walcott.] SUMMARY— COLORADO. 351 



higher slopes of the mountains, according to Prof. Bradley, in the Teton 

 range. The same series of deposits evidently occurs in the Gros Ventre 

 range, and in the Buffalo Fork Peak uplift. In the Gros Ventre rauge 

 the quartzites were seen in immediate contact with the unconformable 

 Archean schists. 1 



The superjacent limestone, called the " Lower Quebec limestone" by 

 Prof. St. John, occurs in the Teton rauge and the Gros Ventre. But 

 it is iu Buffalo Fork Peak that the best section was obtained. Here 

 there is an exposed thickness of from 50 to 75 feet of bluish and dark 

 drab, brecciated, thin bedded, rough weathering limestone, above which 

 occurs what he calls the passage beds to the " Upper Quebec limestone." 

 These beds are yellowish, arenaceous, micaceous clay, with indurated 

 layers charged with a small orbiculoid shell and thin layers of dirty drab 

 limestone, the weathered surfaces of which are crowded with the frag- 

 mentary remains of trilobites and other fossils. Among others there have 

 been identified the genera Conocoryphe and Dikelocephalus. The 

 upper portion of the deposit is here composed of bluish drab shales and 

 brownish gray shuly sandstones. It reaches a probable thickness be- 

 tween 100 and 200 feet. 



The superjacent limestone called the u Upper Quebec limestone v 

 shows almost the same development in the Teton and Gros Ventre 

 ranges and the Mount Putnam area of Idaho. The rock consists of 

 generally thin bedded, fragmentary, sometimes brecciated limestones, 

 color gray, grayish buff, and pinkish, carrying small sized trilobites and 

 a gasteropod resembling Eaphistoma. In the Teton range the series 

 of rocks has a thickness of 100 feet or more, and forms mural exposures 

 on the canon walls. 



A review of the reports of Messrs. Bradley and St. John shows that 

 the Upper Cambrian horizon is to be recognized in the Teton, Gros 

 Ventre, and Buffalo Peak Mountains, and that it is composed of a basal 

 zone of varying thickness, upon which rests a limestone carrying Up- 

 per Cambrian fossils. This limestone is the equivalent of the " Lower 

 Quebec n of Prof. St. John's section. His " Upper Quebec n is to be 

 referred to the base of the Lower Silurian (Ordovician) or correspond- 

 ing to the Calciferous zone of the New York section. 



COLORADO. 



The identification of rocks of Cambrian age in Colorado has been 

 made, with one exception, upon stratigraphic and lithologic evidence. 

 The exceptional instance is that mentioned by Mr. S. F. Emmons, who 

 found a distinctly Upper Cambrian genus, Dikelocephalus, in a bed of 

 greenish chloritic shale that he assumed to occur above the main body 

 of the quartzite and near the base of the transition series that passes 



1 Report of the geological field work of the Teton division. T7. S, Greol. Sur. of the Terr., 11th Ann, 

 Rep., 1879, p. 481, 



