270 DEPARTMENT OF TEE INTERIOR 



2 GEORGE V., A. 1912 



series. Lastly, it may be noted, as good evidence, that the huge basal conglo- 

 merate of the Summit series contains myriads of pebbles manifestly derived 

 from ledges quite similar in composition to those of belts A, B, C, D, F, and 

 G. Since the strikes and dips of the Irene conglomerate are nearly or quite 

 parallel to those in belt A of the older terrane, one might doubt the existence 

 of the unconformity at the base of the conglomerate, were it not especially for 

 the similarity of the dolomitic pebbles in the conglomerate to the dolomitic 

 bands in the Priest Eiver series. Largely for this reason a pre-Beltian age 

 is ascribed to all the schistose rocks (not intrusive) situated, within the 

 Boundary belt, between the Irene conglomerate and the down-faulted Kitchener 

 quartzite at the western edge of the Kootenay River alluvium. This great Priest 

 River group presents a structural problem as yet quite unsolved. 



Correlation. — It is, of course, too early to attempt a fixed correlation of the 

 Priest River terrane with the other pre-Oambrian terranes of the Cordillera, 

 but it is not without interest to observe that in various regions there are thick 

 masses of ancient sedimentaries which appear to correspond both lithologically 

 and in stratigraphic relations to the Priest River terrane as exposed along the 

 Boundary line. A few references to typical sections in the Belt mountains 

 of Montana, the Black Hills of South Dakota and adjoining portions of Wyom- 

 ing, the Fortieth Parallel region, and the sections worked out by Dawson on 

 the main line of the Canadian Pacific railway, may be useful as showing the 

 places where possible equivalents of the Priest River terrane may be sought. 



In the Three Forks, Montana, folio of the United States Geological Survey 

 (1896) Peale describes the ' Cherry Creek beds ' as a series of mica-schists, 

 quartzites, gneisses, and marbles or crystalline limestones. These beds are 

 highly inclined, apparently conformable to one another, and, notwithstanding 

 the obscurity of the folding, are known to total thousands of feet in thickness 

 (at least 7,000 feet shown in columnar section). The series is lying 'probably' 

 unconformably upon ; Archean gneisses ' and is unconformably underlain by 

 the Belt terrane, i.e., by equivalents of the lower members oi the Rocky Mountain 

 Geosynclinal prism as just described in this report. 



In the Hartville, Wyoming, folio (1903), W. S. T. Smith and K H. Darton 

 describe, under the name of the ' Whalen group ' a series of schists, gneisses, 

 quartzites, and limestones, which are said to resemble closely the ' Algonkian ' 

 rocks of the Black Hills. These rocks have high, or even vertical dips. They 

 appear to resemble also the pre-Cambrian schists of the area covered by the 

 Sundance, Wyoming, folio, which are unconformably overlain by the Middle 

 Cambrian Deadwood formation. The Algonkian rocks of the Black Hills 

 have not been adequately described but include garnetiferous and*other mica 

 schists, graphitic schist, ferruginous quartzite and amphibolite.* These meta- 

 morphosed rocks, with high dips, lie unconformably beneath the Middle Cam- 

 brian overlapping strata. 



*T. A. Jaggar, jr., Prof. Paper No. 26, U.S. Geol. Survey, 1904, p. 34. 

 See also Newton and Jennev's Eeport on the Geology and Eesources of the Black 

 Hills of Dakota, Washington, 1880, p. 50. 



