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Abstract: Tectonic Evolution and Structural Styles along the Maranon-Oriente-Putumayo Foreland Basins and their Associated Orogenic Belts

Jerome J. Kendall, Jaime Guerra, Antenor M. Aleman

Variations in structural style along strike in the fold belt of the MOP (Maranon-Oriente-Putumayo) foreland basins reflect changes in mechano-stratigraphy and strain partitioning due to the oblique convergence of the Farallon/Nazca and South American Plates. In Ecuador and Colombia, the fold belt is dominated by thin skin deformation. During the late Senonian (Peruvian Phase of the Andean Orogeny), allochthonous terranes were sutured along the Peltetec Fault and inversion of Jurassic grabens occurred. However along the Peruvian margin, an arc-trench system was present and no terrane accretion occurred. These different tectonic regimes allowed for variation in the styles of deformation in both space and time. The present configuration of the fold and thrust belt associated with the MOP foreland basins are dominated by orogen parallel strike-slip faults. Changes in structural style occur both along and across the basins.

The buttressing effect of granitic plutons, basement involved uplifts, the orientation of Jurassic grabens, and salt involved features partially control the deformation style that is present in the MOP. In Ecuador, the Triassic plutons halted the middle Eocene eastward propagation of the fold and thrust belt. The Cosanga/Mendez Fault, in the north, impinges on these uplifts and marks the change from thin skinned basement involved deformation to the west to thick skinned vertical deformation to the east. In Peru, the Maranon "Geanticline" was the hinterland from which thrusting propagated eastward and westward. In the Peruvian Maranon basin, salt provide a detachment surface for thin skinned deformation.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France