122 MORLEY E. WILSON 
eastern North America, and corresponds in general to the Lake 
Superior-Lake Huron geological province. In a structural way, 
the rocks of the Timiskaming region may be divided into three 
elements which are strikingly differentiated from one another: 
to the first of these belong the older complex; to the second the 
Cobalt series (Huronian) and Nipissing (Keweenawan) diabase; 
and to the third the Pleistocene and Recent deposits. 
The first subdivision, the older complex, consists of two classes 
of rocks: (1) the surficial, consisting of basic to acid volcanic 
flows, conglomerate, greywacke, arkose, and slate; and (2) the 
plutonic, consisting of granite, granodiorite, diorite, and related 
rocks. The rocks of the second class, as far as has been observed, 
are intrusive into the surficial class although the presence of 
pebbles and bowlders of granite in the conglomerate shows con- 
clusively that an older granite occurs somewhere in the region 
and that a great erosion interval is represented. 
From an examination of a general geological map of north- 
eastern Canada, it may be seen that a wide belt of granite and 
related rocks (Laurentian) extends continuously from Georgian 
Bay to the Gulf of St. Lawrence, while to the north of this, there 
is a belt in which rocks of the surficial class predominate and which 
extends from the north shore of Lake Huron to Lake Mistassini. 
It seems probable that the southern granitic belt represents an 
ancient geanticlinal mountain core and the adjacent belt on the 
north a geosynclinal intermontane belt, but denudation proceeded 
so far in pre-Cambrian times that this synclinorium was cut off 
close to its base so that the surficial members of the complex are 
intruded by numerous small isolated batholiths of granitic rocks 
which have effected marked local changes in the structural trend 
of the rocks in their vicinity. 
On the profoundly denuded surface of this ancient complex 
lies the second structural element, the Cobalt series (Huronian). 
In striking contrast with the complicated plications of the older 
element, the structure of these rocks is comparatively simple. 
They have been very slightly folded into broad, gently pitching 
anticlines and synclines, the dip being usually less than 20 degrees. 
