2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 11
Presentation Time: 8:00 AM-12:00 PM


ROSAS-ELGUERA, J., Ciencias de la Tierra, Universidad de Guadalajara, Av. Revolucion No. 1500, Guadalajara, 44840, Mexico, jrosas@ccip.udg.mx

Intense and widespread Late Cenozoic tectonic and volcanic activity in central Mexico has been associated to the subduction of the Cocos and Rivera plates beneath North America plate. The western-central part of Mexico is segmented by the Tepic-Zacoalco, Colima, and Chapala grabens they form the so called Guadalajara triple junction. These structural systems outline continental crustal blocks as the Michoacan and Jalisco blocks. Geometry and sense of slip of a total of 125 striated faults, corresponding to Late Miocene-Pliocene, were measured along the 115 km long and up to ~37 km wide Chapala graben. The paleostress regime responsible for the observed deformation was computed by fault slip data inversion. The trend of the measured mesofaults displays a dominant E-W direction in Chapala graben. Although some faults shows a small left-lateral component of motion most of them shows pitches higher than 45° and inclinations ranging between 45° a and 75°. On the other hand, paleomagnetic data have shown counterclockwise rotations to the northern and in eastern Chapala graben suggesting that a left-lateral transtension played a principal role in their early phases of formation. These structural and paleomagnetic data in the Chapala graben can be explained if a left-lateral component, in a transtensive framework, associated to the SE-motion of the Michoacan block is considered.