6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
formation was named for a local trail near the East Fork River 
about 18 miles northeast of Dubois (Love, 1939, pp. 73-79). The 
Tepee Trail formation was provisionally assigned a late Eocene age 
on the basis of a small number of vertebrate fossils and the posi- 
tion of the formation above strata of middle Eocene age and beneath 
strata assigned an Oligocene age. Love commented (1939, p. 78) 
on the similarity in composition and age between the Tepee Trail 
formation and the strata in the northeastern part of the Wind River 
Basin of middle(?) and late Eocene age. 
Masursky (1952) traced the Tepee Trail formation of Love east- 
ward along the north side of the Owl Creek Mountains to a point in 
T. 43 N., R. 100 W., Hot Springs County. Tourtelot and Thompson 
(1948) mapped the andesitic sequence of middle(?) and late Eocene 
age westward along the northern margin of the Wind River Basin to 
a point in T. 6 N., R. 4 E., which is about 30 miles southeast of the 
easternmost area of the Tepee Trail formation of Love mapped by 
Masursky. The andesitic sequence is correlated with the Tepee Trail 
formation of Love on the basis of lithologic and compositional simi- 
larity, and age; the name “Tepee Trail” is here applied to the 
andesitic sequence in the northeastern part of the Wind River Basin. 
The Tepee Trail formation in the northeastern part of the Wind 
River Basin forms a belt of outcrop along the south side of the Owl 
Creek and Big Horn Mountains. The south boundary of the belt is 
relatively straight and is everywhere marked in the area shown in 
figure 2 by a normal fault along which the Tepee Trail formation 
has been dropped down against the Wind River formation. The north 
boundary of the belt of outcrop is highly sinuous, reflecting the over- 
lap of the Tepee Trail on the rough topography of the pre-Tertiary 
rocks of the mountains. Isolated masses of strata rich in volcanic 
material and assigned to the Tepee Trail formation occupy the upper 
part of stream basins on both the south and north sides of the moun- 
tains. Examples are upper Clear Creek in T. 4o N., R. 88 W. (fig. 2), 
and the basins of Trout, Lone Tree, and Nowood Creeks on the 
north side of the Big Horn Mountains, and West Bridger and smaller 
creeks to the west on the north side of the Owl Creek Mountains. 
Lysite Mountain is a plateau-like remnant of the Tepee Trail forma- 
tion in which the strata lap southward on and across both the Big 
Horn and Owl Creek Mountains and extend into the Wind River 
Basin. The Tepee Trail strata of Lysite Mountain form a sharp 
escarpment facing north into the Big Horn Basin about 8 miles north 
of the north edge of the area shown in figure 2. 
The maximum thickness of the Tepee Trail formation is not readily 
