L68 A. C. LAWSON — THE PRE-PALEOZOIC SURFACE. 



granites. Therefore, these depressions and hills of Laurentian must neces- 

 sarily have existed at the bottom of the Paleozoic ocean when the limestone 

 beds were being deposited.' 9 



Mr. A. J'. Low, of the Geological Survey of Canada, who has been more 

 recently engaged in tracing out the northern limits of the Paleozoic on the 

 north side of the St. Lawrence, west of Quebec city, informs the writer that 

 at several places he has noted the superposition of the Trenton or Lorraine 

 beds directly upon the hummocky Laurentian surface, and that there has 

 been no reduction of the surface where it projects from beneath the escarp- 

 ments, below that where the flat strata rest upon it. He notes the following 

 localities as affording particularly good sections : — Between Lorette village 

 and St. Ambrose railway station, Q. L.St. J. railway; west of Belair station, 

 C. P. railway: Ponl Rouge station, C. P. railway (section on Jacques Cartier 

 river); Deschambault, near railway station. Air. Low also informs the 

 writer that the undisturbed limestones of Lake Mistassini, in southern Lab- 

 rador, may be observed to rest upon hummocky Laurentian surfaces ; and 

 that on the Bast-main coast of Hudson's hay similar flat lying strata may 

 lie seen in the transverse section afforded by Richmond gulf, resting on a 

 very hummocky surface. 



In eastern < mtario, the best evidence we have hearing on this question is 

 contained on Air. E. ( 'oste's "Geological and Topographical Map of the 

 Madoc and Marmora Mining District." recently published by the Geological 

 Survey of Canada. N<> report accompanies the map as yet, hut the writer 

 has had the benefit of frequent conversations with Messrs. Coste, Ami, and 



White, who were employed in the field-work necessary for its < struction. 



Prom the map and from the information thus supplied, it is clear that in the 

 area mapped we have a remarkably striking illustration of the superposition 

 of flat, undisturbed Paleozoic strata (Birdseye and Black Liver) upon a 

 very hummocky and mamniui I lated Archean .-urface. The northern border 

 of the Paleozoic is lure very irregular in outline, and beyond the limit of 

 the main area there are very numerous outlier- scattered over the country. 

 Both along the edge of the escarpment and at the periphery of many of 

 tin- outlier.-, the flat strata may he seen resting directly on the rounded 

 hummocks; and these, out beyond the escarpment, often risehigh above the 

 lower horizontal strata. Many of the outliers, also, are mere patches resting 

 in aitu upon the Bteep Blopes of these hummocks. Many are bul a few 

 chains in diameter, and others only a few yards. Further, there may be 

 repeatedly Been projecting through the upper surface of the Birdseye and 

 Black River formations rounded knobs of the Archean, in the shape of in- 

 liers well within the Paleozoic area. These are clearlj the crests of partially 



■ it., p, is. 



