GEOLOGY OF FRANKLIN COUNTY 91 



In a somewhat more recent paper by Dr A. E. Barlow the rela- 

 tions between the "Laurentian" and the Grenville series are thus, 

 described i 1 



The relations of these two members of the archaean in central. 

 Ontario suggest in the strongest manner that in the Grenville 

 series we have a truly clastic group of strata which has slowly 

 sunk down into, and have been invaded by, much greater volumes 

 of the granites and gneisses of the Laurentian when these latter 

 were in a plastic condition. . . The contact between the 

 gneisses and granites of the Laurentian on the one hand, and the 

 limestones and associated rocks of the Grenville series on the 

 other, is, wherever examined, one of intrusion. 



There are three possibilities in regard to the age of the undeter- 

 mined gneisses of Franklin county, their igneous origin being 

 admitted. 



1 They may in whole or part represent a more ancient series 

 than the Grenville. 



2 They may represent a somewhat later series intrusive in 

 the Grenville, but older than the great gabbro, syenite and granite 

 intrusions. 



3 They may represent thoroughly foliated phases of these later 

 intrusions. 



In the writer's present judgment they w r ill be found to belong 

 partly under 2 and partly under 3 but more specially the former. 2 

 All the later intrusions, so far as examined by the writer, while 

 quite gneissoid, show at least rather massive cores, though the- 

 anorthosites are much more massive than the more acid rocks. 

 But in northern Franklin county are wide areas of rather fine 

 grained gneisses in which no such cores are visible. Furthermore- 

 these gneisses, and the Grenville rocks as well, are cut by numer- 

 ous dikes of a peculiar and very characteristic, rusty-looking 

 gabbro-diorite or norite diorite, while not a single case of such a 

 dike has yet been seen cutting the anorthosites, nor the syenites 

 and granites. A large dike of this character is found at the 

 summit of Catamount mountain, in Clinton county, in a rock 

 which resembles the later granite, though it has not been shown 



lBarlow, A. E. Ottawa naturalist. Feb. 1899. 12: 205-17. 



2It is by no means impossible that in part they belong under 1. 



