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Post-Oligocene rotations in southern Ecuador and northern Peru and the formation of the Huancabamba deflection in the Andean Cordillera

Earth and Planetary Science Letters
Publication Date
DOI: 10.1016/0012-821x(90)90035-v


Abstract A paleomagnetic study of more than 410 samples from 41 sites from Paleocene to early Oligocene volcanic and intrusive formations in southern Ecuador and northern Peru reveals a pattern of rotations in opposite senses on both sides of the Huancabamba deflection. The amplitude of the rotations is ∼ 25° clockwise north of the deflection and ∼ 20° anticlockwise south of it. North of the deflection, the results do not allow us to ascertain whether the rotation arises from oroclinal bending or from block rotation in a distributed shear. South of it, the absence of geological evidence for widespread strike-slip faulting suggests that the results reflect a rotation of the Peruvian margin which could be related to the shortening documented in Southern Peru and to the uplift of the Central Andes.

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