yo H. C. COOKE 



vicinity of Madoc, Ontario, contributory to the problem of corre- 

 lation." In this paper they state that in this district " an old green- 

 stone series, with associated acidic, igneous rocks, similar to the 



Keewatin of the Lake Superior region, is widely developed 



It has been proved by the writer that the Keewatin here is the oldest 

 series in the region. The limestones are found to have been deposi- 

 ted on the surface of the Keewatin. An ancient Keewatin lava has, 

 in places, been subjected to Httle denudation before the deposition of 

 the Grenville limestone, which fills the cracks and openings in the 

 ropy surface of the lava." This evidence, though interesting, is 

 scarcely convincing, principally because it assumes that the basic 

 lava apparently underlying the limestone is correlative with the 

 Keewatin lavas of Lake Superior region. As basic lavas are found 

 in the Lake Superior region, not only in the Keewatin, but through- 

 out the whole pre-Cambrian, such an assumption cannot be accepted 

 without proof. Exception might also be taken to the vahdity of 

 the evidence advanced in regard to the relative ages of the lavas 

 and the Hmestones. These rocks are all tilted into vertical atti- 

 tudes; so that calcite might easily be carried by meteoric water 

 from the limestone and deposited in cracks in the lava, even though 

 such cracks were not formed till long after the folding was com- 

 pleted. Again, such cracks might have formed during the folding, 

 and the limestone have flowed into them under the pressure of 

 deforming forces. Either of these hypotheses would explain the 

 presence of Hmestone in the cracks in the lava near the contact, 

 regardless of whether the limestone had lain above or below the 

 lava before deformation took place. 



In 1 9 14 Miller and Knight pubhshed a more extensive paper^ 

 on the relationships of the rocks of eastern Ontario. In this paper 

 they still maintain the conformable relationships of the Grenville 

 to the "Keewatin," but without adducing much new evidence. 

 They describe in the ActinoHte-Cloyne area a nuclear mass of 

 greenstone surrounded by Grenville sediments. Regarding the 

 relationships of the two, they state: "In the first place it is clear 

 that the greenstone is not a deep-seated intrusive, or batholith, 



^ Rept. Out. Bur. of Mines, 1907, Part i, p. 221. 

 ^ Ibid., 1914, p. 2. 



