Human influence on seagrass habitat fragmentation in NW Mediterranean Sea     

Monica Montefalcone  Valeriano ParraviciniMatteo Vacchi  Giancarlo AlbertelliMarco Ferrari  Carla MorriCarlo Nike Bianchi 《Estuarine, Coastal and Shelf Science》2010

Habitat fragmentation in meadows of Posidonia oceanica, the most important and abundant seagrass in the Mediterranean Sea, was investigated at a region-wide spatial scale using a synthetic ecological index, the Patchiness Index (PI). We tested the hypothesis that human impacts are the major factor responsible for habitat fragmentation in P. oceanica meadows contrasting fragmentation of meadows located in “anthropized” areas with that of meadows located in areas with low anthropization and considered as virtually “natural”. We also related fragmentation of meadow with the morphodynamic state of the submerged beach (i.e. distinctive types of beach produced by the topography, the wave climate and the sediment composition) in order to investigate the influence of one natural component on the seagrass meadow seascape. Results demonstrated that fragmentation in the P. oceanica meadows is strongly influenced by the human component, being lower in natural meadows than in anthropized ones, and that it is little influenced by the morphodynamic state of the coast. The use of landscape approaches to discriminate natural disturbance from human impacts that affect seagrass meadows is thus recommended for the proper management of coastal zones.  相似文献   

Compound and hybrid clinothems of the last lowstand Mid-Adriatic Deep: Processes,depositional environments,controls and implications for stratigraphic analysis of prograding systems     

Fabiano Gamberi  Claudio Pellegrini  Giacomo Dalla Valle  Daniele Scarponi  Kevin Bohacs  Fabio Trincardi 《Basin Research》2020,32(2):363-377

Clinoforms with a range of scales are essential elements of prograding continental margins. Different types of clinoforms develop during margin growth, depending on combined changes in relative sea level, sediment supply and oceanographic processes. In studies of continental margin stratigraphy, trajectories of clinoform ‘rollover’ points are often used as proxies for relative sea-level variation and as predictors of the character of deposits beyond the shelf-break. The analysis of clinoform dynamics and rollover trajectory often suffers from the low resolution of geophysical data, the small scale of outcrops with respect to the dimensions of clinoform packages and low chronostratigraphic resolution. Here, through high-resolution seismic reflection data and sediment cores, we show how compound clinoforms were the most common architectural style of margin progradation of the late Pleistocene lowstand in the Adriatic Sea. During compound clinoform development, the shoreline was located landward of the shelf-break. It comprised a wave-dominated delta to the west and a barrier and back-barrier depositional system in the central and eastern area. Storm-enhanced hyperpycnal flows were responsible for the deposition of a sandy lobe in the river mouth, whereas a heterolithic succession formed elsewhere on the shelf. The storm-enhanced hyperpycnal flows built an apron of sand on the slope that interrupted an otherwise homogeneous progradational mudbelt. Locally, the late lowstand compound clinoforms have a flat to falling shelf-break trajectory. However, the main phase of shelf-break bypass and basin deposition coincides with a younger steeply rising shelf-break trajectory. We interpret divergence from standard models, linking shelf-break trajectory to deep-sea sand deposition, as resulting from a great efficiency of oceanographic processes in reworking sediment in the shelf, and from a high sediment supply. The slope foresets had a large progradational attitude during the late lowstand sea-level rise, showing that oceanographic processes can inhibit coastal systems to reach the shelf-edge. In general, our study suggests that where the shoreline does not coincide with the shelf-break, trajectory analysis can lead to inaccurate reconstruction of the depositional history of a margin.  相似文献   

A map-matching algorithm dealing with sparse cellular fingerprint observations     

Andrea Dalla Torre  Paolo Gallo  Chris Marshall  Angelo Montanari  Federico Pittino 《地球空间信息科学学报》2019,22(2):89-106

ABSTRACT

The widespread availability of mobile communication makes mobile devices a resource for the collection of data about mobile infrastructures and user mobility. In these contexts, the problem of reconstructing the most likely trajectory of a device on the road network on the basis of the sequence of observed locations (map-matching problem) turns out to be particularly relevant. Different contributions have demonstrated that the reconstruction of the trajectory of a device with good accuracy is technically feasible even when only a sparse set of GNSS positions is available. In this paper, we face the problem of coping with sparse sequences of cellular fingerprints. Compared to GNSS positions, cellular fingerprints provide coarser spatial information, but they work even when a device is missing GNSS positions or is operating in an energy saving mode. We devise a new map-matching algorithm, that exploits the well-known Hidden Markov Model and Random Forests to successfully deal with noisy and sparse cellular observations. The performance of the proposed solution has been tested over a medium-sized Italian city urban environment by varying both the sampling of the observations and the density of the fingerprint map as well as by including some GPS positions into the sequence of fingerprint observations.  相似文献   

Drainage network detection and assessment of network storage capacity in agrarian landscape     

Federico Cazorzi  Giancarlo Dalla Fontana  Alberto De Luca  Giulia Sofia  Paolo Tarolli 《水文研究》2013,27(4):541-553

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An analysis of intersystem biases for multi-GNSS positioning   总被引：4，自引：3，他引：1  

Andrea Dalla Torre  Alessandro Caporali 《GPS Solutions》2015,19(2):297-307

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Seismic vulnerability assessment of urban environments in moderate-to-low seismic hazard regions using association rule learning and support vector machine methods   总被引：2，自引：2，他引：0  

Ismaël Riedel  Philippe Guéguen  Mauro Dalla Mura  Erwan Pathier  Thomas Leduc  Jocelyn Chanussot 《Natural Hazards》2015,76(2):1111-1141

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Joint analysis of Rayleigh- and Love-wave dispersion: Issues, criteria and improvements     

Giancarlo Dal Moro  Fabrizio Ferigo 《Journal of Applied Geophysics》2011,75(3):573-589

Joint analysis of Rayleigh- and Love-wave dispersion is performed with the aim of evaluating how their joint use can improve retrieved vertical V_S profiles. In fact, non-uniqueness of the solution and complex energy distribution among different modes represent problems which, if not properly considered, can eventually lead to ambiguous or erroneous subsurface models.Some tests performed on synthetic datasets show that for the deepest layers the improvements obtained by the joint inversion cannot be considered as fully decisive in terms of ultimate solution of non-uniqueness. Nevertheless joint analysis of dispersive properties of Rayleigh and Love waves reveals as a highly valuable tool able to clarify possible interpretation issues of the single components. Under some stratigraphical circumstances, velocity spectra of Rayleigh waves can in fact be extremely complex in terms of energy distribution among different modes and erroneous interpretations of dispersion curves can thus occur. Beneficial aspects of the joint analysis is shown in the light of possible inconsistencies of the Pareto front, since major interpretative errors can be revealed in the outcomes of the proposed inversion procedure. Two field datasets are analysed also suggesting some improvements in the field acquisition procedures aimed at the acquisition of both Rayleigh and Love waves.  相似文献   

Emplacement temperatures of pyroclastic and volcaniclastic deposits in kimberlite pipes in southern Africa     

Giovanni Fontana  Conall Mac Niocaill  Richard J. Brown  R. Stephen J. Sparks  Matthew Field 《Bulletin of Volcanology》2011,73(8):1063-1083

Palaeomagnetic techniques for estimating the emplacement temperatures of volcanic deposits have been applied to pyroclastic and volcaniclastic deposits in kimberlite pipes in southern Africa. Lithic clasts were sampled from a variety of lithofacies from three pipes for which the internal geology is well constrained (the Cretaceous A/K1 pipe, Orapa Mine, Botswana, and the Cambrian K1 and K2 pipes, Venetia Mine, South Africa). The sampled deposits included massive and layered vent-filling breccias with varying abundances of lithic inclusions, layered crater-filling pyroclastic deposits, talus breccias and volcaniclastic breccias. Basalt lithic clasts in the layered and massive vent-filling pyroclastic deposits in the A/K1 pipe at Orapa were emplaced at >570°C, in the pyroclastic crater-filling deposits at 200–440°C and in crater-filling talus breccias and volcaniclastic breccias at <180°C. The results from the K1 and K2 pipes at Venetia suggest emplacement temperatures for the vent-filling breccias of 260°C to >560°C, although the interpretation of these results is hampered by the presence of Mesozoic magnetic overprints. These temperatures are comparable to the estimated emplacement temperatures of other kimberlite deposits and fall within the proposed stability field for common interstitial matrix mineral assemblages within vent-filling volcaniclastic kimberlites. The temperatures are also comparable to those obtained for pyroclastic deposits in other, silicic, volcanic systems. Because the lithic content of the studied deposits is 10–30%, the initial bulk temperature of the pyroclastic mixture of cold lithic clasts and juvenile kimberlite magma could have been 300–400°C hotter than the palaeomagnetic estimates. Together with the discovery of welded and agglutinated juvenile pyroclasts in some pyroclastic kimberlites, the palaeomagnetic results indicate that there are examples of kimberlites where phreatomagmatism did not play a major role in the generation of the pyroclastic deposits. This study indicates that palaeomagnetic methods can successfully distinguish differences in the emplacement temperatures of different kimberlite facies.  相似文献   

Simultaneous simulation of the three components of seismic accelerograms at locations around seismological stations     

Chiesa  Daniela Dalla  Miguel  Letícia Fleck Fadel  Riera  Jorge Daniel 《Journal of Seismology》2021,25(6):1361-1384

Journal of Seismology - This paper proposes a new numerical procedure, based on an evolutionary optimization algorithm, for the simultaneous generation of the three components of the seismic ground...  相似文献   

Quantitative analysis of H2O and CO2 in cordierite using polarized FTIR spectroscopy     

Giancarlo Della Ventura  Francesco Radica  Fabio Bellatreccia  Andrea Cavallo  Francesco Capitelli  Simon Harley 《Contributions to Mineralogy and Petrology》2012,164(5):881-894

We report a FTIR (Fourier transform infrared) study of a set of cordierite samples from different occurrence and with different H₂O/CO₂ content. The specimens were fully characterized by a combination of techniques including optical microscopy, single-crystal X-ray diffraction, EMPA (electron microprobe analysis), SIMS (secondary ion mass spectrometry), and FTIR spectroscopy. All cordierites are orthorhombic Ccmm. According to the EMPA data, the Si/Al ratio is always close to 5:4; X _Mg ranges from 76.31 to 96.63, and additional octahedral constituents occur in very small amounts. Extraframework K and Ca are negligible, while Na reaches the values up to 0.84 apfu. SIMS shows H₂O up to 1.52 and CO₂ up to 1.11 wt%. Optically transparent single crystals were oriented using the spindle stage and examined by FTIR micro-spectroscopy under polarized light. On the basis of the polarizing behaviour, the observed bands were assigned to water molecules in two different orientations and to CO₂ molecules in the structural channels. The IR spectra also show the presence of small amounts of CO in the samples. Refined integrated molar absorption coefficients were calibrated for the quantitative microanalysis of both H₂O and CO₂ in cordierite based on single-crystal polarized-light FTIR spectroscopy. For H₂O the integrated molar coefficients for type I and type II water molecules (ν₃ modes) were calculated separately and are ^[I]ε?=?5,200?±?700?l?mol^?1?cm^?2 and ^[II]ε?=?13,000?±?3,000?l?mol^?1?cm^?2, respectively. For CO₂ the integrated coefficient is $ \varepsilon_{{{\text{CO}}_{ 2} }} $ ?=?19,000?±?2,000?l?mol^?1?cm^?2.  相似文献