Renewed uplift of the Central Andes Forearc revealed by coastal evolution during the Quaternary

Vincent Regard (1) , Marianne Saillard (1) , Joseph Martinod (1) , Laurence Audin (1, 2, 3) , Sébastien Carretier (1) , Kevin Pedoja (4) , Rodrigo Riquelme (5) , Paola Paredes (1) , Gérard Hérail (1)

1 LMTG - Laboratoire des Mécanismes et Transfert en Géologie
2 IRD
3 LGCA - Laboratoire de Géodynamique des Chaines Alpines
4 M2C - Morphodynamique Continentale et Côtière
5 Departamento de Ciencias Geológicas

Most of the Pacific coast of the Central Andes, between 15°S and 30°S, display a wide (a couple of kilometres) planar feature, gently dipping oceanwards and backed by a cliff. This morphology, usually of marine origin, is called rasa, and argues for a recent and spatially continuous uplift of the margin over the 1500-km-long coastal region we describe. The cliff foot is found at a similar elevation (˜ 110 m amsl) all over the studied area, with the exception of peninsulas such as the Mejillones Peninsula. The compilation of published chronological data and the extrapolation of re-appraised uplift rates provide evidence for a common cliff foot age of around 400 ka (i.e., Marine Isotopic Stage MIS 11). This, together with other geological constraints, indicates a Quaternary renewal of uplift in the Central Andes Forearc after a late Pliocene quiescence or subsidence.

Mots clés: Andes; Quaternary; subduction; rocky coast; geomorphology; marine terrace

Domaines: Géomorphologie

Vincent Regard, Marianne Saillard, Joseph Martinod, Laurence Audin, Sébastien Carretier, et al.. Renewed uplift of the Central Andes Forearc revealed by coastal evolution during the Quaternary. Earth and Planetary Science Letters, 2010, 297, pp.199-210. ⟨10.1016/J.EPSL.2010.06.020⟩. ⟨insu-00549820⟩