Diamond Tail Formation

The Diamond Tail Formation is a geologic formation in New Mexico. It contains fossils characteristic of the late Paleocene or early Eocene.

Diamond Tail Formation
Stratigraphic range: late Paleocene–early Eocene PreꞒ Ꞓ O S D C P T J K Pg N
Exposure of Diamond Tail Formation on Cerro Colorado, near Lamy, New Mexico
Type	Formation
Underlies	Galisteo Formation
Overlies	Menefee Formation
Thickness	442 m (1,450 ft)
Lithology
Primary	Sandstone
Other	Mudstone
Location
Region	Central New Mexico
Country	United States
Type section
Named for	Diamond Tail Ranch
Named by	Lucas, Cather, Abbott, and Williamson
Year defined	1997
Diamond Tail Formation (the United States) Show map of the United States Diamond Tail Formation (New Mexico) Show map of New Mexico

Description

Diamond Tail Formation near Los Cerros, New Mexico

The Diamond Tail Formation consists of a lower member composed of sandstone and conglomeratic sandstone, a middle member of variegated mudstone, and an upper sandstone member. The formation crops out over a limited area between Sandia Crest and the southern Sangre de Cristo Mountains.

The formation is cut by thrust and strike-slip faults consistent with east-northeast to east-trending tectonic compression of the late stages of the Laramide Orogeny.^[1]

The formation likely correlates with the lower San Jose Formation of the San Juan Basin.^[2]

Fossils

The presence of Hyracotherium teeth dates the formation to the late Paleocene or early Eocene.^[2]

History

The beds now designated as the Diamond Tail Formation were originally part of F.V. Hayden's Galisteo sand group.^[3] By 1997, it was clear that these beds were separated from the remainder of the Galisteo by a significant regional unconformity, and they were split off into the Diamond Tail Formation, named after exposures near Diamond Tail Ranch.^[2]