Search results for "Geomorphology"

Le bassin stéphanien des Cévennes (Massif Central) : un exemple de relation entre sédimentation et tectonique extensive tardi-orogénique dans la chaî…

1996

ResumeLa nature syn-sedimentaire des failles bordieres du bassin houiller stephanien des Cevennes est mise en evidence par la distribution des depots conglomeratiques et greseux de cone alluvial au pied des paleoreliefs de socle. Elle est egalement attestee par les fortes variations d’epaisseur caracterisant les niveaux greseux, silteux et de charbon se distribuant au centre des sous-bassins ainsi que par les directions centripetes d’apport sedimentaire.A l’echelle du bassin, la nature extensive de la structuration syn-sedimentaire est mise en evidence par des failles normales d’orientation NW-SE, NE-SW et NNW-SSE, a fort pendage, structurant les sous-bassins en demi-graben a geometrie sync…

Geophysical and geotechnical investigations to support the restoration project of the Roman ‘Villa del Casale’, Piazza Armerina, Sicily, Italy

2011

A multidisciplinary geophysical and geotechnical study, including some non-invasive geophysical applications, was carried out during the restoration of the ‘Villa del Casale’, a Roman villa discovered near Piazza Armerina (Sicily, Italy) in 1929, famous for its Roman floor mosaics. The project aims were to characterize the geology of the subsoil and provide information for solving the main building structural problems including the subsidence of some parts of the floor and the detachment of the tesserae (i.e., the tiles) of the mosaics. Another goal was the detailed study of the underground structures of the Corridor of the Great Hunt, a part of the villa strongly affected by subsidence and…

The Bossons glacier protects Europe's summit from erosion

2013

13 pages; International audience; The contrasting efficiency of erosion beneath cold glacier ice, beneath temperate glacier ice, and on ice-free mountain slopes is one of the key parameters in the development of relief during glacial periods. Detrital geochronology has been applied to the subglacial streams of the north face of the Mont-Blanc massif in order to estimate the efficiency of erosional processes there. Lithologically this area is composed of granite intruded at ~303 Ma within an older polymetamorphic complex. We use macroscopic features (on ~10,000 clasts) and U-Pb dating of zircon (~500 grains) to establish the provenance of the sediment transported by the glacier and its subgl…

Two-dimensional numerical modeling of fracturing and shear band development in glacier fronts

2014

In this contribution we present a two-dimensional numerical model of a deforming glacier front. The model is based on a hybrid lattice spring network approach where particles in the model can deform in a volume conservative visco-elastic manner but at the same time they can be compressed elastically and fracture by discrete failure. We restrict ourselves to a simple setting where the glacier sits on a frictionless slope that dips with 5–10°, the ice block is fixed on one side and has a free surface on the other. The glacier varies in viscosity and can flow at the base, whereas it is brittle at the top. Results show that the head of the glacier is unstable. Failure happens as a combination o…

1999

The tholeiitic dolerites that crop out in three diapirs of the SE of the Iberian Chain (Alfarp, Quesa and Lugar Nuevo de Fenollet, Valencia), are the expression of evolved (low Ni, Cr and mg* values) basic magmas, injected into poorly lithified sediments (lutites, marls and gypsum) which represent the Upper Triassic (Keuper facies)-Hettangian boundary, developing sills with reduced thickness. Their mineral and whole-rock geochemical compositions indicate a continental tholeiitic affinity and certain similarities to a MORB composition and, on the other hand, show that the Alfarp dolerites represent the less evolved compositions, whereas the Fenollet dolerites show a significantly greater dif…

Tectonic denudation of a Late Cretaceous-Tertiary collisional belt: Regionally symmetric cooling patterns and their relation to extensional faults in…

2003

Thermochronological data reveal that the Late Cretaceous–Tertiary nappe pile of the Anatolide belt of western Turkey displays a two-stage cooling history. Three crustal segments differing in structure and cooling history have been identified. The Central Menderes metamorphic core complex represents an ‘inner’ axial segment of the Anatolide belt and exposes the lowest structural levels of the nappe pile, whereas the two ‘outer’ submassifs, the Gördes submassif to the north and the Çine submassif to the south, represent higher levels of the nappe pile. A regionally significant phase of cooling in the Late Oligocene and Early Miocene affected the outer two submassifs and the upper structural l…

New knowledge on the Monte Conca gypsum karst system (Central-western Sicily, Italy)

2011

The Monte Conca karst system is located in Central-Western Sicily, where Messinian evaporites are widespread. Here, the evaporites lie on lower Messinian-middle Serravallian clayey-marly-sandy deposits and are overlain locally by Pliocene marly limestones. These successions are affected by E-W, and to a lesser degree N-S and NW-SE, high-angle faults that have also produced lateral contacts between the gypsum units and the clayey-marly deposits. The cave passages reachaltogether about 2.4 km in lengthand 130 m in depth, and the system consists of a sink cave, a resurgence and a relict resurgence. At large scale it is characterized by superimposed levels of sub-horizontal galleries connected …

Acqua Fitusa cave: An example of inactive water-table sulphuric acid cave in Central Sicily

2012

Description of the sulphuric acid cave in Sicily (see pdf attached)

The N Variscan margin of the Ruhr coal district (Western Germany): structural style of a buried thrust front?

1988

The Ruhr coal district represents part of an external fold and thrust belt of the Variscan orogen in central Europe. Extensive mining exposed molasse-type, coal-bearing clastic sequences of Upper Carboniferous age, deformed by folding and thrusting. Thrusts range in scale from decameters to 40 kilometers along strike but displacements are below 2.5 km. They are distributed in various stratigraphic levels and no regional detachment horizon is exposed. Displacement is mainly towards NW (towards the foreland) but also towards SE. The thrusts are bound to stockwerk-tectonics and die out towards depth frequently antithetic to the exposed strata. Folds vary in wavelength from decameters to more t…

Fluvial eco-hydraulics and morphodynamics: New insights and challenges

2015

The paper concerns the mechanisms underlying the distribution of the bed shear stress in meandering bends. Literature indicates that cross-stream circulation strongly affects the redistribution of the downstream velocity, but the feedback between them is still poorly understood. The aim of this paper is to gain some insight into how the momentum transport by cross-stream circulation contributes to the bed shear stress redistribution. Experimental analysis, based on a detailed dataset collected in a large-amplitude meandering laboratory flume, is presented. From these data an evaluation is made of the terms in the depth-averaged momentum equations and the analysis is especially devoted to te…