RECAPITULATION OF PALEOZOIC FORMATIONS. 14:1 



Silurian, and are, I understand, supposed to represent the Parting- quartzite. A 

 simpler interpretation would be to refer the entire quartzitic series to the Cambrian, 

 and to suppose the Yule and Parting formations to be absent, owing, possibly, to the 

 unconformity noticed at Leadville between the Leadville limestone and the Parting 

 quartzite. The Cambrian at Red Clifl" would then be somewhat intermediate in 

 thickness as well as in position between the Eagle River section, where it is at least 

 400 feet, and that of the Tenmile district, where it is from 160 to 200 feet. 



In the Tenmile district and the area adjacent the Cambrian, which here also is 

 called the Sawatch cjuartzite, has a thickness of from 160 to 200 feet. It consists of 

 the typical white quartzite, with a conglomerate at its base, but seems to iacl?: the red 

 sandstone which distinguishes its upper portion at some points. However, it is said 

 to pass upward into reddish and greenish argillaceous and calcareous shales, in which 

 have been found fossils belonging to the DikellocepJialuJi fauna of the Upper 

 Cambrian. 



Of the Grand River area north of the Eagle and the Grand we have little or no 

 precise knowledge. The indications are, however, that the Sawatch quartzite with 

 all its distinguishing characters will be generally found there wherever the proper 

 horizon is brought to view. Although, aside from the sections mentioned above, our 

 information is of a reconnaissance character, in view of the frequent mention by 

 geologists of beds of quartzite of the character of the Sawatch and at the right 

 horizon, the wide distribution of this formation in central Colorado is certain. 



The Sawatch quartzite at Leadville, called in the Leadville monograph the Lower 

 quartzite, has an average thickness of abou^t 150 to 200 feet. The lower 100 feet are 

 composed of tinely and thinlj' bedded white saccharoidal quartzite, with a fine- 

 grained conglomerate at its base. The upper 50 feet are shaly in character and more 

 or less argillaceous and calcareous, and transitional to the Silurian limestone above. 

 On the east side of the Mosquito Range, however, the thickness is in some cases 

 diminished to 40 feet. The upper division, which weathers brown or rusty, is 

 extremely variable. On the east flank of Quandary Peak a species of DiJcellocephalus 

 near D. minnesotensis was found at an horizon apparently above the main body of 

 quartzite and near the base of the transitional series. 



We may infer from Stevenson's account that the Sawatch, as part of his 

 Silurian group, is more or less continuously exposed from the Leadville district, 

 where it was first distinguished, to the southern limit of the South Park region. 

 His section, made at Arkansas Canyon, represents it as a grayish-blue fine-grained 

 quartzite resting on hornblendic gneiss and overlain by limestones whose faunas 

 show them to be post-Cambrian in age. The thickness is not given, and the red, 

 sandy member, which elsewhere appears in the upper portion, seems to be missing. 



Endlich's obsei'vations upon this area are confined to the southern portion, and 



