ANALYTICAL ABSTRACTS. II3 



3. The Fundamental Gneiss may be considered as a great mass of erup- 

 tive rock, which has eaten upward and penetrated the Grenville series, while 

 the Grenville series itself represents a series of altered sediments of Lauren- 

 tian, Huronian, or subsequent age. The world wide distribution of the Fun- 

 damental Gneiss (forming as it does, wherever the base of the geological 

 column is exposed to view, the foundation upon which all subsequent rocks 

 are seen to rest) is opposed to this view, as is also its persistent gneissic or 

 banded character. 



The anorthosite series is a gabbro, often regularly laminated and much 

 altered, which is intrusive within the Fundamental Gneiss and the Grenville 

 series. 



The Hastings series has a very local development. It consists largely 

 of calc-schists, mica-schists, dolomites, slates, and conglomerates, thus con- 

 taining much material of undoubtedly clastic origin. The whole district has 

 been subjected to great dynamic action, some of the pebbles of the conglom- 

 erates being distorted in the most remarkable manner. This series may be 

 equivalent to a part of the original Laurentian, may follow above the Gren- 

 ville series, or may prove to be an outlying area of Huronian rocks folded in 

 with the Laurentian. 



The whole of the above series was cut by various acid and basic 

 rocks, metamorphosed and folded before upper Cambrian time, since the 

 Cambrian sediments rest upon them unconformably, and contain fragments 

 of the lower series which show that when deposited they were in their present 

 condition. 



The roche moutonnee surface possessed by the eroded Laurentian rocks 

 was impressed upon them in the first instance in pre-Cambrian times, for 

 along the edge of the nucleus from Lake Superior to the Saguenay, the Paleo- 

 zoic strata may be seen to overlie such surfaces showing no traces of decay, 

 and similar to that exposed over the uncovered part of the area. To what 

 extent the Cambrian, Devonian, and Silurian seas passed over the Laurentian 

 cannot be determined, but it seems probable that in Cambrian times, a not 

 inconsiderable part of the Archean Nucleus was under water, as shown by 

 various outliers of these rocks. What evidence there is indicates that the 

 area in later Paleozoic, Mesozoic, and earlier Tertiary times, was out of water, 

 being subjected to deep-seated decay and denudation, culminating in the 

 glaciation of Pleistocene times. These processes removed all but remnants 

 of the Paleozoic strata. 



Comments. — The question may perhaps be asked whether the visible con- 

 tacts of the pre-Cambrian and Cambrian are sufficiently extensive to warrant 

 the statement that the pre-Cambrian topography was similar to the present 

 topography. May not the tendency to carry in imagination the present forms 

 under the Cambrian have been given undue weight ? 



