A Pliocene–Quaternary compressional basin in the Interandean Depression, Central Ecuador |
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Authors: | Alain Lavenu,Thierry Winter ,Francisco Dá vila |
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Affiliation: | ORSTOM, UR 13, TOA, 213 rue La Fayette, 75 480 Paris cedex 10, France;Laboratoire de Géodynamique et Modélisation des Bassins Sédimentaires, UPPA, avenue de I'Université, 64 000 Pau, France;Laboratoire de Tectonique, Mécanique de la Lithosphére, IPGP, 4 place Jussieu, 75 252 Paris cedex 05, France;Department de Geologia, EPN, Ap. 2759, Ouito, Ecuador |
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Abstract: | The segment of the Interandean Depression of Ecuador between Ambato and Quito is characterized by an uppermost Pliocene–Quaternary basin, which is located between two N-S trending reverse basement faults: the Victoria Fault to the west, and the Pisayambo Fault to the east. The clear evidence of E-W shortening for the early Pleistocene (between 1.85 and 1.21 Ma) favours a compressional basin interpretation. The morphology (river deviations, landslides, folded and flexure structures) demonstrates continuous shortening during the late Quaternary. The late Pliocene-Quaternary shortening reached 3400 ± 600 m with a rate of 1.4 ± 0.3 mm yr−1. The E-W shortening is kinematically consistent with the current right-lateral reverse motion along the NE-SW trending Pallatanga Fault. The Quito-Ambato zone appears to act as a N-S restraining bend in a system of large right-lateral strike-slip faults. The compressive deformation which affects the Interandean Depression during the Pliocene is apparently coeval to the beginning subduction of very young oceanic lithosphere north of the Gulf of Guayaquil. The relatively buoyant new crust may have significantly increased the mechanical coupling in the subduction zone from Pliocene to Present. |
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Keywords: | Andes compressional basin Ecuador neotectonics reverse faults |
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