Caracterización litológica y estructural del corte Atillo-Macas.

Abstract

The Atillo-Macas section contains rocks from the Cordillera Real, the Sub-Andean and part of the Oriente Basin. A shear zone caused by the Cosanga fault separates the red layers of Chapiza and Hollín sandstones, towards the South, from rocks of the Sub-Andean region made up of slate and metasediments determined as the Upano Unit. An intrusive quartz-monzonitic (Pluto Colimbo) affects the rocks of the Upano Unit in its extension. The Upano unit, which is made up of graphite black phyllites, meta-grauvacs and schists of Pl, Bt; it is affected throughout the section by this Pluton. These rocks have a low angle S1 foliation plane, their degree of inclination increases towards the west. The Chigüinda lithologies are graphite shales and Qz, Ms schists. These rocks show two main deformations, and the dip angle increases towards the West. This unit presents folds determined by the dip angle of its layers. The Chigüinda unit is affected by a granodioritic intrusive that is foliated, and separates it from the Agoyán unit. The Agoyán unit is made up of graphite shales, Qz, Ms, Pl shales with band-like size, and quartzites. This area where the Chigüinda and Agoyán units are located is the area with the highest metamorphic grade. The Alao-Paute unit is made up of meta-volcanics, meta-andesites, and tobaceous phyllites. Near the contact with the Maguazo Unit, the rocks of the Alao-Paute Unit composed of meta-volcano sediments are found forming folds. Contact with the Maguazo unit is through a zone of shear caused by a San Antonio regional fault. The Maguazo unit is made up of greenish metavolcano sediments and cherts. These rocks of the Maguazo Unit are overlaid by Sangay volcanosediments.