RESUME OF LITEEATUEE. Ill 



some places lighter colors predominate. In texture the rock is a sandstone with 

 coarse g-rits and shaly layers. Though conglomerates may occur anywhere in the 

 series, they are mostly confined to near the base, where they are often plainly 

 derived from the subjacent rock. In this series, and in the Jurassic above, no fossils 

 of any sort were found. 



The area of Marvine's district completeh^ embraces that of the Denver Basin 

 monograph, and Marvine's Triassic and Jurassic in a general way correspond to the 

 Wyoming and Morrison formations of the latter. Marvine's district also adjoins 

 Peale's on the south, and from the uniformity in the thicknesses assigned to the 

 Triassic and Jurassic by the two authors in their respective areas," it seems that the 

 same limits were adojited by both for these formations. As, in the case of Peale's 

 Jurassic, it was found that onlv the upper portion belonged in the Morrison forma- 

 tion, as defined in the Den^-er monograph, so it seems necessar}^ to assign to the 

 Wyoming formation the lower part of Marvine's Jurassic, to which he gives a 

 thickness of 770, 660, 870, and 400 to 500 feet in difierent sections, while the 

 Morrison averages but 300 feet. As I have had occasion to remark in connection 

 with Peale's report and the Denver monograph, the great variations in the thickness 

 of the Wyoming formation as measured at diflterent points may be due to the presence 

 and inclusion of local undifferentiated remnants of the Carboniferous Fountain beds. 



It is too well known to require repetition that the field of observation of the 

 King survey was along and chiefly to the north of the fortieth parallel, and that it 

 included a strip quite aci-oss the State of Colorado whose northern boundary is the 

 forty-first parallel. Within this occur two areas of Paleozoic outcrop. One of these 

 is found in the Uinta Mountains and their outliers; the other consists of two narrow 

 strips — one on the east, the other on the west side of the Front Range. The rejjort 

 of this survey as it relates to the Uinta Mountains has been discussed elsewhere. I 

 will here consider its discussion of the Paleozoics along the Front Range. It might 

 be added, however, that, instead of the original descriptive account bj^ Arnold Hague, 

 I have considered especially the summary report by King,* in which much the same 

 facts are presented in a more convenient arrangement. 



The beds referred to the Paleozoic by King on the east side of the range begin 

 just south of the forty-first parallel, but on the west side they do not come in until 

 some distance north of it, and therefore are not strictly within the limits of mj^ paper; 

 but as their northern continuation bears somewhat upon the construction to be placed 

 upon the succession farther south, I will summarize King's remarks upon them. 



King's discussion, unfortunatel}', begins with a misstatement of fact, which, 

 though unimportant, nevertheless stands open to correction. He says: " In Colorado 



« In the South Platte section, as I have already had occasion to quote from Peale, the thickness of the Trias is from 

 1,600 to 2,000 feet. 



I>V. S. Geol. Expl. 40th Par., Rept., vol, 1, 1878, pp. 127-139, 249-259. 



