannes?Horak Ivo?Schmerold Kurt?Wimmer Günther?SchaubergerEmail authorView authors OrcID profile 《Theoretical and Applied Climatology》2017,130(1-2):107-118
In vehicles that are parked, no ventilation and/or air conditioning takes place. If a vehicle is exposed to direct solar radiation, an immediate temperature rise occurs. The high cabin air temperature can threaten children and animals that are left unattended in vehicles. In the USA, lethal heat strokes cause a mean death rate of 37 children per year. In addition, temperature-sensitive goods (e.g. drugs in ambulances and veterinary vehicles) can be adversely affected by high temperatures. To calculate the rise of the cabin air temperature, a dynamic model was developed that is driven by only three parameters, available at standard meteorological stations: air temperature, global radiation and wind velocity. The transition from the initial temperature to the constant equilibrium temperature depends strongly on the configuration of the vehicle, more specifically on insulation, window area and transmission of the glass, as well as on the meteorological conditions. The comparison of the model with empirical data showed good agreement. The model output can be applied to assess the heat load of children and animals as well as temperature-sensitive goods, which are transported and/or stored in a vehicle. 相似文献
400.
I. M. Golinskaya V. G. Kurt T. A. Miziakina A. I. Rutkovskii A. C. Smirnov V. M. Shamolin E. Yu. Shafer E. K. Sheffer Yu. N. Gnedin V. V. Kir'yan V. A. Krat G. V. Khozov V. M. Larionov 《Astrophysics and Space Science》1985,115(2):393-397
X-ray bursts of the source A 0535+262 with a characteristic time-scale 5 min have been discovered using the observational data of the Soviet Astron satellite obtained on 7 April, 1983. Similar temporal variations were observed in the IR range on 26 September, 1981, 26–27 October and 16–17 December, 1983. The presence of such bursts gives evidence of strong inhomogeneity in the electron shell around the optical component and an accreting flow of matter in the vicinity of the neutron star. The parameters of the inhomogeneities are estimated. 相似文献