Timberlake Formation
Stratigraphic range: late Paleocene–Eocene PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Underlies	Bluff Creek Tuff
Overlies	Ringbone Formation Cowboy Spring Formation
Thickness	150 meters (490 ft)
Lithology
Primary	Limestone conglomerate
Location
Coordinates	31°36′40″N 108°37′34″W / 31.611°N 108.626°W / 31.611; -108.626
Region	New Mexico
Country	United States
Type section
Named for	Timberlake Ranch
Named by	Zeller and Alper
Year defined	1965
Timberlake Formation (the United States) Show map of the United States Timberlake Formation (New Mexico) Show map of New Mexico

The Timberlake Formation is a geologic formation exposed in the Animas Mountains of southwestern New Mexico. Its age is estimated to be late Paleocene to Eocene.^[1][2]

The formation is primarily limestone cobble conglomerate. The massive conglomerate beds are separated by thinner beds of sandstone, shale, claystone, and tuff. The clasts in the conglomerate are embedded in a red arkosic matrix or a poorly sorted limestone conglomerate matrix. In some locations, the formation contains boulders of limestone conglomerate over 200 feet (61 m) in diameter that appear to be derived from the underlying Cowboy Spring Formation. The formation is separated from the Cowbow Springs Formation, which it strongly resembles, with angular unconformity. Its maximum thickness is 150 meters (490 ft).^[1][2]

The formation was deposited in the Little Hat Top basin, a downwarp on the southern flank of the Hidalgo uplift. It is overlain by the Bluff Creek Tuff, which has been radiometrically dated as 35.1 million years old. This constrains the Timberlake Formation to not be younger than Eocene. The formation is interpreted as a fanglomerate produced by erosion of early Tertiary Laramide uplifts.^[2]

The formation was first named by Zeller and Alper in 1965 for outcrops near Cowboy Spring in the Animas Mountains.^[1] Elston and Erb recommended merging the formation with the underlying Cowboy Spring Formation due to lack of a clear lithological distinction,^[3] but this has not been universally accepted.^[2]

• Elston, W.E.; Erb, E.E. (1977). "Cenozoic volcano-tectonic setting of KCM #1 Forest Federal Well, Animas Mountains, Hidalgo County, New Mexico" (PDF). New Mexico Bureau of Mines and Mineral Resources Circular. 152: 53–62. Retrieved 15 September 2020.
• Seager, William (2004). "Laramide (late Cretaceous-Eocene) tectonics of southwestern New Mexico". In Mack, G.H.; Giles, K.A. (eds.). The geology of New Mexico. A geologic history: New Mexico Geological Society Special Volume 11. pp. 183–202. ISBN 9781585460106.
• Zeller, R.A. Jr.; Alper, A.M. (1965). "Geology of the Walnut Wells quadrangle, Hidalgo County, New Mexico" (PDF). New Mexico Bureau of Mines and Mineral Resources Bulletin. 84. Retrieved 15 September 2020.