Structural geology and tectonics on the northern Chihuahua trough.

摘要

I present results from a study of the structural geology of the northern part of the Chihuahua trough where the Laramide orogeny and the Rio Grande rift affected the region. Laramide style of deformation changes from motion on moderate to low angle thrust and reverse faults within the interior of the basin to basement involved reverse faulting on the adjacent platform. Shortening directions estimated from the geometry of folds and faults and inversion of fault slip data indicate that both basement involved structures and faults within the basin record a similar Laramide age deformation field. Laramide shortening was focused into the relatively weak sedimentary rocks of the Chihuahua trough that piled up on the rigid basin margin. Along strike variations in shortening direction and kinematics are controlled by the curved northeast margin of the trough and reflect stress reorientation along the weak interface between the strong platform and weak basin interior.; In addition, I reconstructed the stress regime of the Rio Grande rift. Structures in the southern Rio Grande rift are consistent with prior inferences that the Rio Grande rift formed during two phases of extension. Low angle normal faults were active during both phases of extension and are not restricted to the first extensional phase, as has been previously inferred. In the East Potrillo Mountains back tilting of W25°SE and W45°SE about a N30°W axis are required in order to obtain two homogeneous stress fields. The corrected fault planes show significant oblique component in these two stress fields; the first stress field corresponds with sigma1 and sigma3 oriented N78E and N69E respectively whereas the second stress is that related to the youngest faults oriented N64W and N61E respectively. In the Franklin Mountains tilting is less significant; however two stress fields with similar orientations but different &phis; values are recognized.; The combined data sets show that the northern Chihuahua trough has been affected by three major deformation events since its formation with the stress fields varying over time. These deformation events led to the production of the complex basin and range structure found throughout northern Chihuahua, southern New Mexico and west Texas. Additionally, these events are similar to those that affected much of the Rocky Mountain region in Colorado and New Mexico. This shows that despite differences in physiography between this region and the Rocky Mountains, it records a similar tectonic history with much of the Rocky Mountain foreland.