Brazos Mountains to 55 million years ago during the Laramide orogeny. To the east and northeast lie the Sangre de Cristo Mountains which share a similar geological history. The Brazos Cliffs, which form a dramatic backdrop to Tierra Amarilla, are formed of Precambrian quartzite. Brazos Mountains The Brazos Mountains is a range in far northern Rio Arriba County, in northern New Mexico in the southwestern United States. A high crest runs from the border with Colorado for over in a south-southeasterly direction. The high point of the range at is on Grouse Mesa, at the Brazos Benchmark. Two miles (3 km) to
Brazos Mountains the view from the west, including from Heron Lake. U.S. Route 64 crosses the southern end of the range at a 10,481 foot (3194 m) pass. Nearby are the photogenic Brazos Cliffs, headwaters of the Rio Brazos and part of the Rio Chama river system. These mountains overlook the Chama River, the largest tributary of the Rio Grande which lies to the east. In essence, these mountains are the southern extension of the South San Juan Range that lies in Colorado. The Brazos Mountains are the southwestern remnants of a Laramide peneplain resulting from the erosion of mountains formed 80