84 GEOLOGICAL SUIIVEY OF THE TERRITOEIES. 



United States Army. Messrs. Smith and Carson, assistants, accompanied 

 me. The examination of the North Park being contemplated in your 

 instructions, I regarded this as the most favorable opportunity that was 

 likely to present itself, affording adequate protection. I was the more 

 desirous of visiting that interesting locality from the fact that the 

 geological character is entirely unknown. Our course from Fort Sanders 

 was nearly southeast, up the Big Laramie Eiver toward its source in the 

 mountains. 



The geology of the plain country through which the Big Laranaie flows 

 is similar to that of the Little Laramie Eiver, about 15 miles to the west- 

 ward. There are comparatively few exposures of the basis rocks, ou 

 account of the superficial drift which covers all the country ; still, we find 

 along the banks of the river, near the stage-station, the same black plastic 

 clay of Xo. 2, with Ostrea congesta and a few remains of fishes, also the 

 chalky marls of No. 3. About two miles above there are long high ridges 

 on either side, extending up for several miles, composed of the rusty 

 jellow sands and sandstones of No. 5. 



The dip of these beds is very gentle — hardly perceptible to the eye. 

 i The Big Laramie is a very clear stream, about 50 yards in width, and 

 averaging two feet in depth, easily forded in most places. Like most of 

 the western streams, the difference between high and low watermark is 

 very great. In the spring and early summer, when the snows of the 

 mountains melt, these streams become formidable rivers. 



The soil along the bottoms appears to be very good ; the gi^ass grows 

 quite heavy, and hundreds of tons of hay are cut here by the settlers for 

 winter use. 



The grazing is excellent, and numerous ranches have been started all 

 through the valley for the purpose of raising stock. Even at this season of 

 the year a great variety of flowers covers the surface; the Compositce and 

 Leguminosce prevail in numbers, and yellow is the dominant color. 



As we approached the foot-hills of the mountains the transition beds, 

 or No. 1, appeared on the ridge, rocks of more recent date having been 

 swept away by erosion. Fragments of pudding-stone and rusty-colored 

 masses of sandstone were scattered here and there, and beneath them 

 were exposed about 6o0 feet of variegated, arenaceous layers, of uncer- 

 tain age, perhaps Jurassic ; then a little higher up the mountain were 

 revealed the red beds, 1,500 feet or more in thickness, presenting a won- 

 derfully picturesque appearance. All these beds seemed to have been 

 lifted up in a nearly horizontal position, so that they present lofty escarp- 

 ments, sometimes cone-like or pyramidal in shape, revealing each layer 

 in the order of succession. The harder layers, yielding less readily to 

 atmospheric influences, project out from the sides, adding much to the 

 novelty of the view. Most of the beds incline from the flanks of the 

 mountain at various angles, 3°, 8^, and 15°, and then continue along the 

 river, following its windings for 25 miles among the mountains, almost 

 to the snow-covered peaks. Ou either side can be seen a number of 

 syeuitic nuclei, but I could not find the unchanged rocks so clearly in 

 contact with them that I could define their relation to each other. 



Before reaching the mountains we passed a series of alkaline lakes, 

 which are simply shallow depressions, receiving the drainage of a small 

 area without any outlet. From these shallow lakes the water is evapo- 

 rated, so that in the autumn the bottoms are dry and covered with a 

 white incrustation, which looks much like water at a distance. One of 

 these lakes contains water, and seems to have a fair supply at all sea- 

 sons. It is about a mile in length and half a mile in width. In the 

 spring these lakes are quite large, and are filled by the overflow of the 



