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
Organ Rock Formation fine-grained sand from the overlying dune facies. This facies is most common at the western extent of the Organ Rock Formation. Plant fossils include "Supaia", "Walchi" and "Yakia" which lived in semi-arid conditions. Fossil vertebrates represent the majority of the faunal assemblage present in the Organ Rock Formation. Animal remains are most commonly preserved within ancient stream channels of the floodplain and channel facies. Within this facies, fossilized bone occurs proximal to conglomeratic lenses. Taxa recovered include: freshwater actinopterygian fishes, temnospondyl amphibians, diadectomorphs, seymouriamorphs, and early synapsids. Fossil fish material, either bone or scale, is infrequent within the Organ Rock