a. B. Grhmell and E. S. Dana— Tertiary Lake Basin. 127 



The Little Belt Mountains lie to the north, and the Crazy 

 Woman Mountains to the southeast, though at a greater distance. 



The Tertiary beds found here consist for the most part of 

 homogeneous cream-colored clays so hard as to be with diffi- 

 culty cut with a knife. The beds are horizontal and rest un- 

 conforraably upon the uj)turned yellow and red slates below. 

 The clavs of which they are formed resemble closely those 

 found in the Miocene beds at Scott's Bluffs near the North 

 Platte River in Wyoming. The deposits at Camp Baker have 

 been extensively denuded and nowhere reach any very great 

 thickness. At a point about three miles southeast of tiie Post, 

 some bluffs were noticed where the Miocene beds attained a 

 thickness of 200 feet, and these were capped by fifty Ceet of 

 Pliocene clays, both beds containing characteristic fossils. In 

 the underlying Miocene beds were found a species of Rhino- 

 ceros, several species of Oreodon Leidy and Eporeodon Marsh, a 

 canine tooth apparently of Elotherium Pomel, and remains of 

 Turtles. In the Pliocene beds the principal fossils were a species 

 apparently of Merychyus Leidy, remains of an equine smaller than 

 the modern horse, and Pliocene Turtles. These fossils have 

 not yet been carefully studied, and for this reason their rela- 

 tions to the remains found in the other lake basins of similar 

 age cannot here be stated. 



We saw the first exposures of these beds a few miles west of 

 the Sulphur Springs, just after crossing a rather high ridge of 

 trachyte through which Deep Creek flows in a narrow and 

 picturesque canon. This point is about six miles southeast of 

 Camp Baker. From here the lake bed was traced continuously 

 along Deep Creek for a distance of fifteen miles, extending 

 quite up to the mountains on the eastern side at least. Beds 

 of the same character, containing similar fossils, were found on 

 White Tailed Deer Creek, a branch of Deep Creek, about 

 seven miles to the north of Camp Baker, as well as on Camas 

 Creek to the southwest of the Post. Traces of this deposit, 

 containing what appear to be remains of Rhinoceros, were also 

 found two miles or more south of Moss Agate Springs, and 

 at a considerable elevation above the creek bed. With more 

 time than we had at command they could no doubt have been 

 traced much farther, although in many places the beds have 

 been washed out, or have been covered by the later local drift. 



These Tertiary beds were all laid down after the elevation of 

 the mountains and the igneous eruptions. They are, as has 

 been said, perfectly horizontal, and are often seen covering 

 over ridges of trachyte. The line of separation between the 

 Miocene and Pliocene beds is in some places well marked. It 

 consists of about six feet of hard sands, interstratified with 



