RECAPITULATION OF PALEOZOIC FORMATIONS. 149 



mations below the Carboniferous limestone, to be practically continuous from Mount 

 Lincoln to the Arkansas, and it is thus represented on the Hayden atlas. The Siki- 

 rian appears upon the west but not upon the east side of South Park, apparentlj' 

 indicating an overlap of the Carboniferous at this point along a line having a north- 

 south trend. In the can3^on of Foufmile Creek the beds referred by Stevenson 

 to the Silurian consist of two limestones separated by 170 feet of sandstone, with some 

 Cambrian quartzites at the base. The lower limestone is 40 feet thick, siliceous, and 

 contains fossils which probably indicate the Ordovician. The upper limestone is 20 

 feet thick, red, argillaceous, fissile, and without distinct fossils. The intermediate 

 sandstones are converted into quartzites, and it seems to me probable that they 

 represent the Parting quartzito. In this event of course the upper limestone would 

 not belong to the Yule. On the other hand the succession at this point suggests the 

 Manitou, Harding, and Fremont formations of the Front Range. In the Arkansas 

 Canyon the Yule compromises 112 feet of limestone, var3ang from dove color to 

 black, overlain by partially altered sandstone with layers of quartzite. The latter 

 probably is the Parting member, and Stevenson is, without much doubt, correct in 

 correlating the limestone with the Lower limestone of the former section. 



Endlich also describes two sections in the South Park region, but without giving 

 the thickness of the constituent beds. They are located in the southern portion of 

 the region, but their exact situation can not now be ascertained. The beds observed 

 at station 56 have at the base a porphvritic granite above which occur 3'ellow and 

 brown q-uartzite, white and pink quartzite, yellowish shales interstratiiied with 

 quartzites, blue limestone alternating with gniy shales, etc. It seems probable 

 that the porphvritic granite is an intrusive rather than an Archean body, in which 

 case the, quartzite, because of its relation with the rest of the section, would better 

 be taken as the Parting quartzite instead of the Sawatch, which would be the 

 natural interpretation if the igneous basement rock were the Archean. The bk^e 

 limestone with Oi'this, crinoids, etc., would then be the Leadville limestone, while 

 the red sandstone above is clearly the Arkansas .sandstone. In the section made at 

 station 53 the beds which appear to belong to the Yule are described as a blue 

 quartzitic limestone with crinoids and Orthoceras, separated from a hard gray 

 limestone with corals and sponges by a thin shale bed. The gray limestone is 

 overlain by white, j-ellow, and pink quartzites, which I take to represent the 

 Parting quartzite, and to be the same series that formed the base of the previous 

 section. The blue siliceous limestone rests immediately upon coai'se-grained red 

 granite. It does not .seem altogether probable that in this instance the granite is 

 intrusive, and in the event of its belonging in the Archean this seems to be an 

 instance of the overlap of the Yule over the Sawatch member. 



The Silurian is accordingly niapped in the Hayden atlas almost continuouslv 

 along the west side of South Park to the Arkansas River, and south of the river in 



