John A. Morel¹

(1) Gustavson Associates, Boulder, CO

ABSTRACT: Structural Style of Detachment Faults Along the East Side of the Northern Rio Grande Rift in the San Luis Basin, Colorado

Previous work along the east side of the northern Rio Grande rift in the San Luis basin of Colorado has assumed a high angle normal fault boundary between the Precambrian and Paleozoic outcrops of the Sangre de Cristo range and the Tertiary sediments of the San Luis basin. Recent seismic work has determined that the boundary is actually formed by low angle detachment faults that become listric as they approach the basement. This is similar to listric detachment faults published for the Albuquerque basin section of the Rio Grande rift in New Mexico. Seismic data is presented that shows the angle of the fault, basin fill development, and the bedding detachment surface. The seismic interpretation is correlated to the stratigraphic section in a recent well which reached the Precambrian basement and to nearby USGS outcrop descriptions in the Sangre de Cristo range. The presentation includes a comparison of regional gravity work to the seismic interpretation.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado