1,720,965 research outputs found
Modern terrigenous-carbonate sediments of the continental shelf of the Gulf of Cagliari [I sedimenti terrigeno-carbonatici attuali della piattaforma continentale del Golfo di Cagliari]
No full textEchographic and sedimentological investigations were undertaken on the shelf of Cagliari with the purpose of underlining the relationships between modern terrigenous and bioclastic sediments and the behaviour of the sedimentary system during the Holocene eustatic rising. The Gulf of Cagliari is a sub-tropical, semi-arid Mediterranean area located in the southern part of the NW striking Oligo- Miocene Sardinian Rift, within which the Pliocene Campidano Graben is superimposed. The Quaternary continental shelf developed transversally to this tectonic trough, being fed by terrigenous sediments derived from the Palaeozoic metamorphic basement and from Tertiary sedimentary and volcanic rocks. The new echographic survey, consisting of 11 lines performed transversally from the coast to the shelfbreak, integrated previously available data and allowed us to divide the shelf into different sedimentary environments. From shore to shelfbreak we first encounter a shoreface, gently sloped and distally seagrass-covered (close to the fair-weather wave base), which ends in a wide trough parallel to the coast. Toward the open shelf is a relief, site of the Posidonia oceanica main bank, reaching a minimum depth of 13 meters under the sea level, followed by its external slope. At a depth of about 30 meters the vegetation becomes rare, as less luminosity limits the growth of Posidonia, and starting from depths of 35÷40 meters a large belt of sand waves appears, with gradually decreasing heigths and increasing frequencies basinward. At the depth of 50 m a flat bottom prevails, followed by several reliefs stretching roughly NE–SW at 55 m depth, interpreted as submerged shore lines. Externally to such structures a narrow outer shelf occurs and the shelf break is observed at a depth of 115÷125 m. Sampling sites were located along the echographic lines and on the foreshore; 98 samples were taken with a 2 dm_ grab-sampler. Compositional and grain size analysis allowed us to identify 8 groups of facies related to present day depositional environments. Shoreface sediments are represented by almost completely terrigenous coarse to medium sands in the eastern sector, and finer mixed terrigenous-bioclastic sands on the S. Gilla shoreface.
Two distinct groups of lithic facies are present near Capo S. Elia and near P.ta Zavorra, due to sediment dispersal from the limestone and andesite outcrops along the cliffed coast. The western inner-shelf depression is characterized by mixed quartzose-bioclastic sandy muds with bivalves. Mixed facies of relict terrigenous sediments and present day biogenic production (mollusks, bryozoans, red algae, echinoids and foraminifers) are on the Posidonia oceanica bank’s fore slope, where the siliciclastic component is found between -30 and -50 meters with decreasing importance seaward. Through the sand-wave belt a transition is observed to bioclastic, poorly sorted gravely sands of red algae and foraminifers. Here the sediment is completely bioclastic with rare breakthroughs of mixed sediments in proximity to the –55 m paleo-shores. From a depth of 75 meters, sediments are represented by fine bioclastic-quartzose sands with bivalves and foraminifers. A peculiar feature of this shelf is the depression in the inner shelf that can be interpreted as the product of paleo-river erosions produced during the “Würmian” low stand (MIS 4-2), associated with terrigenous inputs insufficient to fill up the
available space during the post-glacial sea level rise. Towards the middle shelf the trough is bounded by paleo-reliefs where the Posidonia bank at present overgrows, weakly aggrading and prograding. The depositional facies described document the present day sedimentary system as of a temperate water mixed terrigenous-carbonate shelf. The sedimentation is highly siliciclastic in the inner shelf from fluvial-continental feeding, and bioclastic in the rest of the shelf with a maximum productivity along the intermediate shelf’s Posidonia bank and its foreslope. In the middle and outer shelf the siliciclastic component is related to previous eustatic phases and attributable to continental and nearshore deposits lying underneath the middle-shelf Posidonia bank. Analogous depositional contexts must be attributed to the preceding high stand phases of the Middle-Upper Pleistocene. Otherwise, during glacio-eustatic phases of falling, low-stand and rising sea level, the shelf has been affected by terrigenous continental sedimentation or shoreface sequences that are currently resedimented in the middle and outer shelf. In summary, the depositional model of this shelf is characterised by alternating
phases of terrigenous-carbonate sedimentation of middle latitude, with a poorly rainy, warm Mediterranean climate during highstanding sea-level conditions, and terrigenous phases during low stands with rather rainy, cooler Mediterranean climate
Carta Geo-Litologica dei fondali marini compresi tra Punta Sardegna e la Baia di Porto Pozzo in scala 1:10.000 Sardegna Nord-Orientale – Italia
No full textViene presentata la Carta Geo-Litologica dei fondali marini compresi tra Punta Sardegna e la Baia di Porto Pozzo – Sardegna Nord-Orientale.
Nel corso delle campagne oceanografiche Paleocli.ge 1999–2000 e 2004 sono state studiate le aree marine interne e adiacenti al Parco Nazionale di La Maddalena, tramite sistemi di rilevamento ecografico, sismico e studi sedimentologici, che hanno portato alla realizzazione di sei carte di superficie del fondo mare alla scala 1:10.000 e 1:25.000 (DE MURO S. et alii , 2000).
Sono stati utilizzati natanti dell’Università e del Corpo Forestale e di Vigilanza Ambientale della Regione Sardegna nell’ambito dei Progetti INTERREG II e III, “Ambiente Fisico Valorizzazione della fascia Costiera Sardo-Corsa e gestione delle risorse” e “Geologia e Geomorfologia terrestre e marina dell’ insieme Corsica-Sardegna e della Toscana e applicazioni” e M.P.I. 60%: “Ricostruzioni paleoclimatiche e paleogeografiche pleistocenico-oloceniche dai sedimenti dei bacini Sardo-corsi”.
- INQUADRAMENTO DELL’AREA: l’area indagata, con una estensione di circa 15 km2, si localizza nel tratto costiero tra P.ta Sardegna e la Baia di Porto Pozzo, compreso nei fogli 411160, 412130, 427040, 428010 in scala 1:10.000 della Carta Tecnica Regionale (CTR) dell’Assessorato degli Enti Locali, Finanze, Urbanistica – Servizio Informatico e Cartografico – Regione Sardegna.
Dal punto di vista geologico l’area è caratterizzata dalla presenza di Graniti e Granodioriti biotitici appartenenti al ciclo magmatico ercinico e dal complesso filoniano a composizione variabile. Inoltre affiorano diffusamente Migmatiti nelle aree della penisola di Culuccia e dell’Isuledda (CARMIGNANI L. et alii, 2001).
L’area interna della baia di Porto Pozzo e la zona circostante la foce del Fiume Liscia è caratterizzata da una copertura quaternaria olocenica (depositi alluvionali, colluviali, eolici e litorali).
- ELABORAZIONE DATI: Sono stati utilizzati tre strumenti principali: Side Scan Sonar Edgetech DF-1000, Sub Bottom Profiler Chirp DataSonic, Benna Van Veen (2 dm3) (DE MURO et alii, 2003).
Dall’analisi dei profili ecografici e sismici sono state selezionate le aree per il campionamento sedimentologico.
Nella carta qui presentata sono riportati: la distribuzione degli affioramenti del substrato roccioso, le direzioni di fratturazione, cinque classi granulometriche secondo la classificazione di NOTA, gli spessori e le geometrie dei principali corpi sedimentari, i limiti di distribuzione della prateria di Posidonia oceanica
I SEDIMENTI TERRIGENO-CARBONATICI OLOCENICI DELLA PIATTAFORMA DEL GOLFO DI CAGLIARI
No full textEchographic and sedimentological investigations were undertaken on the shelf of Cagliari with the purpose of underlining the relationships between modern terrigenous and bioclastic sediments and the behaviour of the sedimentary system during the Holocene eustatic rising. The Gulf of Cagliari is a sub-tropical, semi-arid Mediterranean area located in the southern part of the NW striking Oligo- Miocene Sardinian Rift, within which the Pliocene Campidano Graben is superimposed. The Quaternary continental shelf developed transversally to this tectonic trough, being fed by terrigenous sediments derived from the Palaeozoic metamorphic basement and from Tertiary sedimentary and volcanic rocks. The new echographic survey, consisting of 11 lines performed transversally from the coast to the shelfbreak, integrated previously available data and allowed us to divide the shelf into different sedimentary environments. From shore to shelfbreak we first encounter a shoreface, gently sloped and distally seagrass-covered (close to the fair-weather wave base), which ends in a wide trough parallel to the coast. Toward the open shelf is a relief, site of the Posidonia oceanica main bank, reaching a minimum depth of 13 meters under the sea level, followed by its external slope. At a depth of about 30 meters the vegetation becomes rare, as less luminosity limits the growth of Posidonia, and starting from depths of 35÷40 meters a large belt of sand waves appears, with gradually decreasing heigths and increasing frequencies basinward. At the depth of 50 m a flat bottom prevails, followed by several reliefs stretching roughly NE–SW at 55 m depth, interpreted as submerged shore lines. Externally to such structures a narrow outer shelf occurs and the shelf break is observed at a depth of 115÷125 m. Sampling sites were located along the echographic lines and on the foreshore; 98 samples were taken with a 2 dm_ grab-sampler. Compositional and grain size analysis allowed us to identify 8 groups of facies related to present day depositional environments. Shoreface sediments are represented by almost completely terrigenous coarse to medium sands in the eastern sector, and finer mixed terrigenous-bioclastic sands on the S. Gilla shoreface.
Two distinct groups of lithic facies are present near Capo S. Elia and near P.ta Zavorra, due to sediment dispersal from the limestone and andesite outcrops along the cliffed coast. The western inner-shelf depression is characterized by mixed quartzose-bioclastic sandy muds with bivalves. Mixed facies of relict terrigenous sediments and present day biogenic production (mollusks, bryozoans, red algae, echinoids and foraminifers) are on the Posidonia oceanica bank’s fore slope, where the siliciclastic component is found between -30 and -50 meters with decreasing importance seaward. Through the sand-wave belt a transition is observed to bioclastic, poorly sorted gravely sands of red algae and foraminifers. Here the sediment is completely bioclastic with rare breakthroughs of mixed sediments in proximity to the –55 m paleo-shores. From a depth of 75 meters, sediments are represented by fine bioclastic-quartzose sands with bivalves and foraminifers. A peculiar feature of this shelf is the depression in the inner shelf that can be interpreted as the product of paleo-river erosions produced during the “Würmian” low stand (MIS 4-2), associated with terrigenous inputs insufficient to fill up the
available space during the post-glacial sea level rise. Towards the middle shelf the trough is bounded by paleo-reliefs where the Posidonia bank at present overgrows, weakly aggrading and prograding. The depositional facies described document the present day sedimentary system as of a temperate water mixed terrigenous-carbonate shelf. The sedimentation is highly siliciclastic in the inner shelf from fluvial-continental feeding, and bioclastic in the rest of the shelf with a maximum productivity along the intermediate shelf’s Posidonia bank and its foreslope. In the middle and outer shelf the siliciclastic component is related to previous eustatic phases and attributable to continental and nearshore deposits lying underneath the middle-shelf Posidonia bank. Analogous depositional contexts must be attributed to the preceding high stand phases of the Middle-Upper Pleistocene. Otherwise, during glacio-eustatic phases of falling, low-stand and rising sea level, the shelf has been affected by terrigenous continental sedimentation or shoreface sequences that are currently resedimented in the middle and outer shelf. In summary, the depositional model of this shelf is characterised by alternating
phases of terrigenous-carbonate sedimentation of middle latitude, with a poorly rainy, warm Mediterranean climate during highstanding sea-level conditions, and terrigenous phases during low stands with rather rainy, cooler Mediterranean climate
A HOLOCENIC HIGHSTAND CARBONATE-TERRIGENOUS CONTINENTAL SHELF IN THE GULF OF CAGLIARI, SARDINIA
No full textBy means of 11 new echographic lines and 100 surface sediment samples it has been possible to
individualize on the continental shelf of Cagliari Gulf several depositional facies associations between
foreshore and shelf edge. These associations document a suite of peculiar environments that diversified
and stabilized during the Holocene eustatic rise. From shore to shelfbreak we first encounter a
shoreface, gently sloped and distally sea-grass covered which ends in a trough parallel to the coast.
Toward the open shelf is a relief, topping at -12-15 meters, site of the Posidonia oceanica main bank,
followed by a wide foreslope. At a depth of 30 m the vegetation becomes rare, and starting from -35-40
m a large belt of sand waves appears. At the depth of 50 m a flat bottom prevails, followed by
submerged shoreline relieves at -55 m. Externally to such structures a narrow outer shelf occurs and
the shelf edge is observed at a depth of 115-125 m. The inner shelf trough can be interpreted as a
paleo-river valley during the MIS 4-2 and previous lowstands, combined with terrigenous inputs
insufficient to fill the accommodation space produced by the Holocene sea-level rise. Towards the
middle shelf the trough is bounded by paleo-reliefs where the Posidonia oceanica bank at present
overgrows, weakly aggrading and prograding landward and seaward. Compositional and grain-size
analysis of samples allowed us to identify eight depositional facies related to present day environments.
Shoreface sediments are represented by terrigenous coarse to medium sands in the eastern sector of
the gulf, and mixed terrigenous-bioclastic medium to fine sands on the western sector. Two distinct
groups of lithic facies are present near Cape S.Elia and near Zavorra Point, due to sediment dispersion
from the limestone and andesite outcrops along the cliffed coast. The western inner-shelf trough is
characterized by mixed quartzose-bioclastic sandy muds with bivalves and peloidal grains. Mixed facies
of biogenic production and relict terrigenous sediments are present on the Posidonia bank, while
through the sand wave belt a transition is observed to bioclastic, poorly sorted gravely sands with red
algae and foraminifers. Rare breakthroughs of mixed sediments are present in proximity of the -55 m
paleo-shores. Starting from depths of 75 m, sediments are represented by fine bioclastic-quartzose
sands with bivalves and foraminifers. The depositional facies described document this sedimentation as
of a mid-latitude mixed carbonate-terrigenous shelf. The present day sedimentation is highly siliciclastic
in the inner shelf from fluvial-continental feeding, and bioclastic in the rest of the shelf with a maximum
productivity along the middle-shelf Posidonia bank and its foreslope. In the middle and outer shelf the
siliciclastic component is related to previous eustatic phases. The sequential analysis of 3.5 kHz lines
show the Holocenic trasgressive systems tract blanking over a maximum flooding surface, or over a
trasgressive ravinement surface or lowstand erosional truncations. The Holocenic TST, except for the
siliciclastic shoreface, is mostly carbonatic, owing to the highstand-related terrigenous starvation and to
a good bioclastic productivity of molluscs, red algae, briozoans, foraminifers and echinoids. Analogous
depositional contexts should be attributed to the preceding highstand phases of the Middle-Upper
Pleistocene. Otherwise, during glacio-eustatic phases of falling, lowstand and rising sea-level, the shelf
has been mostly interested by terrigenous continental or shoreface deposits that are currently
resedimented in the middle and outer shelf. In summary, the depositional model of this shelf is
characterised by alternated phases of carbonate-terrigenous mid-latitude sedimentation with poorly
rainy, warm Mediterranean climate during highstand conditions, and terrigenous phases during
lowstands with rainy, cold Mediterranean climate
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Carta geologica d’Italia 1:50.000 566 Pula (area marina)
No full textCarta Geologica d'Italia, Foglio 566 Pula (parte a mare
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
