RESUME OF LITERATURE. 97 



argillaceous shale, "and the whole section is topped bj' laj^ers of light-gra}' siliceous 

 limestones for about 200 feet, where a quartzj- parting separates them from others 

 of somewhat darker color."-' Though no fossils were found in these beds, their 

 occurrence and lithology, as the authors point out, make it highlj' probable that the 

 quartzite is the Cambrian and the limestone the Ordovician of the Paleozoic sections 

 of centi'al Colorado. Except that the wording seems to indicate an insignificant 

 thickness for the siliceous bed above the light-colored limestone, one might see in it 

 and in the darker limestone above, representatives of the Parting quartzite and the 

 Leadville limestone. Neither Endlich nor Stevenson, nor, so far as I have ascertained, 

 anj' other geologist, found the older Paleozoics in the Sangre de Cristo Range, 

 except in its northern part, while Lee's section seems to afford positive evidence that 

 they are in places actuallj' absent. 



FRONT RANGE REGION. 



The character and correlation of the Paleozoics of the East as thej' reappear along 

 the front of the Rockj' Mountains after their long sequestration beneath the plains 

 under deposits of later geologic ages is a subject of peculiar interest. In Colorado 

 Paleozoic exposures (except for the lied Beds) are neither numerous nor extensive 

 along the Front Range, and circumstances have combined to make their correlations, 

 both with different outcrops of the same series and with tlie tvpical sections of the 

 East, often a matter of difficulty. 



The Pikes Peak quadrangle, which lies just west of Colorado Springs, contains 

 part of one of the few areas of recognized Carboniferous in this region. Although 

 much literature upon the geology of the Front Range had appeared before the Pikes 

 Peak folio* was published, inasmuch as I shall use the nomenclature and definitions 

 adopted in it for the difierent formations, it seems best to employ the logical rather 

 than the historical order in this discussion. 



The Pikes Peak quadi'angle, therefore, includes portions of two more or less 

 distinct Paleozoic areas, and as thej' seem to have passed through somewhat differ- 

 ent geologic histories, or at least to show differences of note in the histories pre- 

 served to us, it will be more intelligible to consider the sequence in each separately. 

 In the southern part is an area which extends southward and eastward be3'ond the 

 limits of the quadrangle and reaches the well-known locality of Canj'on. In the north 

 is a somewhat smaller area, the southern extremity of the isolated Manitou Park 

 Paleozoic tract. The basal formation in both areas resting upon granite and gneiss 

 is called the Manitou limestone. A small thickness of quartzite and cherty limestone 

 at the base is probably Cambrian, but the main body of the formation is Ordovician. 

 "In Garden Park it consists of fine-grained pink or reddish dolomite less than 100 



aColorado Sci. Soc, Proc, vol. 5, p. 78. '>U. S. Geol. Surv., Geologic Atlas U. S., folio 7, Pikes Peak, 1894. 



14361:— No. 16—03 7 



