FORMATIONS OF THE FRONT RANGE 415 



Manitou limestone yielding Ordovician fossils. Thirty feet of beds, be- 

 lieved to represent this formation, occur at Glen Eyrie, and on Deadman 

 creek a few miles south of Palmer lake Mr Willis T. Lee has discovered 

 some chert} 7 limestones with red clay intercalations yielding Dalmanella 

 testudinnria. Another exposure of this limestone which has yielded no 

 fossils occurs in the southern portion of Perry park. 



The Silurian and Devonian appear to be entirely lacking in the Rocky 

 Mountain front range, although possibly during these periods deposits 

 were laid down which were removed by the vigorous erosion which pre- 

 ceded Carboniferous deposition. 



MILLS A P LIMESTONE 



This representative of the Lower Carboniferous (Mississippian) out- 

 crops in detached basins in Perry park, about Manitou, in the district 

 north of Canyon City, and on the slope of the Wet mountains southwest 

 of Pueblo. It is everywhere distinctly separable from the overlying Red 

 beds which widely overlap its edges. The limestones are most conspic- 

 uous about Manitou, especially in Williams canyon, where they present 

 a thickness of from 200 to 300 feet. They are of gray, purplish, and yel- 

 lowish tints. The exposures in Perry park have been described by Mr 

 Willis T. Lee * as follows : 



"At the base of the formation there are 40 feet of coarse, crumbling sandstones, 

 conglomeratic in places and mottled in varying shades of red and gray, a member 

 which may be older than Carboniferous. Next above is a series, 10 to 15 feet 

 thick, of deep red to white, cherty limestone in layers alternating with red shale, 

 and one of these limestone layers near the top was found to contain the following 

 fossils: Orthothetes inequalis, Spirifer centronatus, Spirifer sp., Spiriferina solidiros- 

 tris (?), Seminula subquadrata{?), Cransena n. sp., Myalina arkansasana, Aviculopecten 



sp." 



In the vicinity of Canyon City and in the small area where the for- 

 mation again appears at the head of Garden park, the limestone is a 

 thinly bedded, variegated, dolomitic rock with a few thin sandstone 

 layers, and in its upper portion there are chert nodules which carry 

 Spirifera rockymontana and "Athyris subtilita " (Mississippian forms). 

 In an outlier 25 miles southwest of Pueblo, described by Mr Gilbert, 

 there is a thickness of 200 feet of gray and purplish limestones, with 

 some shale in their lower part. Spirifera rockymontana occurs near the 

 middle of this series at this locality. 



RED BEDS 



The Red beds along the Rocky Mountain front are distinctly separable 

 into two series, which in the Denver region have been classified by 



*Am. Geologist, vol. 29, pp. 97-98. 



