Neogene uplift of central eastern Patagonia: Dynamic response to active spreading ridge subduction

Benjamin Guillaume (1) , Joseph Martinod (1) , Laurent Husson (2) , Martin Roddaz (1) , Rodrigo Riquelme (3)

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

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.

Mots clés: Patagonia; dynamic topography; subduction; Neogene; triple junction

Domaines: Tectonique

Benjamin Guillaume, Joseph Martinod, Laurent Husson, Martin Roddaz, Rodrigo Riquelme. Neogene uplift of central eastern Patagonia: Dynamic response to active spreading ridge subduction. Tectonics, 2009, 28 (2), pp.TC2009. ⟨10.1029/2008TC002324⟩. ⟨insu-00392782⟩