New Mexico Geological Society Annual Spring Meeting — Abstracts

Cerro Azul is a block of Precambrian quartzite located 35 km southwest of Taos in the Rio Grande rift. The quartzite at Cerro Azul bears a marked similarity to the Ortega Quartzite exposures in the Tusas and Picuris Mountains.

Cerro Azul is in close proximity to the Ortega Quartzite exposed at the Picuris cliffs, 8 km to the east. The quartzite at Cerro Azul displays structural continuity with the major trends recognized in the Picuris.

The Cerro Azul quartzite displays a bedding parallel foliation difined by dark materials, which is commonly folded into tight to isoclinal folds. The same style of folding is common in the Ortega Quartzite at Kiowa MOuntain in the Tusas. A cross-cutting foliation at Cerro Azul is readily apparent in the field and is similar to a fabric present at the Kiowa Mountain exposure.

The deformation best seen in the bedding parallel foliation implies folding and shear in a ductile regime. The presense of the aluminosilicate triple point assemblage: kyanite, sillimanite, and viridine ( Mn- andalusite) indicate temperature and pressure conditions sufficiently high enough for ductile deformation.

Similar structural trends, deformational fabrics, and pressure-temperature conditions suggest that the quartzite at Cerro Azul is correlative with the Ortega Quartzite in the Tusas and Picuris Mountains.