332 M. E. WILSON 
mountain building, and batholithic invasion. Moreover, mountain 
systems throughout the world are generally narrow and linear and, 
where zones of crustal disturbance composed of several mountain 
systems, such as the cordillera of North America, occur, the systems 
composing the zone are generally of varying age. Hence, if granitic 
massifs represent the interior of mountain systems exposed by 
denudation, it is more probable that the northeasterly trending 
pre-Cambrian batholithic zones of the St. Lawrence basin, instead 
of belonging to two and only two periods of batholithic intrusion, 
in reality represent several periods of batholithic development. 
Relationship to igneous intrusions other than batholith—Igneous 
intrusions other than batholiths, especially if they are composed of 
unique rock types, can likewise be employed for purposes of 
correlation, but generally only within a single subprovince. The 
principle has been used for inter-subprovincial correlation in the 
case of the late pre-Cambrian diabase intrusions, however, all of 
which have been generally regarded as Keweenawan in age. 
Folding and metamorphism.—Since folding and metamorphism 
are accompaniments of mountain building and batholithic invasion, 
these criteria are in reality included under the head, “‘ Relationship 
to Batholithic Intrusions.”’ It can be generally inferred that in 
the same district those rocks which are most highly folded and 
metamorphosed are the oldest in age. This does not follow in the 
case of widely separated regions, however; for it has been found 
that rocks which are flat-lying and slightly metamorphosed in one 
district may be highly folded, metamorphosed, and intruded by 
granite batholiths in another locality. 
CONCLUSION 
From the preceding discussion the following conclusions may 
be inferred: that the regional succession of formations within the 
pre-Cambrian of the St. Lawrence basin has not yet been sufficiently 
worked out for the establishment of a definite nomenclature 
applicable to the whole of this territory; that, since the St. 
Lawrence basin extends for approximately 1,000 miles in a direction 
transverse to the trend of pre-Cambrian mountain building and 
batholithic intrusion, it is theoretically improbable that the 
