86,539 research outputs found
IMPLEMENTAZIONE DI TECNICHE NDT DI TERMOGRAFIA AD INFRAROSSI SU PANNELLI IN COMPOSITO GRP PER APPLICAZIONI NAUTICHE
No full textIl presente lavoro descrive l’implementazione di due tecniche di termografia attiva ad infrarossi per il controllo non distruttivo (IRNDT) di delaminazioni sub-superficiali su pannelli in composito (GRP) di grosso spessore, tipicamente impiegati per uso navale. Si è in particolare fatto uso di attrezzature a basso costo consistenti in comuni lampade alogene a bassa potenza come sorgenti di calore esterne, ed una termocamera ad infrarossi a singolo sensore a bassa risoluzione termica e basso frame rate. Le due tecniche implementate sono la Pulsed Thermography (PT) ed una nuova variante di Lock-In Thermography denominata Pulse-Modulated Lock-In Thermography (PMLT), basata sull’analisi in frequenza del segnale termografico del provino riscaldato da una serie di impulsi modulati. Il lavoro descrive in particolare il trattamento del segnale termografico messo a punto al fine di ottimizzare la tracciabilità dei difetti e ricavare informazioni utili sulla loro natur
Globorotalia mariae mariae and G. mariae gratiae: Two new planktonic Foraminifera from the MiddleMiocene of the Mediterranean
No full textTwo new subspecies belonging to the genus Globorotalia, thatwe name G. mariae mariae and G. mariae gratiae, are here described and figured. They were found exclusively within the Middle Miocene and particularly from the early Langhian to the Serravallian of several Mediterranean sedimentary successions. The two subspecies have a slightly different stratigraphic range. Both were recorded from the Globigerinoides sicanus/Orbulina suturalis Zone (MMi4) to the Paragloborotalia partimlabiata Zone (MMi7). However, only G. mariae mariae is recorded from the Globorotalia praescitula Subzone (MMi4b), whereas G. mariae gratiae was found from slightly younger levels, corresponding to the Paragloborotalia siakensis-Praeorbulina glomerosa circularis Subzone (MMi4c). As far as their origin concerns, G. praescitula may have been the ancestor of G. mariae mariae. Subsequently, G. mariae gratiae evolved from G. mariae mariae. Both subspecies disappear in the Paragloborotalia partimlabiata-Globoturborotalita druryi Subzone (MMi7a). Concerning their stratigraphic range it is important to point out that in all the studied sections both subspecies were not found in the interval encompassing the Langhian/Serravallian boundary, and lasting from the upper part of the Praeorbulina glomerosa circularis Subzone (MMi4d) to the uppermost part of the Orbulina suturalis/Globorotalia peripheroronda Zone (MMi5)
Foraminiferal record and astronomical cycles: An example from the Messinian pre-evaporitic Gello Composite Section (Tuscany, Italy)
No full textA high resolution bio-magneto and cyclostratigraphical study has been carried out for the first time on Messinian pre-evaporitic marine deposits (Gello Composite Section) from the Volterra Basin (Italy). Since the investigated deposits manifest no evident lithological cyclicity, others records have been used to recognize the vidences of an astronomical periodicity. The distribution curves of planktonic and benthic foraminifera have been used for paleoenvironmental reconstruction. yclostratigraphical analyses have been based on: i) abundance fluctuations of Bolivina and Bulimina among the benthic foraminifera, Globigerinoides, Orbulina and Turborotalita among the planktonics; ii) CaCO3 content changes; and iii) Shannon-Weaver index variations relative to benthic assemblages. As a result, 18 precession-controlled cycles have been recognized. Moreover, the recognition of the C3An.1r, C3An.1n and C3r magnetozone and some biochronohorizons,
have allowed the tuning of the studied section with the ATNTS (Astronomical Tuned Neogene Time Scale) using the Laskar 2001 (1,1.2) solution of the insolation curve. This multidisciplinary study strongly supports that the onset of evaporitic deposition in Tuscany and in other circum-Mediterranean type-successions, as the Abad Composite Section (Spain) and the Falconara Section (Sicily), was isochronous
Biostratigraphy and chronostratigraphy of the Miocene Pietra leccese in the type area of Lecce (Apulia, southern Italy)
No full textThe Miocene Pietra Leccese formation characterizes the Salentine Peninsula in the southern Italian Apulia Region, where it crops out extensively from north of the city of Lecce to Lèuca. A biostratigraphical (planktonic foraminifera and calcareous nannofossils) and chronostratigraphical study of the Pietra Leccese formation in the Lecce type area is reported. The work is based on 186 samples collected from 19 sections and 5 boreholes. As elsewhere in the Salento area, the sedimentation of the Pietra Leccese spans about 11 Ma, from the late Burdigalian (Globigerinoides trilobus Zone of the planktonic foraminifera, Helicosphaera ampliaperta Zone of the calcareous nannofossils) to the early Messinian (Globorotalia miotumida Zone and Amaurolithus delicatus-A. amplificus Zone of the two groups of organisms respectively). The deposition was interrupted by the repeated action of marine currents, which inhibited the accommodation of the sediments and/or eroded those previously formed, resulting in hiatuses (generally testified to by the occurrence of glauconite mineralization) of different durations even in successions that are located very close each other. The Lecce area was studied by considering four geographical sectors (north-western, north-eastern, south-western, and south-eastern) and three hiatuses were recognized, which in stratigraphical order are: - first hiatus, between the typical Pietra Leccese and the overlying weakly glauconitic Pietra Leccese. This hiatus separates the upper Burdigalian sediments of the G. trilobus Zone and H. ampliaperta Zone (Sphenolithus heteromorphus-Helicosphaera ampliaperta Subzone) from the Langhian ones of the Orbulina suturalis-Globorotalia peripheroronda Zone (O. suturalis Subzone) and S. heteromorphus Zone (S. heteromorphus-Helicosphaera waltrans Subzone). The gap is shorter in the succession of the Seminario Borehole (south-eastern sector). In fact, the first sediments above the hiatus pertain to the upper part of the Praeorbulina glomerosa s.l. Zone (Paragloborotalia siakensis-Praeorbulina glomerosa circularis Subzone) and the lower part of the S. heteromorphus Zone (S. heteromorphus-H. waltrans Subzone); - second hiatus, between the weakly glauconitic and the intensely glauconitic Pietra Leccese. This hiatus separates the upper Langhian sediments of the Orbulina universa (O. suturalis-G. peripheroronda Zone) and the Helicosphaera walbersdorfensis-S. heteromorphus (S. heteromorphus Zone) subzones from the lower Tortonian ones of the Paragloborotalia siakensis and Discoaster bollii (lower part) zones. The gap is shorter in the north-eastern sector (succession of the Morello Borehole) as the sedimentation restarts in the Paragloborotalia partimlabiata (P. mayeri Subzone) and Calcidiscus macintyrei zones. In this sector, further hiatus cannot be ruled out, and it should embrace the interval P. mayeri Subzone (pars) - P. siakensis Zone (pars) of the foraminifera and C. macintyrei Zone (pars) - D. bollii Zone (pars) of nannofossils. - third hiatus, at the top of the glauconite-rich interval. This hiatus occurs between the lowermost Tortonian sediments and the middle Tortonian ones of the Neogloboquadrina acostaensis Zone (lower part) and the Discoaster bellus Zone. The gap is longer in the north-eastern sector since the deposits immediately above the intensely glauconitic interval pertain to the Globigerinoides obliquus extremus and Discoaster surculus zones. A fourth hiatus was also recognized, but only in the area north of Lecce. In the north-western sector, the uppermost Tortonian sediments of Globorotalia suterae and Amaurolithus primus zones directly overlie the middle Tortonian deposits of N. acostaensis and D. bellus zones. The gap is shorter in the north-eastern sector because the lowermost Messinian deposits of G. miotumida and A. delicatus-A. amplificus zones lie on
those of the upper Tortonian belonging to the G. obliquus extremus and D. surculus zones. In the south-eastern sector, the deposition was continuous from the lower Tortonian (N. acostaensis and D. bellus zones) to the lower Messinian (G. miotumida and A. delicatus-A amplificus zones). This resulted in a greater thickness of the formation (about 90 m). However, it
should be noted that in this interval the Pietra Leccese formation presents lithological features that differ from the typical ones. These features are the result of a progressive bathymetric decrease in the marine environment. The decreasing depth and lithological change led to the deposition of the Calcareniti di Andrano formation, the final Miocene unit on the Salentine Peninsula
Revisiting the taxonomy of the intermediate stages in the Globigerinoides–Praeorbulina lineage
No full textDespite the biostratigraphic and chronostratigraphic importance of the Globigerinoides trilobus-Praeorbulina evolutionary lineage in the upper Burdigalian to Langhian interval, some uncertainties concern the taxonomic interpretation of the intermediate stages of this lineage, in particular the generic attribution of the species sicanus De Stefani 1952 and its relationship with Globigerinoides bisphericus Todd 1954 and Praeorbulina glomerosa curva (Blow 1956). In this study, we present: 1) a review of the intermediate stages of the Globigerinoides trilobus-Praeorbulina evolutionary lineage focussing on the different taxonomic concepts of the species bisphericus, sicanus and glomerosa curva which according to Blow (1956; 1969) and Jenkins et al. (1981) gave rise to two different lines of evolution, and 2) our concepts based on the study of assemblages from several Mediterranean successions which have been compared with those of mid- and low-latitude Atlantic Ocean. On the basis of several diagnostic characters, we identified three morphotypes (Morphotypes 1, 2 and 3) within the populations transitional from G. trilobus to Praeorbulina. In our assemblages, Morphotype 3 and Morphotype 2 are the most representative ones and are considered as Globigerinoides sicanus sensu Blow (1956; 1969) and Kennett and Srinivasan (1983) and as a variant of G. sicanus, respectively. In fact, the taxonomic concepts of Blow, which take both the population variability and the gradual stratigraphic evolution of the biocharacters into account, can be better applied to our assemblages than those of Jenkins et al. (1981), which are mainly based on the characteristics of the holotypes without considering the variability of the species. Accordingly, the evolution of Praeorbulina via G. sicanus (senior synonym of G. bisphericus) proposed by Blow (1956; 1969) can be followed in the studied assemblages and the Praeorbulina datum is represented by the first appearance of P. glomerosa curva. On the basis of our data the evolution of P. glomerosa curva from G. sicanus lasts more than one myr. The main evolutionary changes within G. sicanus populations leading to Praeorbulina are the appearance of specimens with three apertures and the gradual increase in the outline sphericity. Near-spherical individuals of G. sicanus with three apertures can be considered very close to P. glomerosa curva, which in turn is characterized by a spherical outline, at least four apertures with the primary aperture nearly undistinguishable from the supplementary ones and a close umbilicus. Ultimately, our re-examination of the intermediate stages between G. trilobus and Praeorbulina results in a re-evaluation of the evolution proposed by Blow (1956; 1969) with significant bio- and chronostratigraphic implications
Revisiting the taxonomy of the intermediate stages in Globigerinoides –Praeorbulina lineage.
No full textThe upper Messinian post-evaporitic succession of Serredi Quarry (southern Tuscany, Italy): new stratigraphic data and geochronology of an ash layer.
No full textAn ash layer, about 1 cm thick, has been found during a reinvestigation of the upper Messinian-Zanclean succession exposed at Serredi Quarry (Fine Basin, Northern Apennines), one of the best known Neogene Tuscan sections.
The Serredi Quarry succession (about 175 m thick) has been subdivided into three intervals: the lower (18 m thick) and middle (132 m thick) ones are separated by an unconformity and are both referable to the Messinian post-evaporitic phase, whereas the upper interval (25 m thick) represents marl deposition following the Pliocene transgression. The lower interval consists of relatively deep-lacustrine, anoxic, thinly laminated mudstones with subordinate sands, whereas the middle one includes lacustrine mudstones (occasionally with pedogenic features) with sands, diagenetic gypsum-rich mudstones, limestones, gravels and selenite gypsum draped by gypsarenites. These lithofacies are typically arranged into marginal-lake, cyclical stacking patterns.
The ash layer is located in the lower interval. It is faintly laminated and composed of almost pure fine-grained glass shards and rare pumices. These characteristics suggest a primary deposition from a pyroclastic fallout. Chemical analyses were carried out on well preserved pumices and glass shards were used for fission-tracks dating, which provided an age of 5.35 + 0.32 Ma. Nevertheless, its age can be further constrained by the fact that
i) the ash layer is about 145 m below the Miocene-Pliocene boundary, and ii) the intervening deposits mainly consist of mudstones with occasional pedogenic features, which are likely to comprise sedimentary hiatuses.
Accordingly, the ash layer probably emplaced in the older part of the determined age interval.
On the whole, the geochronology, geochemistry and the stratigraphic framework of the first ash layer found in the post-evaporitic deposits of Tuscany could represent valuable tools for regional stratigraphic studies on the
Lago Mare phase and long-distance correlation
Calcareous plankton bio-chronostratigraphy of the Maltese Lower Globigerina Limestone member
No full textThe planktonic foraminifera and calcareous nannofossil biostratigraphy of the Maltese Lower Globigerina Lime-
stone member has been investigated. The member was dated to early planktonic foraminiferal P22 Zone and nan-
nofossil NP25 Zone (upper Chattian). A climate-stratigraphic approach, based on the quantitative analyses of cal-
careous nannofossils, was used additionally to achieve a more precise chronology. The species Coccolithus
pelagicus (diameter ⩽ 11 μm) and the genus Umbilicosphaera were selected for the recognition of cold and warm
surface waters intervals respectively. The ratio of their percentages enabled the construction of a Climatic Fac-
tor (CLF) curve. The CLF values were consistent with a warm climatic phase, which is probably represented by
the portion of the oxygen stable isotope curve of Miller et al. above the Oi2c event and below the beginning of
the cooling trend that culminates in the Mi1 event. Considering these two climatic events and the upper bound-
ary of the NP25 Zone, it can be inferred that the deposition of the Lower Globigerina Limestone member took
place between 25.1 and 24.3 Ma
Variations on the Author
No full text“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
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