MINERALS AND GEOLOGY OF CANADA. 1138 
Tertiary deposits. These, which include the great Drift formation, 
and sundry accumulations of more recent origin, are largely developed 
in Canada. 
SKETCH-SECTION OF CANADIAN ROOK-FORMATIONS. 
LE 
fig. 151. 
A—Azoic Strata (Laurentian and Huronian.) 
B=Paleozoic Strata (Chiefly Silurian and Devonian.) 
C=Post-Tertiary deposits (Drift and Modern accumulations.) 
*D—Eruptive rocks (Traps, Trachytes, Syenite, Granite.) 
Our rock-formations, therefore, as shown in the accompanying dia- 
gram, comprise representatives of the Azoic, Paleozoic, and Post- 
Tertiary series, a wide break occurring between the two latter,—to- 
gether with trap dykes and other masses of eruptive origin. The 
subdivisions and leading characters of these will now be considered. 
We commence with the older formations, and proceed upwards to 
those of modern date.* 
AZOIC ROOKS OF CANADA. 
Huronian. 
Laurentian. 
The Canadian rock-formations of Azoic age, are referred to two 
series : the Laurentian, below; and the Huronian above. This sub- 
division, not yet fully recognized by American geologists, was first 
proposed by Sir William Logan ; and the terms “ Laurentian” and 
** Huronian”’ are of his bestowal. Theformer is now adopted in 
Hurope for gneissoid strata of the same ancient date. The Lauren- 
* In the present place, these rock-formations will be considered separately, and in a more 
or less detailed manner as regards structural characters, economics, characteristic fossils 
(when exhibited), localities of instructive exposures, and other allied points of inquiry; and 
afterwards, in a eonnected sketeh, their mutual relations will be shewn, together with the 
special geological areas which occur within the Province. The general reader will scarcely 
gain a clear idea of the Geology of Canada, until after the perusal of this latter section. 
The present details are necessary, however, as an introdnction to this. 
Vou. VILL. K 
