LARAMIE PLAINS. 77 



members of the series are well exposed, the lower red sandstone being quite 

 characteristically but thinly developed, and overlaid by a slightly reddish- 

 gray limestone, possessing a strike of north 20 east, and a dip from 7*^ 

 to 9° west. Near the base of this limestone were procured the following : 



Productus Prattenianus. 

 Produdus cora. 



Along the gentle slope of the plain, directly overlying the Carboniferous 

 limestone, occur the Red Beds of the Triassic. The junction between the 

 two formations is not always so readily traced as east of the mountain, the 

 surface-rock being generally concealed by loose soil, and is frequently only 

 to be followed by the distinctly reddish tinge given to the gravel by the 

 overlying sandstone. In a few localities, red sandstone beds stand out 

 prominently in bench-like formations or bluffs, but usually appear planed 

 down, conforming with other strata in the gentle slope toward the bottom 

 of the valley, lying inclined from 4° to a perfectly horizontal position, and 

 offering but few good exposures. The best exposures of the Red Beds, 

 including, as well, those of the Jurassic group, may be seen near Red Buttes 

 on the railroad where the characteristic and peculiar forms produced by 

 erosion on sandstone^ of horizontal Triassic beds has suggested the name 

 for the station. Over a considerable area, immediately east of the station, 

 sandstones, marls, and clays have been eroded into isolated hills and ridges, 

 exposing the strata in many places for over 100 feet in nearly vertical walls, 

 the heavier and more compact layers preserving the softer and more friable 

 ones beneath from being worn down by atmospheric agencies. Near Red 

 Buttes, the upper members of the Carboniferous are bluish-gray limestones, 

 while the lowest red sandstones lack the intense color usually observed at 

 the base of the series. They have a reddish-yellow tinge, with concentric 

 spots of brick-red, and show more or less of a slialy structure. In compo- 

 sition, they appear to consist of fine grains of quartz, held together by a 

 cementing material of carbonate of lime. All the beds are fine-grained, 

 with occasional layers carrying coarser pebbles, and varying in color, but 

 always exhibiting some shade of red, even up to the top of the Jurassic, 

 the two formations being here very difficult to sej)arate by the lithological 



