1,721,255 research outputs found
Morfologia e morfometria del settore ionico del Golfo di Taranto.
Full text linkIl versante Ionico del Golfo di Taranto è caratterizzato dalla presenza di alti strutturali e bacini che
rappresentano l’espressione morfologica di sistemi di faglie pleistoceniche transpressive. La dorsale di
Amendolara si estende per 45 Km in direzione N130°E, ed è caratterizzato dalla presenza di tre alti
batimetrici minori (denominati Amendolara, Rossano e Cariati). Verso NE, la dorsale di Capo Spulico si
estende per 40 Km in direzione !N115°E.
Durante la Campagna Oceanografica “Teatioca” sono stati acquisiti 1100Km2 di dati batimetrici
multibeam e profili sismici monocanale ad alta (Sparker) ed altissima risoluzione (Subbottom Chirp).
L’analisi integrata dei nuovi dati ha consentito di ottenere una sintesi morfostrutturale preliminare dell’area
sud-orientale del Golfo di Taranto [Santoro et al., 2012].
L’insieme dei dati morfometrici evidenzia un ruolo chiave nell’attività traspressiva della faglia che borda
a SW la dorsale di Amendolara, in quanto la regolarità dei pendii rivolti a S è legata alla deformazione e
sollevamento dei versanti, che tende a superare l’effetto dei processi erosivi (versanti a controllo morfostrutturale).
Il processo di basculamento guidato dall’azione della faglia sembra essere all’originedei processi
responsabili dell’erosione gravitazionale canalizzata sui pendii esposti a nord (versanti a controllo morfosedimentario).
Sette ordini di terrazzi sono stati riconosciuti sul top del Banco di Amendolara, attraverso tecniche di
analisi dei picchi nel diagramma di distribuzione delle quote [Passaro et al., 2011]. Tale dato e le statistiche
sui profili estratti dal DTM testimoniano la presenza di tassi differenziali di sollevamento ed un complessivo
tilt (verso E) del settore frontale ionico dell’Appennino Meridionale, in accordo con quanto suggerito in
letteratura [Ferranti et al., 2009].
Bibliografia
Ferranti, L., Santoro, E., Mazzella, M.E., Monaco, C., Morelli, D., (2009). Active transpression in the
northern Calabria Apennines, southern Italy. Tectonophysics, 476 (1-2), 226-251.
Passaro, S., Ferranti, L., de Alteriis, G., (2011). The use of high resolution elevation histograms for mapping
submerged terraces: a test from the Eastern Tyrrhenian Sea and the Eastern Atlantic Ocean. Quat. Int.,
232, 1-2, 238-249.
Santoro, E., Ferranti, L., Passaro, S., Burrato, P., Morelli, D., (2012). Morphometric analysis in the offshore
of the southern Taranto Gulf: unveiling the structures controlling the Late Pleistocene-Holocene
bathymetric evolution. Rend. On. Soc. Geol. It., 21 (2), 1132-1135
Underwater cave systems in carbonate rocks as semi-proxy indicators of paleo-sea levels
No full textUnderwater caves may yield valuable information on changes in sea level, as they can track the position of an ancient sea level to a variable degree of accuracy. Limestone caves, in particular, develop different morphologies as a function of oscillating sea levels. In carbonate settings, when true coastal caves including precise indicators of sea-level such as notches or beach deposits are lacking (which hold true as paleo-sea levels indicators for any type of lithology), ancient stillstand levels are approximated: 1) by determining a former groundwater level for continental karst processes (which subsequently experiences submersion) provided they acted sufficiently close to the coast; 2) by determining a mixing zone of different solutions leading to hyperkarst processes. The wide range of different typologies developed in the limestone coastal belt of the Tyrrhenian Sea (Italy), yields case-histories which can be taken as representative of the relationships between relative changes in sea levels and the evolution of karst systems. In particular, the occurrence of features related to hyperkarst processes can be reliable "semi-proxy" indicators of paleo-sea levels in absence of more precise markers
Late pliocene-quaternary tectonics of the Matese Massif (Southern Apennines): Late shortening and {"}neotectonic{"} extension,Tettonica tardo pliocenica-quaternaria dei Monti del Matese (Appennino meridionale): Raccorciamenti tardivi e distensione {"}neotettonica{"}
No full textThrust tectonics in the Picentini Mountains, Southern Apennines (Italy)
No full textDetiled geological mapping carried out in the Picentini Mountains, Southern Apennines, Italy, allowed to reconstruct the geometry of the fold and thrust belt in this region. Contractional structures were formed during multiple episodes of ENE to NNE shortening and were cut during later extension by low- and high-angle normal faults. Based on timing of emplacement and geometrical relationships between thrust units, we worked out a kinematic model of thrust tectonics. Basinal (Sicilid and Lagonegro) units were thrust eastward onto a carbonate-platform-basin system (CPBS) starting in the Serravallian-Torto- nian, and were in turn overridden by the CPBS units by means of deeper decollement thrusts. Later contraction, starting from late Tortonian-Messinian times, built up a 15-km-thick antifonnal stack during SSW-NNE shortening. We applied the forward kinematic model of thrust imbrication to perform a qualitative palinspastic restoration of a regional cross-section through this area, based on published interpreted seismics and other subsurface data. The thrust tectonics of the Picentini Mountains and more northward regions was controlled in the internal sectors mostly by envelopment thrusting of carbonate platform thrust sheets, which formerly were the floor complex of the Tortonian thrust belt, while multiple progressive decollement of the basinal roof complex occurred in the external part of the belt. Shallow crustal extension on low-angle faults with transport direction oblique to orthogonal to contractional transport was responsible for contemporaneous thinning during the accretion of the antiformal stack at deeper structural levels
Geomorfologia costiera e subacquea e considerazioni paleoclimatiche sul settore compreso tra S. Maria Navarrese e Punta GoloritzË (Golfo di Orosei, Sardegna).
No full textA coastal and underwater geomorphological study has been carried out between S. Maria Navarrese and Punta Goloritze on the southern sector of the Gulf of Orosei (Eastern Sardinia). The underwater sector was surveyed by means of SCUBA-diving equipment down to a depth of -40 m. In this sector we recognized evidence of a stillstand at -10/12 m, that we correlated to a stage older than the last glacial, and supposedly younger than the 4e; submerged continental deposits, mostly formed by eolianite and coarser gravel intercalations, were extensively mapped. The eolianites are mainly formed by calcareous sands with subhorizontal to cross-stratification, and are continuous with the continental deposits of upper Pleistocene age outcropping along the coastal cliff. Submerged speleothems sampled down to 10 m depth have a radiocarbon age of about 23-22 ka BP; indicating a speleothem growth during the last glacial peak, when in more continental and high-latitude settings glacial conditions halted the water supply and speleothem formation. -from English summar
Evidenze geomorfologiche sommerse nelle aree costiere italiane di uno stazionamento del livello del mare ubicato a circa -20 m e attribuito allo stadio 3
No full textUnderwater investigations along the Italian coasts have shown a recurrent paleo-sea level at -18÷-22 m below the present sea level. Geochronoiogical age determinations on submerged speleothems used as sea-level markers and sampled at around -20 m, suggest that the paleo-sea level corresponds to the highest stand reached by the sea during the isotope stage 3, between 48 and 27 ka. Geomorphological evidence of this paieo-sea level are remains of a subhorizontal abrasion surface, which is visible on cliffs bordering carbonate promontories. Analogous surfaces (terraces) are mainly observed in the Tyrrhenian Sea from Tuscany to Sicily and in Sardinia at similar depths (-16÷-22 m); examples are also visible along the Apulia's coast in the Adriatic Sea. Recurrent geomorphological features of these terraces are: a) discontinuous but frequent occurrence; b) width lower than 10 m; c) location at the base of ancient cliffs; d) notch and pot-holes at the inner margin; e) in many cases terraces are laterally connected with the wave-enlarged mouth and levelled bottom of submerged caves, and with the flat top of ancient buttes. The general tectonic stability since Eutyrrhenian times (stage 5e of the oxygen isotope curve) in the regions where the observed forms occur, confines the relative age to well definite times. The absolute age of the paleo-sea level is yielded by speleothems sampled at about -20 m b.s.l. in Tuscany. These display marine biogenic episodes interlayered with continental ones. The 14C radiometric ages of the different layers keep such alternating episodes within the time span ranging from 27 to 42 ka (Alessio et al. 1992; 1994), namely during the highstand related to the isotope stage 3 (Aharon & Chappel, 1986). It is concluded that abrasion terraces and related morphological features found within the same depth interval formed during the stage 3 oscillating highstand
Middle Pleistocene to Holocene tectonics of the Sannio-Matese Mts. boundary: Geometry, kinematics and fault activity
No full textA multidisciplinary study along the north-eastern and western borders of the Matese and Sannio Mts., respectively, has been devoted to decipher the Quaternary to Recent deformation of this sector of the Apenninic chain (MASCHIO, 2003). The mesostructural and geomorphologic analysis, supported by data from low-magnitude seismic sequences (MILANO et alii, 1999; VILARDO et alii, 2003) has allowed to: (1) map the distribution of Middle Pleistocene-Holocene normal fault systems; (2) assess geometry, kinematics and timing of deformation of the fault systems; (3) estimate averaged slip rates for the main tectonic structures, based on offsets of geomorphologic markers; (4) compare the fault kinematic and seismotectonic frame, (5) suggest a geometric model of the active deformation for this sector of the Apenninic chain, that helps clarify the relationships between exposed faults, historical and instrumental seismicity, and seismicity of boundary segments. In detail, the investigated fault systems present an articulated geometry and a complex kinematics in respect to the NE-SW direction of extension typically observed in the Southern Apennines. The tectonic control of inherited structures on active faulting plays a key role on the geometric arrangement of the arrays, formed by N-S and E-W segments which link each other to NW-SE striking, young deformation zones. Quaternary to Recent deformation appears to be accommodated by slip partitioning both on sub parallel structures and on variously striking but kinematically coordinated faults, active within a non-plane strain environment. The fact that slip is heterogeneously distributed in space is consistent with the focal mechanisms of the 1997-1998 low magnitude seismic sequences (MILANO et alii, 2001; VILARDO et alii, 2003). Inspection of the spatial distribution and differential elevation of remnants of sub-horizontal erosional and/or depositional surfaces, referred to various morphological events, has documented a migration of faulting during the Middle/Upper Pleistocene-Holocene and permitted to estimate vertical slip-rates for most of the segments of the fault systems. The main results are listed as follows: - a NE-dipping fault array in the Matese Mts. is active after 2 Ma (from Sassinoro to Guardiaregia to Roccamandolfi villages) and has a cumulate slip rate up to 0.31 mm/a; - most of the main fault systems of the northern border of the Matese Mts. and of the main antithetic ones of the southern border of the Montagnola di Frosolone are active after 0.7 Ma and have integrated slip rates up to 1.37 mm/a and to 0.33 mm/a, respectively; - range-bounding faults of the Matese and Sannio Mts., together with the N-S oriented Le Piane fault (DI BUCCI et alii, 2002), are active mostly after 0,12 Ma with cumulated slip rate of 1,0 mm/a. We suggest these fault systems are representative of an articulated, NE-dipping seismogenic structure, which is internally constituted of both E-W oriented inherited faults linking major NW-SE younger faults, and has NNW-SSE striking faults at its terminations (i.e. Le Piane and Castelpizzuto faults, towards north and Sassinoro, Collalto and Pescosardo faults, towards south). The cumulate slip rate estimates highlights that most of the strain accumulation is concentrated in the middle of the seismogenic structure, from Sepino-Guardiaregia to Castelpizzuto villages. Slip on the structure boundary can occur both during large earthquakes and low-energy seismic sequences
Late Neogene horizontal and vertical displacement rates during simultaneous contraction and extension in the Southern Apennines orogen, Italy
No full textAssessment of vertical and horizontal displacements and displacement rates within the western Adriatic orogens, where contractional and extensional deformation coexists since the Miocene (PATACCA et alii, 1990; DOGLIONI, 1991), has the potential to supply vital insight into crustal and lithospheric processes operating during continental collision. Using the tight age control on contractional motion provided by synorogenic sequences preserved in outcrop and in petroleum exploration wells, the constraints on extensional motion provided by the crustal structure of the extended hinterland, and the differential elevation of uplifted markers of ancient base level, we establish a regional pattern of vertical and horizontal motion in the Southern Apennines for the last ∼6 Ma, which points to an intricate interplay between lithospheric delamination and crustal structure (FERRANTI & OLDOW, 2005a; 2005b). During latest Miocene to Early Pleistocene, the frontal thrust of the orogen migrated toward the foreland rapidly (∼16 mm/yr) and was accompanied by subsidence with the frontal thrust belt and foredeep remaining at or below sea level. In contrast, the orogenic hinterland experienced extension, which was accompanied by uplift at -0.3 mm/yr along the eastern transition to the contractional belt but net subsidence and formation of the Tyrrhenian basin farther west. Through time, the extensional belt progressively widened toward the northeast at the same rate as the encroachment of the thrust front on the Adriatic foreland. Following a mid-Pleistocene reduction in horizontal displacement rate associated with impingement of the thrust belt on thick crust of the Adriatic interior, the frontal thrust belt and foreland experienced uplift at ∼0.5 mm/yr as contraction stepped to deeper structural levels. Uplift of the eastern margin of the extensional hinterland continued at ∼0.3 mm/yr and is followed by tectonic subsidence along the Tyrrhenian coast of southern Italy. Today, the pattern of mid-Pleistocene displacements continues, as suggested by seismicity and GPS velocities (OLDOW & FERRANTI, 2005). The similarity in migration rates of contractional and extensional fronts across southern Italy over the last 6 million years supports models of crustal delamination and roll-back of the subducted Adriatic slab (ROYDEN et alii, 1987; DOGLIONI, 1991) as a fundamental driving mechanism for deformation along the western margin of Adria. Temporal changes in the vertical and horizontal rates of deformation, however, probably reflect differences in crustal structure and are not directly related to lithospheric processes. The reduction in the horizontal displacement rate associated with the onset of rapid foreland and frontal thrust belt uplift during the Early Pleistocene corresponds to a change from thin - to thick-skinned contraction initiated with the involvement of thick continental crust in regional shortening. Unlike segments of the Apenninic chain in central Italy (LAVECCHIA et alii, 1994; CAVINATO & DE CELLES, 1999), uplift and formation of the Southern Apennine mountain chain was not primarily a response to contractional deformation. Much of the orogenic elevation, at least before the mid-Pleistocene onset of uplift in the frontal thrust belt and foreland, was accrued during the initial stages of extension related to crustal delamination
Studio morfometrico e statistico degli eventi di frananel settore marino orientale del Golfo di Taranto.
Full text linkLa campagna oceanografica “Teatioca” è il frutto della collaborazione fra l’Istituto per l’Ambiente
Marino Costiero (IAMC) di Napoli, l’Università Federico II di Napoli, l’Università di Palermo e Trieste e
l’INGV di Roma. Durante tale campagna, effettuata a bordo della N/O Urania del CNR nel 2011, sono stati
acquisiti dati batimetrici multibeam ad alta risoluzione ed una fitta maglia di dati sismici ad alta (Sparker) ed
altissima (Chirp) risoluzione nell’area ionica del Golfo di Taranto.
L’analisi integrata del Modello Digitale del Terreno (10m, 5m e 2m) generato dai dati multibeam con i
nuovi dati sismo-stratigrafici ha consentito di analizzare in dettaglio l’instabilità dei versanti. Una serie di
computazioni standard sul DTM (aspect, pendenza, gradienti e curvatura del profilo) hanno fornito una
prima valutazione della diversa esposizione dei versanti della dorsale di Capo Spulico e della dorsale di
Amendolara, i due alti strutturali presenti nell’area di studio. Tale area è stata successivamente suddivisa in 9
diversi settori, ognuno dei quali rappresenta un areale morfologico (versante o bacino), allo scopo di
caratterizzare il potenziale di franosità di ogni singola area e di evidenziare eventuali correlazioni fra le
diverse aree. Oltre 400 evidenze di eventi di frana nell’area in esame sono stati cartografate, classificate e
interpretate, fino ad ottenere carte tematiche utili all’interpretazione della franosità dei versanti su larga scala
(carte della pendenza media per ogni evento, della pendenza massima e minima, gradiente medio, etc.). Sulla
base dei dati acquisiti e delle computazioni effettuate sul DTM si è evidenziato che la pendenza non è il
parametro principale in termini di meccanismo di innesco degli eventi di frana. Questa considerazione risulta
anche dall’esame morfologico dei versanti meridionali della dorsale di Capo Spulico e del Banco di Cariati
[Santoro et al., 2012], che sono caratterizzati dai maggiori valori di pendenza nel DTM e dalla scarsità di
processi gravitazionali. I maggiori eventi di frana sono quasi totalmente localizzati sulle pendici nord-est
delle dorsali ridge. Tale distribuzione è principalmente legata alla giacitura dei sedimenti (a franapoggio
verso SO). Un’eccezione è rappresentata dal settore meridionale del Banco di Amendolara, dove sporadici
eventi di scorrimento rotazionale sono probabilmente legati all’attività tettonica della faglia di Amendolara.
L’utilizzo di un approccio statistico multivariato implementato in “R” conferma, infine, la concentrazione
degli eventi sui versanti controllati da evoluzione morfologica rispetto ai versanti controllati dalla tettonica.
Bibilografia
Santoro, E., Ferranti, L., Passaro, S., Burrato, P., Morelli, D., (2012). Morphometric analysis in the offshore
of the southern Taranto Gulf: unveiling the structures controlling the Late Pleistocene-Holocene
bathymetric evolution. Rend. On. .Soc. Geol. It., 21 (2), 1132-1135
Structural evolution and active tectonics in the Southern Taranto Gulf: insights from seismic reflection profiles analysis.
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