Search results for " Tectonic"

Active geodynamic in the central Mediterranean: Transfer of mantle fluids across the north-eastern Sicily

2019

Outgassing of mantle fluids across an tectonically active crustal segment in between two volcanic systems (Etna and Aeolian arc): the Nebrodi-Pelorit…

2018

Mantle-degassing occurs primarily through active volcanic systems and young oceanic lithosphere. Mantle-volatiles are also released by tectonically active continental regions, but the magnitude of this phenomenon is far less characterised. Helium (He) is a powerful tracer to track deep volatile degassing, because the mantle contains more 3He than the crust/atmosphere systems, which are dominated by radiogenic 4He produced in the crust. Here, we studied the volatiles in thermal manifestations discharged along the Nebrodi- Peloritani chain in north-eastern Sicily, with the aim of investigating the origin of thermalism and the related fluids. Thisseismically active region connects the African-…

Seismic Network Evaluation through Simulation: An Application to the Italian National Seismic Network

2011

Abstract A properly organized seismic network is a valuable tool for monitoring seismic zones and assessing seismic hazards. In this paper we propose a new method (seismic network evaluation through simulation, SNES) to evaluate the performance of hypocenter location of a seismic network. The SNES method gives, as a function of magnitude, hypocentral depth, and confidence level, the spatial distribution of the number of active stations in the location procedure and their relative azimuthal gaps, along with confidence intervals in hypocentral parameters. The application of the SNES method also permits evaluation of the magnitude of completeness ( M C ), the background noise levels at the sta…

Modelo de cabalgamiento profundo para el Alto Atlas (Marruecos). Implicaciones sísmicas en la zona de colisión entre Eurasia y Africa

2007

Previous crustal models of the High Atlas suppose the existence of a mid-crustal detachment where all the surface thrusts merged and below which the lower crust was continuous. However, both seismic refraction data and gravity modeling detected a jump in crustal thickness between the High Atlas and the northern plains. Here we show that this rapid and vertical jump in the depth of Moho discontinuity suggests that a thrust fault may penetrate the lower crust and offset the Moho (deep-rooted “thick skinned” model). The distribution of Neogene and Quaternary volcanisms along and at the northern part of the High Atlas lineament can be related to the beginning of a partial continental subduction…

The Mulgandinnah Shear Zone; an Archean crustal scale strike-slip zone, eastern Pilbara, Western Australia

1998

Abstract A large part of the deformation in the Archean Pilbara granitoid-greenstone terrain is localized in relatively narrow shear zones. The Mulgandinnah shear zone (MSZ) is a major one of these, with a width up to 8 km, that can be followed for over 70 km along strike in the Shaw Batholith in the eastern Pilbara. It forms part of the Mulgandinnah Lineament, that can be traced to the Lalla Rookh Basin and the Carlindi Batholith in the north, giving it a total length of over 150 km. The MSZ contains both mylonites and ultramylonites, both of which have foliations that are subvertical to steeply dipping, with the ultramylonitic foliation overprinting the mylonitic foliation to form more lo…

Hotspot distribution, gravity, mantle tomography: evidence for plumes

1999

Abstract Thermal convection is the motor of Earth dynamics and therefore is the link between plate motions, hotspots, seismic velocity variations in the mantle, and anomalies of the gravity field. Small scale mantle anomalies, such as plumes, do, however, generally escape detection by tomographic methods. It is attempted to approach the problem of detection in a somewhat statistical manner. Correlations are sought between spherical harmonic expansions of the fields under study: the hotspot distribution, mantle velocity variations, gravity, heat flow. Using spherical harmonic representations of global fields implies integration and averaging over the whole globe. Thus, although relationships…

Transfer of mantle derived fluids across the Calabrian-Peloritan arc: tectonic and geodynamic implications

2019

Mantle degassing occurs principally through active volcanic systems and young oceanic lithosphere. Tectonically active regions on the continental crust may additionally contribute a (poorly quantified) fraction of the deep CO2 budget. We studied volatiles in thermal manifestations along the seismically active Nebrodi-Peloritani chains (NE Sicily), to investigate the origin of thermalism and the sources of the outgassing fluids. The geological evolution of the area has been controlled by the interaction between the European and African plates and links the African Maghreb with the European Apennines. The collected samples exhibit 3He excess, supporting active outgassing of mantle-derived vol…

Tidal notches, coastal landforms and relative sea-level changes during the Late Quaternary at Ustica Island (Tyrrhenian Sea, Italy)

2017

In this paper we present and discuss data concerning the morphostructural evolution at Ustica Island (Tyrrhenian Sea, Italy) during Late Quaternary. New insights on the relative sea-level changes of Ustica are coming from data collected during a geomorphological field survey around the island, together with the bathymetric analysis of the surrounding seabed and 14C datings on samples of speleothems, flowstones and marine shells found inside three selected sea caves. The survey was mainly accomplished on June 2015 through the first complete snorkel investigation off the about 18 km-long volcanic coast of the island, which allowed to precisely define location, relationship and morphometric fe…

Palaeogeographical evolution of the Egadi Islands (western Sicily, Italy). Implications for late Pleistocene and early Holocene sea crossings by huma…

2019

Abstract The continental shelf morphology offshore of western Sicily suggests that during the Last Glacial Maximum (LGM, 20 ka cal BP), two of the Egadi Islands, Favignana and Levanzo, were connected to Sicily by a wide emerged plain, while Marettimo was only separated from the other islands by a narrow channel. We studied the relative sea-level variation from the LGM until today, focussing on two important time slices: the Mesolithic (9.5–13 ka cal BP) and the Neolithic (6.5–7.5 ka cal BP). In this research, we discuss a sea-level rise model by means of geomorphological, archaeological and geophysical observations and new radiocarbon dating of marine and terrestrial fossil fauna. The resul…

Deformation history during chain building deduced by outcrop structural analysis: The case of the Sicilian fold-and-thrust belt (Central Mediterranea…

2015

Abstract The Sicilian fold-and-thrust belt is located in the central Mediterranean area, and it represents the south-eastern arcuate segment of the Apennine-Maghrebide orogen. The tectonic evolution of the Sicilian belt is documented after outcrop analysis of small-scale structural features carried out throughout the region. Results are consistent with the following four main deformation stages having affected the study area, from the oldest to the youngest: (i) multilayer weakening; (ii) folding-and-thrusting, (iii) extension, and (iv) renewed thrusting. The first deformation stage included three different substages (layer-parallel shortening, bed-parallel simple shear and fold nucleation)…