Oct. 2, 18G8.] ^QO [Ilaydc'ii. 



NOTES ON THE GEOLOGY OF WYOMING AND COLO 



RADO TERRITORIES— No. L 



By F. V. Haydkn. 



The following notes on the Geology of W^'oming Territory, 

 along the line of the Union Pacific Rail Road, were prepared in 

 the field after the labors of the day were completed, but the 

 region examined presents so many features new to geologists, 

 that I desire to have them published in the Proceedings of the 

 American Philosophical Societ}' in advance of my more elabo- 

 rate report. The great interest which is investing all this region, 

 will cause any remarks on the geological structure to be read 

 with satisfaction. 



My examinations properly begin at Cheyenne City, along the 

 line of the Union Pacific Rail Road, but the connection of the 

 geology eastward, with that of the west, will be better under- 

 stood by a resume of the structure of the country from Omaha. 

 At Omaha, and extending aliove that point along the Missouri 

 River for about forty miles, we find that the underl3ang forma- 

 tions belong to the upper or barren coal measures. 



OA'crlapping these are the sandstones of the Cretaceous period, 

 which first reveal themselves immediately along the Missouri 

 River about twenty miles west of Omaha, but are found about 

 ten miles westward, as much as eight or ten miles south of the 

 Platte River. 



Near the mouth of the Elkhorn, the rusty sandstones of the 

 Dakota group occupy the whole country. Near Columbus, and 

 ])e3'ond for twent}^ or thirty^ miles, traces of No. 3 Cretaceous are 

 observed, but they are never conspicuous. Nos. 4 and 5 have 

 not been seen along the Platte. 



About two hundred miles west of the Missouri River, along 

 the Platte, the light colored clays and marks of the Tertiary pe- 

 riod commence, foreshadowed, however, by a thick superficial 

 deposit of fine brown grit, which seems to be of Post Pliocene 

 age, as it is filled with recent fresh water and land sti'ata. HeMx^ 

 Planorbis, Piijja, Physa^ <^c. The Tertiary beds extend uninter- 

 ruptedly to the margin of the Laramie Range, along the line of 

 the Union Pacific Rail Road. 



For one hundred and fifty to two hundred miles west of Omaha 

 the soil is fertile, and, in an agricultural point of view, can hardly 

 be surpassed ; but be3"ond that point there is an absence of wood 

 and water, which will render it impossible to cultivate the west- 



