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Evidence of new diapiric structures in the southern Adria Plate (Eastern Margin of Tethyan Ocean): Implications for Triassic paleogeography and evaporites remobilization during subduction/collision (Northern Ionian Sea, Central Mediterranean)
No full textIt has long been recognized that the Adria Plate, as well as the Dinaric-Hellenic sector, contains a large volume of Triassic salt associated with diapirism, and it is well known that Triassic evaporites in the Mediterranean Sea region were deposited over epicratonic platforms surrounding the Mesozoic passive margin of Tethys Ocean. However, the real extent of these evaporites is still unknown; especially in the deep-water offshore area where publicly available seismic reflection profiles are scarce and petroleum exploration wells are missing. Several authors highlighted the presence of Triassic salt structures, mostly triggered by Meso-Cenozoic compressions and associated with fold-and-thrust belts. Both the lack of data and the later compressions contribute to hiding how a diapiric structure, formed in a passive margin and characterized by dome's geometry, is remoulded to assume a teardrop geometry typical of diapirs in fold-and-thrust belts. Two end members of diapiric structures are discussed: extensional structures formed in a passive margin, and compressional structures formed in a fold-thrust belt. The transformation of one end-member into the other is not well known. In the Northern Ionian Sea, the Apulian foreland, belonging to the southernmost termination of the Adria Plate and considered one of the largest preserved Mesozoic passive margin block of the Tethys Ocean, is a deep-water area associated with the opposing fronts of the nearby Calabrian Arc/Apennines and Dinaric-Hellenic Chains since the Cretaceous. Therefore, it represents an ideal area for investigating both the real extent of Triassic evaporites and the transformation of the diapiric structures under different regional geodynamic contexts. Based on seismic reflection profiles but no petroleum exploration wells, we present evidence of Triassic evaporites in the deep-water portion of the Apulian foreland, as indicated by the interpretation of two diapiric structures never described previously. These two new diapirs likely formed from inherited Mesozoic salt structures such as pillows and/or salt domes. The identification of halokinetic-related sequences affecting the Plio-Quaternary foreland sediments allows constraining the polyphaser evolution of the two diapirs. We suggest they are reactivated in response to the compressive stresses transmitted by the nearby Calabrian Arc/Southern Apennines and Hellenides. But, after the Middle Pleistocene, extensional tectonics, related to Adria Plate flexuring, acted again, and the diapirs were cross-cut by normal faults. These observations and findings are integrated into the geological context that controls the fundamental features of the diapirs, providing new insights on the fate of diapiric structures formed in a passive margin, later involved in a subducting and colliding plate, and before they become part of a fold-and-thrust belt. Furthermore, the study provides new constraints on the Triassic paleogeographic reconstruction of the Northern Ionian and Central Mediterranean Seas at the continental margin of the Tethys Ocean
Is the Sicily Channel a simple Rifting Zone? New evidence from seismic analysis with geodynamic implications
Full text linkThe Sicily Channel is characterized by the presence of prominent WNW-oriented grabens (Pantelleria, Malta, Linosa Graben) which would point out a main extensional phase within this part of the northern African plate. However, the analysis of both seismic and wells data shows evidence of tectonic reactivation and contractional events in a N-S oriented band crossing the Gela Thrust System and the Malta and Linosa Grabens. We present and discuss the timing of the different deformation phases and their potential geodynamic framework with regard to the regional Africa and Europe convergence. We suggest four main deformation phases affecting the Sicily Channel in Neogene time: 1) a contractional phase, related to the thrusting of the Sicily Fold-and-Thrust Belt in the Upper Miocene, related to the evolution of the regional Western Mediterranean Subduction Zone, 2) an extensional phase with the opening of the main grabens in Lower Pliocene, related to the fast rollback of the Calabrian Slab to the East-Southeast of the Sicily Channel, 3) a Plio-Pleistocene contractional phase with inversion structures within the grabens and onset of transpressive deformation along the Capo Granitola-Sciacca Fault Zone (CGSFZ) and Scicli Ragusa Fault System (SRFS), related to the advance of the Gela Thrust System, and 4) a presently active, mild contractional phase affecting the area between the CGFFZ and SRFS, in particular the Malta and Linosa Graben, which might be related to a regional plate reorganization and potential subduction polarity switch north of Sicily
Velocity Model Construction and Time-to-Depth Conversion of a Vintage Seismic Reflection Profile for Improving the Constraints on a Subsurface Geological Model: An Example from the Sicily Channel (Central Mediterranean Sea)
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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
Accretionary wedge collision in the Ionian Sea: Timing and movement of the Calabrian arc and the Mediterranean ridge in the central Mediterranean Sea
No full textIn convergent plate boundaries, the pre-collisional stages, when most of the oceanic crust has already been subducted, are hidden and reshaped inside the tectonic units forming orogenic wedges. The central-eastern Mediterranean Sea is an example of a debated remnant ocean basin ideal for reconstructing these pre-collisional/early collisional stages of the mountain chain, hosting two subduction systems that develop along the irregular Africa-Eurasia plate boundary: the Calabrian and Hellenic Arcs. They include two opposite-verging accretionary wedges—the Mediterranean Ridge and the Calabrian Arc—separated by the Ionian Abyssal Plain, recognized for having an array of deep, reverse/transpressive faults, derived from previous extensional structures aligned with the Kefalonia Transfer Zone. It progressively narrows towards the NE, where the two wedges are facing each other. We analyse a geophysical dataset including bathymetric and seismic reflection profiles to reconstruct the structural evolution of the collisional setting and attempt a kinematic reconstruction at the transition between the Mediterranean Ridge and the Calabrian Arc. Opposite-verging, large-wavelength folds with high deformation rates are present at the transitional area between the two wedges. This structural style is different from the very low, tapered outer accretionary wedge present in the areas where the abyssal plain is still present. Seismo-stratigraphic analyses and kinematic reconstruction suggest that throughout the Pliocene, the Mediterranean Ridge's outward growth was prevalent, while starting from the Middle Pleistocene, the Calabrian Arc structural vergence prevails, and this is possibly related to the Calabrian Arc's clockwise rotation and its SE-ward migration. However, in recent times, such NE-SW-oriented positive inverted faults affect the Calabrian Arc-Mediterranean Ridge contact zone. We propose a polyphasic interaction between the two wedges, requiring a multidisciplinary approach including onshore-offshore correlations to reconstruct its driving mechanisms. These results shed new light on the complexities of the pre-collisional setting of Ceno-Mesozoic and older collisional orogens
The role of the Messinian evaporites in the identification of potential gas storage sites: A review of the Adriatic foreland basin system (Italy)
Full text linkFocusing on the late Miocene succession stratigraphic successions including the evaporite deposits from the Messinian salinity crisis (MSC) of the Adriatic foreland basin, a revision of available boreholes and seismic data allowed us to recognize the presence of reservoirs and seals systems that can be considered of potential interest for the storage of natural and synthetic gas. Potentially good reservoir sites can be found where porous rocks referable to siliciclastic turbiditites (Marnoso-arenacea and Laga Fms) or shallow-water carbonates (Bolognano Fm) preferentially involved in anticlinal structures and covered by thick MSC evaporites, which may represent effective reservoir seals. The integrated reconstruction of porous rocks distribution and facies, thickness, and lateral continuity of the overlying evaporites, allows the identification and zonation of geological settings in the Adriatic foredeep, backbulge and foreland with peculiar stratigraphy and deformations, only partially considered before, that may deserve consideration in the research of potential gas storage sites
New insights into the structural setting of North-Western offshore Sicily, Central Mediterranean
Full text linkThe North-Western offshore region of Sicily, located at the convergence zone of the Eurasian and African
tectonic plates is characterized by intricate geological and tectonic setting. The opening of the Tyrrhenian backarc basin led to the development of Plio-Quaternary extensional basins, which are characterized by inversion
structures. These structures located in the extensional basins of the examined region, have been identified
after the interpretation of several multi-channel seismic reflection profiles. The structural and stratigraphic
analysis was performed in compliance with the grid of seismic reflection profiles and the boreholes available
in the public ViDEPI database. The in-depth analysis of these inverted tectonic structures is attention-worthy.
We identified three basins in the area that highlight the inversion of variable intensity. They were all formed
during the Early Pliocene rifting phase, paired with extensive volcanic activity; the basins also suffered a
contractional episode afterward that resulted in their tectonic inversion. An inversion is registered within these
basins involving the Plio-Quaternary deposits. One among these basins shows a strong impact of inversion on
the entire sedimentary fill and it affects the sea floor.
This contractional episode has been linked to the proximity of the Sicily Maghrebian thrust front (Argnani
& Torelli, 2001) or a shift in the stress direction, signifying a compression in the N-S stress direction (Catalano
& Milia., 1990; Sulli, 2000).
Our analysis of inversion features is in agreement with previous studies in the NW offshore of Sicily and
provides insights into the deformation history of this region
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
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