1,721,041 research outputs found
Radiocarbon dating versus volcanic event stratigraphy: Age modelling of Quaternary marine sequences in the coastal region of the Eastern Tyrrhenian Sea
No full textWe present the results of an integrated stratigraphic study conducted on eight marine sediment cores collected in the Naples and Salerno Bays, Eastern Tyrrhenian Sea. The aim of the study is the understanding of the timing and the impacts on the sedimentary environment of explosive volcanic events that occurred over the coastal zone of the Campania region during the latest Quaternary. Accurate dating and correlation have been essential for the construction of reliable models of the sediment architecture and influx rates in this area, as well as for establishing the links between changes in sedimentation and palaeoenvironmental events. While in case of deep marine sequences distal ash layers usually offer a significant potential for accurate geochronology, in the case of shallow marine sequences (continental shelf to upper slope) radiocarbon dating revealed to be essential in order to refine correlation among clusters of marine tephra layers with the equivalent proximal pyroclastic deposit onland, particularly where depositional rates are high and the chemistry and age of tephra layers display little variability. The integrated use of AMS 14C dating on marine materials and the tephrostratigraphic approach based on reconstructions of historical volcanic events is fundamental in order to minimize the uncertainties that affect chronologic constraints derived from radiocarbon-based age models. © 2009 Elsevier B.V. All rights reserved
The submerged structure and stratal architecture of the Neapolitan Yellow Tuff (NYT) caldera, offshore the Campi Flegrei, (Eastern Tyrrhenian Margin): new insights from high resolution seismics and gravity core data
Full text linkThe Campi Flegrei is an active volcanic area defined by a
quasi-circular depression that covers some 200 km2 of the coastal
zone of SW Italy, a large part of which develops off the Naples
(Pozzuoli) Bay (Fig. 1). The area has been active at least since 60
ka BP ( Pappalardo et al., 1999), and is structurally dominated by a
caldera, 6 km in diameter, associated with the eruption of the
Neapolitan Yellow Tuff (NYT), a 40 km3 Dense Rock Equivalent
(DRE) ignimbrite (Scarpati et al., 1993) dated at ca 15 ka BP
(Deino et al., 2004), that covered the district now occupied by the
city of Naples, the Campi Flegrei and a large area of the
continental shelf off the Pozzuoli Bay.
The volcanological evolution of the NYT caldera as been long
described on the basis of outcrop and subsurface studies onland
(Rosi & Sbrana, 1987; Orsi et al., 1996, 2004 and references
therein; Di Vito et al., 1999; Perrotta et al., 2006; Fedele et al.,
2011), but its offshore morphology, detailed structure and recent
stratigraphic setting are still poorly understood.
In this study we integrate geological and geophysical data of
different resolution/penetration obtained from high-resolution
reflection seismic profiles (Sparker and Chirp source) with gravity
core and swath bathymetry to better constrain the shallow
structure, stratigraphic architecture and latest Quaternary to
Holocene evolution of the submerged sector of the NYT caldera
off the Pozzuoli Bay.
Our data clearly image, for the first time, the offshore geometry
of the NYT caldera ring-fault zone, as well as the style and timing
of volcano-tectonic deformation associated with the late stage
evolution of the NYT inner caldera resurgence. Our interpretation
suggests that since 15 ka the offshore sector of NYT inner caldera
underwent significant deformation and uplift (with minor
subsidence episodes) that occurred at almost the same rate as the
post-glacial sea-level rise. Particularly, the inner Pozzuoli Bay
started to deform soon after 15 ka BP, when sea-level rise was
initially faster than uplift. This caused a general increase of the
accommodation space that was progressively filled up by
volcaniclastic sediments. Since ca. 8 ka BP, along with the mid
Holocene decrease in the rate of the sea-level rise, the early NYT
resurgent structure was then uplifted up to the sea-level or even to
partial subaerial exposure. From ca. 8 to 5 ka BP two distinct
layers of volcaniclastic resediments, mostly represented by gravity
flow deposits, formed throughout the Bay. A significant post-
Roman (post 2 ka BP) subsidence phase of ca 10 m is then
recorded offshore Pozzuoli by the drowning of the infralittoral
prograding wedge below the present-day fair-weather wave base.
REFERENCES
Deino AL, Orsi G, de Vita S, Piochi M (2004) The age of the Neapolitan Yellow
Tuff caldera-forming eruption (Campi Flegrei caldera—Italy) assessed by
40Ar/39Ar dating method. J. Volcanol. Geotherm. Res. 133, 157–170.
Di Vito M., Isaia R., Orsi G., Southon J., de Vita S., D’Antonio M., Pappalardo
L., Piochi M., 1999. Volcanism and deformation since 12,000 years at the
Campi Flegrei caldera (Italy), J. Volcanol. Geotherm. Res. 91 (2-4), 221-246.
Fedele L., Insinga D.D., Calvert A.T., Morra V., Perrotta A., Scarpati C., 2011.
40Ar/39Ar dating of tuff vents in the Campi Flegrei caldera (southern Italy):
toward a new chronostratigraphic reconstruction of the Holocene volcanic
activity. Bull. Volcanol. 73, 1323-1336.
Orsi G, de Vita S, Di Vito M, 1996. The restless, resurgent Campi Flegrei nested
caldera (Italy): constraints on its evolution and configuration. J. Volcanol.
Geotherm. Res. 74, 179–214.
Orsi G., Di Vito M.A. Isaia R., 2004. Volcanic hazard assessment at the restless
Campi Flegrei caldera. Bull. Volcanol. 66, 514–530.
Pappalardo L., Civetta L., D’Antonio M., Deino A., Di Vito M., Orsi G.,
Carandente A., de Vita S., Isaia R. & Piochi M., 1999. Chemical and Srisotopical
evolution of the Phlegrean magmatic system before the Campanian
Ignimbrite and the Neapolitan Yellow Tuff eruptions J. Volcanol. Geotherm.
Res. 91, 141-166.
Perrotta A., Scarpati C., Luongo G., Morra V., 2006. The Campi Flegrei caldera
boundary in the city of Naples. In: De Vivo B (ed) Volcanism in the
Campania Plain: Vesuvius, Campi Flegrei and Ignimbrites. Elsevier,
Amsterdam, pp 85–96 (in the series Developments in Volcanology, 9)
Scarpati C., Cole P., & Perrotta A., 1993. The Neapolitan Yellow Tuff- A large
volume multiphase eruption from Campi Flegrei, Southern Italy. Bull.
Volcan. 55, 343-35
Architettura stratigrafica ed evoluzione del Golfo di Pozzuoli negli ultimi 15 ka:una nuova prospettiva sulla caldera del Tufo Giallo Napoletano,Campi Flegrei, margine tirrenico orientale.
Full text linkI Campi Flegrei rappresentano un distretto vulcanico attivo che si sviluppa al confine tra il settore emerso
e sommerso del margine continentale campano. Il distretto vulcanico occupa una superficie di circa 200 km2,
è strutturalmente dominato da una caldera di collasso del diametro di circa 8 km formatasi in seguito
all’eruzione del Tufo Giallo Napoletano (TGN), un deposito ignimbritico del volume di 30-50 km3 Dense
Rock Equivalent, datato a 15 ka B.P. circa, ed è attivo da almeno 78 ka B.P circa.
L’obiettivo di questo lavoro è di ricostruire l’architettura stratigrafica e l’evoluzione vulcanotettonica
tardo-Quaternaria del sistema caldera di collasso - faglia anulare - risorgenza intra-calderica del settore
sommerso della caldera del TGN. A tal fine è stata analizzata una fitta maglia di profili sismici a riflessione
monocanale di alta (Sparker) ed altissima (Subbottom Chirp) risoluzione. I dati sismici sono stati
successivamente integrati sia con quelli ottenuti dall’analisi di carotaggi a gravità e batimetrici multibeam
che con quelli disponibili in letteratura e, nell’insieme, analizzati in ambiente GIS.
I nuovi dati indicano che il settore interno dell’area collassata a seguito dell’eruzione del TGN evolve
inizialmente in condizioni di mare basso. L’area intra-calderica viene successivamente interessata dalla
formazione di una struttura antiforme (risorgenza intra-calderica) il cui tasso di sollevamento è stato
comparabile con l’innalzamento eustatico nell’intervallo Pleistocene superiore – Olocene [Lambeck et al.,
2011]. A circa 10 ka B.P. il settore centrale della struttura risorgente raggiunge l’esposizione subaerea
(terrazzo morfologico de “La Starza”).
La calibrazione dei profili sismici Chirp con markers tefro-stratigrafici riconosciuti in un carotaggio e
datati al 1538 A.D., 79 A.D. indica l’instaurarsi di un periodo di subsidenza in epoca post-Romana, registrato
dall’annegamento di 10-25 m del cuneo di progradazione infralittorale rispetto alle profondità di equilibrio
funzionale attualmente segnalate in area Mediterranea. L’interpretazione sismostratigrafica rivela, inoltre, la
presenza di fluidi che risalgono attraverso la zona di faglia anulare che delimita la caldera del TGN.
Bibliografia
Lambeck, K., Antonioli, F., Anzidei, M., Ferranti, L., Leoni, G., Scicchitano, G., Silenzi, S., (2011). Sea
level change along the Italian coast during the holocene and projections for the future. Quaternary
International, 232, 250-257
The proximal marine record of Somma-Vesuvius volcanic activity in the Naples and Salerno bays, Eastern Tyrrhenian Sea, during the last 3 kys.
No full textThe tephrostratigraphic analysis of nine gravity cores acquired on the continental shelf of the Naples and Salerno bays documents the proximal record of Somma-Vesuvius volcanic activity during the latest Holocene (last 3 kyrs). Five tephra layers from southern Naples Bay and three tephra layers from northern Salerno Bay were recognised in cores and their sedimentologic structures, textural parameters, stratigraphy and major and trace-element composition described. Proximal products of the well known 79 A.D. eruption along with those of the interplinian activity at 2.7 ka B.P., were identified both in the southern Naples Bay and in the northern Salerno Bay. They represent excellent marker horizons interbedded within the Late Holocene marine record. In addition, several radiocarbon datings provided age constraints on a number of tephras overlaying the 79 A.D. deposits and allowed a detailed stratigraphic reconstruction of medieval (1137 A.D.-685 A.D.) and more recent eruptions as recorded for the first time at sea. These results integrate previous research carried out on subaerial deposits providing new insights on the dispersion, deposition and grain-size distributions, along the northern Campania coastal zone, of recent Somma-Vesuvius products, some of which are still poorly known. The tephrostratigraphic approach to the study of marine sequences of proximal and adjacent areas can thus provide a more detailed description of physical characteristics of pyroclastic deposits, necessary for the correct assessment of volcanic hazard in the area. © 2007 Elsevier B.V. All rights reserved
Tephrostratigraphy of Naples and Salerno bays (eastern Tyrrhenian sea): implications for the late Pleistocene-Holocene evolution of volcanic activity in the Campania region.
No full textVolcanology and petrology of the south-western sector of the Campi Flegrei, southern Italy
No full text
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
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
Architecture of the NYT caldera and inner resurgent dome (Pozzuoli Bay, Campi Flegrei): new insights from seismic reflection and DInSAR data
No full textThe Campi Flegrei and its offshore prolongation (Pozzuoli Bay) are a volcanic area dominated by a collapse caldera
associated with the Neapolitan Yellow Tuff (NYT) eruption, occurred at ~15 ka BP, and by an intra-caldera resurgent
dome. We present new insights into: a) the geometry and kinematics of faults formed inside the caldera, b) the architecture
of the resurgent dome, and c) the relationship between the structural elements of the resurgent dome and ground
deformations. This work is based on the integration of high- and ultra-high resolution seismic data, swath bathymetry
data and ground deformation maps. The main results highlight that the NYT caldera, offshore, is characterized by an
ellipsoidal shape, elongated towards the ESE direction, with axes of ~8 km and ~7 km. It is bounded by a ~6 km long and
1–2 km wide ring fault zone (RFZ) mainly consisting of an inward-dipping normal fault system and antithetic, outwarddipping,
faults. The sedimentary fill of the caldera is up to 60 m thick, and can be divided into six units, characterized by
different seismic facies, composition and depositional process.The inner-caldera resurgent dome, ~ 5 km in diameter, is
limited by inner boundary of RFZ and consists in a broad antiformal structure with brittle deformation localized in an
apical graben. The base of the resurgence corresponds to the thalweg of the Epitaffio valley in the western sector of the
Pozzuoli Bay and the Bagnoli valley in the eastern one. The maximum cumulative uplift of the resurgent dome is ~180
m while its average uplift rate is ~ 9–12 mm/year, between 15.0–6.6 ka BP. A subsidence of ~10 m is suggested by the
drowning of the infralittoral prograding wedge below the present-day storm wave base for the last 2 ka.The deformation
velocity pattern of the Campi Flegrei displays a radial symmetry centered on the Pozzuoli harbor. It is possible to
distinguish three almost-concentric sectors namely S1, S2, S3 with decreasing velocity from S1 (13-32 mm/year) to S3
(0.3-7.7 mm/year). The highest value (26-32 mm/year) is recorded at the Pozzuoli harbor. Sector S1 is bounded by a NE–
SW-trending fault to the west and NW–SE faults to the east. The data suggests that this sector coincides with the resurgent
dome of NYT caldera. The base of the latter corresponds to the faults bordering sector S1, and it can be correlated with
the base of the resurgence recognized offshore. Sector S2 represents a narrow strip located between the base of the
resurgence and the onland prolongation of the inner boundary of the RFZ.The results of our research provide new insights
into the stratigraphic architecture and the shallow structure of the NYT collapse-caldera in the Pozzuoli Bay. Furthermore,
they represent a base to reconstruct the entire onshore-offshore geometry of the inner-caldera resurgence and infer new
constraints on the dynamics of the fluid flow system and magma source at depth
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