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1 LMTG - Laboratoire des Mécanismes et Transfert en Géologie 2 GR - Géosciences Rennes 3 Departamento de Ciencias Geológicas

Abstract : The Chile Triple Junction CTJ episodically migrated northward during the past 14 Ma from 54°S to its present-day position at 46°30-S, as different almost trench-parallel spreading segments entered in subduction. This migration resulted in the opening of an asthenospheric window below Patagonia, inducing a disturbance in the regional mantle convection. On the overriding plate, the middle Miocene time corresponds to a major change in the central Patagonian basin dynamics, with a transition from subsidence to generalized uplift. The detailed mapping and the morphological study of post-middle Miocene terraces evidence regional-scale trench-parallel tilt histories that differ depending on latitude. South of 46°30-S, the slopes of the fluvial terraces indicate a change from northward to southward tilt during late Miocene. Terraces younger than the early Pliocene do not show any trench-parallel tilt. North of 46°30-S, in contrast, only northward tilt, active until the Pleistocene, is recorded. We use a semianalytical model of dynamic topography which suggests that the northward migration of the Chile Triple Junction should be accompanied by a dynamic uplift of the central Patagonian basin. Uplift would cause both north directed and south directed tilt, north and south of the triple junction, respectively, with values of ~0.1­0.2% 500 km east of the trench. Tilt measured in the southeastern part of the central Patagonian basin ~0.1% is comparable to values predicted using the semianalytical model. The dynamic topography associated to the Chile ridge subduction may have exerted a major control on the Neogene dynamics of Patagonia.

Keywords : Patagonia dynamic topography subduction Neogene triple junction





Autor: Benjamin Guillaume - Joseph Martinod - Laurent Husson - Martin Roddaz - Rodrigo Riquelme -

Fuente: https://hal.archives-ouvertes.fr/



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