REPORT OF TEE CHIEF ASTRONOMER 185 



SESSIONAL PAPER No. 25a 



The argument that the Lewis, Galton, and equivalent series should be 

 referred to the pre-Cambrian because they are almost or quite unfossiliferous 

 is a dangerous one. Most of the known Cambrian strata of the world are quite 

 unfossiliferous, as far as present knowledge goes. They have been assigned 

 to this system because a few, generally very thin interbeds bear determinable 

 index species. Even in the Mount Bosworth section of British Columbia, one 

 of the most highly fossiliferous among Cambrian series, Waloott found no traces 

 of life in 1,S55 feet of continuous strata.* The famous Ogygopsis shale at 

 Mt. Stephen is clearly a lens. It peters out rather rapidly and is not repre- 

 sented in either the Mt. Bosworth section or at Castle mountain. Except for 

 a few worm borings, a massive dolomitic limestone totalling 1,680 feet in 

 thickness, at Mt. Stephen, is unfossiliferous. f A thousand feet of the calcareous 

 Nounan formation of Walcott's Blacksmith Fork section in Utah is as poor in 

 organic remains. Why interbeds similar to the Ogygopsis shale fail to appear 

 in the Eorty-ninth Barallel section is not apparent. Barrell has suggested a 

 continental origin for much of the Belt terrane sediment, but we have seen 

 that this is true ;of probably but a small part of the series. That chitinous 

 fossils are relatively abundant at Mount Stephen and very rare in contempor- 

 aneous marine sediments one hundred miles away is not more difficult to under- 

 stand than that chitinous fossils often occur in the Cambrian and generally 

 do not occur in equally unmetamorphosed pre-Olenellus strata. The one 

 contrast means conditions different in space; the other, conditions different 

 in time. In each case explanation is needed. While awaiting complete explana- 

 tion we must regard this negative character of the ' Belt terrane ' as of little 

 direct value in correlation. 



Relative Induration and Metamorphism of the Belt Terrane and Flathead 

 Formation. — One of Peale's arguments for the Algonkian age of the Belt terrane 

 is noted in the first of the foregoing quotations from his writings. The point 

 consists in the recognition of a much greater degree of metamorphism in the 

 Belt terrane rocks as compared with the 'little, if any, induration' of the 

 Elathead sandstone. 



The weight of this argument is considerably lessened by reason of the fact 

 that the Belt terrane where exposed in other regions, is often little folded or 

 sheared and is scarcely at all affected by dynamic metamorphism. Its rocks 

 have truly been well indurated and largely recrystallized under deep-burial 

 conditions, but such alteration by static metamorphism is not of itself evidence 

 of great difference of age between older underlying beds and the younger beds 

 of a rock group. McConnell and Walcott have proved that the Cambrian period 

 was long enough for the accumulation of 11,500 feet of strata, chiefly the 

 slowly deposited limestone, in the Mt. Bosworth district of British Columbia.^ 

 In the same period of time, shales, sandstones, and subordinate limestones 

 might have elsewhere accumulated to even greater thicknesses. It is reasonable 



*C. D. Walcott, Smithsonian Misc. Collections, Vol. 53, No. 1812, 1908, p. 208. 



f C. D. Walcott, Canadian Alpine Journal, Vol. 1, 1908, p. 232. 



ICf. C. D. Walcott, Smithsonian Misc. Collections, Vol. 53, No. 1804, 1908, p. 2. 



