Did the “Autochthonous” European foreland of Corsica Island (France) experience Alpine subduction?     

Maria Di Rosa  Chiara Frassi  Michele Marroni  Francesca Meneghini  Luca Pandolfi 《地学学报》2020,32(1):34-43

Despite the important role played by the Sardinia‐Corsica block in the reconstruction of the Western Mediterranean geodynamics, the extent of involvement of the “Autochthonous” European margin exposed in Corsica (France) (i.e., Hercynian Corsica) in the Alpine orogeny remains uncertain. Stratigraphic and sedimentological studies in the post‐Variscan deposits on the Hercynian Corsica are scarce and even scarcer are the structural and metamorphic constraints. To face these uncertainties, we present new stratigraphic, structural and metamorphic data from the area of Razzo Bianco, Central Corsica, where a complete sequence belonging to the European continental margin is exposed. Field and structural investigations demonstrate that the sequence represents the easternmost edge of the downgoing European plate. Metamorphic studies on the Eocene deposits indicate that the margin was buried at depth up to blueschist facies conditions and, subsequently, it was progressively exhumed mainly through the activation of oblique top‐to‐the NW shear zones.  相似文献   

Fluid flow and pore pressure development throughout the evolution of a trough mouth fan,western Barents Sea     

Jaume Llopart  Roger Urgeles  Carl Fredrik Forsberg  Angelo Camerlenghi  Maarten Vanneste  Michele Rebesco  Renata Giulia Lucchi  Denise Christina Rüther  Hendrik Lantzsch 《Basin Research》2019,31(3):487-513

Using a combination of geophysical and geotechnical data from Storfjorden Trough Mouth Fan off southern Svalbard, we investigate the hydrogeology of the continental margin and how this is affected by Quaternary glacial advances and retreats over the continental shelf. The geotechnical results show that plumites, deposited during the deglaciation, have high porosities, permeabilities and compressibilities with respect to glacigenic debris flows and tills. These results together with margin stratigraphic models obtained from seismic reflection data were used as input for numerical finite element models to understand focusing of interstitial fluids on glaciated continental margins. The modelled evolution of the Storfjorden TMF shows that tills formed on the shelf following the onset of glacial sedimentation (ca. 1.5 Ma) acted as aquitards and therefore played a significant role in decreasing the vertical fluid flow towards the sea floor and diverting it towards the slope. The model shows that high overpressure ratios (up to λ ca. 0.6) developed below the shelf edge and on the middle slope. A more detailed model for the last 220 kyrs accounting for ice loading during glacial maxima shows that the formation of these aquitards on the shelf focused fluid flow towards the most permeable plumite sediments on the slope. The less permeable glacigenic debris flows that were deposited during glacial maxima on the slope hinder fluid evacuation from plumites allowing high overpressure ratios (up to λ ca. 0.7) to develop in the shallowest plumite layers. These high overpressures likely persist to the Present and are a critical precondition for submarine slope failure.  相似文献   

Chemical and mineralogical characterization of the Mineo (Sicily,Italy) pallasite: A unique sample          下载免费PDF全文

A. Zucchini  M. Petrelli  F. Frondini  C. M. Petrone  P. Sassi  A. Di Michele  S. Palmerini  O. Trippella  M. Busso 《Meteoritics & planetary science》2018,53(2):268-283

The Mineo pallasite is characterized here for the first time. The only 42 g still available worldwide is part of the collection of the Department of Physics and Geology, University of Perugia. A multianalytical approach was used, joining field-emission scanning electron microscopy, Raman analysis, X-ray powder diffraction, electron-probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry. Results highlighted that (1) the Mineo pallasite belongs to the Main Group pallasites; (2) the silicate component is essentially olivine, with no pyroxene component; (3) the olivine chemical composition varies in terms of both iron and trace elements; (4) the metal phase is essentially kamacite with the taenite mainly found in the plessite structure; (5) phosphide phases are present as schreibersite and barringerite. The observed compositional variability in olivines as well as their occurrence as both angular and rounded crystals suggest that the Mineo pallasite could have been derived from a large impact of a differentiated parent body with a larger solid body. The resulting pallasite conglomerate consists of the compositionally different olivines, likely coming from different areas of the same differentiated parent body, and the residual molten Fe-Ni.  相似文献   

Accurate ionospheric delay model for real-time GPS-based positioning of LEO satellites using horizontal VTEC gradient estimation     

Alfredo Renga  Flavia Causa  Urbano Tancredi  Michele Grassi 《GPS Solutions》2018,22(2):46

Ionospheric delays compensation is a mandatory step for precise absolute and relative positioning of Low Earth Orbit Satellites (LEO) by GPS measurements. The most frequently used ionosphere model for real-time GPS-based navigation in LEO is an isotropic model proposed by Lear, which uses the Vertical Total Electron Content (VTEC) above the receiver and a mapping function for TEC evaluation along a given ray path. Based on significant assessed results available for ground-based GPS receivers, we propose the use of a different model relying on the thin shell assumption and a bilinear horizontal variation of the VTEC as a function of latitude and longitude in the shell. It is expected that this model is capable of better describing horizontal gradients in the ionosphere, thus improving ionospheric delay estimation, especially in intense ionospheric conditions. This model is referred to as Linear Thin Shell (LTS). LTS performance in estimating undifferenced and double-differenced ionospheric delays is checked by comparing measured and predicted delays computed using flight data from the GRACE mission. Results show that the LTS always outperforms the isotropic model, especially in case of high solar activity. Moreover, the LTS model provides a higher performance uniformity over a wide range of ionospheric delays, thus ensuring good performance in different conditions. The results obtained demonstrate that the LTS model improves the ionosphere delays estimation accuracy by 20 and 40% for undifferenced and double-differenced delays, respectively. This suggests the LTS model can effectively contribute to improving precision in LEO positioning applications.  相似文献   

Recent insights into physiological responses to nutrients by the cylindrospermopsin producing cyanobacterium,Cylindrospermopsis raciborskii     

Michele A.BURFORD  Anusuya WILLIS  Ann CHUANG  Xiao MAN  Philip T.ORR 《中国海洋湖沼学报》2018,(4)

The harmful cyanobacterium Cylindrospermopsis raciborskii is a widespread species increasingly being recorded in freshwater systems around the world. Studies have demonstrated some key attributes of this species which may explain its global dominance. It has a high level of flexibility with respect to light and nutrients, being capable of growth under low and variable light conditions. However, it is the strategy with respect to nutrient utilization that has received more attention. Unlike many bloom forming species, the dominance of this species is not simply linked to higher nutrient loads. In fact it appears that it is more competitive when phosphorus and nitrogen availability is low and/or variable. An important component of this flexibility appears to be the result of within-population strain variability in responses to nutrients, as well as key physiological adaptations. Strain variability also appears to have an effect on the population-level cell quota of toxins, specifically cylindrospermopsins(CYNs). Field studies in Australia showed that populations had the highest proportion of toxic strains when dissolved inorganic phosphorus was added, resulting in stoichiometrically balanced nitrogen and phosphorus within the cells. These strategies are part of an arsenal of responses to environmental conditions, making it a challenging species to manage. However, our ability to improve bloom prediction will rely on a more detailed understanding of the complex physiology and ecology of this species.  相似文献   

The Central-Western Mediterranean: Anomalous igneous activity in an anomalous collisional tectonic setting     

Michele Lustrino  Svend Duggen  Claudio L. Rosenberg 《Earth》2011,104(1-3):1-40

The central-western Mediterranean area is a key region for understanding the complex interaction between igneous activity and tectonics. In this review, the specific geochemical character of several ‘subduction-related’ Cenozoic igneous provinces are described with a view to identifying the processes responsible for the modifications of their sources. Different petrogenetic models are reviewed in the light of competing geological and geodynamic scenarios proposed in the literature.Plutonic rocks occur almost exclusively in the Eocene–Oligocene Periadriatic Province of the Alps while relatively minor plutonic bodies (mostly Miocene in age) crop out in N Morocco, S Spain and N Algeria. Igneous activity is otherwise confined to lava flows and dykes accompanied by relatively greater volumes of pyroclastic (often ignimbritic) products. Overall, the igneous activity spanned a wide temporal range, from middle Eocene (such as the Periadriatic Province) to the present (as in the Neapolitan of southern Italy). The magmatic products are mostly SiO₂-oversaturated, showing calcalkaline to high-K calcalcaline affinity, except in some areas (as in peninsular Italy) where potassic to ultrapotassic compositions prevail. The ultrapotassic magmas (which include leucitites to leucite-phonolites) are dominantly SiO₂-undersaturated, although rare, SiO₂-saturated (i.e., leucite-free lamproites) appear over much of this region, examples being in the Betics (southeast Spain), the northwest Alps, northeast Corsica (France), Tuscany (northwest Italy), southeast Tyrrhenian Sea (Cornacya Seamount) and possibly in the Tell region (northeast Algeria).Excepted for the Alpine case, subduction-related igneous activity is strictly linked to the formation of the Mediterranean Sea. This Sea, at least in its central and western sectors, is made up of several young (< 30 Ma) V-shaped back-arc basins plus several dispersed continental fragments, originally in crustal continuity with the European plate (Sardinia, Corsica, Balearic Islands, Kabylies, Calabria, Peloritani Mountains). The bulk of igneous activity in the central-western Mediterranean is believed to have tapped mantle ‘wedge’ regions, metasomatized by pressure-related dehydration of the subducting slabs. The presence of subduction-related igneous rocks with a wide range of chemical composition has been related to the interplay of several factors among which the pre-metasomatic composition of the mantle wedges (i.e., fertile vs. refractory mineralogy), the composition of the subducting plate (i.e., the type and amount of sediment cover and the alteration state of the crust), the variable thermo-baric conditions of magma formation, coupled with variable molar concentrations of CO₂ and H₂O in the fluid phase released by the subducting plates are the most important.Compared to classic collisional settings (e.g., Himalayas), the central-western Mediterranean area shows a range of unusual geological and magmatological features. These include: a) the rapid formation of extensional basins in an overall compressional setting related to Africa-Europe convergence; b) centrifugal wave of both compressive and extensional tectonics starting from a ‘pivotal’ region around the Gulf of Lyon; c) the development of concomitant Cenozoic subduction zones with different subduction and tectonic transport directions; d) subduction ‘inversion’ events (e.g., currently along the Maghrebian coast and in northern Sicily, previously at the southern paleo-European margin); e) a repeated temporal pattern whereby subduction-related magmatic activity gives way to magmas of intraplate geochemical type; f) the late-stage appearance of magmas with collision-related ‘exotic’ (potassic to ultrapotassic) compositions, generally absent from simple subduction settings; g) the relative scarcity of typical calcalkaline magmas along the Italian peninsula; h) the absence of igneous activity where it might well be expected (e.g., above the hanging-wall of the Late Cretaceous–Eocene Adria–Europe subduction system in the Alps); i) voluminous production of subduction-related magmas coeval with extensional tectonic régimes (e.g., during Oligo-Miocene Sardinian Trough formation).To summarize, these salient central-western Mediterranean features, characterizing a late-stage of the classic ‘Wilson Cycle’ offer a ‘template’ for interpreting magmatic compositions in analogous settings elsewhere.  相似文献   

Hypogeal geological survey in the “Grotta del Re Tiberio” natural cave (Apennines, Italy): a valid tool for reconstructing the structural setting     

Alice Ghiselli  Marzio Merazzi  Andrea Strini  Roberto Margutti  Michele Mercuriali 《Central European Journal of Geosciences》2011,3(2):155-168

As karst systems are natural windows to the underground, speleology, combined with geological surveys, can be useful tools for helping understand the geological evolution of karst areas. In order to enhance the reconstruction of the structural setting in a gypsum karst area (Vena del Gesso, Romagna Apennines), a detailed analysis has been carried out on hypogeal data. Structural features (faults, fractures, tectonic foliations, bedding) have been mapped in the ”Grotta del Re Tiberio” cave, in the nearby gypsum quarry tunnels and open pit benches. Five fracture systems and six fault systems have been identified. The fault systems have been further analyzed through stereographic projections and geometric-kinematic evaluations in order to reconstruct the relative chronology of these structures. This analysis led to the detection of two deformation phases. The results permitted linking of the hypogeal data with the surface data both at a local and regional scale. At the local scale, fracture data collected in the underground have been compared with previous authors’ surface data coming from the quarry area. The two data sets show a very good correspondence, as every underground fracture system matches with one of the surface fracture system. Moreover, in the cave, a larger number of fractures belonging to each system could be mapped. At the regional scale, the two deformation phases detected can be integrated in the structural setting of the study area, thereby enhancing the tectonic interpretation of the area (e.g., structures belonging to a new deformation phase, not reported before, have been identified underground). The structural detailed hypogeal survey has, thus, provided very useful data, both by integrating the existing information and revealing new data not detected at the surface. In particular, some small structures (e.g., displacement markers and short fractures) are better preserved in the hypogeal environment than on the surface where the outcropping gypsum is more exposed to dissolution and recrystallization. The hypogeal geological survey, therefore, can be considered a powerful tool for integrating the surface and log data in order to enhance the reconstruction of the deformational history and to get a three-dimensional model of the bedrock in karst areas.  相似文献   

Erratum to: Central European Journal of Geosciences, volume 3, number 2     

János Kovács  Szabolcs Á. Fábián  Gábor Varga  Karoly Németh  Corina Risso  Francisco Nullo  Gabor Kereszturi  Titusz Bugya  Szabolcs Á. Fábián  Noémi L. Görcs  István P. Kovács  Bertalan Radvánszky  Gabriella Barta  Rudolf Musil  Alice Ghiselli  Marzio Merazzi  Andrea Strini  Roberto Margutti  Michele Mercuriali  Rauf Gardashov  Daria Gushchina  Boris Dewitte  Martin Michálek  Marián Putiš  Christoph A. Hauzenberger  Jindřich Šancer  Martin Štrejbar  Aneta Maleňáková  George Migiros  George D. Bathrellos  Hariklia D. Skilodimou  Theodoros Karamousalis 《Central European Journal of Geosciences》2011,3(2):229-229

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In memory of a great mentor and good friend: Eugenio Fresi (1943–2010)     

Maria Cristina Gambi  Michele Scardi 《Marine Ecology》2011,32(2):258-260

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Human-induced coastal landslide reactivation. Monitoring by PSInSAR techniques and urban damage survey (SE Spain)   总被引：1，自引：1，他引：0  

Davide Notti  Jorge Pedro Galve  Rosa María Mateos  Oriol Monserrat  Francisco Lamas-Fernández  Francisca Fernández-Chacón  Francisco Javier Roldán-García  José Vicente Pérez-Peña  Michele Crosetto  José Miguel Azañón 《Landslides》2015,12(5):1007-1014

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