Sly Gap Formation
Stratigraphic range: Frasnian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Underlies	Percha Formation, Contadero Formation
Overlies	Onate Formation
Thickness	114 feet (35 m)
Lithology
Primary	limestone
Other	siltstone, shale
Location
Coordinates	33°19′56″N 106°27′27″W / 33.3322°N 106.4574°W / 33.3322; -106.4574
Region	New Mexico
Country	United States
Type section
Named by	F.V. Stevenson
Year defined	1945
Sly Gap Formation (the United States) Show map of the United States Sly Gap Formation (New Mexico) Show map of New Mexico

The Sly Gap Formation is a geologic formation in south-central New Mexico. It preserves fossils dating back to the Frasnian Age of the late Devonian period.^[1]

Description

The formation consists of about 114 feet (35 m) of brown, yellow, or gray limestone and siltstone and brown to greenish-gray shale. It disconformably overlies the Onate Formation and is overlain by the Percha Formation^[1][2] or the Contadero Formation.^[2] It pinches out in the west in the Basin and Range province.^[1]

Fossils

The formation includes crinoidal siltstone beds and many other beds are fossiliferous, bearing crinoid, brachiopod, bryozoan, anthozoan, cephalopod, gastropod, fish, and coral remains.^[1]