FORMEB EXTENSION OF THE PALEOZOIC. 171 



has been explored, the indications that it was once very extensively if not 

 wholly covered by formations of Paleozoic age are both numerous and im- 

 portant. The lines of examination have been chiefly confined to the 

 ordinary routes of travel followed by the fur traders, and these are not 

 numerous. "When the country comes to be more closely explored there is 

 every reason to suppose that many other outliers, such as those of lakes St. 

 John, Mistassini, Nipissing, and Temiscaming and the Ottawa river, will be 

 found scattered over its surface, and that the evidence of the once wide-spread 

 distribution of the Paleozoic formations will accumulate. 



Transgressions and Oscillations in Level. — But here a word of caution and 

 modification is necessary. While the evidence indicates that a covering of 

 Paleozoic (Cambrian to Devonian) once spread over the Archean surface, it 

 does not indicate that the rocks of the lower horizons were thus widely 

 spread. On the contrary, it is to be noted that thei*e are distinct evidences 

 of the transgression of the formations of higher horizons over the limiting- 

 edges of the lower. Thus, on Lake Superior, the Nipigon rocks may be dis- 

 tinctly observed to overlap the northern edge of the Animikie formation and 

 extend northward far beyond it. In the St. Lawrence and lower Ottawa 

 region, rocks of Potsdam and Calciferous age are abundant. Further 

 north these are absent, and in the upper Ottawa outliers the Chazy rests 

 directly upon the gneiss. In the vicinity of Madoc this also is lacking, and 

 the Birdseye and Black River beds rest directly upon the gneiss. This 

 appears to be true also of the outliers on Lake Nipissing. Thus, in ascend- 

 ing the Ottawa, the Chazy overlaps or transgresses both Potsdam and Calcif- 

 erous, while at Madoc and Nipissing all of these are transgressed by the 

 Birdseye and Black River. This, in turn, and all older formations, were 

 trausgressed by the Niagara, as is indicated by beds of that age resting 

 directly on the Archean on Lake Temiscamany. 



In the Province of Quebec the same condition of affairs is found. 

 In the vicinity of the St. Lawrence, the Chazy and Calciferous rocks 

 abound. To the north of this, in the Saguenay country, Laflamme remarks 

 as a noteworthy fact, that in all the points of contact which he has been 

 able, to observe between the Laurentian and the Trenton, the latter rests 

 directly upon the former, no traces of Potsdam, Calciferous, or Chazy being 

 seen. Moreover, whilst the Utica formation is present only in a few instances, 

 still debris from it are found on the shores of the lake (St. John), and very 

 often inland to such au extent that we are forced to conclude that the whole 

 area of the Trenton was formerly covered with this formation. 



Thus, while the evidence indicates that the Archean "nucleus" was once 

 covered very extensively by Paleozoic formations of one horizon or another, 

 it appears probable that it was not extensively submerged till the time of 

 the Trenton, and that it was much more extensively submerged during the 



XXTII— Bull. Geoi,. Sue. Am., Vol. t, 1880. 



