526 C. P. BERKEY — STRATIGRAPHY OF THE UINTA MOUNTAINS 



Again, if the Uinta basal member is the true " Weber," then all known 

 Paleozoic beds have greatly thickened in passing eastward from the 

 Wasatch as a standard. The 6,000-foot Weber has become from 10,000 

 to 14,000 feet thick. The 2,000 feet of Carboniferous post-Weber shales 

 and limestones have become 5,000 to 6,000 feet of shales, quartzites, con- 

 glomerates, limestones, and sandstones. While if the pre-Weber forma- 

 tions may be assumed to have maintained nearly their normal thickness, 

 and may be counted as present underneath the exposed beds, then we 

 should be confronted with a probable thickness of 20,000 to 25,000 feet 

 of Carboniferous, including one erosion interval in the Uinta mountains — 

 a very extraordinary formation, to say the least. Besides, it would make 

 still more difficult an explanation of the " Red Creek " baraboo by enor- 

 mously increasing its abruptness and its great height above the old floor, 

 a range of 20,000 to 25,000 feet. It would seem more promising to try 

 the evidence along a different line. Instead of thickening formations, 

 all persisting eastward, may they not rather be thinning and pinching 

 out under ordinary overlap conditions? Such behavior, in view of the 

 comparatively small development of the whole Paleozoic still farther 

 east in Colorado and Wyoming, as low as 1,200 feet, and its entire absence 

 in certain areas farther southeastward, is consistent with much local 

 evidence. 



It is worth noting in this connection that the pre-Carboniferous strata 

 in central Colorado* amount to only from 300 to 800 feet. 



The thickest bed of quartzite in the Wasatch is given as 12,000 feet, 

 and belongs clearly to the Cambrian, at least in its upper part. A sim- 

 ilar thickness of the same formation might be expected in the Uintas, and 

 if the great basal quartzite is placed here the comparison is not only satis- 

 factory as to thickness, but also as to general character of rock. Both are 

 dense, hard quartzites, with occasional shale layers — sometimes red in 

 color and often striped, usually showing massive bedding structures. This 

 similarity was noted by Emmons, f who says "the lower beds of this 

 group (the Uinta quartzites) resemble perhaps the Cambrian rather than 

 the Weber quartzite of the Wasatch." Later, in a footnote, recognizing 

 the unconformity described by Powell, the Cambrian age of these quartz- 

 ites is further emphasized. 



In a later article J Mr Emmons even suggests the Algonkian age of the 

 Uinta sandstones, basing this conclusion upon the investigations of Mr 

 Walcott in the Big Cottonwood region. 



* U. S. Geological Survey Folio 48, Ten-mile quadrangle, Colorado ; U. S. Geological Survey Folio 

 9, Anthracite-crested Butte quadrangle, Colorado. 

 fU. S. Geological Exploration of the Fortieth Parallel, vol. ii, p. 199. 

 X Emmons : Orographic movements of the Rocky mountains. Bull. Geol. Soc. Am., vol. i, p. 258. 



