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Etude structurale et paléomagnétique de la courbure des systèmes plissés et chevauchants des arcs de Nice, de Castellane et du Nord-Est de Taiwan

Abstract : Numerous mountain belts across the world are curved. The western Alps are one of the most emblematic examples. A main question is the contribution of the inherited structures to the curvature of orogens and foreland thrust belts. The determination of potential vertical axis rotations is a major goal in order to restore the initial geological context and to understand the development of such structure. I carried out several paleomagnetic studies together with Anisotropy of Magnetic susceptibility analyses (which could give us the shortening direction prior to the folding stage), and also a paleostress and a structural study of the Nice arc, the Castellane arc (south-western Alps) and the north-east Taiwan fold and thrust belt. For These area the inherited structural framework and the geodynamical context are well constrained. From my results, three main conclusions can be drawn: (1) the curvature of the Castellane arc is related to large rotations of 60° anticlockwise rotation of its eastern branch during Oligocene; (2) the curvature of the Nice arc is inherited from the Mesozoic structural network ; (3) the curvature of the North-East Taiwan is due to the southward motion of the Ryukyu arc on the last 6.5 Ma generating increasing clockwise rotations from 20° at the South-West to 40° at the North-East. More specifically, I highlight a simple clockwise rotation of the Nice region directly related to an unique ~N-S compression rather than to the successive E-W and N-S compressions, of Oligocene and Miocene age respectively. The Oligo-Miocene sedimentary formations of Taiwan, in the Taipei arc and the Hengchun Peninsula, recorded a 50-60° anticlockwise rotation certainly related to the subduction-collision transition. The Castellane arc, the Taipei arc and the Hengchun Peninsula show important remagnetization. These remagnetizations can be related to sedimentary and/or tectonic burying. Finally, an analysis of the geodetic data versus the paleomagnetic data in Taiwan points out the consistency of the deformation over the last 6.5 Ma.
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Submitted on : Friday, September 21, 2012 - 1:27:59 PM
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Lionel Sonnette. Etude structurale et paléomagnétique de la courbure des systèmes plissés et chevauchants des arcs de Nice, de Castellane et du Nord-Est de Taiwan. Tectonique. Université Nice Sophia Antipolis, 2012. Français. ⟨tel-00734306⟩



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