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Latest Pleistocene-Holocene tectonics of the Ecuadorian Andes

Authors
Journal
Tectonophysics
0040-1951
Publisher
Elsevier
Publication Date
Volume
205
Identifiers
DOI: 10.1016/0040-1951(92)90421-2
Disciplines
  • Earth Science

Abstract

Abstract A structural study was carried out in the most tectonically active areas of the Ecuadorian Andes, including part of the Interandean Valley, the Cordillera Real and the Subandean Zone. Since the Pleistocene, the region has undergone complex wrench tectonics which are still active. Apparently, two different stress states have coexisted within different parts of the Andean range during the latest Pleistocene and Holocene: 1. (1) The external part of the chain, including the Cordillera Real and the westernmost part of the Subandean Zone, has been subject to a east-northeast-west-southwest direction of greatest principal stress. Associated motions are partitioned between right-lateral oblique thrusting and pure right-lateral strike-slip faulting along north-south to north-northeast trending structures. As a whole, these define a right-lateral transpressive shear zone. 2. (2) In the Interandean Valley, which lies above a major Tertiary suture zone, deformations are consistent with a north-south direction of greatest horizontal principal stress associated with recent development of a left-lateral transtensional shear zone. In the first zone, fault displacements are at least an order of magnitude larger than in the second zone. The present tectonics of the area is explained by a kinematic model, in which the wedge-shaped Cordillera Real crustal block, bounded to the east by a right-lateral shear zone and to the west by a left-lateral shear zone, is being uplifted and extruded northward with respect to the Cordillera Occidental and to the stable South American foreland. This motion is the result of oblique convergence between the Nazca and South American plates.

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