[ADAMS & BARLOW] ALKALI SYENITES OF EASTERN ONTARIO 7 



Algona. This represents a distance of about 103 miles. Within this 

 belt from the township of Glamorgan north-east to the Ottawa river, over 

 a distance of about eighty-three miles, the nepheline syenites and their 

 aBsociated rocks are represented by very, frequent exposures, constituting 

 an almost continuous development. 



Geological Eelations. 



The area in which the nepheline syenites occur is underlain by the 

 Laurentian System of Logan. According to Logan, this system m^is 

 composed of the Fundamental Gneiss, with an overlying series of very 

 ancient sediments consisting chiefly of limestones, and which subse- 

 quently came to be known as the Grenville Series. Logan considered 

 both series to be of sedimentary origin, the well defined bedding of the 

 upper series being in the Fundamental Gneiss, represented by a gneissic 

 structure which he regarded as representing an almost obliterated bed- 

 ding. The contact of these two series in the single area which he worked 

 out in detail, namely, the district lying north of Grenville, which is 

 situated about half-way between the cities of Montreal and Ottawa ou 

 the north shore of the St. Lawrence, is of such a character as to lend 

 some colour to this old V/ernerian view. 



A careful examination of the very large areas in which the relations 

 of these two series has since been closely studied, shows, however, that in 

 all cases the so-called Fundamental Gneiss breaks up through the over- 

 lying Grenville Series, the contact being an intrusive one, so that over 

 wide stretches of country in the Province of Quebec and in Eastern On- 

 tario the " Laurentian System " is composed of a great series of sedimen- 

 tary rocks chiefly limestone, invaded and intensely altered by enormous 

 intrusions of the Fundamental Gneiss. In Western Ontario a similar 

 relation ia always seen where the oldest stratified series in that part of 

 the Dominion, namely, the KeoAvatin Series, comes in contact with the 

 Fundamental Gneiss. In fact, the same remarkable relation has been 

 found in all parts of the world where the oldest sediments have been 

 studied. There is no floor to the sedimentary series, no basement of 

 granitic or other rocks on which the oldest sediments of the geological 

 column repose and from which they have been derived, but, instead, the 

 oldest sedimentary series float on enormous intrusions of granite, which 

 break up through them in every direction. 



It is in such an area that the rocks described in the present paper 

 occur. The limestones with their associated sedimentary gneisses and 

 amph'ibolites (Grenville Series) are excellently developed, being of great 

 areal extent and of great thickness. Through this Grenville Series the 

 granite batholiths of the Fundamental Gneiss are well np, being (vfton 



