118 CARHDNIKKROUS FORMATIONS AND KAUNAS OF C'OLt)KAJJ<>. 



SO sj)()r!idic tluit witli this oxcoptioii it nii{>-ht easily ho that none ciuiio under his 

 observution. 



The PuebU) (juadningle corners with tiie Pi Ives IVak (juadi'angle, which lies 

 immcdiatel}' to the northwest, and it is l)ounded upon the south by the Walsenl)uro- 

 quadrano'le. ]\Iany of the formations occurrino- in the Pikes Peak are found also in 

 the Pueblo (juadrangle. The Paleozoic section consists of the Harding sandstone, 

 Millsap limestone, and Fountain formation, above which follows the Morrison 

 formation. 



The Cambrian and the Manitou limestone of the Pikes Peak quadrangle appear to 

 be wanting in the one under consideration, the earliest deposits preserved being a white 

 sandstone which rests on the Archean, and which Gilbert correlates with the Harding 

 sandstone. Above the Harding follows a series of gray and purple limestones 200 

 feet in thickness, with some shales in the lower part and with 30 feet of coarse gva.y 

 and red sandstone on top. This series Gilbert calls the Millsap limestone, from 

 which it would appear that the Fremont limestone of the Pikes Peak c^uadrangle is 

 regarded as absent. His position upon this point is stated as follows: 



"In a bed near the middle of the overlying limestone were foand a few fossil 

 shells of Spir/lfera rocky jnontana, a Carboniferous species found also in the Millsap 

 limestone of the Pikes Peak quadrangle, but nothing was found to mark the jDresence 

 of the Fremont limestone (Silurian), which in the Pikes Peak district separates the 

 Harding and Millsap foi-mations. The application of the name Millsap to the whole 

 series of the Pueblo district is a somewhat arbitrary procedure, and is subject to cor- 

 rection when more facts are available.'' 



As the Millsap limestone in the Pikes Peak quadrangle is onlj^ .30 feet in thick- 

 ness, and as the Fremont is reported by Cross as 270 feet at Can3'on, the natural 

 expectation would be that the Millsap would be the one to die out in the Pueblo 

 quadrangle. There can, however, be little doubt of the upper half at least of 

 Gilbert's Millsap being correctly correlated. In any event, that formation shows a 

 much increased thickness, and should it prove that the whole bed represents the 

 Millsap, it will afford but one more instance of the sporadic and fragmentary repre- 

 sentation of the Paleozoic horizons along the eastern line of the Front flange. It is 

 not clear whether Gilbert includes in the Millsap the 30 feet of sandstone above the 

 calcareous portion, but this would seem to be the case. One would think that these 

 beds belonged to the Fountain formation. In view of the conditions observed in 

 the Pikes Peak quadrangle I do not see how there could be conformity between 

 the Millsap and Harding formations in the Pueblo quadrangle, especially if the 

 Fremont limestone is absent, so that the Millsap rests on the Harding. 



The Fountain formation in the Pueblo quadrangle has a thickness of 2,100+ feet, 

 as against a maximum of 1,000 feet in the Pikes Peak quadrangle. The question 

 might be raised whether a part of this does not represent the Wyoming forma- 



