190 ('A1jhoniii"p:r()Us fokmations and Kaunas of Colorado. 



In central Colomdn the Maroon I'onnatioii. \ai'ialilc in color and in (lie details 

 of its lithology, but unil'oriu as to its genmul character, is over considerable areas 

 followed l)y what seouis to be a distinct .series, characterized bj' a persistent brick- 

 red color. Tins is the Triassic series of most writers. The evidence derived from 

 fossils is, iinl'ortunately, lacking, as these beds have proved for the most part unfos- 

 siliferous in Colorado; but, basing their opinion upon whatever evidence was avail- 

 able, most geologists who have examined the strata on Iwth sides of the Front Range 

 agree in correlating the bright-red series of the eastern flank with the similar though 

 (juite differently associated beds of the western flank. This is ti'ue of Peale, Mar- 

 vine, Hayden, Hague, P^mmons, King, and others. Emmons, indeed, uses for a 

 formation in the Tenmile district the same formational name which was employed for 

 the Red Beds in the Denver Basin, viz, Wyoming formation. It seems necessar3\ 

 therefore, to adopt as probably correct this correlation, in which all seem to concur, 

 until the final paleontological test can be applied. If Cross and Hayden were correct 

 in their statements relative to the Fountain beds, we have in that formation the 

 equivalent of the Maroon conglomei'ate of the interior region. 



.Considering the Red Beds as I have traced them through the work of others 

 from the north to the south line of Colorado, there appear to be two distinct series, 

 showing a certain amount of system and regularity in their development and dis- 

 tribution. The lower of these, the Fountain formation of Cross, is probably of 

 Carboniferous age. Its greatest development is southward. The other is the 

 Wyoming formation, whose age still remains in dispute, but is probably Triassic, 

 though Darton has brought evidence, which ought not to be disregarded, tending to 

 show that it is equivalent to the " Permian " of the Mississippi Valley. If this is so 

 the overlap of this series upon the Carboniferous assumes especial importance, but 

 it would militate against the correlation with the "'Triassic" of the west side of the 

 Front Range, supposed to be the same as the Dolores formation of southwestern 

 Colorado in which the remains of Triassic vertebrates have been found. 



In the Sangre de Cristo Range the sandstones and conglomerates which carry 

 Carboniferous fossils attain a thickness of 5,000 feet. Endlich has there given these 

 strata the name "Arkansas sandstone," and they are without much doubt equivalent 

 to the Maroon formation of central Colorado. It seems highly probable that the 

 beds which Hills included in his Badito formation in the Wet Mountains only 20 miles 

 to the east, though but 200 feet in thickness, belong to the same series. This area 

 seems to be disconnected" to the north and to the south. 



Another disconnected area of jDrobably the same series occurs in the Pueblo 

 quadrangle immediately north. Here it reaches a thickness of 2,100 feet, increased 



aThe word disconnected is employed in the sense of " without visible connection." Probably all these areas are 

 continuous under cover except the Manitou Park basin, which in the true sense is disconnected. 



