排序方式： 共有9条查询结果，搜索用时 281 毫秒
1
1.
PETRA LUDWIG 《Polar research》1991,9(1):65-76
The change from continental to marine conditions in the Middle Carboniferous on Brøggerhalvøya started at the end of the Bashkirian with short-term transgressive events at the top of the Brøggertinden Formation. Local basin subsidence was responsible for the pulsatory nature of the transgression. The establishment of a shallow marine carbonate-dominated environment is represented by the Moscovian Scheteligfjellet Member which overlies the post-Caledonian red beds of the Brøggertinden Formation. The Scheteligfjellet Member is the lowermost member of the Nordenskioldbreen Formation and shows distinct lateral facies variations. Three facies associations can be distinguished: lagoonal facies, shoal facies and open marine facies. The succeeding two members were deposited in subtidal areas of the carbonate platform. A basin subsidence event at the Carboniferous/Permian boundary was responsible for a short shift into deeper depositional environments during a time of worldwide regression. After this a continuous regression led to supratidal conditions at the top of the Nordenskioldbreen Formation. 相似文献
2.
MARSCHALL HORST R.; LUDWIG THOMAS; ALTHERR RAINER; KALT ANGELIKA; TONARINI SONIA 《Journal of Petrology》2006,47(10):1915-1942
High-pressure (HP) metamorphic blocks enclosed in a mafic toultramafic matrix from a mélange on the island of Syrosare rimmed by tourmaline-bearing reaction zones (blackwalls).The B isotopic composition of dravitic tourmaline within theseblackwalls was investigated in situ by secondary ion mass spectrometry.Boron in these tourmalines is unusually heavy, with 11B valuesexceeding +18 in all investigated samples and reaching an extremevalue of +28·4 in one sample. Blackwalls formed duringexhumation of the HP mélange at a depth of 20–25km at temperatures of 400–430°C, by influx of externalhydrous fluids. The compositions of the fluids are estimatedto be in the range of 100–300 µg/g B with 11B valuesof +18 to +28. The high 11B values cannot be explained by tourmalineformation from unmodified slab-derived fluids. However, suchfluids could interact with the material in the exhumation channelon their way from the dehydrating slab to the site of tourmalineformation in the blackwalls. This could produce exceptionallyhigh 11B values in the fluids, a case that is modelled in thisstudy. The model demonstrates that subduction fluids may beeffectively modified in both trace element and isotopic compositionduring their migration through the material overlying the subductingslab. Blackwall tourmaline from Syros has a large grain size(several centimetres), high abundance, and an exceptionallyhigh 11B value. The formation of tourmaline at the contact betweenmafic or felsic HP blocks and their ultramafic matrix involvedfluids released during dehydration reactions in the subductingslab. It forms a heavy-boron reservoir in hybrid rocks overlyingthe subducting slab, and may, thus, have a significant impacton the geochemical cycle of B and its isotopes in subductionzones. KEY WORDS: boron isotopes; tourmaline; subduction zone; fluid, high pressure 相似文献
3.
PETRA KUPPINGER 《Geographical review》2005,95(3):348-372
ABSTRACT. Rapid construction of new spaces like hotels, malls, private clubs, and gated communities in Greater Cairo, Egypt produces structures disconnected spatially and conceptually from most of the existing urban fabric. Their spatial concepts and practices, as well as architectural forms and expertise, are based largely on globally available models. Planning and construction are guided by the search for security in the face of real or imagined fear of the urban masses and political upheaval. Concrete walls, guarded entrances, and high‐tech security technology bear witness to these fears. Analysis of the Mena House Hotel, the Grand Egyptian Museum project, and the First Mall in Giza shows how these projects globalize Cairo and localize the global. Often these globalized spaces are remade by creating local and regional ties and design features that were not anticipated by the planners. Such changes shed light on underlying dynamics and contribute to a better understanding of in situ globalization. Whereas their physical features tend to accentuate their globalized nature, these spaces do not exist in isolation from their geographical and cultural contexts. Their everyday realities tell tales of reterritorialization that are frequently overlooked in scholarly debates. 相似文献
4.
Ten things higher education needs to know about GIS in primary and secondary education 总被引：4，自引：0，他引：4
This paper examines the status of efforts to implement GIS in Kindergarten to Grade 12 (K-12) education in the United States. Factors promoting and impeding the growth and diffusion of GIS are identified and suggestions for action on the part of higher education GIS specialists are made. In the United States more science teachers have adopted GIS geography/social studies teachers for several reasons. These include science teacher preservice preparation and the essentially different natures of the respective disciplines. Preservice education and teachers' perceptions of geography emerge as key factors influencing the diffusion of GIS in K-12 classrooms. The need for on cognition and GIS before effective curricula and instruction can be developed is emphasized. Three strategies directed at higher education GIS specialists may help implement this eduational innovation. They are: (1) modelling GIS instruction in content classes; (2) including GIS in preservice preparation classes; and (3) outreach to professors who tach educational technology to educate than regarding GIS. The addendum by Paul Heinrich which follows this paper compares US and UK experiences in the diffusion of GIS in elementary and secondary schools. 相似文献
5.
6.
7.
DUAN Jilin LIU Yanpeng ZHU Lixin MA Shengming GONG Qiuli Alla DOLGOPOLOVA Simone A. LUDWIG 《《地质学报》英文版》2023,97(4):1252-1267
Geochemical maps are of great value in mineral exploration. Integrated geochemical anomaly maps provide comprehensive information about mapping assemblages of element concentrations to possible types of mineralization/ore, but vary depending on expert’s knowledge and experience. This paper aims to test the capability of deep neural networks to delineate integrated anomaly based on a case study of the Zhaojikou Pb-Zn deposit, Southeast China. Three hundred fifty two samples were collected, and ea... 相似文献
8.
MARKUS FUCHS DENIS-DIDIER ROUSSEAU PIERRE ANTOINE CHRISTINE HATTÉ CAROLINE GAUTHIER SLOBODAN MARKOVI&#; LUDWIG ZOELLER 《Boreas: An International Journal of Quaternary Research》2008,37(1):66-73
The Surduk loess section in Serbia provides a 20 m thick pedosedimentary record of the last interglacial–glacial climatic cycle (Upper Pleistocene). Based on optical dating, a chronostratigraphy could be established for the last climatic cycle, yielding the first numerical ages of a loess record from the middle Danube basin. Infrared-stimulated luminescence (IR-OSL) dating has been applied to the polymineral silt fraction using a multiple aliquot additive-dose protocol to determine the equivalent dose ( D E ). Within error limits, all age estimates are in stratigraphic order. Owing to the application of shine-plateau tests, the samples showed no evidence of insufficient bleaching. The Surduk loess section comprises three major periods of soil formation. Based on the IR-OSL chronostratigraphy, the lowermost pedocomplex is attributed to the Last Interglacial and to the Early Glacial (Marine Isotope Stage – MIS 5e to 5a). The middle part of the section exhibits a succession of weakly developed brown soils and a humic horizon, named 'Surduk soil', formed during MIS 3. On top of the section, recent soil formation is related to the Holocene. Thick loess deposits are preserved between these palaeosols and are attributed to the Lower and Upper Pleniglacials (MIS 4 and 2), respectively. Estimated mean sedimentation rates are 0.1–0.2 mm/yr for the last glacial cycle, with a strong increase to 0.6 mm/yr with onset of the Pleniglacial. 相似文献
9.
DENIS-DIDIER ROUSSEAU GEORGE KUKLA LUDWIG ZÖLLER JANKA HRADILOVA 《Boreas: An International Journal of Quaternary Research》1998,27(3):200-207
The cause of the rapid transition from lush grasslands and woodlands of the Early Glacial interstadiul to Pleniglacial barrens in Europe is still a mystery. In the loess sections of Bohemia and Austria this transition is associated with thin layers of fine-grained airborne dust known as 'markers', believed to be deposited by major contineiital-scale dust storms. Here we present evidence that a similar. sharply delimited layer with a minimum TL age of 64.9 ± 6.9 ka separates the autochthonous humus steppe soils from abiogenic sediments of the Achenheim 1 pedocomplex in France. The soil complex has been previously correlated on pedostratigraphic grounds with marine oxygen isotope stage (MIS) 5. Given its age and stratigraphic position, the dust layer correlates with the PKII marker in Bohemia. The rccogiiition of a marker in Achenheim suggests that the development of the Early Glacial steppe soils ended abruptly not only in central Europe, but also in Alsace, France, prior to 65 ka, possibly as a result of a single continental-scale dust storm. 相似文献
1