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
Organ Rock Formation been definitively recovered from this formation . As one moves younger in time through the Organ Rock Formation, temnospondyls becomes less abundant with respect other major groups such as diadectomorphs and early synapsids. This could track the general trend of aridification as indicated by sedimentology of the formation. This trend is globally recognized during the Early Permian, supported by many lines of geologic evidence including significant deposits of calcretes, eolianites, and evaporites. Organ Rock Formation The Organ Rock Formation or Organ Rock Shale is a formation within the late Pennsylvanian to early Permian Cutler Group and is deposited across southeastern