174 A. G. Peak— Age of the Rocky Mountains in Colorado. 



only cut away these rocks but also tore out and removed the 

 metamorphic rocks to a depth of 6,000 feet along this 

 the Arkansas." 



He restricts the sedimentaries to the Paleozoic. Why could 

 not this erosion have removed not only the Paleozoic 

 the Mesozoic strata? When we go to the north end of the 

 Sawatch- Range we find the entire series, from Lower Silurian 

 to Upper Cretaceous, present. It is true that the lower strata 

 project beyond the upper, the latter having been removed by 

 erosion. Starting at one of the Archaean peaks at the northern 

 end of the range and going northward, we meet first with a bed 

 of quartette dial. This forms the capping of 



the spur, and at Eagle River disappears from sight beneath the 

 beds forming the bluffs on the north side of the river. In the up- 

 per portion of these beds which are conformable to the quartzite, 

 I, in 1873, Carboniferous and Permian fossils.* Fol- 

 i "' V! "- lll( ' "UU-rop< down Eagle River, we find appearing, one 

 after the other, the ,,tl.<-r members of the series, Trias, Jura and 

 Cretaceous, resting on the Carboniferous in regular order and 

 conformable. f On the west side of the Sawatch Range the 

 entire series is a -a i ;,+ The lines i>f out- 



crop can betraee.i f,„m Eade River to the Elk Mountain*. 

 Between the Elk Mountains and the Sawatch Range there is a 

 gap occupied by the Upper Gunnison, or Taylor River, in 

 which the - a | !S e n t. Were it not for the Elk 



Range, in which we have the result of eruptive action, the 

 sedimentary rocks would be seen dipping away from the 

 &a watch Range to the westward and becoming horizontal in 

 the plateau region.§ 



The upheaval of this range, with the subsequent erosion, 

 has so modified the beds and removed so much material, that 

 difficult at first sight to understand the relations of the 

 •s to the metamorphics of the Sawatch Range. 

 .. ^ ujudl aiways make allowances for enormous erosion in this 

 region There are evidences of it on all sales in the Sawatch 

 and Elk Mountains. 



In Southwestern Colorado and Northern New Mexico, the 

 Irtassic is also present. (See Report of Macomb, Geology, by 

 JNewberry : also Cope, pp. 981-1017, Report of Chief of Engi- 

 neers Part II, for 1875.) Mr. Holmes and myself have also 

 identified the Red Beds in Western and Southwestern Colorado, 

 and m the forthcoming Reports of the Survey thev will be 

 described. 

 I think I have shown that the Red Beds (Triassic) are 



