Tectono-sedimentary evolution of the External Liguride units (Northern Apennines,Italy): insights in the pre-collisional history of a fossil ocean-continent transition zone

Abstract

In the Northern Apennines, the External Liguride (EL) units are interpreted as derived from the domain that joined the Ligure–Piemontese oceanic basin to the Adriatic plate continental margin. The EL units can be divided into two different groups according to the lithostratigraphic features of the basal complexes underlying the Upper Cretaceous–Lower Tertiary carbonate flysch (e.g. Helminthoid flysch). The first group includes the western successions characterized by Santonian–Campanian sedimentary melanges where slide blocks of lherzolitic mantle, gabbros, basalts, granulites, continental granitoids are represented. The second group is represented by the eastern successions where the Cenomanian–Campanian basal complexes mainly consist of sandstones and conglomerates where the mafic and ultramafic rocks are scarce or completely lacking. Their original substrate is represented by the Middle Triassic to Lower Cretaceous, mainly platform carbonate deposits, found as slices at the base of the eastern successions.

The stratigraphic features shown by the basal complexes allow the reconstruction of their source area that is assumed to be also representative for the pre-Upper Cretaceous setting. The proposed reconstruction suggests the occurrence in the EL domain of two distinct domains. The eastern domain was characterized by a thinned and faulted continental crust belonging to the Adriatic continental margin. The western domain was instead floored by subcontinental mantle associated with lower and upper continental crust, representing the ocean–continent transition. This setting is interpreted as the result of the opening of the Ligure–Piemontese oceanic basin by passive rifting, mainly developed by simple shear, asymmetric extension of the continental crust. © 2001 Éditions scientifiques et médicales Elsevier SAS     

Current Behaviour and Dynamics of the Lowermost Italian Glacier (Montasio Occidentale,Julian Alps)

Smaller glaciers (<0.5 km²) react quickly to environmental changes and typically show a large scatter in their individual response. Accounting for these ice bodies is essential for assessing regional glacier change, given their high number and contribution to the total loss of glacier area in mountain regions. However, studying small glaciers using traditional techniques may be difficult or not feasible, and assessing their current activity and dynamics may be problematic. In this paper, we present an integrated approach for characterizing the current behaviour of a small, avalanche‐fed glacier at low altitude in the Italian Alps, combining geomorphological, geophysical and high‐resolution geodetic surveying with a terrestrial laser scanner. The glacier is still active and shows a detectable mass transfer from the accumulation area to the lower ablation area, which is covered by a thick debris mantle. The glacier owes its existence to the local topo‐climatic conditions, ensured by high rock walls which enhance accumulation by delivering avalanche snow and reduce ablation by providing topographic shading and regulating the debris budget of the glacier catchment. In the last several years the glacier has displayed peculiar behaviour compared with most glaciers of the European Alps, being close to equilibrium conditions in spite of warm ablation seasons. Proportionally small relative changes have also occurred since the Little Ice Age maximum. Compared with the majority of other Alpine glaciers, we infer for this glacier a lower sensitivity to air temperature and a higher sensitivity to precipitation, associated with important feedback from increasing debris cover during unfavourable periods.     

GIS,multi‐criteria and multi‐factor spatial analysis for the probability assessment of the existence of illegal landfills

This work deals with the identification of potentially contaminated areas using remote sensing, geographic information systems (GIS) and multi‐criteria spatial analysis. The identification of unknown illegal landfills is a crucial environmental problem in all developed and developing countries, where a large number of illegal waste deposits exist as a result of fast, and relatively unregulated, industrial growth over the past century. The criteria used to perform the spatial analysis are here selected by considering the characteristics which are ‘desirable’ for an illegal waste disposal site, chiefly related to the existence of roads for easy access and to a low population density which facilitates unnoticed dumping of illegal waste materials. A large dataset describing known legal and illegal landfills and the context of their location (population, road network, etc.) was used to perform a spatial statistical analysis to select factors and criteria allowing for the identification of the known waste deposits. The final result is a map describing the likelihood of an illegal waste deposit to be located at any arbitrary location. Such a probability map is then used together with remote sensing techniques to narrow down the set of possibly contaminated sites (Silvestri and Omri, 2008 Silvestri, S. and Omri, M. 2008. A method for the remote sensing identification of uncontrolled landfills: formulation and validation.. International Journal of Remote Sensing, 29(4): 975–989. [Taylor & Francis Online] , [Google Scholar]), which are candidates for further analyses and field investigations. The importance of the integration of GIS and remote sensing is highlighted and represents a key instrument for environmental management and for the spatially‐distributed characterization of possible uncontrolled landfill sites.     

A finite element analysis of direct shear tests on stiff clays

A finite element analysis is presented of some direct shear tests carried out on samples of a stiff, heavily overconsolidated clay. The effects of softening are accounted for through a simple material model which views this phenomenon as a consequence of an intrinsic loss of strength of the material taking place when plastic strains increase. After illustrating the main characteristics of the finite element approach, with particular reference to the correct determination of the non-reversible strains, its use in the interpretation of the mentioned shear tests is discussed. Some comments are also presented on the mesh dependence of the numerical results, and on the use of a relation between material parameters and element size which reduces this negative effect. Finally, the solution procedure is applied to the simulation of a compression test in order to investigate the possibility of numerically detecting the ‘spontaneous’ (i.e. not directly induced by the boundary conditions) formation of shear zones within the specimen.     

The quantitative analysis of OH in vesuvianite: a polarized FTIR and SIMS study

A well-characterized suite of vesuvianite samples from the volcanic ejecta (skarn or syenites) from Latium (Italy) was studied by single-crystal, polarized radiation, Fourier-transform infrared (FTIR) spectroscopy and secondary-ion mass-spectrometry (SIMS). OH-stretching FTIR spectra consist of a rather well-defined triplet of broad bands at higher-frequency (3,700–3,300 cm^–1) and a very broad composite absorption below 3,300 cm^–1. Measurements with E//c or Ec show that all bands are strongly polarized with maximum absorption for E//c. They are in agreement with previous band assignments (Groat et al. Can Mineral 33:609, 1995) to the two O(11)–H(1) and O(10)–H(2) groups in the structure. Pleochroic measurements with changing direction of the E vector of the incident radiation show that the orientation of the O(11)–H(1) dipole is OHc~35°, in excellent agreement with the neutron data of Lager et al. (Can Mineral 37:763, 1999). A SIMS-based calibration curve at ~10% rel. accuracy has been worked out and used as reference for the quantitative analysis of H₂O in vesuvianite by FTIR. Based on previous SIMS results for silicate minerals (Ottolini and Hawthorne in J Anal At Spectrom 16:1266, 2001; Ottolini et al. in Am Mineral 87:1477, 2002) the SiO₂ and FeO content of the matrix were assumed as the major factors to be considered at a first approximation in the selection of the standards for H. The lack of vesuvianite standards for quantitative SIMS analysis of H₂O has been here overcome by selecting low-silica elbaite crystals (Ottolini et al. in Am Mineral 87:1477, 2002). The resulting integrated molar absorption FTIR coefficient for vesuvianite is _i=100.000±2.000 l mol^–1 cm^–2. SIMS data for Li, B, F, Sr, Y, Be, Ba REE, U and Th are also provided in the paper.     

Back analysis procedures for the interpretation of field measurements in geomechanics

A survey is presented of some recent developments of the numerical techniques for back analysis in the field of geomechanics, with particular reference to tunnelling problems. In the spirit of Terzaghi's observational design method, these techniques are seen as practical tools for interpreting the available field measurements, in order to reduce the uncertainties that in many instances affect the parameters governing the solution of complex geomechanics problems. Both deterministic and probabilistic viewpoints are considered and some significant applications to practical problems are illustrated.     

The Loci of Satellite Positions: A Constellation Design Approach

In special cases in which satellite constellations can be described by a limited set of parameters, a correlation between the latter and the constellation characteristics (i.e. shape and kinematics of the satellite configurations) has been investigated. Such cases may be a useful starting point for designing more complex constellations in order to achieve better the desired performances. Therefore, this proves to be one way to fix an initial set of parameters once the desired behaviour of the constellation has been established on the basis of the operational purposes required. This revised version was published online in August 2006 with corrections to the Cover Date.     

Pore pressure tension cut off in two-phase finite element analyses

In the coupled finite element analysis of the two-phase, saturated soils the pore pressure could decrease below the atmospheric pressure in particular when the plastic dilation of the skeleton is accounted for. The consequent reduction of the bulk modulus of the liquid phase is here modelled in a simplified manner through a tension cut off on the pore pressure. Two alternative approaches are outlined in the framework of the finite element method. The first one introduces a unilateral constraint on the nodal pore pressures and involves manipulations on matrices of the assembled mesh, whilst the second approach requires calculations solely at the element level. The effects of the pore pressure tension cut off are illustrated through some undrained test examples in elastic–plastic regime.     

Isotopes du milieu et circulations dans les aquiferes du sous-sol Vénitien

L'enfoncement de la plaine de Venise, quel'on peut estimeràprès de 1 cm/an sous le site historique, est liéàla surexploitation des nappes artésiennes profondes. L'investigation hydrogéologique est rendue délicate par la nature de l'aquifère composéde plusieurs centaines de mètres de dépo?ts quaternaires continentaux et marins. Au sein de ce complexe les nappes se superposent en un système multicouche artésien. L'étude du régime de ces nappes aétéentrepris par les moyens géochimiques et isotopiques (oxygène 18, deuterium, tritium, carbone 13 et carbone 14).Les teneurs en isotopes stables montrent l'existence de deux familles d'eaxu profondes attribuablesàune recharge “froide” (δ¹⁸O= ?10 et ?12‰). Ces eaux sont nettements différentes de celles des nappes phréatiques (δ¹⁸O ? ?8‰). Les apports profonds peuvente?tre respectivement liés aux bassins des rivières préalpines Brenta et Piave (δ¹⁸O ? ?10‰) d'une part et au paléocours de l'Adige, fleuve alpin d'autre part. Les eaux alpines ont un gisement limitéàl'aplomb de la lagune etàla partie sud-ouest de la plaine. Les eaux de type préalpin occupent le reste de la plaine, c'est-à-dire plus grande partie.La détermination des vitesses d'écoulement pose le problème de la validitédes temps estimésàl'aide des teneurs en¹⁴C.Les teneurs en¹³Célevées des eaux alpines montrent clairement que les activités en¹⁴C de celles-ci ne sont pas significatives par suite d'unéchange avec l'aquifère ou d'une surcharge en carbone ancien dissous.Pour les eaux qui viennent du domaine préalpin, on observe dans les zones de recharge de fortes teneurs en³H: 85à120 UT alliéesàdes activités relativement faibles en¹⁴C (60à70%). Les teneurs en¹³C indiquent que le carbone dissous n'a pas subi d'échange avec l'aquifère. La discussion de l'ensemble des données suggère que la circulation est rapide dans la zone de recharge oùl'alimentation en eaux d'altitude se faitàpartir d'infiltrations en provenance du réseau hydrographique ou (et) du système karstique des préalpes. Dans les parties basses de la plaine les vitesses sont faibles et décroissent, vers l'Est ou en profondeur, de 3 m/anà1 m/an. Il est possible qu'une rupture dans l'intensitédes vitesses d'écoulement interviennent dans la partie occidentale de la plaine sous l'effet d'une discontinuitésédimentologique majeure (limite occidentale des dépo?ts marins).