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Cooling history of the Dauphinoise Zone (Western Alps, France) deduced from the thermopaleomagnetic record: geodynamic implications
Crouzet C., Ménard G., Rochette P.
Tectonophysics 340, 1-2 (2001) 79 à 93 - http://hal-insu.archives-ouvertes.fr/insu-00349903
Articles dans des revues avec comité de lecture
Cooling history of the Dauphinoise Zone (Western Alps, France) deduced from the thermopaleomagnetic record: geodynamic implications
Christian Crouzet 1, Gilles Ménard 2, Pierre Rochette 3
1 :  Institut für Geologie und Palaeontologie, Abteilung Geophysik, Universität Tübingen
Universität Tübingen
Allemagne
2 :  Laboratoire de géodynamique des chaines alpines (LGCA)
http://lgca.obs.ujf-grenoble.fr/
CNRS : UMR5025 – OSUG – INSU – Université de Savoie – Université Joseph Fourier - Grenoble I
1381 rue de la Piscine 38400 Saint-Martin d'Hères
France
3 :  Centre européen de recherche et d'enseignement de géosciences de l'environnement (CEREGE)
http://www.cerege.fr
CNRS : UMR6635 – Institut de recherche pour le développement [IRD] – INSU – Université de Provence - Aix-Marseille I – Université Paul Cézanne - Aix-Marseille III
CEREGE EUROPOLE MEDITERR. DE L'ARBOIS - BP 80 13545 AIX EN PROVENCE CEDEX 4
France
A post-tectonic thermoremanent magnetization, carried by pyrrhotite, has been previously demonstrated in the Dauphinoise Zone of the French Western Alps. The paleomagnetic signal is interpreted to record successive partial thermoremanent magnetizations acquired in normal and reverse geomagnetic fields during the slow cooling of the epimetamorphic marly limestones. A comparison between the derived magnetic polarity sequence versus temperature (thermopaleomagnetic record) and the magnetostratigraphic time scale, taking into account radiochronological constraints, allows us to derive 21 age/temperature couples between 24.1 Ma/302 °C and 20.2 Ma/182 °C, for the Bourg d'Oisans area. Combining these thermopaleomagnetic data with other P, T, t and structural data, a geodynamical model is proposed for the tectono-metamorphic evolution of the Dauphinoise Zone. The thickening contemporaneous with the main syncleavage folding occurs around 26.5 Ma. Depending on the hypothesis considered to explain the excess of heat, the Bourg d'Oisans area was buried to 8.6 km (fluids hypothesis) or 12.5 km (tectonic hypothesis). In both cases, these depths imply the existence of overlying units, which might come from the internal zones, actually cropping out eastward of the Penninic front. A tectonic denudation is proposed just before 24.1 Ma in order to explain our observations. After this denudation, a faster cooling occurs. It is probably related to the dissipation of the thermal anomaly, induced by the tectonic denudation, and with the increase of the erosion due to the underthrust of a more external crustal slice. This interpretation is supported by the similar fluctuations of cooling rate derived here and subsidence of the Molasse basin. Afterwards, the cooling slowed down. During this time, the studied area seems to be passively moved westward in the hanging wall of the External Crystalline Massifs thrust, without significant deformations.
Anglais
2001

Tectonophysics
Publisher Elsevier
ISSN 0040-1951 
internationale
2001
340
1-2
79 à 93

Dauphinoise Zone – thermopaleomagnetic record – cooling rate