Grayburg Formation
Stratigraphic range: Guadalupian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Unit of	Artesia Group
Underlies	Queen Formation
Overlies	San Andres Formation
Thickness	294 feet (90 m)
Lithology
Primary	Dolomite
Other	Sandstone, anhydrite
Location
Coordinates	32°50′38″N 104°01′01″W / 32.844°N 104.017°W / 32.844; -104.017
Region	New Mexico Texas
Country	United States
Type section
Named for	Grayburg pool
Named by	R.I. Dickey
Year defined	1940
Grayburg Formation (the United States) Show map of the United States Grayburg Formation (New Mexico) Show map of New Mexico

The Grayburg Formation is a geologic formation in west Texas and southern New Mexico.^[1] It preserves fossils dating back to the Guadalupian Epoch of the Permian Period.^[2]

Description

The formation is found mostly in the subsurface and consists mostly of dolomite with some sandstone and anhydrite.^[1] The formation becomes more dominantly carbonate rock near the Guadalupe Reef and the beds become thicker. Away from the reef, the formation becomes increasingly dominated by sandstone.^[2]

The formation is interpreted as shallow marine sediments deposited on the San Andres platform, which flanked the Delaware and Midland Basins. The interbedded carbonate rocks and sandstone reflect fluctuations in sea level.^[3]

History of investigation

The formation was first defined by Robert I. Dickey in 1940 based on well logs. Dickey assigned the formation to the now-defunct Whitehorse Group.^[1] D.B. Tait, W.S. Motts, and M.E. Spitler reassigned the formation to the Artesia Group in 1962.^[4] V.C. Kelley subsequently adjusted the definition of the lower contact of the formation, in 1971.^[2]