PRE-CAMBRIAN OP SOUTHEASTERN B.C. 
91 
“Walcott recognizes the Cambrian-Ordovician equivalent 
of McConnell’s Castle Mountain group as occurring near 
Belton, Montana, and Nyack creek, Montana. At these locali- 
ties, massive bluish and greenish limestones bearing a species 
of Raphistoma and Stromatoporoid form, were found in great 
development. As shown by Plate 6 of Walcott’s paper, the 
field habit of these limestones is extremely similar to that of the 
Siyeh limestone at Mt. Siyeh, which is less than 15 miles distant 
from the Nyack Creek locality. It is difficult to avoid the 
suspicion that these Castle Mountain limestones are, in truth, 
identical with the Siyeh limestone in which, therefore, Middle 
Cambrian fossils may at some future time be discovered.” 1 
The discovery of lowest Middle Cambrian fossils in the 
Burton formation, 3535 feet above the Siyeh formation, points 
out that the Siyeh limestone cannot be Middle Cambrian, and 
since the Siyeh formation occurs below the unconformity which 
exists between the Pre-Cambrian and the Cambrian in the 
Rocky Mountain geosynclinal, it is concluded that the Siyeh 
is Pre-Cambrian in age. 
This conclusion is supported by Walcott in the following 
words. 
“The series of limestones at the head of Nyack creek illus- 
trated by Plate 6, are of Cambrian or Ordovician age, as indicated 
by fragments of fossils that I found in them. I do not think the 
Siyeh limestone is to be correlated with them nor with the 
Castle Mountain limestones of McConnell.” 2 
1 Daly, R. A., Geol. Surv., Can., Memoir 38, 1913, p. 183, 
2 Walcott, C. D., Geol. Surv. Amer., Bull., vol. 17, 1906, p. 19. 
