182 CARBONIFEROUS FORMATIONS AND FAUNAS OF COLORADO. 



tinuouslj' exposed from the Wyoming lino soutliward to the (xreenhorn Mountains 

 bolt)no- to the well-known Rocky Mountain Red Beds. These have usuallj' been 

 referred to the Triassic, but occasionally the lower portion has been called Carbonif- 

 erous. The evidence in either case is for the most part indirect, remote, and un.«at- 

 isfactory. It would hardly be worth while to quote every opinion which has been 

 expressed as to the age of the Red Beds of the Front Range in Colorado or to 

 recapitulate all the terms in which these strata have been described, but some of the 

 more important evidence and some of the more significant sections will be repeated 

 in the pages following. 



Except for the Sangre de Cristo Range, which is composed largel}^ of Carbonif- 

 erous sandstones and conglomerates, the only areas of Carboniferous beds repre- 

 sented upon the Hayden atlas along the mountain front from the north to the south 

 line of the State consist of five small disconnected areas. One of these is on the 

 Wyoming line, another is in Pleasant or Perry Park, a third in Manitou Park, a 

 fourth in the Garden of the Gods, and the last in the Wet Mountains southwest of 

 Pueblo. That near the north line and that in Perry Park is Upper Carboniferous; 

 in Manitou Park and southwest of Pueblo, Lower Carboniferous, while in the Garden 

 of the Gods both Lower and Upper Carboniferous seem to occur. 



King recognizes three series in the Red Beds as they appear upturned on the 

 flanks of the Front Range in Wyoming and in northern Colorado. On the east side 

 of the range the lower division is composed of red limestone and reddish sandstone, 

 and has a thickness of about 150 feet. It contains no fossils, but is regarded by 

 King as representing all of Paleozoic time prior to the Carboniferous, and he corre- 

 lates it with the Primordial of the Black Hills, which it resembles lithologically and 

 which has a similar stratigraphic position. 



Above this series follows one composed chiefly of limestone and having a thick- 

 ness of about 700 feet. The limestones are blue, graj^ and red in color, siliceous 

 and sandy, and more or less interstratified with sandstones and conglomerates. They 

 contain fossil shells which show the geologic age to be Pennsylvanian. These strata 

 in several ways suggest the Rico foi'mation of the San Juan region. 



Upon these rests the Triassic. Of this series King says: " Taken as a whole, 

 and with the exception of the gypsum and limestone beds, which nowhere within 

 our field of observation exceed 40 feet in thickness, it is essentiall}^ a sandstone 

 series, for both clays and shales are exceedingly arenaceous, and the dominant 

 color is a brick red for the lower half of the series and variable lighter reds, pinks, 

 and yellowish reds for the upper half. While this division of color holds good in 

 general, it is often varied by extremely brick-red, almost vermilion-colored beds 

 appearing near the top, and light ones intercalated in the region of the heavy red 

 lower strata." The thickness of this series is from 300 to 850 feet. It rests with 



