REPORT OF THE CHIEF ASTRONOMER 177 



SESSIONAL PAPER No. 25a 



Lower Cambrian horizons in the great series." Fossils were obtained in suffi- 

 cient abundance to show that the base of the massive dolomitic limestone is 

 the plane separating the Middle Cambrian from the Lower Cambrian in the 

 region. McConnell's early view of the correlation is, therefore, finally estab- 

 lished. It follows that, if the Siyeh formation and Castle, Mountain dolomite 

 are synchronous deposits, a critical horizon in the Forty-ninth Parallel series 

 has been somewhat definitely fixed. Walcott also found Lower Cambrian fossils 

 in the Lake Louise formation, at a zone about 3,000 feet below the top of the 

 Bow Biver group. 



Summary. — The evidences for the correlation may be restated in summary 

 form. 



In composition, in colours of fresh and weathered surfaces, in character 

 of bedding and general influence on mountain forms, the Siyeh and Castle 

 Mountain limestones are almost identical. The similarity is specially marked 

 in the occurrence of the highly peculiar molar-tooth structure in both lime- 

 stones. The correlation on these grounds is strengthened through the strong 

 improbability that two rnagnesian limestones of such immense thickness and 

 of similar characters should have been deposited so near together as these Bow 

 Biver and Boundary line sections and yet be of widely different dates of forma- 

 tion. The discovery of fossiliferous Castle Mountain limestone in large devel- 

 opment at Nyack creek, only ten or fifteen miles from Siyeh mountain itself, 

 renders this improbability all the more convincing. § • 



The Siyeh limestone in the Galton, Clarke, and Lewis ranges is underlain 

 by red quartzitic sandstones which correspond in essential features to the 

 quartzite at the top of the Bow Biver formation. Certain whitish and massive 

 beds in this quartzite also strongly recall the Ripple quartzite of the Summit 

 series, a formation which, on independent grounds, has been correlated with 

 the Wigwam and Grinnell formations. 



Finally, the Bow Biver conglomerate is as strikingly similar to the Monk 

 grit of the Summit series as the Castle Mountain limestone is like the Siyeh. 

 Also on independent grounds the Wolf grit has been correlated with the Appe- 

 kunny quartzite-metargillite which underlies the Grinnell and thus belongs to 

 a stratigraphic horizon below the 1,500-foot Bow Biver quartzite at Laggan 

 and Eldon. 



Not only are there close similarities of lithological detail between the 

 northern and southern rock-groups; the succession of formations is alike. The 

 differences between the successive members of the two sections is due simply 

 to the expected differences subsisting between contemporaneous sediments laid 

 down in the one sea-basin. The Castle Mountain-Bow Biver group of strata 

 is, in a sense, a composite of the entire pre-Silurian geosynclinal as exposed 

 at the Forty-ninth Parallel. The Castle Mountain formation has its nearest 

 lithological equivalent in the extreme eastern. Lewis series at the Boundary 



* C. D. Walcott, Smithsonian Miscellaneous Collections, Vol. 53, No. 1804, 1908, p. 

 1 and No. 1812, 1908, p. 167. 



§ Of. C. D. Walcott, Bull. Geol. Soc, America, Vol. 17, 1906, p. 13. 

 25a — vol. ii — 12 



