KECAPITULATION OF PALEOZOIC FORMATIONS. 208 



hypothesis, on the whole, seems to me altogether untenable. The Paleozoic series 

 in Colorado as it now stands is so incomplete that the column in its entirety would 

 probabh" far exceed even the great thickness of the Uinta sandstone. This becomes 

 obvious from the consideration that the Maroon formation represents only a moiety 

 of Carboniferous time, yet it alone is half as thick as the Uinta. Again, the 

 supposition is incredible that all Paleozoic time could be represented b^ a uniform 

 series of sediments like the Uinta sandstone. Much more incredible is it that the 

 Uinta represents a frequently interrupted and eroded series. 



The Cambrian quartzites, though at most but 600 feet in thickness in Colorado, 

 are expanded to 12,000 feet in the Wasatch. It would seem likely that this series 

 is represented in the Uinta Mountains by considerable thicknesses <* proportional to 

 its intermediate position, and it is admissible that the Parting quartzite, or even the 

 siliceous Yule limestone, may be represented there bj^ modified and less important 

 measures; but the persistence of the Leadville as a limestone horizon is so striking 

 that I should hesitate to adopt anj^ mere hypothesis which demanded its local muta- 

 tion into sandstones and conglomerates. It seems to me more probable, however, 

 that a period of uplift and erosion during Carboniferous time destroyed in the Uinta 

 area the older sediments, perhaps already thinned by previous erosion, down into the 

 Cambrian beds; and that upon the base thus formed was spread the waste so similar 

 in character to the much older sediments that it now has the casual aspect of a single 

 continuous series. Which of the two erosion epochs whose occurrence during Car- 

 boniferous time I have tentativelj^ hypothecated performed this work, it is impossible 

 to say. If the one which intervened between Leadville sedimentation and that of 

 the Weber limestone, whose existence seems to be established, it is evident that the 

 Uinta sandstone must include, besides the AVeber quartzite and Maroon formation, 

 thicknesses of shales and sandstones representing the Pennsylvanian portion of the 

 Wasatch limestone, unless the latter is conceived to be entii-ely lacking in the Uinta 

 Mountains of Colorado. The absence of the Pennsylvanian Wasatch might, however, 

 be accounted for by the suppositious unconforniitj' between the Maroon and Weber 

 formations of Colorado, owing to which also the 5,400 feet of upper Wasatch wedge 

 out to a few hundred in that State. If this erosion were performed or consummated 

 by the still more hypothetical occurrence which has been suggested between the two 

 divisions of the Maroon itself, these calcareous beds of the upper Wasatch, as well 

 as the Mississippian ones and even part of the Maroon-Weber series itself, would 

 appear to be equallj' unrepresented. On the other hand, it is possible that the whole 

 of the Uinta sandstone may be of Pennsylvanian age. 



" Peale remarks, under the caption '' Silurian Age: ' "There was a much greater development in Mr Marvine's district 

 and further details will be found in his report." (Hayden's V. S. Geol. Geogr. Surv. Terr., (8th] Ann. Eept.. for 1874, 187S, p. 

 110.) It ig not clear whether this refers to the Silurian as a whole or to one or several of the divisions which Peale 

 recognizes. Most of his Silurian series (probably 600 feet) is Cambrian {Sa watch quartzite) and his statement is somewhat 

 favorable to the hypothesis adopted above. Marvine's district lay to the north and northwest of that of Peale. Unfor- 

 tunately his report never came to publication. 



