108 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



upper Carboniferous limestone is found in the northern part of the Front Range 

 near the Wyoming line and in the Culebra Range it appears to merge into the 

 Fountain Red Beds, which he believes to be the exact equivalent of the Lower 

 Wyoming of Eldridge and the Badito of Hills, and to represent the Amsden 

 formation and overlying Tensleep sandstone of the Bighorn Mountains and the 

 Minnelusa formation of the Black Hills. The lower Red Beds of the Rocky 

 Mountain Front Range have yielded no fossils, but undoubtedly merge into 

 limestones both on the north and the south and can be correlated with formations 

 in the Black Hills and the Bighorn Mountains. Darton says further: 



"'Throughout the Black Hills, the Bighorns, and much of the region to the 

 south the upper Carboniferous and Red Bed series presents a general succession 

 as follows, beginning at the top: A thick mass of gypsiferous, red, sandy shales; 

 a thin mass of thin-bedded limestone; a thin mass of red sandy shales; a thick, 

 hard, light-colored, fine-grained sandstone; and, at the base, limestones and sand- 

 stones giving place to sandstones and conglomerates, the basal series lying uncon- 

 formably upon the Mississippian limestones, on Cambrian, or on old granites 

 and schist. 



"'Near the Colorado- Wj'oming State line the upper Carboniferous limestone 

 may be seen to merge into red sandstones, apparently by the expansion of included 

 reddish sandy layers observed northwest of Cheyenne and a corresponding 

 thinning of the limestones. A mass of red sandstones and conglomerates, which 

 lies at the base of the limestones for some distance, is seen also to thicken gradually 

 to the south. 



"'The name "Fountain formation" has been used to comprise all of the red 

 beds in the region northeast of Canyon and southwest of Pueblo, and if, as I 

 believe, the Chugwater (upper Wyoming) formation thins out a short distance 

 south of the Garden of the Gods, the Fountain formation corresponds in the main 

 to the lower Wyoming, and is the product of similar conditions at the same 

 geological epoch. I do not see the slightest reason for supposing that the two 

 formations are not equivalent. 



"'The character of the beds northwest of Pueblo and in the Garden of the 

 Gods region is precisely the same as in the district west and north of Denver, 

 and although I made special search I could find no evidence of overlaps or uncon- 

 formities of any kind within the great uniform mass of red grit deposits. 



"'The upper and lower Wyoming are very distinct from each other from the 

 Garden of the Gods north to the State line, as recognized by the geologists of 

 the Hayden survey and clearly set forth in the Denver monograph, where the 

 terms "lower Wyoming" and "upper Wyoming" were introduced. The upper 

 Wyoming consists mainly of fine-grained sediments extending from the "creamy 

 sandstone," which I believe to be the equivalent of the Tensleep, to the base 

 of the Morrison formation. It consists mainly of bright-red shales, always 

 with a thin limestone layer or series toward its base, and from Platte Canyon 

 northward with a massive pinkish sandstone at its top. The included limestone 

 is believed to represent the Minnekahta horizon of the Black Hills and other 

 regions, indicating a short but widespread interval of limestone deposition at 

 this epoch in the West. The few fossils found in this limestone unfortunately 

 do not settle its age, but there appears to be but little doubt that its representative 

 in the Black Hills is Permian. The overlying red shales, with gypsum, in northern 

 Colorado may be Permian or Triassic, for the fossils in the limestones which occur 

 near the top of the extension of this series into the Bighorn uplift do not indicate 

 whether the beds are Paleozoic or Mesozoic. 



