236 A. P. COLEMAN—CLASTIC HURONIAN ROCKS. 
from the gneiss into the green Huronian rocks. The loops so character- 
istic of the Huronian farther west are, however, to be seen only indis- 
tinctly, if at all, on Bell’s map of the region. Adams and Barlow show 
the same relationships between the Hastings and Grenville series of east- 
ern Ontario and the underlying Ottawa gneiss,* and Adams maps sim- 
ilar curving bands of the Grenville crystalline limestones sinking into 
the gneisses below, in his report on the Laurentian area north of the 
island of Montreal.f These two series are probably the eastern equiva- 
lents of the western Huronian, the Grenville series having undergone a 
more intense metamorphism than the usual Huronian. The conglom- 
erates found by Adams prove that these rocks were undoubtedly of sedi-_ 
mentary origin. 
Still farther east, in the great Labrador peninsula, Lowe describes 
crystalline limestones and garnetiferous, graphitic gneisses forming bands 
in the Laurentian, though his evidence as to the relation of the ordinary 
Huronian to the underlying Laurentian is not so conclusive. He recog- 
nizes in some of the mica-gneisses sedimentary beds like Lawson’s Rainy 
Lake Couchiching, but in other places speaks of Huronian rocks as rest- 
ing unconformably on the Laurentian, though in some cases they are 
more or less interfolded with the Laurentian.¢ 
On the other hand, according to Van Hise, Logan’s original Huronian, 
north of the lake from which it got its name, seems to be of later age 
than the underlying Laurentian, since he finds basal conglomerates or 
breccias containing fragments of Laurentian rock at two localities. Bar- 
low, who has examined the same region, thinks, however, that there also 
the contact is eruptive. 
From Van Hise’s admirable “ Principles of North American pre-Cam- 
brian Geology ” one finds that a conglomerate of the Huronian rests dis- 
cordantly on the foliated edges of the Basal Complex at many points 
south of lake Superior,|| and Dr Dawson informs me that characteristic 
Huronian beds rest on an eroded Laurentian surface in New Brunswick. 
It may be that at more southerly points the thickness of the Huronian 
series is considerably less than in the typical Archean region, and hence 
that the floor on which the sediments rested was not softened: or fused, 
as happened farther north. On the other hand, it is not impossible that 
in the states south of the lakes rocks of a somewhat later age, resting on 
‘the upturned edges of the Archean (including the Rainy Lake Huronian) 
have been looked on as Huronian. Van Hise includes mica-schists, green 
* Am. Jour. Sci., vol. iii, March 1897. 
+ Geol. Survey of Canada, 1895, part J. 
{ Geol. Survey of Canada, 1895, part L, p. 196, ete, 
2N. Am. Pre-Cambrian, 1896, p. 777. : 
| Ibid,, p. 784, 
