RECAPITULATION OF PALEOZOIC FORMATIONS. 183 



apparent conformity upon the Carboniferous, but makes a striking overlap upon the 

 Archean. No fossils occur in it except obscure and ill-preserved fragments of wood. 



On the west side of the range these beds appear with somewhat increased 

 thickness. The Paleozoic series measures 1,200 feet instead of 850, Carboniferous 

 fossils occurring 200 feet above the base. 



Too much importance need not attach, in the case of the lower division, to King's 

 correlation with the Black Hills Primordial, and as there appears to be really no 

 satisfactory evidence for distinguishing the lower series from that above, it seems 

 best for the time being to assign both to the Upper Carboniferous. The striking- 

 overlap of the Triassic sediments, however, would seem to sanction their recognition 

 as distinct from the Carboniferous. In the Laramie quadrangle an overlap of this 

 sort occurs, which according to Knight is only apparent, the lower beds of the 

 Triassic which lie next the granite being continuous with the Carboniferous farther 

 north. It is possible that other supposed cases of overlap may find a similar 

 explanation, but without doubt some are real. 



The Paleozoic series does not, upon the west side of the range, extend into 

 Colorado territorj% but its outcrop upon the east side reaches a short distance into 

 the State. It is with little doubt these beds that are represented in the Hayden atlas 

 near the Wyoming line, and as they appear under the Carboniferous color without 

 any Silurian intervening between them and the granite, it would seem that Hayden 

 also did not recognize King's lower series as older than the Coal Measures. 



Marvine examined the Red Beds in the northern part of the Front Range 

 region, and describes them as varying in thickness from 1,600 or 2,000 to 400 feet, 

 and consisting of red sandstones. The texture varies from coarse grits and moder- 

 ately coarse sandstones, with fine examples of cross bedding, to quite fine-grained 

 and shaly layers, which occasionally make up a considerable thickness. The con- 

 glomerates are mostly confined to near the base, where they are plainly derived from 

 the subjacent rock. Dark red is the prevailing color, though light red, yellow, and 

 cream-colored beds are frequent, and maj^ in places predominate. 



These rocks, which rest upon the granite, Marvine refers, as was customary, to 

 the Triassic, and probably they are, for the most part at least, the equivalent of 

 King's Triassic, the Paleozoic series being concealed by overlap. In some of the 

 thicker sections, however, I suspect that Carboniferous beds are present. 



Part of the area examined by Marvine forms the subject of the detailed work 

 by Emmons, Cross, and Eldridge, the results of which appeared as the Denver Basin 

 monograph. 



To the Red Beds series as it occurs in the Denver Basin, Emmons, Cross, and 

 Eldridge give the name Wyoming formation. They describe it as consisting of 

 brilliant red conglomerates, sandstones, and shales, with thin limestones and gypsum 



