72 CARBONIFEROUS FORMATIONS AND FAUNAS OF COLORADO. 



lished t)v Rutl'ner in ISTst", the, geology heing described by F. Hawn. One of the 

 routes trin er.sed l)y Riiffncr's reconnaisiinfo in the Ute country crosses the southern 

 end of the Elk Mountains. The descriptive treatment, as one might expect from 

 the rapidity with which the party must have traveled, consists of little more than 

 mere notes, and 1 am unalile to recognize with certainty the different rock groups 

 distinguished in the Anthrat-ite-Crested Butte folio except in one instance, where 

 Coal Measure iossils are cited from an exposure of shale and sandstone some 200 

 feet thick, near the mouth of Spring Creek (p. 78). These probably belong to the 

 Weber formation, and in that case the heavy limestone just below is the Leadville 

 limestone. The Carboniferous age of all the beds both here and elsewhere in which 

 Coal Measure fossils were obtained was recognized by Hawn, but in the Elk 

 Mountains it seems from the context (p. 83)«impossible to avoid the conclusion that 

 he referred the anthracite coal seams, at the head of Anthracite Creek, to the same 

 period. 



The field of work assigned to Endlich for the season of 1873 was styled the San 

 Luis region. His report for the year* deals chiefly with the line of Paleozoic out- 

 crops along the Mosquito and Sangre de Cristo ranges, but he also discusses portions 

 of the Front Range and Elk Mountain areas. Of the Paleozoics in the latter area 

 coming under Endlich's survey I shall here briefly speak. The series in the Sangre 

 de Cristo and Front ranges are considered elsewhere. 



The Gunnison River, cutting through the Elk Mountains, dissevers their south- 

 ern end, which, under the name of Fossil Ridge, forms an area of Paleozoic outcrop 

 distinct from the larger bodj^ north of the river. The geologic sequence at Endlich's 

 station 38, which is situated on Fossil Ridge, is described as follows: 



' ' The lowest members that can well be distinguished are about 320 feet of light 

 graj^ to bluish to almost white limestones, with quartzitic segregations characteristic 

 to the strata of that horizon, and spai'se remains of crinoids. Although the identifi- 

 cation is necessarily not a verj^ thorough one, these beds have been referred to the 

 Silurian. Above that follow 80 feet of yellow and gray shales, regarded as Devo- 

 nian; then 175 feet of variegated shales, partly sandy, with isolated banks of limestone, 

 weathering smooth]}^, with a steep face; 260 feet of light-gray and yellowish lime- 

 stones follow, interstratified with narrow bands of shale, and partly altered so as to 

 appear like marble; the whole is covered by iO feet of light shales, separated from 

 46 feet of the same material by a 20-foot stratum of dark-blue Carboniferous lime- 

 stone full of fossils, etc. Upon this follow 150 feet of light-blue and j-ellow lime- 

 stones, dolomitic in part, etc. Single bands of quartzite appear also, and almost all 

 the sti'ata contain a few fossils. Overlying these are 50 feet of yellow, reddish, and 

 whitish shales without any fossils, etc.'' 



a Rep. Eeconnaisance in the Ute Country in 1873, by Lieut. E. H. EufEner. Washington, 1874. 43d Cong., 1st ses.s., 

 House Ex. Doc, No. 193. 



tU. S. Geol. Geog. Surv. Terr., [Seventh] Ann. Kept,, for 1873, 1874, pp. 305-357. 



