GEOLOGICAL SURVEY OF THE TERRITORIES. 



CHAPTER I. 



FROM CHEYENNE TO FOET FETTEEMAN. 



During the summer of 1869 my explorations were directed southward 

 from Fort D. A. Eussell, near Cheyenne, Wyoming Territory, along the 

 eastern base of the Rocky Mountains, through Colorado into New Mex- 

 ico, as far as the Placier Mountains. In order that I might trace the 

 different geological formations northward in their geographical exten- 

 sion and connect the results of the two seasons' examinations, 1 thought 

 it best to commence the labors of the present year at the same point and 

 proceed northward, by way of Laramie Peak and South Pass. 



Fort D. A. Eussell is located on the north bank of Crow Creek, a small 

 tributary of the South Platte. The rocks which underlie the country in 

 every direction are evidently of modern date, and belong to the upper 

 tertiary. They are cut through by the little streams, and we find ex- 

 posed a moderately thick deposit of gravel and boulders resting upon an 

 irregular surface of the indurated marls, sands, and clays of the lake 

 sediments. This is the case in the valley of Crow Creek near the fort, 

 where the vertical bluffs are formed of aluminous marl, with a greater 

 or less admixture of sand. There are also layers of fine indurated sand- 

 stone, with small cavities filled with clay and irregular seams of whitish 

 silicious material scattered through all the beds. Near the base of the 

 mouutains are small fragments of feldspar. Resting upon what ap- 

 pear to be true tertiary strata are beds of greater or less thickness, 

 composed of sand, gravel, and water- worn boulders, passing up into two 

 to four feet of unstratified marl, with a foot or so of soil. Our course 

 from Cheyenne was directly north along the military wagon-road to Fort 

 Laramie, and our first camp was on Lodge Pole Creek. The surface of 

 the country is beautifully undulating, consisting of rounded hills, ridges, 

 and valleys; but not a tree or bush is to be seen. The same formations 

 occur on Lodge Pole Greek that are noted above on Crow Creek. The 

 strata are the same on all the branches from the foot of the mountains to 

 the North Platte. Horse Creek and its branches are nearly desti- 

 tute of trees of any kind, and the water is so low that it can hardly 

 be called a running stream ; still the soil is good, the bottoms quite 

 broad, and grass fine. For pastoral purposes this valley is very de- 

 sirable. In order that we may study the geological structure of the 

 country with success we must travel along the base of the mountains, 

 where the different strata are exposed by the elevation of the mountain 

 ranges. To explore the more mountainous portions, we must travel on 

 horseback, and make the road in the plains, which our wagons must 

 adhere to, our base of operations. We can thus make side trips with 

 pack animals to any portion of the country, however rugged the surface, 

 if it presents any objects of interest. 



August 7. — This morning the train proceeded across the plains north- 

 ward to the Chugwater, a distance of about thirty-five miles. With 

 Mr. Gifford and four or five assistants I followed the valley of Lodge 

 Pole Creek to the foot of the mountains, about sixteen miles distant. 

 The surface of the country was undulating and covered with a fair growth 



