1,720,963 research outputs found
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
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
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
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
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
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
