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1.
Luis A. Spalletti Ignasi Queralt Sergio D. Matheos Ferrn Colombo Jorge Maggi 《Journal of South American Earth Sciences》2008,25(4):440-463
The Upper Jurassic Tordillo Formation is exposed along the western edge of the Neuquén Basin (west central Argentina) and consists of fluvial strata deposited under arid/semiarid conditions. The pebble composition of conglomerates, mineralogical composition of sandstones and pelitic rocks, and major- and trace-element geochemistry of sandstones, mudstones, and primary pyroclastic deposits are evaluated to determine the provenance and tectonic setting of the sedimentary basin. Conglomerates and sandstones derived almost exclusively from volcanic sources. The stratigraphic sections to the south show a clast population of conglomerates dominated by silicic volcanic fragments and a predominance of feldspathic litharenites. This framework composition records erosion of Triassic–Jurassic synrift volcaniclastic rocks and basement rocks from the Huincul arch, which was exhumed as a result of Late Jurassic inversion. In the northwestern part of the study area, conglomerates show a large proportion of mafic and acidic volcanic rock fragments, and sandstones are characterised by a high content of mafic volcanic rock fragments and plagioclase. These data suggest that the source of the sandstones and conglomerates was primarily the Andean magmatic arc, located west of the Neuquén Basin. The clay mineral assemblage is interpreted as the result of a complex set of factors, including source rock, climate, transport, and diagenesis. Postdepositional processes produced significant variations in the original compositions, especially the fine-grained deposits. The Tordillo sediments are characterised by moderate SiO2 contents, variable abundances of K2O and Na2O, and a relatively high proportion of ferromagnesian elements. The degree of chemical weathering in the source area, expressed as the chemical index of alteration, is low to moderate. The major element geochemistry and Th/Sc, K/Rb, Co/Th, La/Sc, and Cr/Th values point to a significant input of detrital volcanic material of calcalkaline felsic and intermediate composition. However, major element geochemistry is not useful for interpreting the tectonic setting. Discrimination plots based on immobile trace elements, such as Ti, Zr, La, Sc, and Th, show that most data lie in the active continental margin field. Geochemical information is not sufficiently sensitive to differentiate the two different source areas recognized by petrographic and modal analyses of conglomerates and sandstones. 相似文献
2.
A framework of region-based spatial relations for non-overlapping features and its application in object based image analysis 总被引：2，自引：0，他引：2
Yu Liu Qinghua Guo Maggi Kelly 《ISPRS Journal of Photogrammetry and Remote Sensing》2008,63(4):461-475
Object based image analysis (OBIA) is an approach increasingly used in classifying high spatial resolution remote sensing images. Object based image classifiers first segment an image into objects (or image segments), and then classify these objects based on their attributes and spatial relations. Numerous algorithms exist for the first step of the OBIA process, i.e. image segmentation. However, less research has been conducted on the object classification part of OBIA, in particular the spatial relations between objects that are commonly used to construct rules for classifying image objects and refining classification results. In this paper, we establish a context where objects are areal (not points or lines) and non-overlapping (we call this “single-valued” space), and propose a framework of binary spatial relations between segmented objects to aid in object classification. In this framework, scale-dependent “line-like objects” and “point-like objects” are identified from areal objects based on their shapes. Generally, disjoint and meet are the only two possible topological relations between two non-overlapping areal objects. However, a number of quasi- topological relations can be defined when the shapes of the objects involved are considered. Some of these relations are fuzzy and thus quantitatively defined. In addition, we define the concepts of line-like objects (e.g. roads) and point-like objects (e.g. wells), and develop the relations between two line-like objects or two point-like objects. For completeness, cardinal direction relations and distance relations are also introduced in the proposed context. Finally, we implement the framework to extract roads and moving vehicles from an aerial photo. The promising results suggest that our methods can be a valuable tool in defining rules for object based image analysis. 相似文献
3.
Ice core evidence for secular variability and 200-year dipolar oscillations in atmospheric circulation over East Antarctica during the Holocene 总被引：3，自引：0，他引：3
Barbara Delmonte Jean Robert Petit Gerhard Krinner Valter Maggi Jean Jouzel Roberto Udisti 《Climate Dynamics》2005,24(6):641-654
Two Holocene ice core records from East Antarctica (Vostok and EPICA-Dome C) were analysed for dust concentration and size
distribution at a temporal resolution of 1 sample per ~50 years. A series of volcanic markers randomly distributed over the
common part of the ice cores (from 9.8 to 3.5 kyear BP) ensures accurate relative dating (±33 years). Dust-size records from
the two sites display oscillations structured in cycles with sub-millennial and secular scale frequencies that are apparently
asynchronous. The power spectra of the composite sum (Σ) of the two dust-size records display spectral energy mostly for 150-
to 500-year periodicities. On the other hand, the 200-year band is common to both records and the 200 year components of the
two sites are out-of-phase (100-year lead or lag) over ~5.5 kyear, a phenomenon also reflected by a significant (>99% conf.
lev.) band in the power spectra of the composite difference (Δ) of the two size records. During long-range transport, mineral
dust originating from the Southern Hemisphere continents is graded to a variable extent depending on the altitude and duration
of atmospheric transport. Relatively coarse dust is associated with air mass penetration from the middle–lower troposphere
and conversely relatively fine dust with upper troposphere air masses or the influence of subsidence over the Antarctic plateau,
a hypothesis already proposed for the changes that occurred during the Last Glacial Maximum to Holocene transition (Delmonte
et al. 2004b). Moreover, we assume that the overall fluctuation of air mass advection over Antarctica depends on the meridional pressure
gradient with respect to low latitudes, i.e. the Antarctic Oscillation (AAO). We therefore suggest a regional variability
in atmospheric circulation over East Antarctica. The 150–500 year power spectrum of the composite (Σ) parameter represents
the long term variability of the AAO, imprinted by secular internal oscillations probably related to the southern ocean-climatic
system. On the other hand, the Δ dust composite parameter suggests a persistent atmospheric dipole over East Antarctica delivering
coarser (finer) dust particles alternatively to Vostok and Dome C regions with a bi-centennial periodicity. Indeed, a seesaw
phenomenon in dust size distribution was already observed at three East Antarctic sites during the last deglaciation (Delmonte
et al. 2004b) and was interpreted as a progressive reduction of the eccentricity of the polar vortex with respect to the geographic south
pole. Interestingly, the Δ parameter shows a pronounced 200-year oscillation mode, throwing new light on the unresolved question
of a possible relationship between climate and solar activity. 相似文献
4.
Constructed wetlands, especially mangroves, have been studied for their usefulness in sewage treatment but the effects of mangrove vegetation and a sewage load on mangrove macrofauna have been given little attention. Ocypodid crabs are important components of mangrove forests and constitute good bioindicators of the functioning of the ecosystem as a whole. In constructed mangrove mesocosms, three vegetation treatments (bare substratum, and Avicennia marina and Rhizophora mucronata seedlings) were subjected to 0, 20, 60 and 100% sewage loads from a nearby hotel. The physiological condition of introduced Uca annulipes and Uca inversa was evaluated in terms of their RNA/DNA ratio after one, five and twelve months, and used as an indicator of ecological function in the system. Crab condition in 0% sewage load was similar to that of wild crabs throughout, suggesting no significant effects of the mesocosms on their RNA/DNA ratio. Overall, both species coped well with the administered sewage loads, suggesting good ecological function in the system. Both species manifested similar patterns in RNA/DNA ratio, being more affected by seasonal fluctuations than by sewage load and vegetation presence and type. Higher RNA/DNA ratios were recorded in the long compared to the short rainy season. Sewage enhanced crab condition in the bare substratum and R. mucronata treatments, especially after one year, probably as a result of enhanced food availability. Uca inversa may be more sensitive to sewage pollution than U. annulipes. In A. marina, no difference in crab condition was observed between sewage loads, and this mangrove yielded the best reduction in sewage impacts. Our results support the usefulness of constructed mangrove areas in sewage treatment, especially if planted with A. marina and inhabited by physiologically healthy ocypodid crabs to enhance the system's performance. 相似文献
5.
Five commercially available in Estonia brands of bottled water have been analysed for 59 chemical elements by ICP-QMS and ICP-AES techniques to assess the quality of domestic mineral waters in scope of the European Groundwater Geochemistry Project initiated by the Geochemistry Expert Group of EuroGeoSurveys. Contents of 9 cations and anions, pH and electrical conductivity (EC) were measured in the bottled mineral waters by IC, titration and photometric methods. The data showed a significant difference between natural undiluted mineral water (Värska Originaal) characterised by the highest values of pH, EC and majority of trace elements studied, and other domestic waters sold in Estonia. 相似文献
6.
E. Carlsson A. Fedorov E. Budnik H. Gunell J.-A. Sauvaud Y. Futaana H. Andersson J.D. Winningham J.R. Sharber A.J. Coates D.O. Kataria H. Koskinen P. Riihelä J. Kozyra E. Roelof S. Livi K.C. Hsieh M. Grande J.-J. Thocaven S. Orsini M. Maggi P. Bochsler J. Woch K. Asamura 《Icarus》2006,182(2):320-328
Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO+2/O+ and O+2/O+. The following ratios averaged over all events and energies were identified: CO+2/O+ = 0.2 and O+2/O+ = 0.9. The values measured are significantly higher, by a factor of 10 for O+2/O+, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O+, followed by O+2 and CO+2. We estimate the loss of CO+2 to be by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found. 相似文献
7.
E. Kallio T.L. Zhang R. Jarvinen P. Janhunen J.-A. Sauvaud J.-J. Thocaven H. Andersson K. Brinkfeldt M. Holmström M. Yamauchi W. Baumjohann A.J. Coates D.O. Kataria K.C. Hsieh M. Grande T. Säles P. Riihelä N. Krupp J.G. Luhmann S. Orsini A. Mura M. Maggi P. Brandt K. Szego R.A. Frahm J.R. Sharber P. Bochsler 《Planetary and Space Science》2008,56(6):796-801
Plasma and magnetic field measurements made onboard the Venus Express on June 1, 2006, are analyzed and compared with predictions of a global model. It is shown that in the orbit studied, the plasma and magnetic field observations obtained near the North Pole under solar minimum conditions were qualitatively and, in many cases also, quantitatively in agreement with the general picture obtained using a global numerical quasi-neutral hybrid model of the solar wind interaction (HYB-Venus). In instances where the orbit of Venus Express crossed a boundary referred to as the magnetic pileup boundary (MPB), field line tracing supports the suggestion that the MPB separates the region that is magnetically connected to the fluctuating magnetosheath field from a region that is magnetically connected to the induced magnetotail lobes. 相似文献
8.
使用基于伴随方法的反演策略,研制出了南加州地壳的三维地震模型。该模型涉及到16次层析成像迭代,需要6800次波场模拟和总计80万个中心处理单位小时。与南加州地震中心给出的最初三维模型比较,该新的地壳模型揭示了更强的非均匀性,包括±30%的局部变化。模型说明了诸如沉积盆地和横跨断层的构造反差的浅部特征。也揭示了深部的地壳特征,从而帮助重建诸如俯冲捕获洋壳碎块的南加州构造。新模型有助于对地震危险性做出更实际而准确的评估。 相似文献
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10.
Massimo Fracassini Paola Maggi Laura E. Pasinetti 《Astrophysics and Space Science》1986,128(2):363-368
The results of research on pairs of PSR which were possibly components of disrupted binaries, seem to advance further arguments in favour of the idea, suggested by some authors, that most of PSR were formed in binary systems. 相似文献