204 CAKHONIKKKOUS KOKMATIONS AN]) KAUNAS (»K COLORADO. 



Ill this caso (lie uiiconl'oi'iiiit y hetwccii the, Red Ci'eok iind Uiiita formations 

 would corro.spond to that which follows the Leadville limestone in central Colorado." 



This siip])osition would bo most favoral)ly ontertainod in connection with the 

 hypothesis that the Pennsylvanian portion of the Wasatch limestone becomes ti'ans- 

 formed in the Uintas into sands and clays, while the several hypothetical unconform- 

 ities within the Pennsylvaniiui series of Colorado, and especially that above the 

 Maroon beds, might be appealed to as the cause of the diminished representation in 

 that region. That the Wasatch limestone of Utah or the Weber limestone of Colo- 

 rado is represented in the Uinta Mountains seems to me rather doubtful, the proba- 

 bility being that the Maroon-Weber series rests directly upon the pre-Carboniferous, 

 chieflj' Cambi'ian, quartzites, with the Wasatch limestone on one hand and the Lead- 

 ville and Weber limestones on the other wedging out convergingh^ in the direction 

 of the Uinta Mountains. The overlap of the Maroon-Weber series upon the Cam- 

 brian in the Uinta Mountains would then be but another expression of the same 

 readjustments by which in the Crested Butte quadrangle it came in contact with the 

 Archean. 



While it is true that no unconformities are known within the Uinta sandstone, 

 the}' may have escaped detection because of the uniform composition of the series 

 and the difficulty of tracing individual beds. 



Accepting provisionally^ the correlation of the Maroon-Weber series of Colorado 

 with the upper portion of the Uinta sandstones, the correlation of the Wyoming 

 formation (the so-called "Triassic") in the Uinta section and the determination of 

 its geologic age are beset with still greater uncertainties. 



Powell's Jurassic of the Uinta Mountains is clearlj^ the same as that of King, 

 and King expresses absolute certainty of the Jurassic of the Front Range being the 

 same as that of the Uinta Mountains. Between the Jurassic and Maroon formations 

 in central Colorado is found the Wyoming formation, wtose average thickness 

 seems to be 1,500 feet (it is possiblj' 2,600 feet at Aspen). Within equivalent limits 

 in the eastei'n end of the Uinta Range, according to Powell's section, are his 

 Carboniferous and part of his Mesozoic groups, comprising the Lodore group, with 

 a thickness of 465 feet; the Red Wall group, with a thickness of 2,460 feet; the Lower 

 Aubrey group, with a thickness of 805 feet; the Upper Aubrey, with a thickness of 

 1,575 feet; the Shinarump, with a thickness of 1,095 feet; the Vermilion Cliff, with a 

 thickness of 615 feet; and the White Cliff, with a thickness of 1,025 feet. The whole 

 comes to a total of 8,090 feet. 



It has elsewhere been remarked that though Powell gives a combined thickness 

 of over 5,000 feet to his Carboniferous groups in the Uinta Mountains, King allows 



oThis unconformity would have to be Invoked to account for the absence of the Ogden quartzite and of the Wasatch 

 and Ute limestones. In default of evidence as to the age of the Red Creek quartzite it might be taken as equivalent to the 

 Cambrian series of the Wasatch Mountains. 



