96 CARBONIFEROUS FORMATIONS AND FAUNAS OF COLORADO. 



\'cry rooeutly W. T. Lee" published ii detailed .section taken at tlie crest of the 

 Siingre de Cristo Range directly west of Trinidad, Colo., between the sources of 

 the Middle Fork and the North Fork of the Purgator3' River. This point is near 

 Culebra Peak, not far from the southern border of the State. Lee's section comprises 

 about 400 feet of strata immediately overlying the Archean granite. Lithologically 

 the series consists of coarse grits, conglomerate, and sandstones, with some shales and 

 a number of thin limestones. Upper Carboniferous fossils were found in abundance 

 about 150 feet above the base, and an extensive fauna is cited. Lee calls attention to 

 the fact that Endlich had mapped Lower Carlioniferous rocks at this point. Everj' 

 test shows the inaccuracy of Endlich's work; but Stevenson, as long ago as ISSl, 

 described the section in such a manner as to leave no reasonable doubt that the Lower 

 Carboniferous was generallj^ absent from the Sangre de Cristo Range, at least from 

 Spanish Peaks southward to Costillo Peak. The whole series is referred hj him to 

 the Carboniferous, apparently on paleontologic evidence, though no identified spe- 

 cies are cited. Upper Carboniferous fossils had long been known from this series, 

 however, having been obtained chieflj' from the vicinitj' of the Sangre de Cristo Pass. 

 The horizon of the earlier collections with relation to the granite was never, I believe, 

 ascertained. The fauna cited by Lee is much moi"e abundant than had ever been 

 previouslj- known from these rocks, and the stratigraphic position is far lower than 

 any fossilifei'ous horizon mentioned b}' Stevenson. The combined evidence, both 

 stratigraphic and paleontologic, tends to confirm Stevenson's early reference of the 

 entire series to the Upper Carboniferous. The Lower Carboniferous and earlier 

 Paleozoics must be either entirelj' missing or represented by local fragments, for 1 

 little doubt that thej' once extended over this region. Geologically the beds described 

 by Lee doubtless belong at the base of Stevenson's lower series, which I am disposed 

 to correlate with the lower portion of the Maroon formation. 



The collections made at this point have recently come into my hands, though too 

 late to be incorporated into the paleontologic discussion. The fauna, while not 

 without individuality, is distinctly related to that of the Hermosa formation and of 

 the "Weber limestone and lower Maroon series, and quite distinct from that of the 

 Rico formation. 



In 1898 E. C. and P. H. Van Diest published a note on the geology of the 

 western slope of the Sangre de Cristo Range in Costillo County.* The area of 

 observation was along the Rito Seco, northeast of the town of San Luis. In this 

 area Endlich had indicated (Hayden atlas) extensive areas of Upjier Carboniferous. 

 Apparentl}' this series does not occur there, but instead Archean, Cambrian, and 

 Silurian strata were found. The Sawatch here consists of white saccharoidal 

 quartzites, with a thin basal conglomerate. These are succeeded by a thin bed of 



<• Jour. Geol., vol. 10, 1902, pp. 393-396. 6 Colorado Sci. See, Proc, vol. 5, 1898, pp. 76-80. 



