Tensleep Formation
Stratigraphic range: Late Pennsylvanian-very Early Permian ~308–298 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Underlies	Phosphoria & Chugwater Formations
Overlies	Sacajewea & Amsden Formations
Thickness	up to 535 feet (160 m)
Lithology
Primary	Sandstone
Other	Limestone
Location
Coordinates	42°36′N 108°12′W / 42.6°N 108.2°W / 42.6; -108.2
Approximate paleocoordinates	4°18′N 35°12′W / 4.3°N 35.2°W / 4.3; -35.2
Region	Wyoming
Country	USA
Type section
Named for	Ten Sleep, Wyoming
Named by	N.H. Darton[1]
Year defined	1904
Tensleep Sandstone (the United States) Show map of the United States Tensleep Sandstone (Wyoming) Show map of Wyoming

The Tensleep Sandstone is a geological formation of Pennsylvanian to very early Permian age in Wyoming.^[2]

The formation is composed of fine- to medium-grained sandstone, light gray and yellowish gray; generally slightly to moderately calcareous; some dolomite and sandy dolomite beds; mostly thick to massive sets of low-angle, wedge-planar crossbeds of dunes. Forms cliffs 61-91m (200-300 feet) thick.^[3]

In 1932 Edward Branson and Maurice Mehl reported the discovery of a fossil trackway in the formation.^[4] A new ichnospecies, Steganoposaurus belli, was erected for these footprints.^[4] The tracks were probably made by a web-footed animal slightly less than three feet long.^[4] This creature was originally presumed to be an amphibian, but the toe prints it left behind were pointed like a reptile's rather than round like an amphibians. The actual trackmaker may have been similar to the genus Hylonomus.^[5] The ichnogenus Tridentichnus are similar footprints preserved in the Supai Formation of Arizona.^[6]

• Lockley, Martin and Hunt, Adrian. Dinosaur Tracks of Western North America. Columbia University Press. 1999.