The formation consists of coarse
conglomerate, red and white
sandstone, and red
clay. Its total thickness is , of which is conglomerate. The formation rests
unconformably on the
Cretaceous Mesaverde Group and is overlain by the
Oligocene Spears Formation. The formation was deposited in a
basin that developed in Eocene time in eastern Arizona and west-central New Mexico. The basin was mostly a system of
braided streams subject to frequent
flash floods, with
meandering streams restricted to the easternmost part of the basin.
Paleocurrent directions showed that stream flow was generally to the east-northeast. 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. Deposition ended with the eruption of the
Mogollon-Datil volcanic field, which disrupted the Baca
drainage and buried the basin in
volcaniclastic rock. ==Fossils==