Experiences of a “semantics smackdown”     

Adam M. Leadbetter  Adam Shepherd  Robert Arko  Cynthia Chandler  Yanning Chen  Nkemdirim Dockery  Renata Ferreira  Linyun Fu  Robert Thomas  Patrick West  Stephan Zednik 《Earth Science Informatics》2016,9(3):355-363

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Instrumental neutron activation analysis,gamma spectrometry and geographic information system techniques in the determination and mapping of rare earth element in phosphogypsum stacks     

Renata Coura Borges  Déborah Inês Teixeira Fávaro  Vanessa Godoy Caldas  Dejanira da Costa Lauria  Alfredo Victor Bellido Bernedo 《Environmental Earth Sciences》2016,75(8):705

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The role of life‐history traits,selective pressure and hydrographic boundaries in shaping the genetic structure of the transparent goby,Aphia minuta          下载免费PDF全文

Paolo Ruggeri  Andrea Splendiani  Massimo Giovannotti  Tatiana Fioravanti  Giulia Occhipinti  Paola Nisi Cerioni  Vincenzo Caputo Barucchi 《Marine Ecology》2016,37(3):518-531

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530 Ma syntectonic syenites and granites in NW Namibia — Their relation with collision along the junction of the Damara and Kaoko belts     

Renata S. Schmitt  Rudolph A.J. Trouw  Cees W. Passchier  Silvia R. Medeiros  Richard Armstrong 《Gondwana Research》2012,21(2-3):362-377

The Lower Ugab and Goantagab structural domains are located at the junction between the N–S trending Kaoko and the E–W trending Damara belts (NW Namibia), where Neoproterozoic metavolcano-sedimentary sequences were intruded by several syenitic/granitic plutons. We present here new U–Pb ages on zircon grains from the Voetspoor and Doros plutons. Together with petrological, geochemical and structural data we evaluate the timing of the deformation and relation to the geodynamics during the final stage of Gondwana amalgamation.The plutons are composed of three main rock types: hornblende quartz-syenite, syenodiorite and biotite granite. The two former are predominant and show genetic correlation such as magma mingling structures and similar geochemical signatures. The biotite granite occurs in the SW parts of the intrusions and clearly cuts the syenitic rocks. Although the plutons are mainly isotropic, the structures around them demonstrate that their intrusion occurred during a second deformation phase (D2) with a component of sinistral solid state rotation with respect to the wall rocks in response to D2 transpression. Four samples were dated using U–Pb SHRIMP methodology in single zircon grains. A hornblende monzodiorite from the Voetspoor pluton yielded an age of 534 ± 4.5 Ma. A hornblende monzonite from the Doros pluton produced an age of 528 ± 5 Ma. The biotite granite facies was sampled in the Doros intrusion and yielded an age of 530 ± 4.5 Ma. In addition, a granitic vein folded by D2 close to the northeastern contact of the Doros pluton with the encasing phyllites (Amis River Formation) was also dated, yielding an age of 533 ± 6 Ma. The data show that all granite–syenite from Doros and Voetspoor intrusions are contemporaneous and crystallized in the period between 539 and 522 Ma within the errors. D1–D2 deformational phases took place under greenschist facies (biotite zone) conditions and during D3 the metamorphic grade was slightly lower. We interpret that the plutons are coeval to peak metamorphism of the region (530–520 Ma) and that D2 and D3 sinistral transpressional phases are due to collision in the Damara Belt. The E–W compressional event and second metamorphic episode in the Kaoko Belt occurred between 580 and 560 Ma and are apparently unrelated to the thermo-tectonic evolution described here, although D1 might be partially related to this event. The sinistral transpressional D2 phase resulted probably from the position of the area considered at the junction between the belts, and not in the frontal Damara collision further to the east. This new interpretation is consistent with the Ar–Ar ages for the region (about 500 Ma), interpreted to reflect cooling of the orogen. The enrichment in LREE, K, Rb, Ba and Sr, and depletion in Nb of these basic to intermediate alkalic rocks could indicate that they partially derived from melting of a subcontinental lithospheric mantle that was affected by subduction and the granitic rock types represent lower crust contamination. We interpret that they could be related to heating in the mantle caused by asthenosphere influx in a zone of slab-breakoff during collision between Kalahari and Congo cratons.  相似文献   

Fecal Sterols in Estuarine Sediments as Markers of Sewage Contamination in the Cubat?o Area, S?o Paulo, Brazil     

Valquíria Campos  Renata Fracácio  Leonardo F. Fraceto  André H. Rosa 《Aquatic Geochemistry》2012,18(5):433-443

Sterol biomarkers serve as an alternative method for detecting sewage pollution. Sterols were extracted from samples of surface sediment collected in Cubat?o (the Vila dos Pescadores and Vila Esperan?a communities) and quantified using GC–MS after Soxhlet extraction, cleanup, and derivatization. Fecal contamination was evaluated based on the concentration of coprostanol and the ratio of the selected sterols. The most abundant sterol was cholestanol, followed by coprostanol. The concentrations of coprostanol in surface sediments ranged from a minimum of 4.21?μg?g^?1 dry sediment (Vila dos Pescadores station) to a maximum of 8.32?μg?g^?1 dry sediment (Vila Esperan?a station). A coprostanol concentration of about 10?μg?g^?1 was found, indicating areas of high sewage contamination. Coprostanol levels at sewage stations were higher than in other Brazilian coastal areas, which may be attributed to the fraction of the population without sanitation services.  相似文献   

Geomorphic features extraction from high-resolution topography: landslide crowns and bank erosion   总被引：5，自引：0，他引：5  

Paolo Tarolli  Giulia Sofia  Giancarlo Dalla Fontana 《Natural Hazards》2012,61(1):65-83

In recent years, new remote-sensed technologies, such as airborne and terrestrial laser scanner, have improved the detail and the quality of topographic information, providing topographical high-resolution and high-quality data over larger areas better than other technologies. A new generation of high-resolution (≤3 m) digital terrain models (DTMs) is now available for different areas and is widely used by researchers, offering new opportunities for the scientific community. These data call for the development of a new generation of methodologies for an objective extraction of geomorphic features, such as channel heads, channel networks, bank geometry, debris-flow channel, debris-flow deposits, scree slope, landslide and erosion scars, etc. A high-resolution DTM is able to detect the divergence/convergence of areas related to unchannelized/channelized processes with better detail than a coarse DTM. In this work, we tested the performance of new methodologies for an objective extraction of geomorphic features related to shallow landsliding processes (landslide crowns), and bank erosion in a complex mountainous terrain. Giving a procedure that automatically recognizes these geomorphic features can offer a strategic tool to map natural hazard and to ease the planning and the assessment of alpine regions. The methodologies proposed are based on the detection of thresholds derived by the statistical analysis of variability of landform curvature. The study was conducted on an area located in the Eastern Italian Alps, where an accurate field survey on shallow landsliding, erosive channelized processes, and a high-quality set of both terrestrial and airborne laser scanner elevation data is available. The analysis was conducted using a high-resolution DTM and different smoothing factors for landform curvature calculation in order to test the most suitable scale of curvature calculation for the recognition of the selected features. The results revealed that (1) curvature calculation is strongly scale-dependent, and an appropriate scale for derivation of the local geometry has to be selected according to the scale of the features to be detected; (2) such approach is useful to automatically detect and highlight the location of shallow slope failures and bank erosion, and it can assist the interpreter/operator to correctly recognize and delineate such phenomena. These results highlight opportunities but also challenges in fully automated methodologies for geomorphic feature extraction and recognition.  相似文献   

A constitutive model for granular materials with grain crushing and its application to a pyroclastic soil     

Manuela Cecconi  Antonio DeSimone  Claudio Tamagnini  Giulia M.B. Viggiani 《国际地质力学数值与分析法杂志》2002,26(15):1531-1560

A constitutive model for granular materials is developed within the framework of strain–hardening elastoplasticity, aiming at describing some of the macroscopic effects of the degradation processes associated with grain crushing. The central assumption of the paper is that, upon loading, the frictional properties of the material are modified as a consequence of the changes in grain size distribution. The effects of these irreversible microscopic processes are described macroscopically as accumulated plastic strain. Plastic strain drives the evolution of internal variables which model phenomenologically the changes of mechanical properties induced by grain crushing by controlling the geometry of the yield locus and the direction of plastic flow. An application of the model to Pozzolana Nera is presented. The stress–dilatancy relationship observed for this material is used as a guidance for the formulation of hardening laws. One of the salient features of the proposed model is its capability of reproducing the stress–dilatancy behaviour observed in Pozzolana Nera, for which the minimum value of dilatancy always follows the maximum stress ratio experienced by the material. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Structural features and mechanical behaviour of a pyroclastic weak rock     

Manuela Cecconi  Giulia MB Viggiani 《国际地质力学数值与分析法杂志》2001,25(15):1525-1557

The results of an extensive programme of laboratory testing on intact and reconstituted samples of a pyroclastic weak rock from the volcanic complex of the Colli Albani (Central Italy) are presented. The deposit is known as Pozzolana Nera and may be assimilated to a bonded coarse grained material. The nature of bonds and the micro‐structural features were examined by means of diffractometry, optical and electron microscopy. As bonds are made of the same constituents of grains and aggregates of grains, bond deterioration and particles breakage upon loading are indistinguishable features of the mechanical behaviour. The testing programme consisted mainly of one‐dimensional and drained and undrained triaxial compression tests in a wide range of confining pressures up to 58 MPa. As confining stress increases, the mechanical behaviour of the material changes from brittle and dilatant to ductile and contractant; for both brittle and ductile behaviour failure is associated with the formation of shear surfaces separating the sample in several parts at the end of test. The experimental stress–dilatancy relationships are compared with the classical stress–dilatancy theories for a purely frictional material and for a material with friction and cohesion between particles. The analysis of the data indicates that peak strength results from the interplay between degradation of inter‐particle bonds, increasing friction between particles and increasing rate of dilation. Copyright © 2001 John Wiley & Son, Ltd.  相似文献   

UAV RGB,thermal infrared and multispectral imagery used to investigate the control of terrain on the spatial distribution of dryland biocrust     

Javier Blanco-Sacristán  Cinzia Panigada  Rodolfo Gentili  Giulia Tagliabue  Roberto Garzonio  M. Pilar Martín  Mónica Ladrón de Guevara  Roberto Colombo  Thomas P. F. Dowling  Micol Rossini 《地球表面变化过程与地形》2021,46(12):2466-2484

Biocrusts (topsoil communities formed by mosses, lichens, bacteria, fungi, algae, and cyanobacteria) are a key biotic component of dryland ecosystems. Whilst climate patterns control the distribution of biocrusts in drylands worldwide, terrain and soil attributes can influence biocrust distribution at landscape scale. Multi-source unmanned aerial vehicle (UAV) imagery was used to map and study biocrust ecology in a typical dryland ecosystem in central Spain. Red, green and blue (RGB) imagery was processed using structure-from-motion techniques to map terrain attributes related to microclimate and terrain stability. Multispectral imagery was used to produce accurate maps (accuracy > 80%) of dryland ecosystem components (vegetation, bare soil and biocrust composition). Finally, thermal infrared (TIR) and multispectral imagery was used to calculate the apparent thermal inertia (ATI) of soil and to evaluate how ATI was related to soil moisture (r² = 0.83). The relationship between soil properties and UAV-derived variables was first evaluated at the field plot level. Then, the maps obtained were used to explore the relationship between biocrusts and terrain attributes at ecosystem level through a redundancy analysis. The most significant variables that explain biocrust distribution are: ATI (34.4% of variance, F = 130.75; p < 0.001), Elevation (25.8%, F = 97.6; p < 0.001), and potential solar incoming radiation (PSIR) (52.9%, F = 200.1; p < 0.001). Differences were found between areas dominated by lichens and mosses. Lichen-dominated biocrusts were associated with areas with high slopes and low values of ATI, with soil characterized by a higher amount of soluble salts, and lower amount of organic carbon, total phosphorus (P_tot) and total nitrogen (N_tot). Biocrust-forming mosses dominated lower and moister areas, characterized by gentler slopes and higher values of ATI with soils with higher contents of organic carbon, P_tot and N_tot. This study shows the potential to use UAVs to improve our understanding of drylands and to evaluate the control that the terrain has on biocrust distribution.  相似文献   

Analysis of the effects of different storm events on shoreline dynamics of an artificially embayed beach     

Renata Archetti  Claudia Romagnoli 《地球表面变化过程与地形》2011,36(11):1449-1463

A five‐year dataset of Argus‐derived mean intertidal positions has been analysed to characterize the shoreface variability in a beach protected by a system of groynes and a parallel low crested structure (Lido di Dante Ravenna, Italy). For the period 2004–2009, 84 intertidal beach bathymetries and shorelines at the zero sea level were used as indicators to assess beach changes in between a number of selected surveys and to determine characteristic patterns of the beach response to storm events from different directions. Variations in the shoreline at the zero sea levels have been quantified and analysed in conjunction with nearshore wave conditions and provenance linked to storm events. These fall into two categories: (1) storm events occurring during Bora (north‐eastern) wind conditions and (2) storm events occurring during Scirocco (south‐eastern) wind conditions. The results show that, apart from main beach advances of the whole protected beach due to nourishments periodically carried out, a marked variability is observed among the four sub‐cells into which the shoreface behaviour has been separately analysed. In particular, a dependence of beach rotation in the ‘artificially embayed’ area on the substantially bi‐directional wave climate has been shown: Bora and Scirocco storm events produce shoreline rotation in counterclockwise and clockwise directions, respectively, due to the occurrence of longshore currents in the opposite direction in the nearshore. An attempt was made to correlate the shoreface dynamics for the main rotation events (14 selected ones) to the wave attack intensity (as the total energy flux due to storm events). A relationship seems to occur (for each storm category) between the shoreline displacements estimated for each sub‐cell and the total energy flux computed for inter‐survey periods, supporting the occurrence of a link between the observed morphological changes and the hydrodynamic forcing associated with storm events in the five‐year monitoring period. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献