MINERALS AND GEOLOGY OF CANADA. ," 



range formed, from Labrador to the Arctic Sea, the northern shore 

 line of the ocean during the Lower Silurian period. The land to the 

 north, being thus above the level of the sea, would receive no depo- 

 sition of Lower Silurian strata ; but an after movement of depression 

 must have ensued during the Upper Silurian epoch, bringing down 

 this northern district beneath the sea, and so enabling the sediments 

 of the latter period to be laid down upon its area. 



5. Great Southern JBasin of Cartada : Its subdivisions : — The 

 southern geological area of Canada, is in itself divisible into three 

 smaller basins : (1) the Basin of the lakes ; (2) The Basin of the St. 

 Lawrence ; and (3) The Eastern or Metamorphic Basin. The two 

 first of these are separated from each other by the gneissoid belt of 

 the Upper St. Lawrence alluded to above ; whilst the third or Eastern 

 Basin is separated from the St. Lawrence area by a remarkable dislo- 

 cation, accompanied by physical and chemical changes of great 

 moment. This dislocation is evidently connected with the elevation 

 of the Appalachian mountain chain. ' As traced in Canada by Sir Wm. 

 Logan, it runs from near the northern extremity of Lake Champlain 

 in a general north-easterly direction to the St. Lawrence, which it 

 crosses immediately above Quebec ; and then turns to the east, traver- 

 sing the northern part of the Island of Orleans and passing down the 

 river into the Gulf, from whence it appears to re-enter the south shore 

 a few miles above the mouth of the Magdalen River in Gaspe. The 

 strata within the area circumscribed by this dislocation, are thrown up 

 generally into highly inclined beds ; and they exhibit, in other respects, 

 many signs of the action of powerful disturbing forces. See under the 

 head of the " Calciferous Formation," on a preceding page. In the 

 more central portion of the area, also, they are much altered, or con- 

 verted into crystalline schists, &c., and rendered metalliferous by meta- 

 morphic agencies. The strata of the Lake and St. Lawrence Basins, 

 on the other hand, betray few signs of these disturbing influences, 

 except in the case of the upper copper-bearing Series of Lake Superior, 

 and in parts of Gaspe, as described fully in a preceding division of 

 this Essay. 



6. The Lake Basin of Canada : — Of this geological basin, properly 

 speaking, only the north-eastern and northern portions actually occur 

 within the boundaries of the Proidnce. It includes all the area to the 

 east or left of the Laurentian district marked 1 — 1 in the sketch-map 

 fig. 243. Though affected here and there by slight local disturbances. 



