Modelling the extension of heterogeneous hot lithosphere   总被引：2，自引：0，他引：2  

Dimitrios Sokoutis  Giacomo Corti  Marco Bonini  Jean Pierre Brun  Sierd Cloetingh  Thomas Mauduit  Piero Manetti 《Tectonophysics》2007,444(1-4):63-79

The consequences of weak heterogeneities in the extension of soft and hot lithosphere without significant previous crustal thickening has been analysed in a series of centrifuge models. The experiments examined the effects of i) the location of heterogeneities in the ductile crust and/or in the lithospheric mantle, and ii) their orientation, perpendicular or oblique to the direction of bulk extension. The observed deformation patterns are all relevant to the so-called “wide rifting” mode of extension. Weak zones located in the ductile crust exert a more pronounced influence on localisation of deformation in the brittle layer than those located in the lithospheric mantle: the former localise faulting in the brittle crust whereas the latter tend to distribute faulting over a wider area. This latter behaviour depends in turn upon the decoupling provided by the ductile crust. Localised thinning in the brittle crust is accompanied by ductile doming of both crust and mantle. Domains of maximum thinning in the brittle crust and ductile crust and mantle are in opposition. Lateral differences in brittle crust thinning are accommodated by lateral flow in the ductile crust and mantle. This contrasts with “cold and strong” lithospheres whose high strength sub-Moho mantle triggers a necking instability at the lithosphere-scale. This also differs from the extension of thickened hot and soft lithospheres whose ductile crust is thick enough to give birth to metamorphic core complexes. Thus, for the given lithospheric rheology, the models have relevance to backarc type extensional systems, such as the Aegean and the Tyrrhenian domains.  相似文献   

Fluidization and de-aeration of pyroclastic mixtures: The influence of fines content,polydispersity and shear flow     

Piero Bareschino  Teresita Gravina  Lucio Lirer  Antonio Marzocchella  Paola Petrosino  Piero Salatino 《Journal of Volcanology and Geothermal Research》2007

Fluidization of pyroclastic solids has long been indicated as one key to explain the enhanced mobility of dense pyroclastic gravity currents and their associated hazard. However there is a lack of characterization of the actual pattern and extent of fluidization establishing in real pyroclastic flows and some authors still raise arguments about the relevance of fluidization to the mobility of dense pyroclastic gravity currents. The present paper addresses the fluidization of pyroclastic granular solids with a specific focus on the analysis of factors that may promote homogeneous fluidization and retard solids de-aeration and consolidation. These factors include fines content, particle polydispersity and the establishment of shear flow.  相似文献   

Local Habitat and Seascape Structure Influence Seagrass Fish Assemblages in the Venice Lagoon: The Importance of Conservation at Multiple Spatial Scales     

Luca Scapin  Matteo Zucchetta  Adriano Sfriso  Piero Franzoi 《Estuaries and Coasts》2018,41(8):2410-2425

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Distribution of the geochemical signature caused by the 2011 Tohoku-oki tsunami in Misawa harbor,northern Japan     

Frenken  Mike  Bellanova  Piero  Nishimura  Yuichi  Reicherter  Klaus  Schwarzbauer  Jan 《Natural Hazards》2022,114(1):313-333

Natural Hazards - The 2011 Tohoku-oki tsunami left a characteristic geochemical signature in the sediments of the Misawa harbor on the Aomori coastline (northern Japan), not only in vertical...  相似文献   

Effect of two different habitats on spine and gonad colour in the purple sea urchin Paracentrotus lividus          下载免费PDF全文

Piero Addis  Davide Moccia  Marco Secci 《Marine Ecology》2015,36(2):178-184

This study investigates the effect of different Mediterranean habitats on spine and gonad colouring and gonadal index in the purple sea urchin Paracentrotus lividus (Echinodermata: Echinoidea). Specimens were collected in winter 2012 in Posidonia oceanica meadows and rocky bottom areas at two sites in Southern Sardinia (Italy, Tyrrhenian Sea). Colorimetric analyses of spines and gonads were conducted with a digital colorimeter using CIELAB colour spaces, which defines the colour in terms of three coordinate values: lightness (L*), redness (a*) and yellowness (b*). Lightness and redness of the spines differed significantly between habitats, whereas colour spaces of the gonads did not. A careful analysis of the gonad index showed it to be significantly affected by habitat, registering higher values in rocky bottom locations. In conclusion, it seems that habitat does affect spine colour but not gonad colour. Spine colour seems to be site‐dependent, whereas the gonad index depends solely on the habitat.  相似文献   

Detection of leaf structures in close-range hyperspectral images using morphological fusion     

Gladys Villegas  Wenzhi Liao  Ronald Criollo  Wilfried Philips  Daniel Ochoa 《地球空间信息科学学报》2017,20(4):325-332

Abstract

Close-range hyperspectral images are a promising source of information in plant biology, in particular, for in vivo study of physiological changes. In this study, we investigate how data fusion can improve the detection of leaf elements by combining pixel reflectance and morphological information. The detection of image regions associated to the leaf structures is the first step toward quantitative analysis on the physical effects that genetic manipulation, disease infections, and environmental conditions have in plants. We tested our fusion approach on Musa acuminata (banana) leaf images and compared its discriminant capability to similar techniques used in remote sensing. Experimental results demonstrate the efficiency of our fusion approach, with significant improvements over some conventional methods.  相似文献   

A habitat-specific fish-based approach to assess the ecological status of Mediterranean coastal lagoons   总被引：1，自引：0，他引：1  

Anita Franco  Patrizia Torricelli  Piero Franzoi 《Marine pollution bulletin》2009,58(11):1704-1717

A habitat approach was promoted in the framework of ecological status assessment of transitional waters, assuming the importance of habitat heterogeneity to the overall system status. The approach was applied to the use of fish-based multimetric indices by adapting them to seagrass and marsh habitats in the Venice lagoon, Italy, through selection of appropriate metrics and reference conditions. While for marsh habitats, no clear patterns resulted, the index response for seagrass was consistent with the habitat degradation and loss recorded in the lagoon between 2002 and 2005 and with the higher habitat disturbance in southern and central lagoon sub-basins. The assessment of individual habitats is presented as a first step in the process of evaluating the overall condition of a Mediterranean lagoon environment, which should also take account of the diversity of habitats and their availability within the system to properly define an overall index of ecological status.  相似文献   

Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley,O‘ahu,Hawai‘i     

Piero Bellanova  Mike Frenken  Bruce Richmond  Jan Schwarzbauer  Seanpaul La Selle  Frances Griswold  Bruce Jaffe  Alan Nelson  Klaus Reicherter 《Sedimentology》2020,67(3):1230-1248

Far-field tsunami deposits observed in the Kahana Valley, O‘ahu, Hawai‘i (USA), were investigated for their organic-geochemical content. During short high-energy events, (tsunamis and storms) organic and chemical components are transported with sediment from marine to terrestrial areas. This study investigates the use of anthropogenic based organic geochemical compounds (such as polycyclic aromatic hydrocarbons, pesticides and organochlorides) as a means to identify tsunami deposits. Samples were processed by solid–liquid extraction and analyzed using gas chromatography–mass spectrometry. A total of 21 anthropogenic marker compounds were identified, of which 11 compounds were selected for detailed analysis. Although the tsunami deposits pre-date industrial activity in Hawai‘i by several hundred years, distinct changes were found in the concentrations of anthropogenic marker compounds between sandy tsunami deposits and the surrounding mud/peat layers, which may help in identifying tsunami deposits within cores. As expected, low overall concentrations of anthropogenic markers and pollutants were observed due to the lack of industrial input-sources and little anthropogenic environmental impact at the study site. This geochemical characterization of tsunami deposits shows that anthropogenic markers have significant potential as another high-resolution, multi-proxy method for identifying tsunamis in the sedimentary record.  相似文献   

Viruses and Bacteria in Karst and Fractured Rock Aquifers in East Tennessee,USA   总被引：2，自引：0，他引：2  

Trisha B. Johnson  Larry D. McKay  Alice C. Layton  Sidney W. Jones  Greg C. Johnson  Jennifer L. Cashdollar  Daniel R. Dahling  Leah F. Villegas  G. Shay Fout  Daniel E. Williams  Gary Sayler 《Ground water》2011,49(1):98-110

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Sediment accumulation rates in European lakes since AD 1850: trends,reference conditions and exceedence     

Neil L. Rose  David Morley  Peter G. Appleby  Richard W. Battarbee  Tiiu Alliksaar  Piero Guilizzoni  Erik Jeppesen  Atte Korhola  Jaan-Mati Punning 《Journal of Paleolimnology》2011,45(4):447-468

Sediment accumulation rate (SAR) is an important physical parameter in all lakes and increases have been observed in many over the last c.100 years. This has been ascribed to changes in land-use and land-management causing accelerated catchment soil erosion and an increase in autochthonous organic matter production. The EU Water Framework Directive requires that assessment of biological, hydromorphological and chemical elements of water quality should be based on the degree to which present day conditions deviate from those expected in the absence of significant anthropogenic influence, termed reference conditions. Currently however, the reference condition for sediment accumulation rate for lakes of different types is undefined. To improve our understanding of the controls on SARs we compiled SAR and lake typology data for 207 European lakes derived from ²¹⁰Pb dated cores to assess how rates have changed through time (in 25 year classes) both overall and for lakes of different types. Seventy-one percent of these sediment cores showed surface SARs higher than “basal” (mainly nineteenth century) rates, 11% showed no change while 18% showed a decline. Lakes were then classified into lake-types using four variables: alkalinity (3 classes), altitude (3 classes), maximum depth (2 classes) and lake area (2 classes). This generated a possible 36 lake classes of which 25 were represented in the dataset. Nine lake-types contained >10 lakes. Little change in SAR occurred prior to 1900 and most increases occurred in more recent periods, in particular 1950–1975 and post-1975. This indicates a general acceleration in SAR in European lakes during the second half of the twentieth century. Reference SARs were estimated for six lake-types with the highest number of sites. European mountain lakes had the lowest reference SAR (0.005 ± 0.003 g cm⁻² yr⁻¹) while lowland, high alkalinity sites had the highest (0.03–0.04 g cm⁻² yr⁻¹). SARs for other lake-types ranged between 0.012 and 0.024 g cm⁻² yr⁻¹. Using the mountain lake-type as an example, the 1850 reference SAR appears to show good agreement with available data for lakes beyond Europe indicating these values may be more broadly applicable. Contemporary SARs in lakes of all classes showed exceedence over their defined reference SAR. This may be partly due to diagenetic processes. Greatest exceedences were found in shallow, low altitude lakes and these are considered to be the ones under the greatest threat from continued elevation of SAR. It is considered that climate change may play a progressively more important role in driving SAR in the future.  相似文献