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1907-8.] THE GEOLOGY OF THE LAKE WENDIGOKAN REGION. 357 
more large granite pebbles than that south of the lake and away to the 
east. This condition is due to the origin of the material composing the 
large band to the north being largely in the rocks north of the iron range 
exposures, while that farther south has been derived from the outcrops 
of the formation in that part of the region. And I think it also favours 
the suggestion already made that the material composing this rock was 
largely the loose mantle rock which covered the land when the sea trans- 
gressed upon it, at the close of the Laurentian period. After such a 
period of vulcanism as that which marked the Laurentian, the rocks 
would doubtless be in a shattered condition and readily disaggregated 
by weathering. The coarseness of some of the conglomerate shows that 
the boulders contained in it could not have been transported any great 
distance by water unless the land to the north were very much higher 
than it is at the present time, and the streams had very strong currents. 
The presence of these large granite pebbles when extensive exposures 
of granite are not found within many miles to the north or south is signi- 
ficant, though these may have existed, been eroded and covered by later 
formations. Should this suggestion fail to satisfy the conditions, their 
presence might be explained by supposing they were carried from the 
granite outcrops to the north by glacial action. ‘There are no direct evi- 
dences of glacial conditions in this region during the Huronian period, 
but since there are evidences of these conditions in other parts of Ontario, 
it may not be unreasonable to suppose that they also existed in this more 
northern region. 
THE HURONIAN ARKOSE. 
The origin of this formation has already been discussed in the outline 
of the Historical Geology of the region. It is quite common around Lake 
Wendigokan, where it appears to exist in synclines of the older rocks, but 
scarce in the iron range regions around Sand Creek and Sturgeon River. 
The absence of much jasper in the rocks, though some is found, and the 
presence of arkoses closely associated with the slates and iron formation, 
have previously been given as reasons for placing these rocks in the Kee- 
watin system, but the nature of the rocks, their association with the con- 
glomerate, and the absence of arkose pebbles in the conglomerate seem to 
be better reasons for placing them in the Huronian. These are generally 
massive grey rocks weathering brown on the surface in places, and they 
differ from our more recent arkoses in being very firm and compact. They 
often appear as rounded hummocky masses retaining the smoothed surface 
made by glacial action. In some of the hand specimens, quartz fragments 
can be detected readily with the naked eye, and in the field the rock has a 
