ob GEOLOGICAL SURVEY OF TH[E TEKRITOEIES. 



more modern beds which underlie the plains from the east base of the 

 mountains to the Missouri Eiver. 



The plateaus between Monument Creek and the upheaved ridges are 

 formed to a great extent of a thick deposit of materials of quite modern 

 origin. There are ashen-brown and gray clays covered with a consid- 

 erable thickness of a sort of unstratified drift material, composed mostly 

 of the debris of the Metamorphic rocks, the red feldspathic predomi- 

 nating. This curious deposit fills up the inequalities of the surface in 

 many places produced by the disturbance of the older sedimentary beds. 

 Between the railroad-depot at Colorado Springs and the " Little Gar- 

 den of the Gods," the road, passes over a beautiful plateau, from which 

 the view of the country in all directions is exceedingly fine. This pla- 

 teau is underlaid by the modern deposit, and here it must reach a 

 thickness of 200 to 400 feet at least, and possibly more. The origin and 

 time of this deposit is somewhat obscure as yet, but an attempt will be 

 made to clear up its history in another place. It is undoubtedly Post- 

 Pliocene, and belongs to some portion of the Post-Glacial era of this 

 region. The deposit may be seen with a greater or less thickness all 

 along the eastern flanks of the mountains, and is composed of the ma- 

 terials worn from the rocks in the immediate vicinity. In treating of 

 the influences of water and ice in carving out the present mountain- 

 forms, I shall dwell more fully on this subject. 



CHAPTER II. 



COLORADO MOUNTAINS, SOUTH PARK, PARK RANGE, UPPER ARKAN- 

 SAS VALLEY. 



In order that the annual reports may be read with greater interest 

 by the general imblic, I have presented the- matter in a narrative form 

 as far as possible, stopping here and there to discuss a topic more in 

 detail as it is suggested by some iDeculiar feature along the route. This 

 plan has enabled me heretofore to introduce more readily local details 

 of interest, both of a practcal as well as scientific nature. 



Our starting-point was Denver, the most important town in Colorado. 

 The country between Denver and the mountains has already been de- 

 scribed in so much detail that we will hasten on toward the South 

 Park by the old stage-road. After passing the base of tLc mountains 

 we meet with only changed rocks, until we descend into the depression, 

 or basin, known as the South Park. The metamorphic schists and 

 granites in their almost numberless varieties which compose the central 

 portions of these mountain-chains will be discussed by Mr.Marvine, who 

 spent most of the season among them. 



We entered the mountains by way of the Turkey Creek Caiion ; here 

 we had a most excellent opportunity to study the connection of the 

 Triassic rocks with the underlying metamorphic. The coarse sediments 

 of the Triassic were deposited upon the irregular surface of the schists, of- 

 tentimes filling up deep depressions. The canon has been carved out of the 

 schists so that they can be studied with ease on either side, and as the 

 stream passed through the sedimentary beds toward the plains the most 

 perfect cross-sections were made. The stratification of the schists is 

 even more distinct than that of the sedimentary beds. The south side 

 of the caiion is very rugged and precipitous ; the inclination of the schists 



