RECAPITULATION OF PALEOZOIC FORMATIONS. 177 



are quartz and feldspar, evidently derived from the Archean. The Maroon formation 

 consists predominantljr of coarse graj^ and red sandstone, in some places passing into 

 conglomerates, with many irregularly developed beds of limestone. The red color 

 is more common than in the Weber grits, and results from iron oxide in the cement, 

 and not from the presence of pink feldspar. The limestones of the Maroon differ 

 from those of the Weber in physical characters, and are generall}^ nonmagnesian. 

 The Maroon as here defined is limited b}' the Robinson limestone below and the 

 Jacque Mountain limestone above. The Wyoming formation has a maximum 

 thickness of 1,500 feet, consisting principally of sandstones of an intensely brick- red 

 color, with a modei'ate development of thin shales, and with limestones generall^^ 

 absent. The sandstones are often coarse, sometimes conglomeratic, and composed 

 mainly of Archean debris. Archean bowlders 2 feet in diameter are cited. 



The name '"Wyoming formation " was first used in this connection in the Denver 

 Basin monograph," and by its emploj'ment in the Tenmile district a correlation is 

 suarg'ested with the bright colored Red Beds which occur on the eastern flank of the 

 Colorado range. Emmons says that this name was used for these beds "not because 

 of any fossil evidence of their age that could be found, but because by their position 

 and petrological character they most nearly correspond to the beds of this formation 

 which elsewhere in the Rocky Mountain region have, on fossil evidence, been 

 determined to be Ti'iassic. If the Permian is represented in Colorado, the evidence 

 of which appears to the writer as j-et verj- uncertain, it would be included in these 

 beds, which have evidently been deposited in direct and unbroken succession over 

 the Upper Carboniferous." 



It can be admitted that the Weber shale of this section is the equivalent, in a 

 general way at least, of the formation called by the same name at Aspen and in the 

 Crested Butte region, and that the Weber grits and Maroon bear the same relation 

 to the Maroon formation of the Crested Butte quadrangle and Aspen. The 

 Wyoming formation appears to be the equivalent of the Triassic of the Aspen 

 section. 



While in a general way this seems to be the appropriate correlation of the 

 different sections, there appear to be certain discrepancies in the litliologic character 

 of the beds correlated. For instance, the origin of the material of the Weber grits of 

 the Tenmile district seems to be the Archean, while the lower part of the Maroon 

 at Crested Butte is derived from the older sedimentary series. Also it appears that 

 the Maroon series at Aspen and the upper portion of the Maroon in the Crested 

 Butte quadrangle are characterized by a dark-reddish color, more than is the case in 

 the Tenmile district. The Wj'oming formation of the Tenmile district appears to 

 be more conglomeratic than the Tiias of the Aspen section. Emmons states that 



nU. S. Geol. Surv., Mou., vol. 27, 1896, p. 61, 



14364— No. 16—03 12 



