STRUCTURAL FEATURES OF THE PRE-CAMBRIAN 271 



of the former presence of the sediments; but it is not necessary 

 to rely on these as there is a sufficiency of the comparatively 

 unaltered fragments for purposes of recognition. The highly 

 garnetiferous character of the greater number of them renders 

 their derivation from the Nemenjish or the Grenville series almost 

 indubitable. 



Summary.- — The writer bases the correlation of the Nemenjish 

 series with the Grenville series on the following facts: (i) The 

 Nemenjish series possesses unusual petrographic characteristics, 

 in that approximately 50 per cent of the rocks of the series are 

 garnetiferous. (2) The granite batholith separating the Nemenjish 

 and the Grenville series is loaded with recognizable inclusions 

 of these peculiar garnetiferous schists. (3) The composition of 

 the Grenville on the southern border of the granite batholith is 

 identical with that of the Nemenjish series, i.e., garnetiferous 

 mica and hornblende gneisses, with a little crystalline limestone. 

 This passes to the south into Grenville of normal composition by 

 increase in the amount of limestone, without much change in the 

 character of the altered clastic members. 



Relations to older formations. — The relation of the Nemenjish 

 series to the lava series appears to be one of perfect structural 

 conformity, although this determination is weakened by the fact 

 that the contact was observed at one place only. As described, 

 the sediments were found resting on the old surface of a basaltic 

 lava flow, and with the same dip and strike as the lava. At the 

 contact the sediments were thin beds similar to the tuffs elsewhere 

 observed interbedded with the lavas; but these became mingled 

 with beds of sediments similar to the overlying material a short 

 distance above the base, and within a few hundred feet were 

 entirely replaced by them. When these sediments were first seen, 

 it was supposed that they probably belonged to the Mattagami 

 series, and a very careful search was made along the contact 

 with the lavas for evidences of unconformity, but none were 

 found. There is not a trace here of the conglomerate which 

 uniformly lies at the base of the Mattagami series, and appears 

 to be at least 300 feet thick wherever it has been possible to meas- 

 ure it. There is no evidence of the presence here of any large 



