[2] The formation was deposited in a basin that developed in Eocene time in eastern Arizona and west-central New Mexico.

Shallow floodplain lakes and a large, shallow closed lake in the eastern part of the basin were also present, though lacustrine beds are nearly absent due to extensive river delta formation.

[3] Deposition ended with the eruption of the Mogollon-Datil volcanic field, which disrupted the Baca drainage and buried the basin in volcaniclastic rock.

[4] The formation is relatively poor in vertebrate fossils, and only six of biostratigraphic significance have been found.

[2] The formation was first described by R.H. Wilpolt and his coinvestigators in 1946 and named for exposures in Baca Canyon in the Bear Mountains.