Impact of mechanical anisotropy and power-law rheology on single layer folding   总被引：1，自引：0，他引：1  

Thomas Kocher  Stefan M. Schmalholz  Neil S. Mancktelow   《Tectonophysics》2006,421(1-2):71-87

The infinitesimal and finite stages of folding in nonlinear viscous material with a layer-parallel anisotropy were investigated using numerical and analytical methods. Anisotropy was found to have a first-order effect on growth rate and wavelength selection, and these effects are already important for anisotropy values (normal viscosity/shear viscosity) < 10. The effect of anisotropy must therefore be considered when deducing viscosity contrasts from wavelength to thickness ratios of natural folds. Growth rates of single layer folds were found to increase and subsequently decrease during progressive deformation. This is due to interference between the single layer folds and chevron folds that form in the matrix as a result of instability caused by the anisotropic material behaviour. The wavelength of the chevron folds in the matrix is determined by the wavelength of the folded single layer, which can explain the high wavelength to thickness ratios that are sometimes found in multilayer sequences. Numerical models including anisotropic material properties allow the behaviour of multilayer sequences to be investigated without the need for resolution on the scale of individual layers. This is particularly important for large-scale models of layered lithosphere.  相似文献   

Mineralogical and geochemical patterns of urban surface soils, the example of Pforzheim, Germany   总被引：6，自引：0，他引：6  

Stefan Norra  Mahesh Lanka-Panditha  Utz Kramar  Doris Stüben 《Applied Geochemistry》2006,21(12):2064-2081

This study presents a combined geochemical and mineralogical survey of urban surface soils. Many studies on urban soils are restricted to purely chemical surveys in order to investigate soil pollution caused by anthropogenic activities such as traffic, heating, industrial processing, waste disposal and many more. In environmental studies, chemical elements are often distinguished as lithogenic and anthropogenic elements. As a novel contribution to those studies, the authors combined the analysis of a broad set of chemical elements with the analysis of the main mineralogical phases. The semi-quantification of mineralogical phases supported the assignment of groups of chemical elements to lithogenic or anthropogenic origin. Minerals are important sinks for toxic elements. Thus, knowledge about their distribution in soils is crucial for the assessment of the environmental hazards due to pollution of urban soils. In Pforzheim, surface soils (0–5 cm depth) from various land use types (forest, agriculture, urban green space, settlement areas of various site densities) overlying different geological units (clastic and chemical sediments) were investigated. Urban surface soils of Pforzheim reflect to a considerable degree the mineral and chemical composition of parent rocks. Irrespective of the parent rocks, elevated concentrations of heavy metals (Zn, Cu, Pb, Sn, Ag) were found in soils throughout the whole inner urban settlement area of Pforzheim indicating pollution. These pollutants will tend to accumulate in inner urban surface soils according to the available adsorption capacity, which is normally higher in soils overlying limestone than in soils overlying sandstone. However, inner urban surface soils overlying sandstone show elevated concentrations of carbonates, phyllo-silicates and Fe and elevated pH values compared with forest soils overlying sandstone. Thus, in comparison to forest soils overlying sandstones, inner urban soils overlying sandstone affected by pollution concurrently possess elevated concentrations of mineral phases typically providing relatively high adsorption capacities for heavy metals.  相似文献   

Signal restoration through deconvolution applied to deep mantle seismic probes     

W. Stefan  E. Garnero  R. A. Renaut 《Geophysical Journal International》2006,167(3):1353-1362

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Multi-stage thrusting at the "Penninic Front" in the Western Alps between Mont Blanc and Pelvoux massifs     

Stefano Ceriani  Bernhard Fügenschuh  Stefan M. Schmid 《International Journal of Earth Sciences》2001,90(3):685-702

The different segments of the tectonic boundary between external (European) and internal (Penninic) units in the Western Alps, the so-called Penninic Front (PF), formed at different times and according to different kinematic scenarios. During a first episode (Eocene), the PF corresponds to a transpressive suture zone between Penninic and European units. North- to NNW-trending stretching lineations, found along internal nappe contacts within the Penninic units, are related to this episode. This subduction zone was sealed by the Priabonian flysch of the Aiguilles d'Arves, a detrital trench formation that formed during the final stages of subduction. During a second episode, starting in mid-Oligocene times, the PF, imaged along the ECORS-CROP profile, acted as a WNW-directed thrust. This thrust, the Roselend Thrust (RT), only partially coincides with the PF. South of Moûtiers, the RT propagates into the Dauphinois units, carrying the former Eocene PF (including the Priabonian flysch) passively in its hangingwall. South of the Pelvoux massif the RT finds its continuation along the "Briançonnais Front", an out-of-sequence thrust behind the Embrunais-Ubaye nappes. On a larger scale, our findings indicate oblique (sinistral) collision within the future Western Alps during the Eocene, followed by westward indentation of the Adriatic block.  相似文献   

Synthesis and Preliminary Characterisation of New Silicate, Phosphate and Titanite Reference Glasses   总被引：3，自引：0，他引：3  

Stephan Klemme  Stefan Prowatke  Carsten Münker  Charles W. Magee  Yann Lahaye  Thomas Zack  Simone A. Kasemann  E. Joan A. Cabato  Benjamin Kaeser 《Geostandards and Geoanalytical Research》2008,32(1):39-54

Eleven synthetic silicate and phosphate glasses were prepared to serve as reference materials for in situ microanalysis of clinopyroxenes, apatite and titanite, and other phosphate and titanite phases. Analytical results using different micro-analytical techniques showed that the glass fragments were homogeneous in major and trace elements down to the micrometre scale. Trace element determinations using inductively coupled plasma-mass spectrometry (ICP-MS), multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS), laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) and secondary ionisation mass spectrometry (SIMS) showed good agreement for most elements (Li, Be, B, Cs, Rb, Ba, Sr, Ga, Pb, U, Th, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Er, Tm, Yb, Lu, Zr, Hf, Ta, Nb) studied and provide provisional recommended values.  相似文献   

Fabric development in a fragment of tethyan oceanic lithosphere from the piemonte ophiolite nappe of the western Alps, Valtournanche, Italy     

W.Stefan Vogler 《Journal of Structural Geology》1987,9(8)

South of the Matterhorn the Valtournanche cuts through Alpine serpentinites, metagabbros, meta-pillowbasalts and metasediments—dismembered remnants of the Jurassic Tethyan oceanic crust, reassembled in the Piemonte ophiolite nappe. This study deals with a serpentinized ultramafic to mafic layered complex stemming from a spreading ridge environment. Cumulus fabrics of various kinds can be read through antigorite pseudomorphs, still allowing the detailed reconstruction of deep oceanic crust. Relics of igneous and metamorphic olivine prove crustal conditions during deformation. Fracturing of cumulus olivine was succeeded by plastic flow that activated low-temperature slip systems. Concomitant recrystallization produced metaperidotite only along shear zones, which are ascribed to subduction of the oceanic crust. At the turning point from subduction to obduction a static metamorphic event resulted in recovery and grain growth of recrystallized olivine. Afterwards serpentinization of the complex took place still under static conditions. Deformation of the serpentinite led to a sequence of four phases, involving non-penetrative cleavage formation, stretching and folding. This deformation is structurally related to obduction of the complex although partly accompanied by subduction zone metamorphism. Final movements of the ophiolites were due to cataclastic thrusting forming subnappe boundaries.  相似文献   

Paleoclimatic estimates from water and energy budgets of East African Lakes   总被引：1，自引：0，他引：1  

Stefan Hastenrath  John E. Kutzbach 《Quaternary Research》1983,19(2):141-153

The Turkana, Nakuru-Elmenteita, and Naivasha basins in the Rift Valley of East Africa experienced high water levels during the period of 10,000–7000 yr B.P. Analyses of the modern hydrologic and energy budgets for these basins, along with that of Lake Victoria, were used to infer the amount of precipitation that would have been required to maintain the enlarged paleolakes of the early Holocene. Precipitation must have been at least 150–300 mm/yr (15 to 35%) above the modern average. The precipitation estimates were fairly consistent among the various basins, but no quantitative estimate was made for the additional precipitation required to account for overflow from the Rift Valley lake basins. Discharge from the Lake Victoria basin around 1880 A.D. was considerably above the more recent average, and the increased discharge into the White Nile for that period might have been similar to that of the early Holocene. A sensitivity analysis showed that temperature changes were probably not too important for changing the hydrologic-energy budget; changes of albedo, Bowen ratio, and cloudiness were likely to have been of greater importance.  相似文献   

Electricity regulation in the Chinese national emissions trading scheme (ETS): lessons for carbon leakage and linkage with the EU ETS     

Yingying Zeng  Stefan E. Weishaar  Hans H. B. Vedder 《Climate Policy》2018,18(10):1246-1259

Carbon leakage is central to the discussion on how to mitigate climate change. The current carbon leakage literature focuses largely on industrial production, and less attention has been given to carbon leakage from the electricity sector (the largest source of carbon emissions in China). Moreover, very few studies have examined in detail electricity regulation in the Chinese national emissions trading system (which leads, for example, to double counting) or addressed its implications for potential linkage between the EU and Chinese emissions trading systems (ETSs). This article seeks to fill this gap by analysing the problem of ‘carbon leakage’ from the electricity sector under the China ETS. Specifically, a Law & Economics approach is applied to scrutinize legal documents on electricity/carbon regulation and examine the economic incentive structures of stakeholders in the inter-/intra-regional electricity markets. Two forms of ‘electricity carbon leakage’ are identified and further supported by legal evidence and practical cases. Moreover, the article assesses the environmental and economic implications for the EU of potential linkage between the world’s two largest ETSs. In response, policy suggestions are proposed to address electricity carbon leakage, differentiating leakage according to its sources.

Key policy insights

• Electricity carbon leakage in China remains a serious issue that has yet to receive sufficient attention.

• Such leakage arises from the current electricity/carbon regulatory framework in China and jeopardizes mitigation efforts.

• With the US retreat on climate efforts, evidence suggests that EU officials are looking to China and expect an expanded carbon market to reinforce EU global climate leadership.

• Given that the Chinese ETS will be twice the size of the EU ETS, a small amount of carbon leakage in China could have significant repercussions. Electricity carbon leakage should thus be considered in any future EU–China linking negotiations.

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Large-scale modes impact on Iraq climate variability     

Jasim?Al-KhalidiEmail author  Mihai?Dima  Sabina?Stefan 《Theoretical and Applied Climatology》2018,133(1-2):179-190

The impact of large-scale modes on Iraq climate is investigated here based on winter and spring fields of temperature and precipitation. The temperature data (1971–2010) was recorded at 8 stations whereas the precipitation fields (1981–2010) were recorded at 18 locations. Empirical orthogonal function analyses were performed in order to characterize the spatial variability of the Iraq climatological parameters. The relationships between the global sea surface temperature, sea level pressure, and geopotential height fields with the dominant modes of Iraq temperature and precipitation were also investigated. Correlation and regression maps emphasize links between Iraq climate and large-scale modes, like the Atlantic Multidecadal Oscillation and the El Niño Southern Oscillation phenomenon.  相似文献   

Groundwater recharge,flow and hydrogeochemical evolution in a complex volcanic aquifer system,central Ethiopia     

Molla Demlie  Stefan Wohnlich  Frank Wisotzky  Birhanu Gizaw 《Hydrogeology Journal》2007,15(6):1169-1181

Hydrochemical, multivariate statistical and inverse hydrogeochemical modeling techniques were used to investigate groundwater recharge, flow and the hydrochemical evolution within the Akaki volcanic aquifer system, central Ethiopia. The hydrochemical and multivariate statistical techniques are mutually supportive and the extracted information was analyzed together with environmental isotope data. Results reveal five spatial groundwater zones with defined hydrochemical facies, residence times, stable isotopic signals and hydrochemical evolution. These zones are designated as the (1) Intoto, (2) central, (3) Filwuha fault, (4) south zones and (5) a highly polluted sub-sector identified within the central zone. Both the hydrochemical and multivariate statistical analyses have shown the central sub-sector as being spite of differentially polluted by , Cl⁻ and and its tritium content shows recent recharge. Due to the fact that the main recharge source is precipitation, the hydrochemical and environmental isotope data clearly indicated that the central and southern sectors are also recharged from domestic waste water and leakage from water mains and reservoirs. Inverse hydrogeochemical modeling demonstrated reactions of silicate minerals in a CO₂ open system and precipitation of kaolinite, chalcedony, and rare calcite satisfy the observed change in water chemistry from north to south following the regional flow direction.

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Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.

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Résumé Des techniques relevant de l’hydrochimie, des statistiques multivariées et de la modélisation inverse hydrogéochimique, ont été utilisées dans le cadre de l’étude de la recharge des eaux souterraines, de l’écoulement et de l’évolution hydrochimique dans le système volcanique aquifère d’Akaki au centre de l’Ethiopie. Les techniques hydrochimiques et multivariées se supportent mutuellement et l’information extraite a été analysée avec les données isotopiques environnementales, des temps de résidence, des signaux isotopiques stables et une évolution hydrochimique. Ces zones ont été désignées comme le (1) Intoto, (2) le centre, (3) la faille de Filwuha, (4) les zones sud et (5) un sous-secteur fortement pollué identifié dans la zone centrale. Les analyses statistiques hydrochimiques et multivariées ont montré que le sous-secteur central a été différemment pollué par , Cl⁻ et , tandis que la teneur en tritium montre une recharge récente. Malgré le fait que la principale source de recharge soit les précipitations, les données hydrochimiques et isotopiques indiquent clairement que les secteurs centres et sud sont également rechargés par les eaux usées domestiques et les fuites de réservoirs et canalisations d’eau. La modélisation hydrogéochimique inverse a démontré les réactions des minéraux silicatés dans un système ouvert au CO₂, et la précipitation de kaolinite, de calcédoine, et la rareté de la calcite satisfont les changements observés dans la chimie de l’eau du nord vers le sud en suivant la direction régionale de l’écoulement.

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Resumen Se utilizaron la hidroquímica y técnicas de modelación hidrogeoquímica inversa y estadística multivariada, para investigar la recarga del agua subterránea, el flujo y la evolución hidroquímica, dentro del sistema acuífero volcánico Akaki, Etiopía Central. La hidroquímica y las técnicas estadísticas multivariadas se complementan entre si y la información así extraída se analizó junto con los datos de isótopos ambientales. Los resultados revelan cinco zonas diferentes de agua subterránea, con facies hidroquímicas, tiempos de residencia, improntas isotópicas estables y una evolución hidroquímica definidas. Estas zonas se designan como (1) Intoto, (2) Central, (3) Falla de Filwuha, (4) las Zonas del sur y (5) un sub-sector altamente contaminado identificado dentro de la zona central. Tanto los análisis estadísticos multivariados como la hidroquímica, han mostrado al sub-sector central como contaminado diferencialmente por , Cl⁻ y y su contenido de tritio muestra una recarga reciente. A pesar del hecho que la fuente principal de recarga es la precipitación, los datos de hidroquímica y de isótopos ambientales indican que los sectores central y del sur, también se recargan a partir de agua doméstica usada y del goteo de las conducciones del acueducto y de sus reservorios. El modelamiento hidrogeoquímico inverso demostró reacciones de minerales silicatados en un sistema de CO₂ abierto, y la precipitación de caolinita, calcedonia, y rara vez de calcita, satisfacen el cambio observado en la química de agua del norte a sur, siguiendo la dirección del flujo regional.

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