198 D. D. CAIRNES SECTION ALONG YUKON-ALASKA BOUNDARY 



and cherty conglomerate. The limestone beds are generally quite crystal- 

 line, and range from nearly white through various shades of gray to al- 

 most black in color ; on fresh fractures, however, these rocks are typically 

 dark bluish gray to nearly black. The upper limestone beds in places con- 

 tain chert pebbles whicli are sufficiently abundant locally to constitute 

 typical cherty conglomerates. The chert pebbles are well rounded and 

 usually about the size of marbles, but some were noted as large as 11/^ to 2 

 inches in diameter. In color most of the pebbles are some shade of gray, 

 but occasional black individuals were noted. In places, also, thin beds of 

 chert, similar in appearance to the pebbles, occur intercalated with the 

 limestones, and particularly in the vicinity of Ettrain Creek the forma- 

 tion is characteristically composed of closely interbedded limestones and 

 cherts, the limestone beds ranging in most places from 4 to 12 inches in 

 thickness, and the chert beds being dark gray to almost black in color and 

 ranging in thickness from 2 to 6 inches. In the vicinity of Ettrain Creek, 

 also, this series contains intercalated beds of fossiliferous calcareous sand- 

 stone, which apparently indicates a transition there between the typically 

 calcareous Carboniferous beds of the north and the more arenaceous and 

 argillaceous Carboniferous members farther south. 



A number of fossils were collected from these beds in the northern 

 portion of the district where this group is most prominently developed. 

 These have been reported on by Doctor Girty, who considers them to be 

 partly of Pennsylvanian and partly of Upper Mississippian age. 



The name Racquet group was first applied in the writer's report on the 

 previous season's work along the boundary,^^ and was intended to include 

 all the somewhat massive dominantly calcareous Carboniferous beds of 

 that district. Limestones, cherts, cherty conglomerates, and breccias that 

 lithologically very closely resemble the members of the Racquet group are 

 extensively developed on Macmillan River. *° The Racquet group is also 

 probably included in the Braeburn limestones, which are extensively de- 

 veloped in Yukon*^ and northern British Columbia,*^ and are dominantly 

 of Carboniferous age, but may include also Devonian members. This 

 group also corresponds lithologically with portions at least of the Lower 

 Cache Creek group*^ of British Columbia and Yukon, which, however, has 



39 D. D. Cairnes : Geol. Surv., Canada, Sum. Rept, 1911, pp. 30, 31. 



« R. G. McConnell : Ann. Rept., Geol. Surv. of Canada, vol. xv, 1902, pp. 31A-34A. 



^ D. D. Cairnes : Preliminary memoir on the Lewes and Nordenskiold Rivers coal dis- 

 trict. Geol. Surv., Canada, Memoir No. 5, 1910, pp. 28, 29. 



^ D. D. Cairnes : Portions of Atlin district, British Columbia, with special reference 

 to lode mining. Geol. Surv., Canada, Memoir No. 27, 1912, pp. 53-54. 



*3 G. M. Dawson : Ann. Rept, Geol. Surv. of Canada, vol. vii, 1894, pp. 37B-48B. 

 J. C. Gwillim : Ann. Rept., Geol. Surv. of Canada, vol. xii, 1899, pp. 16B-18B. 

 D. D. Cairnes : A portion of Conrad and Whitehorse mining districts, Yukon. Geol. 

 Surv., Canada, 1908, pp. 25-29. 



