Zia Formation
Stratigraphic range: Miocene 23–14.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Zia Formation badlands northwest of Jemez Pueblo
Type	Formation
Unit of	Santa Fe Group
Underlies	Cerro Conejo Formation, Cochiti Formation
Overlies	Galisteo Formation
Thickness	300 m (980 ft)
Lithology
Primary	Sandstone
Location
Coordinates	35°31′27″N 106°44′55″W / 35.5241523°N 106.748613°W / 35.5241523; -106.748613
Region	New Mexico
Country	United States
Type section
Named for	Zia Pueblo, New Mexico
Named by	Regan
Year defined	1903
Zia Formation (the United States) Show map of the United States Zia Formation (New Mexico) Show map of New Mexico

The Zia Formation is a geologic formation in the southwestern Jemez Mountains and northwestern Santo Domingo basin. It contains vertebrate fossils that date it to early to middle Miocene in age.

The Zia Formation is a very soft quartz sandstone. The type section rests on about 10 meters (33 ft) of laminated greenish clay beds that in turn rest on the Galisteo Formation.^[1] The upper contact is with the Cerro Conejo Formation,^[2] with the Cochiti Formation, or with Miocene volcanic rocks of the Jemez volcanic field.^[1][3]

The formation is divided (in ascending stratigraphic order) into the Piedra Parada Member, the Chamisa Mesa Member. and the Canada Pilares Member.^[4]

The formation is interpreted as eolian deposits derived from volcaniclastics of the Jemez volcanic field. These were first transported south by the Jemez River, then transported by wind from the west.^[5]

The Piera Parada Member contains fossils mostly of camels (Stenomylus, Oxydactylus, and Michenia) and rhinos (Diceratherium.) These are characteristic of the late Arikareean faunal stage, 22 to 19 million years ago.^[6]

The Chamisa Mesa Member contains four fossil quarries from which fossils have been found that are characteristic of the Hemingfordian faunal stage, 20.6 to 16.3 million years ago. These include specimens of Menoceras, Protolabis, Aepycamelus, Subparacosoryx, Promartes, Tomarctus, Cynarctoides,^[1] and Blickomylus.^[6]

The formation was first described by Regan in 1903, who named it the Zia Marl. T. Galusha renamed it the Zia Sand Formation and divided it into the lower Piedra Parada Member and the upper Chamisa Mesa Member. He also recognized a subtle disconformity about 120 m above its base.^[1]

In 1981, C.E. Gawne assigned a sequence of reddish beds above the Chamisa Mesa Member to the Zia Formation as the Canada Pilares Member.^[4] In 1997, R.H. Tedford and Steven Barghoorn added an additional sequence of beds above the Canada Pilares Member to the Zia Formation as the Cerro Conejo Member. However, two years later, they recommended moving this member into its own formation.^[2][7]

• List of fossiliferous stratigraphic units in New Mexico
• Paleontology in New Mexico

• Connell, S.D. (2008). "Refinements to the stratigraphic Santa Fe Group, northwestern Albuquerque basin, New Mexico" (PDF). New Mexico Geology. 38 (1): 14–35. Retrieved 11 August 2020.
• Connell, S.D.; Koning, D.J.; Cather, S.M. (1999). "Revisions to the stratigraphic nomenclature of the Santa Fe Group, northwestern Albuquerque basin, New Mexico" (PDF). New Mexico Geological Society Field Conference Guidebook. 50: 337–354. Retrieved 10 June 2020.
• Galusha, T. (1966). "The Zia Sand Formation, new early to medial Miocene beds in New Mexico" (PDF). American Museum Novitates. 2271. Retrieved 23 August 2020.
• Gawne, C. E. (December 1981). "Sedimentology and stratigraphy of the Miocene Zia sand of New Mexico". GSA Bulletin. 92 (12_Part_II): 2484–2552. Bibcode:1981GSAB...92.2484G. doi:10.1130/GSAB-P2-92-2484.
• Manley, Kim (1978). "Geologic map of the Bernalillo NW quadrangle, Sandoval County, New Mexico". National Geologic Map Database. U.S. Geological Survey. Retrieved 21 March 2020.
• Tedford, R.H.; Barghoorn, Steven (1999). "Santa Fe Group (Neogene), Ceja del Rio Puerco, northwestern Albuquerque basin, Sandoval County, New Mexico" (PDF). New Mexico Geological Society Field Conference Guidebook. 50: 327–336. Retrieved 11 August 2020.