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131.
132.
Mikls Kedves 《Ore Geology Reviews》1990,5(5-6)
Samples of manganese carbonate and oxide layers from the Úrkút ore deposit were investigated for organic remains, especially for spores and pollen grains. Light (LM), Transmission Electron (TEM), and Scanning Electron Microscopy (SEM) methods were used. LM revealed several new sporomorph taxa; a microstratigraphic standard was established by reconstructing vegetation zones surrounding the sedimentary basin. Index fossils of palynomorphs and the relative abundance of other taxa support a Liassic (Lower Jurassic) age for these layers. TEM data were used to establish: (1) important new understanding about the phylogeny of the pollen-exine ultrastructure and, in particular, the tectate columellar ectexine of the Mesozoic gymnospermous pollen grain, Spheripollenites; and (2) the degree of destruction of the exine ultrastructure helps to reconstruct taphonomical processes during sedimentation and to unravel biopolymer-type molecular structures in the walls of palynomorphs. The SEM method aided in the taxonomy of the microfossils. Combined TEM and SEM methods revealed that submicroscopic surface degradation may be a consequence of bio-degradation during deposition of manganese ore. 相似文献
133.
The three GC coeluting C40 bis-phytanes with head-to-tail, tail-to-tail and head-to-head linkages considered to be archaebacterial markers, have been recognized in petroleum by enhanced mass-fragmentography. Supporting evidence has been obtained by the simultaneous occurrence of two C21–C24 series of isoprenoid and quasi-isoprenoid hydrocarbons that are supposedly formed during the catagenetic degradation of the isomeric C40 isoprenoids. The C21–C24 quasi-isoprenoid hydrocarbons have been identified conclusively for the first time by comparison with authentic standards. 相似文献
134.
Maria Nikkarinen Eeva Kallio Pekka Lestinen Matti Ayrs 《Journal of Geochemical Exploration》1984,21(1-3)
The variation of Cu and Zn contents with grain size was studied in the size fractions: 2000-500 μm, 500-64 μm, 64-2 μm and minus 2 μm. The fixation to different minerals was investigated in the 500-64 μm and minus 64 μm fractions with microscope, microprobe, electron microscope and X-ray diffraction after heavy-liquid separation.The distribution of Cu and Zn between the four size fractions is very similar in all target areas. The contents tend to be highest in the minus 2 μm fraction, and to decrease with increasing grain size except for an increase in the coarsest material. This feature is typical in mineralized areas with till having anomalously high Cu and Zn contents.The anomalous Cu and Zn in the till of Talvivaara are mainly fixed to chalcopyrite and sphalerite, respectively, which indicates that the main part of the material originates from fresh bedrock and that postglacial alterations are slight. In the till of Outokumpu and Maaselkä sulphides are rare. We assume that in Outokumpu the reason for this is the postglacial weathering of sulphides and that in Maaselkä a great deal of till derives from highly weathered, sulphide-poor, preglacial regolith. In both target areas Cu in till seems to fix to limonite and also to clay minerals, particularly in Maaselkä. Zinc seems mainly to be hosted by limonite in Outokumpu. 相似文献
135.
A detailed local structural map of the Mérens Fault zone at Port Vell (Vall Ferrera) reveals that the main fault-related mylonite band splits westwards into a network of mylonite zones. These consist of bands of highly-strained rocks exhibiting tightened folds, transposed foliations and extensive obliteration of pre-existing structures. Evidence of continuity of marble layers across the Port Vell mylonite zone, and structural and metamorphic similarities on both sides of the Port Vell mylonite band, indicate that there is no significant throw across it.The mylonite foliation forms parallel to the axial planes of tight folds in or near the mylonite zone which can be related to more open folds in adjacent areas. The Port Vell mylonite band corresponds to a pinched W-E axial trending late fold.In order to estimate the importance of these results, a review of the controversial geological significance of mylonite belts in the Pyrenees, with special emphasis on the Mérens Fault, introduces the paper. 相似文献
136.
It is presently widely accepted that the solar low p modes show asymmetric profiles when their power spectrum is analysed and that the fact of fitting symmetric profiles yields systematic effects in the obtained frequencies which could affect the results of inversions. In this paper the low p-mode profiles are analysed using wavelets to denoise the power spectra of the modes. This denoising method is applied both to artificial data generated by Kosovichev (the Hare and Hound exercise) and to real data obtained with the GOLF instrument. The asymmetries as well as the frequencies obtained are studied in both cases. The results show that although the obtained p-mode profiles present a slightly negative asymmetry, the use of symmetric profiles to fit the power spectra does not introduce any systematic effect in the obtained frequencies. 相似文献
137.
Selection of regional historical rainfall time series as input to urban drainage simulations at ungauged locations 总被引:1,自引:0,他引:1
P.S. Mikkelsen H. Madsen K. Arnbjerg-Nielsen D. Rosbjerg P. Harremoës 《Atmospheric Research》2005,77(1-4):4
It has become established practice during the past 20 years to use high-resolution historical rainfall time series as input to hydrological model packages for detailed simulation of urban drainage systems. However, sufficiently long rain series are rarely available from the exact catchment in question and simulations are hence often based on available rain series from other locations. Extreme rainfall properties of importance to the performance of urban storm drainage systems vary significantly even in regions with only minor physiographic differences. Part of this variation can be explained by regional variations of the mean annual rainfall and the remaining statistical residue can be interpreted as statistical uncertainty.In Denmark, more than 75 high-resolution rain gauges are installed across a total area of 43,000 m. About 40 gauges had sufficiently long records to be included in a comprehensive national investigation where newly developed statistical regionalisation procedures were used to model the regional variation of extreme rainfalls. On this basis, a spreadsheet model was made available for estimation of extreme design rainfalls and the associated uncertainty at any location in the country. Statistics were furthermore computed to classify historical rainfall time series according to the developed regional model, and this makes it possible to assess the uncertainty related with using different historical rain series for simulations at ungauged locations.This research indicates that use of historical point rainfall data at ungauged locations introduces a significant uncertainty that is largely overlooked in today's practice. The engineering recommendation is to select historical rain series based on an evaluation of the local physiographic characteristics (e.g., the mean annual rainfall) and a (pre-defined) desired safety level of the simulations. 相似文献
138.
139.
Andrs Folguera Víctor A. Ramos Toms Zapata Mauro G. Spagnuolo 《Journal of Geodynamics》2007,44(3-5):129-148
The Andes between 36°30′ and 37°S represent a Cretaceous fold and thrust belt strongly reactivated in the late Miocene. Most of the features that absorbed Neogene shortening were already uplifted in the late Cretaceous, as revealed by field mapping and confirmed by previous fission track analysis. This Andean section is formed by two sectors: a western-inner sector generated by the closure of the upper Oligocene-lower Miocene intra-arc Cura Mallín basin between the middle and late Miocene (Guañacos fold and thrust belt), and an eastern-outer sector, where late Triassic-early Jurassic extensional depocenters were exhumed in two discrete phases of contraction, in the latest early Cretaceous and late Miocene to the Present, respectively (Chos Malal fold and thrust belt). Late Miocene deformation has not homogeneously reactivated Cretaceous compressive structures, being minimal south of 37°30′S through the eastern-outer sector (southern continuation of the Chos Malal fold and thrust belt). The reason for such an inhomogeneous deformational evolution seems to be related to the development of a late Miocene shallow subduction regime between 34°30′ and 37°45′S, as it was proposed in previous studies. This shallow subduction zone is evidenced by the eastward expansion of the arc that was accompanied by the eastern displacement of the orogenic front at these latitudes. As a result, the Cretaceous fold and thrust belt were strongly reactivated north of 37°30′S producing the major topographic break along the Southern Central Andes. 相似文献
140.