New Mexico Geological Society Annual Spring Meeting — Abstracts

The Salado Mountains make up the southern half of an east-tilted late Tertiary fault block located 12 miles west of Truth or Consequences, New Mexico. The oldest rocks exposed are Precambrian metadiorite, muscovite schist, and granite which are overlain by approximately 2000 feet of Paleozoic sedimentary rocks. During Laramide time, the southern half of this area was uplifted as a basement-cored block along an the east-trending high angle fault. Drag folding along the trend of this zone may suggest a component of left-lateral strike slip movement. This uplift resulted in the gentle doming of the area and the formation of east-trending extensional structures to the north of the fault margin. An intermediate compositon dike dated at 43.7±1.7my intrudes the fault zone, providing an upper time limit Laramide deformation in this area. Inatermediate composition flows and laharic breccia, and silicic crystal-lithic and lithic ash-flow tuffs buried these structures during mid-Tertiary time.

Late Tertiary extensional block faulting raised the Salado Mountains at least 1500 feet along a north-northwest trending, west-dipping fault zone and rotated them approximately 21° to the east. The trend of faults, as well as major tensional fractures, indicate a σ₃ direction of N70E-S70W. This bounding fault cuts Laramide structures. Uplift and erosion of the late Tertiary block has exposed a stock of intermediate compositon north of the Salado Mountains in the Garcia peaks. Smaller scale north-trending extensional faults occur on the east side of these mountains.