Abstract

ARRIAGADA, César et al. The Maipo Orocline: A first scale structural feature in the Miocene to Recent geodynamic evolution in the central Chilean Andes. AndGeo [online]. 2013, vol.40, n.3, pp.419-437. ISSN 0718-7106.

In this paper we show the results of a paleomagnetic study carried out along the western Andes of central Chile from 30° to 36°S. Whereas paleomagnetic analysis from Jurassic to Late Cretaceous rocks in the Pampean flat slab segment shows small or non significant clockwise vertical-axis rotations, results obtained in Late Jurassic to Neogeone rocks to the south, on the normal subduction segment, show sistematically clockwise rotations up to 40°. Paleomagnetic rotations are coeval with thrusting along the High Andes in Late Miocene times. We propose a coupled Bolivian Orocline-Juan Fernández Ridge (JFR) model where a far-field component of clockwise rotation related to the formation of the Bolivian Orocline was first acquired by the margin between 31° and 33°S. The same area was later rotated by a slight counterclockwise component related to the subduction of the JFR over the last 10 Ma. South of 33°S the clockwise rotations related to the Bolivian Orocline component were amplified by the subduction of the JFR.

Keywords : Central Andes; Maipo Orocline; Bolivian Orocline; Juan Fernández Ridge; Paleomagnetism.

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