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811.
Bayet-Goll Aram Esfahani Fariba Shirezadeh Daraei Mehdi Monaco Paolo Sharafi Mahmoud Mohammadi Amir Akbari 《International Journal of Earth Sciences》2018,107(6):2233-2263
International Journal of Earth Sciences - The Tournaisian–Visean carbonate successions of the Esfahan–Sirjan Basin (ESB) from Sanandaj–Sirjan Zone, Iran, have been used to... 相似文献
812.
Trophic levels (TLs) of fish were estimated on three sampling dates (March, May, and August 2006) for different fish sizes in the Cabras Lagoon (Sardinia, Italy). A temporal TL variation for Atherina boyeri, Gobius niger, and Engraulis encrasicolus was observed. In March and May, the TL ranged from 3.3 to 3.4, characterizing these species as secondary consumers, while in August, this range moved to between 3.7 and 3.8, indicating a TL shift towards tertiary consumers. For Liza ramada, TL was consistently lower in small individuals (mean TL 2.5) than in larger individuals (mean TL 3.0). Increased TL of the fish species A. boyeri, G. niger, and E. encrasicolus in August was consistent with the seasonal changes in the macrobenthic assemblage in this system, with a dominance of primary consumers (benthic deposit feeders) in winter–spring and a dominance of secondary consumers (the nereidids Alitta succinea and Hediste diversicolor) in summer. These fish species took advantage of the high availability of nereidids leading to a rise in their TL values. Furthermore, the increase of TL with size of L. ramada, the most economically valuable fish species in the Cabras Lagoon, indicated an ontogenetic diet shift, the juveniles being omnivorous, while the adults being secondary consumers. We conclude that variability in the trophic levels of fish due to species traits, ontogenetic diet shifts, and variation in prey availability should be taken into account to further understand the food web structure of coastal lagoons. 相似文献
813.
Paolo Davini Chiara Cagnazzo Pier Giuseppe Fogli Elisa Manzini Silvio Gualdi Antonio Navarra 《Climate Dynamics》2014,43(1-2):71-85
The relationship between atmospheric blocking over Europe and the Atlantic eddy-driven jet stream is investigated in the NCEP/NCAR Reanalysis and in a climate model. This is carried out using a bidimensional blocking index based on geopotential height and a diagnostic providing daily latitudinal position and strength of the jet stream. It is shown that European Blocking (EB) is not decoupled from the jet stream but it is mainly associated with its poleward displacements. Moreover, the whole blocking area placed on the equatorward side of the jet stream, broadly ranging from Azores up to Scandinavia, emerges as associated with poleward jet displacements. The diagnostics are hence applied to two different climate model simulations in order to evaluate the biases in the jet stream and in the blocking representation. This analysis highlights large underestimation of EB, typical feature of general circulation models. Interestingly, observed blocking and jet biases over the Euro-Atlantic area are consistent with the blocking-jet relationship observed in the NCEP/NCAR Reanalysis. Finally, the importance of sea surface temperatures (SSTs) is investigated showing that realistic SSTs can reduce the bias in the jet stream variability but not in the frequency of EB. We conclude highlighting that blocking-related diagnostics can provide more information about the Euro-Atlantic variability than diagnostics simply based on the Atlantic jet stream. 相似文献
814.
The Bündnerschiefer of the Swiss-Italian Alps is a large sedimentary complex deposited on the Piemonte–Liguria and Valais oceans and associated continental margins from the upper Jurassic to Eocene. It is made of a large variety of sequences associated or not with an ophiolitic basement. The Bündnerschiefer makes an accretionary prism that developed syn-tectonically from the onset of alpine subduction, and it records orogenic metamorphism following episodes of HP metamorphism. The Bündnerschiefer shares important similarities with the Otago schists of New Zealand and with the Wepawaug schists of Connecticut, both of which form accretionary prisms and have an orogenic metamorphic imprint.With the aim of testing the hypothesis of mobility of chemical components as a function of metamorphic grade, in this work I present fifty-five bulk chemical analyses of various lithological facies of the Bündnerschiefer collected along the well-studied field gradient of the Lepontine dome of Central Switzerland, in the Prättigau half window of East Switzerland, and in the Tsaté Nappe of Valle d'Aosta (Italy). The dataset includes the concentration of major components, large ion lithophile elements (Rb, Sr, Ba, Cs), high field strength elements (Zr, Ti, Nb, Th, U, Ta, Hf), fluid-mobile light elements (B, Li), volatiles (CO2, S), REEs, and Y, V, Cr, Co, Sn, Pb, Cu, Zn, Tl, Sb, Be, and Au. These data are compared against the compositions of the global marine sediment reservoir, typical crustal reservoirs, and against the previously measured compositions of Otago and Wepawaug schists. Results reveal that, irrespective of their metamorphic evolution, the bulk chemical compositions of orogenic metasediments are characterized by mostly constant compositional ratios (e.g., K2O/Al2O3, Ba/Al2O3, Sr/CaO, etc.), whose values in most cases are undistinguishable from those of actual marine sediments and other crustal reservoirs. For these rocks, only volatile concentrations decrease dramatically as a function of metamorphic temperature, and significant deviations from the reservoir signatures are evident for SiO2, B, and Li. These results are interpreted as an indication of residual enrichment in the sediments, a process taking place during syn-metamorphic dehydration from the onset of metamorphism in a regime of chemical immobility. Residual enrichment increased the absolute concentrations of the chemical components of these rocks, but did not modify significantly their fundamental ratios. This poor compositional modification of the sediments indicates that orogenic metamorphism in general does not promote significant mass transfer from accretionary prisms. In contrast, mass transfer calculations carried out in a shear zone crosscutting the Bündnerschiefer shows that significant mass transfer occurs within these narrow zones, resulting in gains of H2O, SiO2, Al2O3, K2O, Ba, Y, Rb, Cu, V, Tl, Mo, and Ce during deformation and loss of Na2O, CO2, S, Ni, B, U, and Pb from the rock. These components were presumably transported by an aquo-carbonic fluid along the shear zone. These distinct attitudes to mobilize chemical elements from orogenic sediments may have implications for a potentially large number of geochemical processes in active continental margins, from the recycling of chemical components at plate margins to the genesis of hydrothermal ore deposits. 相似文献
815.
816.
Thermal behaviour of liottite, the ABABAC six-layer member of the cancrinite-sodalite supergroup, has been investigated in
situ real-time using laboratory parallel-beam X-ray powder diffraction data. Thermal expansion has been analysed from 323 to 1,223 K with
temperature steps of 25 K. Dependence of the hexagonal cell parameters from temperature indicates a different behaviour with
respect to afghanite, an ABABACAC eight-layer member of the supergroup. Three different regimes were observed, the last coincident
with the starting of the conversion of liottite to haüyne (prevailing) and leucite-HT (minor). A smaller thermal expansion
as compared to afghanite was observed. Isothermal annealing at 1,173 K led to a more extended conversion to haüyne, an a-parameter contraction, and a c-parameter expansion with respect to the starting RT cell parameters. 相似文献
817.
Excavation of the Aica-Mules pilot tunnel for the Brenner base tunnel: information gained on water inflows in tunnels in granitic massifs 总被引:1,自引:1,他引:0
Paolo Perello Alessandro Baietto Ulrich Burger Stefan Skuk 《Rock Mechanics and Rock Engineering》2014,47(3):1049-1071
The construction of the Aica-Mules tunnel, completed in 2010, provides a relevant case history for improving the knowledge of hydrogeological issues related to the excavation of deep tunnels in granitic massifs. The Aica-Mules tunnel is a 10 km-long structure, forming part of the high-speed railway connection between Austria and Italy across the Alpine chain, located at an average depth of 500–1,000 m below the surface. Prior to and during the construction, intense hydrogeological monitoring was set up, allowing the collection of abundant data concerning: (1) the evolution of water inflows into the tunnel; (2) the chemistry and temperature of drained groundwater; and (3) the influence of tunnel drainage on springs. Based on detailed analysis of geological/hydrogeological data, this article provides an insight into the permeability distribution in granitic rocks affected by relevant brittle tectonic deformation, and the consequences of water inflow during excavation. The available time series from the principal water discharges in the tunnel have been used in order to test the reliability of some of the most commonly applied analytical methods for the forecast of water inflows into tunnels. 相似文献
818.
Fatemeh Jalayer Raffaele De Risi Francesco De Paola Maurizio Giugni Gaetano Manfredi Paolo Gasparini Maria Elena Topa Nebyou Yonas Kumelachew Yeshitela Alemu Nebebe Gina Cavan Sarah Lindley Andreas Printz Florian Renner 《Natural Hazards》2014,73(2):975-1001
Identifying urban flooding risk hotspots is one of the first steps in an integrated methodology for urban flood risk assessment and mitigation. This work employs three GIS-based frameworks for identifying urban flooding risk hotspots for residential buildings and urban corridors. This is done by overlaying a map of potentially flood-prone areas [estimated through the topographic wetness index (TWI)], a map of residential areas and urban corridors [extracted from a city-wide assessment of urban morphology types (UMT)], and a geo-spatial census dataset. A maximum likelihood method (MLE) is employed for estimating the threshold used for identifying the flood-prone areas (the TWI threshold) based on the inundation profiles calculated for various return periods within a given spatial window. Furthermore, Bayesian parameter estimation is employed in order to estimate the TWI threshold based on inundation profiles calculated for more than one spatial window. For different statistics of the TWI threshold (e.g. MLE estimate, 16th percentile, 50th percentile), the map of the potentially flood-prone areas is overlaid with the map of urban morphology units, identified as residential and urban corridors, in order to delineate the urban hotspots for both UMT. Moreover, information related to population density is integrated by overlaying geo-spatial census datasets in order to estimate the number of people affected by flooding. Differences in exposure characteristics have been assessed for a range of different residential types. As a demonstration, urban flooding risk hotspots are delineated for different percentiles of the TWI value for the city of Addis Ababa, Ethiopia. 相似文献
819.
A deep-seated slow movement controlled by structural setting in marly formations of Central Italy 总被引:1,自引:1,他引:0
The site investigation of low-gradient slopes composed by marly rocks usually focuses on shallow slides in weathered mantling material as it is assumed that the underlying bedrock has higher strength, but deeper investigations may reveal larger, active, deep-seated movements. A typical example of this is found in Montemartano (Perugia, Central Italy). Here aerial photo interpretation and field observations indicate that active movements involve the shallower portion of the slope, formed by a very old and large landslide body extending over an area of about 0.5 km2. Borehole core logging and probe inclinometer monitoring reveal that the area corresponding to the deep-seated landslide is moving at a maximum rate of 70 mm/year down to a maximum depth of 40 m. A comparison of inclinometer and piezometer data indicates that the movement seasonally reactivates even when rainfall and piezometer levels are below average values and suggests that structural setting of the whole slope influences both groundwater flow and movement kinematics. This hypothesis is reinforced by seepage analyses and stability analyses yielding a mobilized shear strength close to residual strength of the clayey interbeds of the marly limestone formations. This implies that instability occurs along bedding over a large part of the slide. The importance of these phenomena in land management policy is discussed and the critical aspects of their investigation and monitoring are addressed. The reconstruction of landslide geometry/stratigraphy and geotechnical characterization of the materials is closely considered, particularly as these are complicated by the limited representativeness of field and laboratory investigations in this type of material. 相似文献
820.
Landslide susceptibility assessment in Apulian Southern Apennine: heuristic vs. statistical methods 总被引:2,自引:1,他引:1
Roberta Pellicani Paolo Frattini Giuseppe Spilotro 《Environmental Earth Sciences》2014,72(4):1097-1108
In this paper, a bivariate-heuristic model (modified Stevenson’s method) and two multivariate statistical procedures (discriminant analysis and logistic regression) were used in order to assess and map landslide susceptibility in the north-western side of Daunia region (Apulia, Southern Italy). The whole Daunia region is characterized by complex and composite landslides, which are located on clayey slopes, near urban centers, affecting structures and infrastructures. The high predisposition to landsliding of the Daunia hillslopes is related to the very poor strength properties of clayey formations. The comparative analysis of landslide susceptibility using different methods, on the same test site and with the same inventory map allowed understanding the dependence of the results from the dataset and the capability of models under different levels of use, from expert to simple operator. By comparing the performance of the three models through the success rate curves, it emerges that the simple modified Stevenson’s method produces reliable outcomes, comparable with those deriving from more complex multivariate statistical models. This result is related to the characteristics of clayey slopes, in which the landslide occurrence is so much controlled by the poor strength properties of the clayey formations that the multivariate analysis of a large set of morphometric, geological and land-use variables results to be somehow superfluous. This suggests that, for clayey slopes, a simple, easy-to-manage bivariate-heuristic model based on expert opinion can be used with reliable results. 相似文献