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111.
Clemens Lebling 《International Journal of Earth Sciences》1912,3(7):483-508
Ohne Zusammenfassung
Hahn, Allgäuer Alpen s. G. R. II. 207. 相似文献
112.
The Ballachulish Igneous Complex consists of an outer quartz diorite and an inner granite, emplaced at about 300 MPa, initially
at 1000 to 1050 °C. The contact aureole (0.5–2 km wide) occurs in metapelites and metapsammites plus minor graphitic slates,
carbonate rocks and metaquartzites. A textural examination of the arkosic Appin Quartzite, which was previously believed to
have melted only within a few metres of the intrusion, demonstrates that partial melting occurred up to 500 m away from the
vertical eastern contact. Coupling petrographic observations with Qtz-Ab-Or-H2O phase relations, we determined both the amounts of actual melt and the maximum possible amounts of melt in the samples.
Melting efficiency was everywhere less than 100% and decreased with distance from the intrusion. Though perhaps not the only
possible source of fluid throughout the aureole, simple models demonstrate that H2O evolution from the pluton would have been volumetrically sufficient and persisted long enough to account for the observed
partial melting. A time-integrated fluid flux of 7000 kg/m2 from the pluton is necessary to account for the observed amounts of partial melt in the Appin Quartzite. From its inefficiency,
we infer that infiltration of the Appin Quartzite cannot have occurred along interconnected grain-edge channels. Rather, it
was controlled by hydraulic fracturing, with fracture density determining melting efficiency. Bulk-rock permeability is calculated
to be 10−20 m2, an order of magnitude lower than that necessary to permit pervasive flow of all the fluid exsolving from the pluton. There
is little difference between the calculated time-integrated fluid flux through the Appin Quartzite on the eastern flank and
an estimate of the infiltrating flux through the pelitic Leven Schist on the western flank in the time interval during which
both rock types were above their solidus temperature, despite differences in their equilibrium quartz-H2O dihedral angles at temperatures immediately below the solidus, and differences in the attitude of the contact. The rates
of H2O expulsion from the cooling pluton are consistent with highly efficient fracture-dominated flow, allowing insufficient time
for textural equilibration.
Received: 26 March 1998 / Accepted: 8 March 1999 相似文献
113.
M. S. Clemens K. M. Baxter P. Alexander D. A. Green 《Monthly notices of the Royal Astronomical Society》1999,308(2):364-376
We present both observations and modelling of the atomic hydrogen in the closely interacting galaxies NGC 3395 and 3396. The observations were made with the VLA in both C- and D-arrays. We detect a large 'tail' of H i extending to a projected distance of 63 kpc (10 arcmin) south-west of the pair, as well as two smaller galaxies, IC 2604, 14 arcmin to the south-west, and IC 2608, 14 arcmin to the south-east. However, these galaxies appear to have had at most a minor influence on the dynamics of NGC 3395/6. By means of N -body simulation we show that the tail is gas that has been stripped from NGC 3395 during a prograde encounter with NGC 3396, and that the pair has had one previous close approach. It is shown that the galaxies are within 5 × 107 yr of their second perigalactic passage. Comparison of the time-scales for starburst activity with those from the simulations shows that the current starbursts are a result of the current close approach and not the first one. The interaction between NGC 3395 and 3396 has flattened the rotation curve of NGC 3396 owing to the parameters of the interaction. This naturally explains the more nucleated radio continuum structure observed in this galaxy, as significant infall and a subsequent central starburst would be expected in this scenario. The velocity structure and line profiles of the H i are best explained if both cloud–cloud collisions between the two gas discs and tidal forces have been important. 相似文献
114.
Automated recognition of quasi‐planar ignimbrite sheets as paleosurfaces via robust segmentation of digital elevation models: an example from the Central Andes 下载免费PDF全文
Balázs Székely Zsófia Koma Dávid Karátson Peter Dorninger Gerhard Wörner Melanie Brandmeier Clemens Nothegger 《地球表面变化过程与地形》2014,39(10):1386-1399
Quasi‐planar morphological surfaces may become dissected or degraded with time, but still retain original features related to their geologic‐geomorphic origin. To decipher the information hidden in the relief, recognition of such features is required, possibly in an automated manner. In our study, using Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM), an existing algorithm has been adapted to recognize quasi‐planar features fulfilling specified criteria. The method has been applied to a study area of the Central Andes with Miocene to Quaternary volcanic edifices, tilted ignimbrite surfaces, and basin‐filling sediments. The result is a surface segmentation, whereas non‐planar features (gullies, tectonic faults, etc.) are sorted out. The main types of geomorphic features that can be distinguished and interpreted are as follows. (1) The west‐dipping western margin of the Altiplano is differentiated into segments of the lower sedimentary cover that of increased erosion by tectonic steepening at intermediate levels, and an upper plane with limited erosion. (2) In the central part of the Western Cordillera, the Oxaya ignimbrite block shows a ‘striped’ bulging pattern that results from a smoothly changing surface dip. This pattern is due to continuous folding/warping of the ignimbrite block possibly related to gravitational movements. (3) To the west, large, uniform planes correspond to flat, smooth, tectonically undisturbed surfaces of young sedimentary cover of the Central Basin. (4) The evolution of Taapaca volcanoes with sector collapse events and cone‐building phases is shown by several segments with overlapping clastic aprons. (5) To the east, on the western margin of the Altiplano, young intermontane basins filled by Upper Miocene sediments show progressively increasing dip toward basin margins, reflected by a circular pattern of the segmentation planes. We show that the segmentation models provide meaningful images and additional information for geomorphometric analysis that can be interpreted in terms of geological and surface evolution models. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
115.
J. C. Clemens M. H. van Kerkwijk Y. Wu 《Monthly notices of the Royal Astronomical Society》2000,314(2):220-228
We have used time-resolved spectroscopy to measure the colour dependence of pulsation amplitudes in the DAV white dwarf G29-38. Model atmospheres predict that mode amplitudes should change with wavelength in a manner that depends on the spherical harmonic degree ℓ of the mode. This dependence arises from the convolution of mode geometry with wavelength-dependent limb darkening. Our analysis of the six largest normal modes detected in Keck observations of G29-38 reveals one mode with a colour dependence different from the other five, permitting us to identify the ℓ-value of all six modes and to test the model predictions. The Keck observations also show pulsation amplitudes that are unexpectedly asymmetric within absorption lines. We show that these asymmetries arise from surface motions associated with the non-radial pulsations (which are discussed in detail in a companion paper). By incorporating surface velocity fields into line profile calculations, we are able to produce models that more closely resemble the observations. 相似文献
116.
117.
Comparison of Boundary-Layer Profiles and Layer Detection by AMDAR and WTR/RASS at Frankfurt Airport
At Frankfurt airport (EDDF) vertical soundings of the lower atmosphere from two independent sources are available. One of
them is a wind and temperature profiler (wind temperature radar and radio acoustic sounding system, WTR/RASS) located at the
western end of the main pair of runways. The second source is aircraft meteorological data relay (AMDAR), i.e. measurements
operationally collected by approaching and departing aircraft. Together, both offer a rare opportunity to compare the performance
of these widely used systems. We use 1 year of continuous data to calculate systematic temperature and wind vector differences
between both measurement systems. The differences show a clear season-dependent structure in conjunction with typical inversion
heights. Possible causes for this behaviour are discussed. Second, we compare the ability of both systems to identify inversion
and wind-shear layers above the airport. AMDAR-detected layers are typically higher than wind profiler detections. The layer
base is usually detected with more agreement than the top. The mutual probability of detection of inversions is found to be
mostly between 40 and 60%. 相似文献
118.
Plant source water apportionment using stable isotopes: A comparison of simple linear,two‐compartment mixing model approaches 下载免费PDF全文
Plant source water identification using stable isotopes is now a common practice in ecohydrological process investigations. Notwithstanding, little critical evaluation of the approaches for source apportionment have been conducted. Here, we present a critical evaluation of the main methods used for source apportionment between vadose and saturated zone water: simple mass balance and Bayesian mixing models. We leverage new isotope stem water samples from a diverse set of tree species in a strikingly uniform terrain and soil conditions at the Christchurch Botanic Garden, New Zealand. Our results show that using δ2H alone in a simple, two‐source mass balance approach leads to erroneous results, particularly an apparent overestimation of groundwater contribution to xylem. Alternatively, using both δ2H and δ18O in a Bayesian inference framework improves the source water estimates and is more useful than the simple mass balance approach, particularly when soil and groundwater contributions are relatively disproportionate. We suggest that plant source water quantification methods should take into consideration the possible effects of 2H/1H fractionation. The Bayesian inference approach used here may be less sensitive to 2H/1H fractionation effects than simple mass balance methods. 相似文献
119.
Regional dynamical downscaling with CCLM over East Asia 总被引:1,自引:1,他引:0
Dinan Wang Christoph Menz Thorsten Simon Clemens Simmer Christian Ohlwein 《Meteorology and Atmospheric Physics》2013,121(1-2):39-53
Inspired by the framework of the Coordinated Regional Climate Downscaling Experiment (CORDEX), the hindcast (1971–2000) and projection (2021–2050) simulations based on a resolution of $0.44^\circ$ over the East Asia domain are performed with the regional climate model COSMO-CLM (CCLM). The simulations are driven by ERA-40 reanalysis data and output of the global climate model ECHAM5. This is the first time that the CCLM is adapted and evaluated for the East Asia Monsoon region; the setup is considered a starting point for further improvements in this region by the CCLM community. The evaluation results show that the CCLM is able to reasonably capture the climate features in this region, especially the monsoon dynamics on small scales. However, total precipitation in the northern part of the domain, over the Tibetan Plateau, and over east Indonesia has a pronounced wet bias. The projected climate change under the A1B scenario indicates an overall annual surface temperature increase of 1–2 K, but no significant precipitation changes. 相似文献
120.
Precipitation amounts simulated by the regional climate model COSMO-CLM are compared with observations from rain gauges at German precipitation stations for the period 1960–2000. The model overestimates precipitation by about 26 %. This bias is accompanied with a shift of the frequency distribution of rain intensities. The model overestimation varies regionally. A correction function is derived which adjusts rain intensities at every model grid point to the observations. 相似文献