Section IV., 1897. [ 117 ] Trans. R. S. C. 



IV. — Notes on the Archœan of Eastern Canada. 

 By E. W. Ells, LL.D., F.G.S.A. 



(Read June 22nd, 1897.) 



Much attention has been directed to the study of the Archtean rocks 

 of Canada during the last fifty years, not only from their economic im- 

 portance as the source from which many of our most valuable mmerals 

 are derived, but from their very extended development throughout eastern 

 and northern Canada. They have been described under various names, 

 such as Primitive, Archœan, Laurentian, Huronian, Azoic, Eozoic, and 

 by other titles, some of which were apparently designed to illustrate 

 some peculiarity of distribution or feature in connection with their struc- 

 ture, while other names have been suggested and adopted by certain 

 geologists, which, in so far as Canadian nomenclature is concerned, in 

 connection with these rocks, are apparently almost without meaning, 

 and tend rather to confusion than to the simplification of the problem as 

 to their true relations. 



The greatest area of these rocks, which are undoubtedly the oldest 

 of our rock formations, lies to the north of the St. Lawrence and the 

 Great Lakes ; whence it extends northward almost, or in places quite, 

 to the Arctic sea. There are, however, a number of other areas scattered 

 through the provinces of New Brunswick and Nova Scotia, as well as in 

 the eastern portion of the province of Quebec, which have been conclu- 

 sively shown to belong also to the great Ai'chœan complex, though for 

 many years they were regai-ded as of much more recent date. Through- 

 out the greater part of these areas there is a marked similarity in the 

 character and general features of the rocks belonging to this great period. 



The Archaean is usually divided into two principal portions, viz., the 

 Laurentian and the Huronian. Of these, the Laurentian member has 

 been divided into two, and sometimes three parts, while the upper, or 

 Huronian, has also been, bj" some, arranged and described as comprising a 

 lower and upper division. The earlier arrangement and classification of 

 the Laurentian by Logan, who may be regarded as the first to attenapt 

 the detailed stud}' of the rocks which compose the system, was into a 

 lower and an upper portion. The former of these comprised a great 

 thickness of gneiss and limestone, with quartzite, granites, etc., all, or 

 the greater part, of which were supposed to be originally of sedimentary 

 origin ; while the latter comprised a very considerable area of anorthosite 

 rocks, also regarded as altered sediments, which were supposed to rest 

 upon the strata of the lower Laurentian. In this lower division were 

 included the Fundamental Gneiss and the Grenville series of limestone 

 and associated strata. 



