Paleomagnetism of the Talpa de Allende and Mascota grabens, western Mexico: A preliminary report

Abstract

The Jalisco Block of Western Mexico is thought to be undergoing internal deformation associated with its proposed NW translation relative to the North America plate. This deformation has resulted in the formation of several graben structures within the northern portion of the Jalisco Block; two of which are the Talpa de Allende and Mascota grabens.
An analysis of paleomagnetic data collected at six distinct, recent, lava flows within the Talpa de Allende and Mascota grabens fail to indicated any statically significant (95% confidence level) motions in this area. Specifically, the expected direction of the geocentric axial dipole field at the site location (D=0°, I=37°)lies within the 95% confidence cone associated with the mean direction calculated for these six sites (D=352.2°, I=24.0°, α₉₅=16.8°).
However, the flattening parameter associated with the mean direction of these six sites (12.8±13.1), along with the close proximity of both the North American reference pole and the expected field direction at the side to the corresponding 95% confidence cones of the paleomagnetic results, indicates that additional data may allow for the resolution of the proposed northward movement of the Jalisco Block or of local tiling associated with faulting.