Revista mexicana de ciencias geológicas
versión On-line ISSN 2007-2902
SANTAMARIA-DIAZ, Alfredo; ALANIZ-ALVAREZ, Susana Alicia y NIETO-SAMANIEGO, Ángel Francisco. Cenozoic deformations in the Caltepec fault cover, Tamazulapam region, southern Mexico. Rev. mex. cienc. geol [online]. 2008, vol.25, n.3, pp. 494-516. ISSN 2007-2902.
The Tamazulapam region is located in the southern extension of the Caltepec fault, which places the Acatlán and Oaxaca complexes in contact. In the Tamazulapam region, both complexes crop out but the contact is covered by Mesozoic and Cenozoic rocks. This paper presents the detailed stratigraphy of the area and a structural analysis in order to establish if the Caltepec fault has exerted a structural control on the Cenozoic deformation. The structural analysis is difficult because the faults show a multiple fault pattern with complex kinematics. In order to resolve the kinematics of this region, we propose the use of Cinematic Compatibility Diagrams (CCD), which illustrate the whole possible movement of faults under a unique stress tensor. The CCD show that in the western side of the fault, where the Acatlan Complex constitutes the basement, the Cenozoic deformation occurred in two tectonic events, the first one under a tectonic transcurrent regime with a maximum shortening towards NE-SW during the late Eocene-Early Oligocene, followed by the second event, extensional, with maximum extension in the same direction, which occurred during late Oligocene (between 26 and 29 Ma). The direction and regime type of these events correspond with previous deformational events recorded in other areas in southern Mexico. In contrast, in the eastern side, where the Oaxaca Complex constitutes the basement, the deformation is heterogeneous, probably generated by the synchronous movement of the Oaxaca and the Tamazulapam faults above a detachment formed partially by anhydrites. The differences in the deformation styles on both sides of the southern extension of the Caltepec fault shows that, in this case, the basement fault influenced the deformation style of the Cenozoic units.
Palabras llave : Basement fault; heterogeneous deformation; kinematic compatibility; Cenozoic; Caltepec fault; Tamazulapan fault; Oaxaca; Mexico.