Subhorizontal shear zones and their relation to nappe movements in the Cantal and Mifiarros units. Eastern Betic Zone (Spain)

Abstract

The Cantal and Miñarros units, two of the tectonic units that belong to the Internal Zone of the Betic Cordillera, bear evidence of a ductile shear deformation which led to the development of mylonites. In the Cantal unit, the mylonitic deformation began during the last part of a second penetrative deformation phase; it is restricted to the unit and is unrelated to its present-day position over the Palomas unit on which it has been emplaced later, under much more brittle conditions. In contrast, the mylonitic deformation observed in the Miñarros unit extends for a few metres into its relative autochthon (Lomo de Bas unit) where it affects third phase folds; these observations allow us to establish a direct relationship between the shear deformation and emplacement of the Miñarros unit over the Lomo de Bas unit. The distribution of the stretching lineations in the shear zones considered and the study of the preferred crystallographic c-axis orientation of quartz in the associated mylonites show that the direction of movement within the Cantal unit was from WSW to ENE, and that the Miñarros unit was emplaced from S to N.