Nappe structures in the Sierra de Los Organos, western Cuba

Abstract

Sierra de los Organos, western part of the Cordillera de Guaniguanico, Cuba, have been formed at Middle Eocene time, the nppes being transported northwards. Their tectonic style can be characterized by differential displacement of the rook masses forming ultimately partial nappes; subsequent structural inversion of the tectonic units relative to their original position; and zonation of tectonic deformations. Three lineation types have been recognized, representing different deformation phases. The oldest lineation type occurs within metamorphosed units. It may be related to metamorphic processes acting previously to the nappe overthrusting toward the north. The main lineation occurs in all tectonic units and resulted from the main overthrusting phase. The youngest lineation has originated after the main orogenic phase. Among small folds, the northerly displacements occur most commonly although southerly ones prevail in the Alturas de Pizarras del Norte. Nappe-scale units of the Sierra de los Organos reveal features of gravitation structures. Serpentinites and ultrabasic rocks present within the mélange zones solid gravitationally down at the final stage of wildflysch sedimentation. They came from another facies-structural zone. Sedimentary basin of the Sierra de los Organos represented the southern part of Cuban orthogeosyncline, south to Zaza eugeosynclinal zone. During the main orogenic phase, tectonic units of the Sierra de los Organos were thrust over Zaza zone which may have been already folded during the Late Cretaceous or at the Cretaceous-Paleogene boundary. A subduction zone occurred probably in the southern part of leptogeosyncline and the northern part of Cuban eugeosyncline. Rotations and displacements along the Caribbean faults have resulted from differential displacements of the North and South American continents toward the west.