•)2 CARBONID'EKOUS FORMATIONS AND KAUNAS OF COLORADO. 



wliirli is drscriliod " as a gray, chcrtj' limestone containing .small fragments of 

 Cyathophylliim. This is succeoded l)y hard, ferruginous gray and blue sandstone, 

 which in all probability belongs in Endlich's Arkansas sandstone. The point at 

 which this observation was made is on the Arkansas River above its pass through 

 the Sangre de Cristo Range and somewhat above the mouth of the Little Arkansas. 

 This place can not be far from the locality, near Salidti, at which were found the 

 fossils in our collections repi'esenting the Devonian and Mississippian phases of the 

 Leadville limestone. 



As a portion of the extensive area embraced in Stevenson's report in Volume 

 III of the Wheeler surve}^ the geology of the highlands on the west side of South 

 Park, more or less directh^ connecting southward with the Sangre de Cristo Range, 

 is briefl}^ described.* What he says about the former should properly be considered 

 in the section of this discussion devoted to the South Park region, but I believe that 

 its relations will be easier appreciated in connection with the beds belonging to the 

 Sangre de Cristo division. 



To the Silurian Stevenson refers ' ' all strata underlying the Carboniferous lime- 

 stone;" (page 357) and, thus defined, it is exposed in numerous outci'ops along the area 

 mentioned. In his section of the Silurian made on Bald Peak in the canyon of 

 Fourmile Creek (page 357), the five lowest beds (6 to 10) can safely be referred to the 

 Sawatch quartzite. They consist of sandstones, and have a combined thickness of 162 

 feet. The 40-foot limestone represented as bed 6 is probablythe Yule limestone, though 

 it appears to be here of onl}' half the usual thickness. The 170 feet of sandstone 

 overlying can hardly be anything but the Parting quartzite, and possibly with it 

 should be included the 20 feet of limestone of bed 1. The Sawatch quartzite is 

 reported at numerous scattered localities. Its color varies from white to dark blue, 

 and it ranges in thickness up to 200 feet. In the canj^on of the Arkansas a veiy 

 dift'erent section of these beds is given. I quote as follows (page 359): 



Section in canyon of Arlcansas River. 



Peet. 



1. Sandstone, partially altered, with layers of quartzite; somewhat argillaceous; weathers to 



ochery color; contains many large fragments of jasper 75 



2. Clay, calcareous, indurated, reddish, weathers into mud 20 



3. Limestone, siliceous above, more argillaceous below, with thin layers of comparatively pure 



bluish limestone .- 27 



4. Limestone, varying from dove color to black; several argillaceous layers; near the top vast 



numbers of crinoidal stems, with many sections of cyathophylloid corals and Braehiopoda. 

 As these are not silicified they can not be separated. Near the base is a thin, argillaceous 

 layer which contains many compressed individuals of Rhynchosjnra sp. and occasionally a 

 bryozoan. From this layer was obtained also a fragment of a large trilobite 35 



attuflner., op. cit., p. 80. ^U. S. Geog. Geol. Surv. \V. 100th Mer., Rept., vol. 3, 187.5, pp. 307-501. 



