W OARHONIKKROUS FORMATIONS AND FAUNAS OF COLORADO. 



disappoiir and aii> not t'i)uiid at all farther south, and the Arkansas sandstone gen- 

 erally rests directly upon the Archean. An exception to this statement seems to 

 exist in the vicinity of Trinchei'a Peak, where a grayish-brown, compact shale, sandy 

 in part, and interhedded with limestone, was seen conformably iinderl^-ing the red 

 Carboniferous sandstone. The position and character of these strata make it 

 probable that they represent the We1)er formation, or else, as suggested by Endlich, 

 the hoi'izon of the Ouray and Leadville limestones. 



It was in the southern part of this area mapped by Endlich as " Lower Carbonif- 

 . erous" that Lee made a section and collected fossils as hereinafter described. The 

 fauna obtained by Lee not far above the contact with the Archean is unquestion- 

 ably of Pennsylvanian age, and is related to that of the Hermosa formation and 

 of the AVeber limestone and lower Maroon formation. LTnless still lower rocks 

 occur in other parts of the ai'ea. it is evident that the "Lower Carboniferous" 

 color, so far as the "Lower Carboniferous" of the Hayden survej' is understood 

 to be equivalent to the Leadville limestone, is wrongly introduced in the vicinity 

 of Trinchera Peak. 



The remainder of the Paleozoic consists of the Arkansas sandstone, whose out- 

 crop covers large areas on both sides of the Sangre de Cristo Range, extending as 

 far south as Costillo Peak. This foi'matiou is made up chieflj^ of red sandstone, with 

 which are interstratified red shales and blue limestones. In the vicinity of Costillo 

 Peak Endlich reports some whitish sandstones and a quartzitic bed in association 

 with the red sandstone (page 122). Although in his previous work the Arkansas 

 sandstone had been placed in the Carboniferous, the first paleootologic evidence was 

 not obtained until 1875. Hayden" had, however, collected Carboniferous fossils in 

 this range in 1869 and Ruffner in 1873.'' Endlich cites Productits semireticulatus, 

 Seinimda siMilita, and Spirifer at one station, Calamites and Sigillaria at another, 

 while a third furnished Productus, Orthis, Spirifer, and crinoids. The latter fauna 

 suggests those which he obtained in 1873 from rocks of supposed Mississippian age, 

 but otherwise are diagnostic only of the Carboniferous as a whole. The thickness 

 of the Arkansas sandstone is here given as 2,000 feet, while farther north it was 

 reported by the same author as in one place not less than 5,000 feet. This great 

 diminution in bulk, conjoined with the entire absence of the series which Endlich 



oApparently the first adequate evidence as to the age of these beds was obtained by Hayden in 1869 (U. S. Geol 

 Surv. Terr., Ann. Kept, for 1867, 1868. and 1869, 1873, p. 175), who observed near Sangre de Cristo Pass an extensive series of 

 reddish sandstones, some of which contain impressions of Calamites, while from a bed of limestone, in a series of alter- 

 nating limestones and sandstones, were obtained several species of Frodiictiis, ' 'Spirifer subtilita, Ehynchonella roekymmitana, 

 Spirifer lineatus, and numerous corals and crinoidal stems." The names of species in this list are singularly mangled, but 

 it is evidently an Upper Carboniferous fauna that is presented. These were found near the junction of the sedimentaries 

 with the (Archean?) granite. 



In his paleontologic report the year following Meek lists (U. S. Geol. Survey Wyoming, etc., Preliminary Kept. 

 [Fourth Ann. Kept.], 1871, p. 295) Productus punctatits, Produetus semireticidaius, and Seminula subtilita from Sangre de 

 Cristo Pass. 



bKuffner's Kept Kecou. Ute Country, 43(1 Cong., 1st sess.. House Ex. Doc. No. 193, p. 61. 



