Named as the upper member of Kirtland Shale for a small spring in sec 1, T24N, R12W, San Juan Co, NM in the San Juan basin. Rocks designated Naashoibito in this report were assigned to the basal Ojo Alamo by Bauer (1916). A section measured at the spring is designated the type section. Is 22-26 ft thick at type where it is divisible into a basal gray coarse- to granule-size sandstone with siliceous pebbles succeeded by olive-green shale and clay, white, fine- to coarse-grained, soft sandstone, and gray to green silty clay and shale. The basal unit was Bauer's basal conglomerate of Ojo Alamo; overlying units were the medial part of Bauer's Ojo Alamo. Overlies upper shale member of Kirtland; unconformably underlies Ojo Alamo Sandstone restricted. Reference section designated as section measured in sec 16, T24N, R11W, where member: is 84 ft thick; overlies upper shale member, Kirtland; unconformably underlies Ojo Alamo restricted; consists of sandstone, buff to white, fine- to coarse-grained, gray, plastic clay, sandy shale, and purple-weathering claystone; and divisible into basal and medial units of Bauer. Mapped in Hunter Wash-Coal Creek area. Has a dinosaur fauna. Of Montana or Late Cretaceous age. Geologic map; nomenclature chart; cross section.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Follows definition of Bauer (1916) in which three units distinguished at Ojo Alamo Wash, T24N, Rs11 and 12W--used as type locality for Ojo Alamo in this report, San Juan Co, NM, San Juan basin. These are 1) lower massive conglomeratic sandstone, 2) medial silty shale and soft conglomeratic sandstone, and 3) upper massive conglomeratic sandstone. The three units are 6 to 122+ m thick. Authors believe Bauer's definition should be retained rather than restricted definition of Ojo Alamo to upper sandstone of Baltz, Ash, Anderson (1966). Authors also believe Naashoibito Member should be used only in Ojo Alamo Wash and that it should be reassigned from the Kirtland Shale to the Ojo Alamo. Right femur of a hadrosaurian dinosaur found at type locality in lower sandstone. History of use described (Bauer to present). Ojo Alamo at Hunter Wash, South Mesa, Barrel Spring, Pot Mesa, Portales, Gasbuggy sites described. Age of Ojo Alamo using Bauer's definition is Late Cretaceous and Paleocene. Geologic map; stratigraphic diagrams.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Pollen (PROTEACIDITES, BALMEISPORITES, INTERPOLLIS, GUNNERA, KURTZIPITES, ULMOIDEIPITES) collected near Farmington, NM in the San Juan basin, from mudstone above the base of a conglomeratic sandstone that has been assigned by some to the Naashoibito Member of the Kirtland Shale and by others to the lower part of the Ojo Alamo, are of early or of late Maastrichtian age. The upper part of the Ojo Alamo intertongues with the Nacimiento Formation and has yielded palynomorphs (MOMIPITES, ULMOIDEIPITES) of early Paleocene age. The Naashoibito or lower Ojo Alamo is separated from the upper Ojo Alamo by an unconformity. If the Naashoibito or lower Ojo Alamo is early Maastrichtian, at least half of the Maastrichtian is missing in the southwestern San Juan basin. Correlation diagram.

Source: GNU records (USGS DDS-6; Denver GNULEX).