2 GEORGE V. SESSIONAL PAPER No. 25a A. 1912 



CHAPTER XXIII. 



FIEST CALCAREOUS FOSSILS AND THE ORIGIN OF THE PRE- 

 SILURIAN LIMESTONES. 



Introductory — Abstract of Chapter. 



The writer has spent most of each of three field seasons in the study of the 

 Cambrian-Belt geosynclinal and, as abundantly indicated in the previous chapters, 

 failed to find calcareous fossils at any point, unless the doubtful forms referred' 

 to Cryptozoon be of truly organic origin. Essentially the same experience was 

 met with by Peale, Weed, Pirsson, Walcott, Weller, Willis, Ransome, Calkins, 

 MacDonald, Lindgren, Dawson, McEvoy and others who have worked on these old 

 rocks. Where so many geologists and expert paleontologists have not succeeded 

 in this principal quest, it is clear that fossils of any kind are generally very 

 much rarer than are those of younger Paleozoic formations in the Cordillera. 



The cause of the failure of calcareous fossils is one of the leading paleon- 

 tological and geophysical problems in connection with the prism. The explanation 

 cannot be found in the supposition that the fossils were once present and have 

 been removed or have become unrecognizable through the metamorphism of the 

 strata. The static metamorphism actually undergone has not been of the kind 

 or degree which would involve the wholesale destruction of shells or skeletons. 

 On the other hand the rocks are strikingly free from evidences of dynamic 

 metamorphism except in certain limited areas of the Boundary belt. The rock- 

 exposures are generally large and favourable to the discovery of fossils if they ■ 

 were really enclosed in the rocks. The organic remains found in the Greyson, 

 Altyh, Castle Mountain, and Bow River formations, are almost entirely tests 

 or fragments of crustaceans, in which the material is largely chitin. Whatever 

 discoveries there may be in the futiire, it is certain that calcareous animal 

 remains are exceedingly rare in the Cambrian and Beltian rocks of the whole 

 Forty-ninth Parallel section. They are likewise very rare or quite absent in 

 the thick sedimentary mass of the Priest River terrane, in which the writer was 

 able to find not a single trace of organisms. 



This unfossiliferous character of the different terranes is all the more note- 

 worthy because of the immense thicknesses of limestones represented. The 

 obvious fact that the limestones have not the characters of deposits dxie to the 

 accumulation of shells or to coral growth and thus to processes generally credited 

 with the formation of marine limestones, offers a second problem closely related 

 to the first. The writer has offered a hypothetical explanation of (1) the lack 

 of calcareous fossils in these Forty-ninth Parallel formations, and (2) the 

 general failure of fossils in the pre-Cambrian and most Cambrian forma- 

 25a— vol. iii— 42 643 



