124 REPORT UNITED STATES GEOLOGICAL SURVEY. 



explain the relative position of all the groups involved in the movement. 

 On its western side we iind a corresponding arrangement of the Fox Hills 

 series, with the exception that the dip is relatively larger, and permits 

 but a smaller area to be exposed. The entire structure or the country 

 west of this anticlinal is exceedingly simple, consisting mainly in a shal- 

 low synclinal basin toward the south and an almost unbroken plain to 

 the north. 



Section XV runs nearly east and west. We find the anticlinal uplift 

 (0) culminating in the elevation of the granitic syenite (a) which forms 

 Rawlings Peak. To the eastward, Silurian quartzites (6) are resting di- 

 rectly upon it. At the horizon indicated (P) we find the deposit of red 

 paint. Calciferous strata (c) occupy a very subordinate position, under- 

 lying the Subcarboniferous Group (d). Here we begin to notice a decided 

 diminishing of the clips. Massive beds of Carboniferous limestone (c) are 

 almost totally covered by loose drift (o), and appear only on a small 

 ridge, where the higher members of the group are exposed. Permian 

 beds (/") crop out overlying them. Their eastern continuation, the Triassie 

 beds (g), and the larger portion of Jurassic strata (h) are covered by the 

 drift (n) of the second valley. Ascending the ridge eastward, we pass 

 over the members of the Dakota Group (*), and reach the Colorado 

 shales (k). Following the eastward slope of these beds, which gradually 

 dimmish in dip, we find an extensive lake deposit (m), extending to the 

 base of the Fox Hill series (I). On the western side of the anticlinal we 

 find the same succession, with an increased dip of the beds, however. 

 Here we are enabled to obtain a better section, as but one deposit of 

 drift (p) especially interferes with our observations. On this side the 

 Laramie Group (q) has been introduced, which covers the Fox Hills. 



Near Salt Wells the Fox Hills beds are well developed and occupy a 

 very prominent position. A valley of approximately semicircular shape 

 lies directly north of the railroad, bordered entirely by steep, brown 

 bluffs. We find upon examination that these are composed of the char- 

 acteristic shales and sandstones of the Fox Hills series. Dipping off in 

 every direction, they present a most typical partiversal arrangement of 

 the strata. Near the base they are composed of thinly bedded sand- 

 stones. These are followed by yellow and brown shales, more or less 

 arenaceous and micaceous. Above these we find a succession of sand- 

 stones and shales, containing carbonaceous strata. A recess in the bluffs 

 is caused by the higher series of shales. The latter are covered by sand* 

 stone strata of varying thickness, separated from each other by shales. 

 Some good coal is found in this horizon. Near the top we find massive 

 yellow sandstones overlaid by thin beds of shale and some white sand- 

 stones. Throughout the group fragments of Inoceramus are very plenti- 

 ful, but other fossils appear to be rare. On every side the beds are con- 

 formably overlaid by strata of the Laramie Group. In speaking of the 

 Tertiary Groups of this region sections will be given showing the arrange- 

 ment of strata at this locality. The thickness of the Fox Hills Group 

 here is about 1,200 to 1,300 feet. 



POST-CRETACEOUS. 



Laramie Group. 



The Laramie Group has a wide distribution in this region. On the 

 west side of the anticlinal we can trace it northward nearly to Whiskey 

 Gap. There the drift obscures all definition as to its termination, but I 

 am inclined to think that it juts directly against the granites of the 



