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La transition raccourcissement-extension Oligocène dans l'édifice de nappes de l'Arc Calabro-Péloritain (Italie méridionale). Nouvelles données structurales, métamorphiques et géochronologiques sur le Massif de l'Aspromonte.

Abstract : The geodynamic evolution of the Mediterranean area is characterized by the superimposition of convergence and extensional tectonic phases marked by the opening of sedimentary and oceanic basins onto a former thickened crust. The Calabro-Peloritan Arc (CPA) located astride the southern end of continental Italy and the northeastern Sicily corresponds to a segment of the former south-European active margin. This area, together with the Kabylian and Betico-Rifan massifs, was involved successively in shortening tectonics, associated to the subduction of the Tethyan oceanic lithosphere, and in extensional tectonics during the opening of the western Mediterranean basins. The CPA is a nappes-pile made of Alpine oceanic-derived units tectonically overlain by Hercynian metamorphics. This tectonic edifice was then transported onto the Apennine chain during the opening of the Tyrrhenian basin. The study presented here focused on the Aspromonte Massif which corresponds to the southern part of the CPA. The main purposes were to precise the geometry and the tectonometamorphic evolution of the units forming the uppermost part of the nappes-pile in order to better understand the conditions of the shortening to extension transition and the Oligocene Mediterranean kinematics. A multidisciplinary approach was used implying structural geology, microstructural and petrographic analysis of sampled rocks, thermobarometric estimates of the successive metamorphic phases and their dating by 40Ar/39Ar geochronology.
Except for the evidences of a rather poorly constrained Hercynian evolution, the main results obtained show, a two steps Alpine evolution. The first step corresponds to a stacking phase; the second one corresponds to an extensional reworking of the entire nappes-pile. Metamorphic and geochronological data suggest that the piling was initiated in the middle of Eocene (~45 Ma) or earlier, while extension started probably in the lower Oligocene (since 33 Ma) and lasted until the middle Oligocene (27 Ma) without change in orientation. This second deformation phase leads to the progressive exhumation of the deepest units, partly controlled by a strong tectonic denudation. The kinematic directions of this reconstituted structural evolution, replaced in their initial position and orientation, before the CPA formation, imply a shortening direction in agreement with the bulk convergence direction between African and European plates at Eocene times. In the contrary, the age of the extensional phase indicates that the western Mediterranean tectonic thinning started probably at least in Lower Oligocene. In addition, its location and orientation suggest that it could be related to the opening of the North-Algerian basin, previously to the opening of the Liguro-Provencal basin and the associated SE-directed Tethyan slab retreat.
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https://tel.archives-ouvertes.fr/tel-00283165
Contributor : Thomas Heymes <>
Submitted on : Thursday, May 29, 2008 - 11:03:06 AM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM
Long-term archiving on: : Friday, May 28, 2010 - 6:37:58 PM

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  • HAL Id : tel-00283165, version 1

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Thomas Heymes. La transition raccourcissement-extension Oligocène dans l'édifice de nappes de l'Arc Calabro-Péloritain (Italie méridionale). Nouvelles données structurales, métamorphiques et géochronologiques sur le Massif de l'Aspromonte.. Géologie appliquée. Université Joseph-Fourier - Grenoble I; Università degli studi di Torino, 2008. Français. ⟨tel-00283165⟩

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