TYPICAL LAURENTIAN AREA OF CANADA. 339 



regard to the underlying Laurentian and Huronian systems. Its 

 present remnants serve to indicate the position of some of the 

 earliest geological basins, which from the attitude of the rocks 

 appear to have undergone comparatively little disturbance. Its 

 extent entitles it to be recognized as one of the most important 

 geological features of North America."/" It \^LOuld, therefore, 

 seem that in Cambrian times a not inconsiderable part of the 

 Archean Nucleus was under water. Outliers of Cambro-Silurian 

 age are also found at several points lying well within the margin 

 of the Nucleus, as for instance in the Ottawa River about 

 Pembroke at a distance of fifty miles, and at Lake St. John at 

 the head of the Saguenay River at a distance of one hundred 

 and thirty miles from its present limit. There is reason to 

 believe that a similar outlier exists in the interior of the northern 

 part of the Peninsula of Labrador, so that the Lower Paleozoic 

 sea must also have covered considerable areas in the eastern half 

 of the Protaxis, where now nothing but Laurentian is to be seen. 

 In that portion of the Protaxis lying to the west of Hudson's 

 Bay strata of Cambro-Silurian and Devonian age extend up from 

 the basin of Hudson's Bay on the east and from the great plains 

 on the west far over the Laurentian Plateau and probably, 

 according to Dr. Dawson, originally inosculated. Strata of 

 Upper Silurian and Devonian age are not known to exist in the 

 eastern half of the Protaxis, of which the typical Laurentian area 

 forms part, with the exception of a small outlier of Niagara age 

 on Lake Temiscamangue at the head waters of the Ottawa — 

 neither do any other deposits of later age occur with the excep- 

 tion of the Glacial Drift. What evidence there is, therefore, 

 would rather indicate that the area, during late Paleozoic, 

 Mesozoic and earlier Tertiary times, was out of water. If so, it 

 must have undergone during this great lapse of ages a process 

 of deep seated decay and denudation, culminating in the exten- 

 sive glaciation to which it was subjected in Pleistocene times. 

 During this latter period the whole area was exposed to 



' G. M. Dawson. — "Notes to accompany a geological map of the northern portion 

 of the Dominion of Canada." Report of the Geological Survey of Canada, 1886. 

 p. 9, R. 



