Structural Geology and Tectonic Development of Northeast Part of Rio Puerco Fault Zone, Sandoval County, New Mexico: ABSTRACT

Abstract

The northeast part of the Rio Puerco fault zone is in the southwestern part of Sandoval County, New Mexico. Three major types of structural features are present within the area: north- to northwest-trending folds; northeast-trending faults of the Rio Puerco fault zone; and north-trending faults. Dominant movement along faults within the area is dip-slip. Two major periods of deformation are evident, the Laramide orogenic movements of late Paleocene through Eocene age, and Basin and Range tectonism of middle Miocene to recent age. Laramide tectonism resulted from a north-trending right-shift force couple related to the northeast drift of the Colorado Plateau, and to vertical forces which led to the development of the Nacimiento uplift. The northwest-trending folds and the northeast-trending normal faults of the Rio Puerco fault zone formed in response to the right-shift force couple. The Rio Puerco faults are interpreted as tension fractures which developed at 45° to the trend of the force couple. A slight clockwise rotation of the southeast part of the Colorado Plateau is evident from tension fracture trends along the fault zone. Miocene tectonic activity was dominated by north-trending, east-dipping normal faults having large stratigraphic separations that were related to the development of the Rio Grand rift. Many of the southeast-dipping normal faults of the Laramide Rio Puerco fault zone were rejuvenated during the Miocene crustal extension. End_of_Article - Last_Page 918------------