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Sequence of deformation in the sicilidi units (northern sicilian chain)
No full textThe foredeep deposits of Northern Sicily, indicated as Sicilidi units, have undergone different deformations' since Oligocene time. The resulting tectonic Structures, analysed in several outcrops in the Eastern Madonie Mts, are 1 cm-to- 100 m in scale and are similar to the larger structures forming the Sicily belt, allowing for scale extrapolation. Also the overprinting relationships of the minor structures recorded in the so-called Tufiti di Tusa reflect the sequence of fault activation which determined the present-day geometry of the tectonic units, suggesting that the tectonic evolution of the foreland basin developed during the stacking of the Maghrebide fold-and-thrust belt. The overprinting relationships between the mesoscopic structures indicate that the flysch-like Succession (Tufiti di Tusa Fin. auct.) experienced layer-parallel extension and sediment compaction, followed by thrusting, low-angle normal faulting and renewed compression/transpression. The earlier episode of extension is related to the tectonic regime which affected the foredeep ahead of the thrust front during the Oligocene. Compression, in places represented by fault reactivation and inversion, reflects the foredeep deformation, progressively incorporated into the belt during the Miocene. The second event of extension overprints folding and faulting, in places inducing negative inversion of the contractional structures during the Late Miocene, and is related to chain collapse on reaching supercritical wedge taper conditions. The transpressional neotectonic structures reflect the shear zone which has affected the Southern Tyrrhenian margin since the Pliocene
The contribution of the pre-existing structures in mountain belt evolution: the example of the negative inversion in the Northen Sicily
No full textSyn-orogenic extension has been recognised in Northern Sicily. Mesoscopic analysis has been carried out in three key areas, where folded-and-thrust Mesozoic-to-Tertiary rocks crop-out. The three examples are inherent to Portions Of tectonic Units Which occupy progressively more internal positions in the Sicilian chain from west to east. The extensional deformation is mainly represented by low-angle normal faults and shear bands. A common kinematic process seems to affect the other sector of the chain during the extension and is represented by a generalized negative inversion of previous layer-parallel shear bands and detachments related to the thrusting. The extensional deformation occurred during the late Miocene. It significantly modifies the architecture of the chain through the sliding-back of the tectonic units and may be related to the evolution of the wedge taper
Plio-Pleistocene strike-slip deformation in NE Sicily: the example of the area between Capo Calavà and Capo Tindari
No full textThe Peloritani Mts. in Northeastern Sicily are part of the Sicilian orogenic belt interposed between the Tyrrhenian basin and the Ionian Basin. In the Tyrrhenian basin crustal thinning has been active since the late Miocene, whereas wedge accretion (External Calabrian Arc) has occurred in the Ionian basin, due to the north-westward subduction of the Ionian Plate below the Calabrian-Peloritani Arc.
Strike-slip tectonics in NE Sicily occurred during Plio-Pleistocene times. Faulting caused a non-uniform uplift rate of the Plio-Pleistocene deposits, which are elevated up to 500 m above sea level. The structural pattern is mainly represented by NW-SE and N-S/NNE-SSW trending transcurrent faults which form asymmetric tectonic depressions. Normal and reverse oblique-slip faults are associated with large-scale strike-slip deformation bends, and form releasing and restraining structures.
The normal faults are mostly listric and flatten at very shallow levels, in places re-activating older thrusts. Transtension in the northern coastal sectors is southwards, counteracted by transpression, which is represented by high-angle reverse faults in the Peloritani thrust front. High seismic activity is mostly located within these bands, both on land and in the Tyrrhenian offshore, indicating active deformation processes. Focal solutions suggest that the Peloritani Mts. are characterised by extension and transcurrent kinematics in agreement with the stress field resulting from the orientation of the outcropping strike-slip structures.
A cards-pack non-uniform rotation around a vertical axis in the Peloritani thrust stack is proposed to explain the geometrical pattern of the strike-slip faults. Within the main W-E trending shear zone, the minor structures result from simultaneous extension, transcurrent movement and compression in each band, transferring the strain from the Tyrrhenian sectors (dominated by crustal thinning) to the Peloritani thrust front
Growth pattern of underlithified strata during thrust-related folding
No full textAsymmetric anticlines with overturned or steeply dipping forelimbs and gently dipping backlimbs are generally interpreted as thrust-related folds. Fold asymmetry occurs as a consequence of forelimb rotation. If deformation takes place in environments dominated by submarine sedimentation, the limbs coincide with the slope (depositional surface) and rotation reflects slope steepening. If folds are nucleated in poorly or unlithified deposits, growth geometry also depends on the properties of the media, such as cohesion and the angle of internal friction. For cohesionless deposits, the tilting of the slope influences the equilibrium of the soft sediments, resulting in gravity-driven flow, re-mobilisation or in situ compaction. The occurrence of mass re-mobilisation is also connected with the limb tilting/lithification ratio. Hence, the presence of non-primary bedding geometries or soft-sediment deformations in folding-related growth strata may provide useful tools for deciphering contractional kinematics. Deformation of underlithified sediments during thrust-related folding is recorded in the outer sector of the Neogene Sicily chain (Central Mediterranean). Deformation occurred during the building of the Pliocene chain. Folding is the driving mechanism of the growth stratal pattern. Fold nucleation and amplification influenced the inclination of the slope of the basin floor where sediments were deposited. Slump and stretching structures in soft sediment occurred during folding and mass accumulation at the base of limbs led to a decrease in slope inclination. Analysis of fault-related fold and gravity-driven geometries enable us to reconstruct the contractional kinematics and the behaviour of syn-tectonic deposits that modify the growth fold pattern in terms of limb-hinge change of length-thickness
Transtensional/extensional fault activity from the Mesozoic rifting to Tertiary chain building in Northern Sicily (Central Mediterranean)
No full textExtensional structures of different ages characterize the Sicilian fold-and-thrust belt. Normal faults ranging in geometry from stepped to listric and formed in different geodynamic settings significantly controlled the pattern of syn-tectonic deposits. Since Mesozoic times Sicily has experienced deformation related to the opening of the Tethys Ocean. Between the Upper Triassic and the Cretaceous normal, strike- and oblique-slip faults, developed in northern Sicily, in the framework of a transtensional deformation regime induced by the oblique rifting of the African and European continental passive margins. Since Tertiary times a reversal in the general relative plate motion induced convergence, followed by collision of the European and African margins. Neogene compressional deformations were locally associated to extensional structures related to the orogenic wedge taper and to the Pliocene-Pleistocene Tyrrhenian Basin evolution. The persistent activity of extensional structures at different times and within different tectonic pictures is magnificently preserved in the following Triassic-to-Recent stratigraphic record: (i) carbonates were deposited on the Jurassic passive margin, formed by neritic platforms and intervening pelagic basins; (ii) the Cretaceous extension in the Africa plate boundary followed Late Triassic-Early Jurassic transtension due to Neotethys stretching; (iii) clastic deposition occurred during Neogene chain building ahead of the advancing thrust front (foredeep deposition) and in the inner sectors of the orogenic wedge (perched deposition in extensional setting); (iv) the perched-basin deposition at the rear of the wedge was probably related to the extensional collapse of the taper during the Late Miocene and (v) the attenuation of previously thickened lithosphere corresponds to the onset of the Tyrrhenian stretching
La distensione tetidea ed il suo controllo sulle strutture compressive del sistema appenninico-maghrebide: l'esempio dei Monti delle Madonie (Sicilia centro-settentrionale)
No full textL'assetto tettonico dei Monti delle Madonie (Sicilia centro-settentrionale) è caratterizzato dalla presenza di un importante lineamento orientato NNW-SSE che si estende per circa 20 Kkm da Gratteri fino a M. Mufara, individuando un settore orientale, dove affiorano le successioni della piattaforma carbonatica panormide, ed un settore occidentale, dove affiorano i depositi del bacino imerese. I risultati di uno studio stratigrafico-strutturale consentono di definire il ruolo svolto da questo lineamento tettonico dal Trias superiore al Pliocene. In particolare, l'analisi cinematica mostra che il lineamento corrisponde alla rampa òlaterale di un sovrascorrimento, attivo durante l'intervallo Miocene medio-Pliocene, lungo il quale le unità panormidi si sono sovrapposte tettonicamente alle unità imeresi. L'analisi stratigrafica ed i rapporti fra le facies delle successioni meso-cenozoiche mostrano che la rampa laterale mio-pliocenica si è impostata su una pre-esistente struttura attiva già dal Trias superiore. Durante l'intervallo Trias superiore-Cretaceo questa struttura ha agito come faglia diretta e/o transtensiva, individuando aree a sedimentazione neritica ed aree a sedimentazione pelagica. A partire dal Cretaceo superiore la struttura distensiva è stata riutilizzata come faglia di trasferimento fra sistemi di faglie dirette orientate W-E che si originano probabilmente in risposta ai movimenti convergenti orientati N-S ed attivi nella futura area mediterranea durante l'intervallo Cretaceo superiore-Oligocene
Multi-scale properties of strike-slip faults crosscutting the Pleistocene carbonate grainstones of Favignana Island (NW Sicily, Italy).
No full textAfter detailed field (stratigraphic and structural) and laboratory analyses of intact and deformed rocky outcrops,
we studied the multi-scale properties of strike-slip faults nucleated and developed in Pleistocene carbonate
grainstones of Favignana Island (Sicily, Italy). This skeletal carbonate rocks ranging in thickness between 5 and
20 meters make up the whole eastern side of the Island, where they unconformably lie on silicoclastic deposits of
the Upper Pliocene.
The studied structures are very similar to those one affecting carbonate grainstones of San vito Lo Capo Peninsula
(Sicily, Italy) and already documented in a recent paper. There strain localization into narrow bands encompass
first compaction, shear, pressure solution formation, their subsequent shearing, and finally cataclasis. The
transitions from one deformation process to another, which were likely controlled by changes in the material
properties, are recorded by different ratios and dissimilar distributions of the fault dimensional attributes.
In Favignana Island, the results of our study allow us to: (i) indentify two conjugate sets of faults trending NW
and NNE, characterized by right-lateral and left-lateral kinematics, respectively; (ii) document the progression of
the deformation from single compactive shear bands, with an offset ranging between mm’s to cm’s, to zones of
compactive shear bands, characterized by a larger amount of offset with discontinuous cataclasis and slip surfaces,
and finally to well developed faults, with an inner cataclastic core surrounded by wider damage zones made up
of compactive shear bands, joints, and possible dilational bands; (iii) decipher that linkage processes, responsible
for fault development, took place by mechanical interaction of adjacent individual structures at any deformation
stage (single bands, zone of shear bands or well developed faults) with formation of characteristic ramp and eye
structures.
Based on their internal architecture and petrophysical properties, the studied strike-slip faults behave as combined
barrier-conduit hydraulic structures to fluid flow. The single compactive shear bands, the shear band zones, and the
cataclastic cores of the faults have a lower porosity relative to the surrounding carbonate host rocks, and therefore
form seals for cross-fault fluid flow. On the contrary, the discrete and undulated slip surfaces present either within
or at the edges of the fault cores enhance the along-fault fluid flow.
Finally, the detailed analyses of macro- and mesostructural features exposed in Favignana Island show that the
overall deformation pattern in the area may be interpreted in terms of strike-slip tectonics driven by a current
stress field geometry characterized by a NW oriented maximum compression. The stress field acting in the area
appears to be directly controlled by the convergence between the African and European plates. The present-day
Africa motion along NNW–SSE- to NW–SE-directed vectors is substantiated by geological, seismological, VLBI
(very long baseline interferometry) and global positioning system data
Evoluzione tettonica mesozoico-terziaria della Sicilia centrosettentrionale
No full textSicily owes its complex geological structure to a switch in tectonic regime from the Mesozoic to the Tertiary. A set of tectonic units outcrops in the northern portion of the island that originated during the Tertiary at the expense of paleogeographic domains of the African Mesozoic continental margin. The pre-orogenic successions show different types of deformation (extensional and transcurrent) related to the Jurassic paleotectonic evolution of the southern
Neotethys margin. The history of the tectonic inversion of the Neotethys shear
zone is recorded in the Cretaceous strata. Extension occurred during late Cretaceous and may be compatible with the tensile stress field related to the Sicilide basin opening. The Neogene deformations are linked to collisional processes and are mostly represented by thrusts and folds. Since the late Miocene onwards, the formation of the Tyrrhenian basin has driven the recent
tectonic evolution of Northern Sicily. Its basin formation was realised through
extension, followed by transcurrent tectonics along its southern margin.Published148-1523.3. Geodinamica e struttura dell'interno della TerraN/A or not JCRreserve
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
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