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Preliminary Geodynamic Section of Central Italy between 41° and 42° N parallels
No full text""The Central Mediterranean region represents the zone where. the evolution of the Thetian collisional chain appears the most. complex (Bigi et al., 1991; Cavinato et al., 1994; Parotto et al.. 1996; Amato et al. 1997; Cassano et al., 2001; Cassinis at al,. 2003; Billi & Salvini, 2003). In the Central Italian peninsula the. chain is elongated roughly NW-SE and results from the Thetian. suture by the collision between a European and an African. microplate. The sector between the N 41° and N 42° parallels is. one of the most complicate tiles of this puzzle (Salvini, 1993).. Important geodynamic differentiations are present along both. sides (Favali et al, 1993; De Alteriis, 1995).. An ideal E-W transect, from W, locates four main. geodynamic blocks (Fig. 1). To the W is the Sardinia-Corsica. Block of European origin with relics of the sedimentary wedge of. his Thetian margin to the E (Bigi et al, 1991). It follows the. Tyrrhenian Sea, a basin characterized by thinned continental. crust topped with Miocene-Quaternary marine sediments directly. lying on Paleozoic basement (Patacca et al., 1990; Serri et al.,. 2001).. The third block corresponds to the Italian Peninsula with its. Apenninic structures that constitutes the orogen of the chain. (Accordi & Carbone, 1988; Parotto & Praturlon, 2004). The. accretionary prism continues to the E offshore, and it is still. active, in the Adriatic Sea (Patacca & Scandone, 2004). This is. the last block and represents the African margin underthrust to. the chain and it is characterized by a meso-cenozoic carbonate. succession deposited in shallow to open seawaters.. The main accepted geodynamic interpretation states that the. Sardinia block represents a European microplates separated in. Oligocene times (about 38 Ma, Patacca et al., 2008 and ref.. therein). The Apennines is the accretionary prism formed from. the collision in Mio-Pliocene times of the collision between this. microplate and the sedimentary wedge of the Adriatic plate of the. African domain (Adriatic Sea). Many geological evidences still. wait to be properly framed:. i) the substantial lack of the European sedimentary wedge in. the reconstruction of the collision zone;. ii) slices of deep water sedimentary successions associated. with ophiolites, related to the suture zone, outcrop both to the N. and to the S (Southern Apennines);. iii) along the proposed section slices of deep water sediments. has been identified in front of both the westernmost and the. easternmost sides of the chain;. iv) carbonate facies in the Apennines shows in Mesozoic. times deeper waters conditions in the most eastern successions. that is towards the African microplate (Accordi & Carbone,. 1988);. v) in eastern Sardinia a Mesozoic succession of shallow water. limestone outcrop (Tacchi), belongs to the European sedimentary. wedge (Bigi et al., 1991), and shows strong analogies with the. westernmost portions of the Apennine carbonate platforms. (comp. Accordi & Carbone, 1988).. A preliminary, admissible balanced cross sections between. the 41°N and the 42° N parallel has been prepared at the regional. scale by using the layered-HCA method as implemented in the. numerical FORC software (Salvini et al, 2001; Salvini F. &. Storti F., 2004). This section has been compared to the computed. lithosphere flexure of the region as derived from the present. topographic profile.. Results provide the possible framing of the Apennine block. within the African vs European domains, and the location of their. suture zone. Found geometry may represent the basis for a. complete geodynamic study of this complex region."
Extensional tectonics in the East Antarctica craton: The Aurora and Concordia Trenches, Dome C
No full textIce cap surface lineaments in the Vostok-Dome C area, East Antarctica. What are they telling us on the East Antarctica craton tectonics?
No full textSince the recent discovery of subglacial lakes beneath the East Antarctic ice cap, the international scientific community have performed extensive geophysical investigations in order to define the poorly known bedrock physiography of the East Antarctic craton. Increasingly available satellite images of remote regions of the globe have provided preliminary constraints for unravelling the tectonic evolution of the East Antarctic plate. Radio echo sounding (RES) data collected in the Vostok-Dome C region revealed the presence of regional, elongated subglacial valleys, namely the Aurora and Concordia trenches (Tabacco et al. 2003). Their marked asymmetric morphology is similar to that of the Vostok lake depression and relates to the activity of two crustal west-dipping listric normal faults of Cenozoic age with a length of over 100 km (Cianfarra et al., 2003). The Radarsat mosaic of Antarctica shows abrupt changes in tones that run across the mosaic and have a length of hundreds to thousands of kilometres. The mosaic therefore reveals for the first time the presence of regional-scale sub-parallel linear features on the ice cap surface expressed on the image mosaic as sharp tonal variations and marked textural anisotropies (see Fig. 1). These intriguing linear features, up to several hundreds of kilometres long and less than 4-5 kilometres wide, will be referred to as lineaments, following Wise (1969) and Wise et al. (1985). This work investigates how the lineament pattern detected on the ice surface relates to the morpho-tectonic setting of the bedrock in the Vostok-Dome C region. Lineaments detected on the Radarsat mosaic of Antarctica and on the ice surface and bedrock morphology DEMs cluster in domains (sensu Wise et al., 1985), similarly to lineaments in emerged regions. Short, well defined lineaments detected on the high-pass spatially filtered Radarsat image depend on the roughness of the bedrock, which is determined by the tectonic setting of the area. Longer lineaments detected on the high-pass spatially filtered Radarsat image relate to ice cap dynamics. These conclusions agree with the findings of Wise et al. (1985), who demonstrated that regional lineaments on the surface of our planet are the surface expression of recent or active tectonic stress fields in the brittle upper crust. The East Antarctic Ice Sheet represents a thin “film” when compared with the about 34 km-thick continental crust. This “film” records tectonic processes in the more brittle upper crust, despite differences in the velocity (up to 2 orders of magnitude) of ice dynamics and tectonics. Radarsat images of Antarctica proved to be an effective tool for investigating ice dynamics and bedrock tectonics in the Vostok-Dome C area
Geodynamic constraints of the peri-Tyrrhenian orogen (Tyrrhenian Sea-Apennines) from lineament swarm analysis
No full text""\\"Regional geodynamics is responsible of a series of effects. that notably include tectonics and seismicity. They in turn control. the morphology of the surface of the planet. The regional. dimension of the peri-Tyrrhenian orogen reveals that its. evolution is deeply involved in a lithospheric scale dynamics. As. a result, we expect different observable and\\\\\\\/or measurable effects. at the various scales from the outcrop evidences to the subcontinental. deformation corridors. Effects at the various scales. not necessarily are directly related, and their relations should be. carefully understood taking into account both their geometry and. spatial distribution. A classical example is represented by an en. echelon system. Each single fracture is the effect of a local. extension, yet their spatial distribution shows that these local. stresses are the effect of a larger scale shear zone with a different. orientation.. Remotely sensed images proved the existence on the Earth. surface of linear features with dimensions spanning over three. order of magnitude: from hundreds of meters to thousand of. kilometers. Such features are referred to image lineaments and. are generally related to alignment of morphological features in. continental environment such as onshore crests, ridges, valleys. and troughs. In the oceans lineaments relate to the scars. associated to the seafloor spreading and fracture zones. Synthetic. scale images of tectonically active regions revealed the existence. of groups of regional scale lineaments on the earth surface. appearing as image textural anisotropies. They clusters around. preferential orientations to form lineament domains. These. domains occupies well defined areas to form lineament swarms.. Lineament domain analysis on regional scale images of the. Earth surface proved a useful tool to investigate regions. characterized by active tectonics (Wise et al., 1985; Funiciello et. al., 1977; Cianfarra & Salvini, 2008).. Both the Tyrrhenian Sea and the Apennines are geodynamic. blocks within the collisional puzzle between Africa and Europe. in the Central Mediterranean area.. In this work we explore the possible relations between these. two blocks by lineaments analysis. The found lineament domains. were interpreted as reflecting the structural grain of these two. geodynamic regions. Lineament detection was done by using. original automatic methods. Domains were identified by. statistical analysis. This work analyses lineaments detectable by. simulating different directions of lighting condition on the. DEMs. This allowed to properly evaluate the influence of the. light condition changes in the lineaments produced by. morphological features. The comparison among the analyses. showed that the different lighting conditions induce rotations of. few degrees of the mean azimuth of each lineament domain. This. rotation relate to the result of two contrasting effects: tectonics,. that tends to enhance linear morphologies, and erosion that. progressively smoothes them. Lineament domains characterised. by small rotations relate to morphologies where the tectonic. processes prevail on the erosional ones. Lineament domains. therefore have rotations inversely proportional to their tectonic. activity.\\""
Fault re-activation, fracture patterns, and cataclasite development in the carbonate rocks of the Narni Anticline. The evolution of a model trap structure in the Apennines, Italy
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Particle size distributions in natural carbonate fault rocks: insights for non-self-similar cataclasis
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Earth and Planetary Science Letters
Volume 206, Issue 1-2, 30 January 2003, Pages 173-186
Particle size distributions in natural carbonate fault rocks: Insights for non-self-similar cataclasis (Article)
Storti, F. , Billi, A., Salvini, F.
Dipartimento Scienze Geol., Univ. degli Studi 'Roma Tre', Rome I-00146, Italy
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Abstract
Particle size distributions of cataclastic rocks influence the mechanical and fluid flow behaviour of fault zones. Available data from natural cataclastic rocks are still controversial and do not fully support a self-similar evolution for the cataclastic process, a concept derived from laboratory experiments and micromechanical modelling. Our analyses of particle size in carbonate fault rocks show power law distributions with fractal dimensions spanning a broad range. This confirms that the idea of a persistent fragmentation mechanism for describing the entire evolution of natural cataclastic fault cores in carbonate rocks is inadequate. Conversely, we propose that the fragmentation mechanism progressively changes with the intensity of comminution. Slip localisation within narrow shear bands is favoured when a favourable cataclastic fabric with fractal dimensions D ∼ 2.6-2.7 is achieved in the fault zone. Intense comminution in the narrow shear zones produces the preferential formation of small diameter particles resulting in particle size distributions characterised by D values approaching or exceeding 3. The non-self-similar evolution of natural cataclastic rocks has an important impact on the frictional and permeability properties of fault zones
Predicting spatial and time distribution of fracturing in fault-related structures by HCA self-determining numerical modeling
No full textEvidences for Neogene-Quaternary tectonics in Svalbard
No full textSvalbard locates along the De Geer Transform Fault that separates the kinematics of North Atlantic and Arctic Ocean and are a continental rise along the North Atlantic portion of this transform. A fold and thrust belt of Paleogene age boards theWestern margin of the Spitsbergen with a NNW-SSE trend. In the ‘60s theWest – Spitsbergen fold and trust belt was related to the relative movements between Laurentia and Eurasia. Specifically, it was regarded to be a transpressive orogen developed at the intra-continental De Geer Transform margin between the Barents and the Greenland Shelves. This setting was suggested by the necessity of a continental transform off the western margin of Svalbard needed to restore the relative openings of the North Atlantic-Arctic Ocean basins, and the Paleogene age of the fold-belt. Later structural studies in other areas of Svalbard suggested that convergent tectonics have been prevailing during much of the fold and thrust development. However this belt can hardly be regarded as a classical orogen resulting from an active continental margin for the lack of evidence for subduction, synorogenic magmatism, metamorphism or a thickened crust. On the other hand, it would be difficult to merely relate this fold and thrust belt to the De Geer Transform Fault. According to Authors a transform fault should produce structures with vergence away from the fault on both sides, whereas the found direction of tectonic transport in North Greenland is the same as in Spitsbergen, i.e. to the E and NE. In this way the transform separation of North-Greenland and Spitsbergen should postdate the formation of the Tertiary North-Greenland and Spitsbergen fold and trust belt. This rises the question on possible Neogene-Quaternary tectonics in Spitsbergen. Evidence for this younger tectonics includes the occurrence of Quaternary volcanism and thermal springs in the northern part of Spitsbergen and the moderate seismicity in Nordaustlandet. Other clues supporting a recent tectonics derive from the analysis of satellite images and air photos, including the glacier and fluvial drainage suggesting a strong tectonic control. Moreover some authors have found in Ny Alesund an uplift rate from GPS measurements higher than those predicted by postglacial rebound models, again suggesting a tectonic contribution. Preliminary results from field work in the Brogger peninsula confirmed the presence of Neogene-Quaternary tectonics. Marine terraces and fluvio-glacial deposits show several N-S elongated steps along the northern projection of N-S trending faults cutting the Meso-Cenozoic rocks. N-S trending faults have been systematically found in Devonian to Tertiary rocks. These faults are characterised by right-lateral, strike-slip movements and the presence of near surface to sub aerial mineralizations on their surfaces, including kinematic indicators. N-S faults with the same kinematics show the presence of deformed Quaternary clastic, unconsolidated deposits within their shear zones. All the found brittle deformation evidence are compatible with the kinematics of the recent activity of the De Geer Transform Fault
Active-hinge-folding-related deformation and its role in hydrocarbon exploration and development-insights from HCA mdeling
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