Douglass : A Geological Reconnaissance. 243 



different from anything I have seen elsewhere. The strata are evi- 

 dently not much disturbed. The rocks are undoubtedly of so-called 

 Fort Union age, though they may be older than the typical Fort Union. 

 The beds here do not look at all like the Tertiary beds in the bad- 

 lands of North Dakota, as they are much darker, have more solidified 

 material, and there is far less lignite, but they contain more fossil 

 shells and more fragments of bones of reptiles. 



From here I continued on the road which goes to the Lake Basin to 

 within a mile or two of where it crosses Sweetgrass Creek. Here, in 

 a little ravine on the east side of the road, some of the rocks of the 

 Fort Union beds are nicely exposed. The ravine extends eastward 

 opening into Sweetgrass Creek. The rocks dip at a low angle. In 

 one place there is an exposure of fifteen feet or more of shales. On 

 top of these are bedded sandstones several feet in thickness. At the 

 contact between the sandstone and shales, is a layer or lens full of 

 Uiiios and gasteropods. Layers of the sandstone above are "plas- 

 tered" with fossil leaves, many of them very beautifully preserved. 

 I saved some samples, but regretted that a large collection could not be 

 made. Following the ravine toward Sweetgrass Creek other shales 

 and laminated sandstones were seen, in both of which are many 

 remains of plants. That night I stopped at the Patterson ranch and 

 examined some bluffs just across Sweetgrass Creek opposite the house. 

 The rocks here are different in lithological character from those which 

 I had previously examined. There are soft shales of various tints, and 

 the sandstones are gray, and more sugary in texture. They much 

 resemble some beds, which occur near the middle of the series on 

 Fish Creek, which I have provisionally referred to the Laramie ; but 

 they probably belong to the Fort Union. After this much of the 

 country west of Sweetgrass Creek was searched. West of the lower 

 portion of the Creek the rocks are of Tertiary age. Farther north the 

 beds of shale and hard thin-bedded sandstones, which underlie the 

 Fort Union, occupy a quite large strip of territory. This formation 

 has a peculiar topography, which enables one to distinguish it from 

 other beds in regions where the rocks are little exposed. There are 

 ridges and hogback-shaped hills covered with grass, and between these 

 hills and ridges are V-shaped ravines and broad flats composed of 

 sandy clay supporting a sparse vegetation. This tract of country is 

 nearly treeless, though in a few places along the ravines, where there 

 are springs, there are a few cottonwood trees. I know of no per- 



