EECAPITULATION OF PALEOZOIC FORMATIONS. 201 



rado follows the Maroon formation, and above the Wasatch limestone the Weber 

 quartzite, both siliceous series of like geologic position and thickness. The Upper 

 Coal Measures and Permo-Carboniferous of the W^asatch section have no obvious 

 equivalents in Colorado, while the equivalence of the Wyoming formation in the 

 Wasatch Mountains is similarly obscure. 



The geologic section of the Wasatch Mountains and that of central Colorado are 

 thus seen to be very similar. Thej^ also show this striking difference — that nearly 

 all the formations are thinner, and many of them much thinner, in Colorado. As a 

 marked exception to this prevalent rule, the Maroon formation of Colorado and the 

 Weber quartzite of Utah have essentially the same mass, namelj^, 4,000 or 6,000 feet 

 in each case. 



There is another possibility, however, which may not be entirely passed over. 

 If the Weber limestone and Weber shale of Colorado stand foi' the Pennsylvanian 

 poi-tion of the Wasatch limestone, this series is reduced from 5,400 feet in Utah to a 

 maximum of about 1,000 feet in Colorado, while in the Uinta Mountains it does not 

 occur at all or has lost its calcareous nature. That it does change character to a 

 considerable extent seems probable. The upper Mississippian fauna, whose presence 

 would indicate less extensive erosion if not uninterrupted sedimentation in Utah 

 dui'ing the transition from Lower to Upper Carboniferous time, was found not in 

 the Wasatch but in the Oquirrh Mountains, where the lithologic series is somewhat 

 different. This fauna is conjectured to correspond in the Wasatch limestone to an 

 indefinite horizon not far below that assumed to mark the division between the 

 Mississippian and Pennsylvanian. In the Oquirrh Mountains, however, the beds 

 immediatelj' following are not limestone, but alternations of limestone containing 

 Coal Measure fossils and quartzite, in which the siliceous beds predorriinate. Either 

 these must be the upper Wasatch of the Wasatch Kange, or else the upper 

 Wasatch is missing." King also instances changes from a calcareous to a siliceous 

 phase in certain beds of the upper Wasatch. The variations in thickness of the 

 lower member of the Maroon formation in several sections in which I have cor- 

 related it have suggested to me that a period of erosion or nondeposition maj^ 

 have intervened between it and the upper Maroon. This fact, taken with the 

 tendency of the upper Wasatch to pass over into siliceous phases, would seem to 

 justify entertaining the suggestion that the upper Wasatch may be equivalent to the 

 Weber limestone and shale combined with the lower Maroon, and the Weber quartzite 

 itself equivalent to the upper Maroon only. This, however, seems less likely than 

 that the Maroon and Weber quartzite and the upper Wasatch and Weber limestone 

 are equivalent. 



While there is little direct evidence supporting this view, I believe that the 



« ProTided, oJ course, that the upper portion of the Wasatch is of Pennsylvanian age. 



