NO. 4 GEOLOGY, WIND RIVER BASIN—TOURTELOT II 
member and are found in a fan-shaped area having its apex in a 
strike valley eroded in the Amsden formation of Pennsylvanian age 
on the north flank of the Owl Creek Mountains. The red color pre- 
sumably is derived from the Amsden formation, which contains red 
fine-grained rocks. Selenium-bearing vegetation on the green and 
brown member is detectable by its odor, particularly in the spring 
or after a shower of rain, in sec. 24, T. 40 N., R. go W., and at sev- 
eral places along the south flank of the Owl Creek Mountains in the 
northwestern part of T. 39 N., R. 91 W., and the northeastern part 
of T. 39 N., R. g2 W. The selenium content of the rocks is thought 
to be related to their volcanic constituents (Beath, Hagner, and Gil- 
bert, 1946). Uranium minerals have been found in the green and 
brown member at a few places (Love, 1954). 
Hendry Ranch member.—The green and brown member is over- _ 
lain by gray and greenish-gray claystone and siltstone and tan silt- 
stone rich in volcanic material in five areas along the northern mar- 
gin of the Wind River Basin. The easternmost, and largest, area lies 
between the Cedar Ridge fault and Badwater Creek in T. 39 N., 
Rs. 88 and 89 W., Natrona County. The other four are in Tps. 39 
and 4o N., Rs. g2 and 93 W., Fremont County, in the western part 
of the map in figure 2. In each of these areas, the gray and greenish- 
gray unit and tan siltstone form the youngest part of the Eocene sec- 
tion. The new name “Hendry Ranch member” is applied to this se- 
quence. The name is derived from Hendry Ranch in the NE4SE} 
sec. 14, T. 39 N., R. 89 W., Natrona County, as shown on the topo- 
graphic map of the Badwater quadrangle. Good but discontinuous 
exposures of the Hendry Ranch member are found south of the ranch 
and to the southeast along Badwater Creek; from them was collected 
the largest part of the late Eocene fauna described by Gazin (1956) 
in Part 2. The type section (fig. 5) of the Hendry Ranch member 
is a composite one including three localities, all in Natrona County: 
locality 15 (fig. 2), NE4 sec. 31, T. 39 N., R. 88 W., which includes 
the contact of the Hendry Ranch member with the fresh-water lime- 
stone of the underlying green and brown member of the Tepee Trail 
formation ; locality 7 (fig. 2), SW4 sec. 14, T. 39 N., R. 89 W., which 
displays typical exposures of fossiliferous gray and greenish-gray 
rocks; and locality 16 (fig. 2), NE} sec. 23, T. 39 N., R. 89 W., 
which contains the tan siltstone that makes up the upper part of the 
Hendry Ranch member. The maximum preserved thickness of the 
Hendry Ranch member is about 550 feet, based on measurements in 
localities 7 and 16 above. 
The lower part of the Hendry Ranch member of the Tepee Trail 
