GEOLOGICAL SURVEY OF THE TERRITORIES. 



163 



limestones is a thin series of fine and coarse sandstone, the layers rest- 

 ing directly upon the granites, being composed of a sort of fine pudding- 

 stone consisting of an aggregate of quart?, pebbles and rusty coarse 

 sand cemented with lime. This may possibly be a remnant of the Pots- 

 dam sandstone which occurs so well developed farther north in the Big 

 Horn, Wind River, and Sweetwater ranges. This same sandstone is 

 observed far north to RedButtes, but I have never been able to find any 

 trace of organic remains. 



Fi£. 16. 



Uplifted Carboniferous Ridges, Jefferson Fork, Upper Missouri. 



FigurelGis introduced in this connection simply to show the ridges 

 of carboniferous limestone, as they are revealed along the flanks of the 

 mountains. This cut will apply to the ridges about ten miles west of 

 Elk Mountain, although the sketch was taken in the valley of Jefferson 

 fork of the Missouri River. Similar examples occur all along the east 

 and west sides of the Laramie range. The figures are introduced in this 

 connection to make more clear the theory of the upheaval of the Rocky 

 Mountain ranges, which has been expressed in this and previous re- 

 ports. 



The red beds are well revealed all along the western flanks of the 

 Laramie range, and are always noticed by the traveler on account of 

 their peculiar brick-red color. The harder layers of this rock are 

 much used for building purposes. I am unable to say yet whether 

 these red sandstones are triassic or Jurassic, though I believe that be- 

 tween these and the cretaceous formations, Jurassic beds occur. Along 

 the Big Laramie the cretaceous rocks come to the surface. The quartz- 

 ites and sandstones which I have usually referred to No. 1, or lower 

 cretaceous, underlie the plain just west of the railroad south of Fort 

 Sanders; and in the banks of the Big Laramie, near the old stage 

 station, No. 2, occurs with its dark plastic laminated clays, with thin lay- 

 ers of fibrous carbonate of lime, to the surface of which are attached 

 great numbers of the ubiquitous Ostrea congesta. In the level plain 

 west of the Big Laramie, No. 3 is exposed fifty to one hundred feet in 



