[ells] CANADIAN GEOLOGICAL NOMENCLATURE 33 



throughout all this area are often in the underlying granite-gneiss, while 

 the synclines are occupied by the rocks of the newer gneiss, limestone 

 and quartzite series. Since the folding of these rocks has practically 

 been along uniform lines, there is often no apparent stratigraphical un- 

 conformity between the rocks of the two series, as the synclines of the 

 newer follow regularly along the anticlines of the older. This gradual 

 disappearance of the upper series northward may be, to some extent, due 

 also to the gradual elevation of the surface, which at the height of land 

 in this direction is about 1,000 to 1,200 feet above the sea. 



South of the Ottawa, the depth of the great basin of newer crystal- 

 line rocks increases, so that, in that portion more nearly approaching the 

 overlying sedimentary formations of Ontario, north of the great lakes 

 Ontario and Erie, these appear under somewhat different conditions. Ln 

 this direction the problem is somewhat complicated by the presence of 

 masses of granite-gneiss and also of granite, the action of which upon the 

 associated members of the overlying series is very manifest, sometimes 

 in the distortion of the beds, which are frequently cut off entirely along 

 their line of strike, while in other portions these are pushed aside as by 

 the intrusion of some great mass of igneous rock. The question there- 

 fore arises whether these granite and granite-gneiss masses shall be as- 

 signed to and classed with, the Fundamental or Laurentian gneiss, or 

 shall be regarded as intrusive masses which shall date in age from the 

 time point of the rocks which they penetrate, as in the case of the so- 

 called Devonian granites .of the east. 



If we assume the time limit merely as the basis of our classification, 

 it would appear that all the later rock masses which have invaded or 

 distorted the stratification of the upper gneiss and limestone, should be 

 separated from the Laurentian proper and assigned to the same position 

 as the Grenville granites and the anorthosites, otherwise we have the 

 apparently startling anomaly of a formation, regarded by all geologists 

 as the oldest in the time scale, assuming a place which makes it more 

 recent than the rocks of the overling series. This, at first glance, 

 appears to be opposed to all recognized principles of nomenclature, since 

 it would practically make the Huronian older than some portions at least 

 of the Laurentian. 



Early in his study of the geology of the Lake of the Woods district, 

 Lawson found himself confronted with this aspect of the question. In 

 this area the relations of the so-called Laurentian granite-gneiss to the 

 series of newer gneiss and schist, which he, for that region, designated 

 by the terms Couchiching and Keewatin, appear to closely resemble the 

 relations found to exist in the deeper portions of the crystalline basin of 

 Quebec, near the lower Ottawa, and in eastern Ontario. After a close 



Sec. IV., 1899. 3 



