Search results for "FEA"
showing 10 items of 4862 documents
Microstructure, porosity and mineralogy around fractures in Olkiluoto bedrock
2012
3D distributions of minerals and porosities were determined for rock-core samples that included water-conducting fractures. The analysis of these samples was performed using conventional petrography methods, C-14-PMMA porosity analysis and X-ray tomography. It seems that the properties of rock around a water-conducting fracture depend on so many uncorrelated factors that no clear pattern emerged even for rock samples with a given type of fracture. We can conclude, however, that the present combination of methods can be used to infer novel structural information about alteration zones adjacent to fracture surfaces.
Tectono-stratigraphic evolution of a basin generated by transpression: the case of the Early Pliocene Lascari Basin (northern Sicily)
2011
Integrated stratigraphy and structural analysis carried out in the Madonie Mts. (Northern Sicily) is aimed to the description of a syn-sedimentary tectonic event, recorded in a small infra-pliocene basin restricted to the Lascari Syncline core. The onset and evolution of the basin was driven by transpressive tectonics, generating a lens-shaped, deep and narrow tectonic depression, bounded by steep and high, tectonically controlled slopes, also reflected in the present-day topography of the area. During the genesis of the basin, the tectonic control interferes with a dramatic sea level oscillation during the Messinian-Early Pliocene time interval. In this paper, the syn-tectonic deposits of …
Nuevos caminos, territorio y paisaje en la Comarca de la Costera (Valencia). La mirada de los viajeros
2019
Por sus condiciones físicas, el valle de la Costera ha sido históricamente un lugar de paso obligado en el itinerario que, desde la llanura litoral valenciana, se dirige al sur y al centro peninsular. A finales del siglo XVIII se construye una moderna carretera y a mediados del XIX entra en servicio el ferrocarril entre Madrid y Valencia. En este trabajo analizamos la relación que se establece entre los caminos y el paisaje, y cómo esta se ha reflejado en los escritos que los viajeros que, entre finales del siglo XVIII y a lo largo de todo el siglo XIX, recorrieron por carretera y ferrocarril el valle de la Costera. Sus relatos integran estas modernas obras públicas con la visión secuencial…
First 13C/12C isotopic characterisation of volcanic plume CO2
2010
We describe analytical details and uncertainty evaluation of a simple technique for the measurement of the carbon isotopic composition of CO2 in volcanic plumes. Data collected at Solfatara and Vulcano, where plumes are fed by fumaroles which are accessible for direct sampling, were first used to validate the technique. For both volcanoes, the plume-derived carbon isotopic compositions are in good agreement with the fumarolic compositions, thus providing confidence on the method, and allowing its application at volcanoes where the volcanic component is inaccessible to direct sampling. As a notable example, we applied the same method to Mount Etna where we derived a δ13C of volcanic CO2 betw…
Millennial-scale climate variability during the last 12.5 ka recorded in a Caribbean speleothem
2013
Abstract We present a speleothem stable oxygen isotope record for the last 12.5 ka based on two stalagmites from western Cuba. The δ18O signal is interpreted to represent past precipitation variability. Both stalagmites show a pronounced transition from higher δ18O values (indicating drier conditions) to more negative δ18O values (suggesting wetter conditions) between 10 and 6 ka. This transition is also visible in a planktonic δ18O record off Haiti. On orbital timescales, the δ18O value of Caribbean precipitation, thus, strongly resembles the oxygen isotope composition of Caribbean surface water. On millenial timescales, the speleothem δ18O record shows a high correlation to a North Atlant…
Geochemistry of streams from Byers Peninsula, Livingston Island
2013
AbstractIn January and February 2009, a series of water samples were collected from streams on Byers Peninsula. These samples were analysed for major elements and δ18O to determine the role of lithology and landscape position on stream geochemistry, and to understand better the hydrology (i.e. residence time of water) of these systems. Precipitation chemistry is enriched in Na+, as are the streams located close to the coast. Streams originating from inland locations have much higher percentages of Ca2+. In contrast, Mg2+ varied little, though streams that are in greater contact with volcanic-derived soils have slightly higher concentrations. Anion percentages varied greatly between streams …
Ice age at the Middle–Late Jurassic transition?
2003
A detailed record of sea surface temperatures in the Northern Hemisphere based on migration of marine invertebrate fauna (ammonites) and isotopic thermometry (δ18O values of shark tooth enamel) indicates a severe cooling at the Middle–Late Jurassic transition (MLJT), about 160 Ma ago. The magnitude of refrigeration (1–3°C for lower middle latitudes) and its coincidence in time with an abrupt global-scale fall of sea level documented through sequence stratigraphy are both suggestive of continental ice formation at this time. Ice sheets may have developed over the high-latitude mountainous regions of Far-East Russia. The drastic cooling just post-dated the Middle–Late Callovian widespread dep…
Fragmentation during Rock Falls: Two Italian Case Studies of Hard and Soft Rocks
2008
In recent years, rock fall phenomena in Italy have received considerable attention for risk mitigation through in situ observations and experimental data. This paper reports the study conducted at Camaldoli Hill, in the urban area of Naples, and at Monte Pellegrino, Palermo, Italy. The rocks involved are volcanic Neapolitan yellow tuff (NYT) in the former area and dolomitic limestone in the latter. Both rocks, even though with different strength characteristics, have shown a significant tendency towards rock fragmentation during run out. This behavior was first investigated by comparing the volumes of removable blocks on the cliff faces (V 0) and fallen blocks on the slopes (V f). It was as…
Comparative tests on different multi-electrode arrays using models in near-surface geophysics
2008
In this paper, the response of different synthetic models to geoelectrical multi-electrode surveys is studied. The models considered are related to two main problems, which are very common in geophysical research regarding hydrogeology and engineering. The first class of models represents buried walls, similar archaeological remains or remains of buried foundations; the other class corresponds to a sea-water intrusion of a fresh water aquifer, which is generally studied in hydrogeophysics. A set of 2D simulations, starting from the synthetic models, was carried out to compare the behaviour of the different arrays when acquiring measurements of electrical resistivity tomography. For each mod…
Range-wide phylogeography and taxonomy of the marine rock pools dweller Tigriopus fulvus (Fischer, 1860) (Copepoda, Harpacticoida)
2021
In the light of the wide distribution and ecological importance of the genus Tigriopus in coastal rock pool habitats, and of its frequent use in aquaculture and as a model organism, we investigated the identity of the Atlantic–Mediterranean Tigriopus populations and elucidated their taxonomy and patterns of morphological and genetic diversity. In order to reach these goals, an “integrative taxonomy” multisource approach was implemented. First, we investigated the constancy and taxonomical value of the morphological characters currently used to distinguish among the Tigriopus species occurring in the Mediterranean and in Eastern Atlantic area north of the Tropic of Cancer, and checked the ac…