Rio Brazos (New Mexico) abruptly west into the Brazos Box, one of the largest canyons in New Mexico with a maximum depth of more than . Here, it passes the Brazos Cliffs, receives Gavilan and Encinado Creeks, and picks up an unnamed tributary which feeds Brazos Falls, reputedly New Mexico's highest waterfall with a total drop of . Northeast of Tierra Amarilla, the river emits from the mountains, receiving Chavez Creek from the right. It passes the settlements of Ensenada, Brazos and Los Ojos before flowing into the Rio Chama about northwest of Santa Fe. The Brazos is a perennial stream, reaching its highest
Calvert Cliffs State Park during that time. The age of the formation is (19-)18–15(-14) million years ago (Ma), i.e. it extends essentially over the Hemingfordian stage. This formation occurs in Maryland and neighboring Virginia. In addition, rocks of the younger Choptank and the St. Marys Formations are exposed here. This makes Calvert Cliffs State Park extremely interesting for its paleoclimatology and paleontology, because the accessible strata provide a good record of the Middle Miocene Climate Transition and document a minor mass extinction event — the "Middle Miocene disruption." Fossil collecting and "rockhounding" are permitted on the beach; the cliffs are closed due the dangers