440 N. H. DARTON STRATIGRAPHY OF THE BLACK HILLS, ETC. 



it includes also an expansion of shore deposits lying beneath the lime- 

 stones near the Colorado-Wyoming state line, and these may possibly be 

 rocks of somewhat greater age. In the southern extension of the lower 

 Wyoming beds into Perry park they lie unconformably on fossiliferous 

 limestones of Mississippian age, and a similar relation exists in the region 

 west of Colorado Springs and at intervals southward. The presence of 

 the unconformity between the Guernsey and Hartville formations in the 

 Hartville region, and its possible extension in the Black hills and Big- 

 horns, suggests that the same unconformity may extend south to and 

 along the Laramie and Rocky Mountain fronts, especially at the top of 

 the Millsap limestone. In this case the lower Wyoming Red beds 

 would comprise some sediments of late Mississippian age. 



The name Fountain formation has been used to comprise all of the Red 

 beds in the region northeast of Canyon City 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 it is the product of 

 similar conditions at the same geologic 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 ard north of Denver, 

 and, although I made special search, I could find no evidence of overlaps 

 or unconformities of any kind within the great uniform mass of deposits 

 of the Fountain or lower W} r oming formation. 



The separateness of upper and lower Wyoming is very distinct from 

 the Garden of the Gods northward 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 Wj'oming and upper W} r oming were 

 introduced. The upper Wyoming consists mainly of fine grained sedi- 

 ments extending from the " Creamy sandstone," which I believe to be the 

 equivalent of the Tensleep, to the base of the Morrison formation. It con- 

 sists mainly of bright red shales, always with a thin limestone layer or 

 series toward its base, and, from Platte canyon northward, having a mass- 

 ive, 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 period in the West. The few fossils found in this limestone unfortu- 

 nately 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. 



