210 T. B. Brooks — Youngest Huronian Rocks. 



If we extend our observations to the older and again non- 

 conformable* Laurentian, we find the rocks still more plicated 

 and metamorphosed, often even to the extent of entirely ob- 

 literating all evidences of stratification. If we suppose the 

 forces which have produced the metamorphosis and the wave 

 forms to have acted regularly and constantly from the beginning 

 of Archaean time to the beginning of the Paleozoic, we may 

 easily suppose the above results produced, viz. : the Laurentian 

 most disturbed and changed, the Huronian next, and the Copper 

 series least, the Silurian practically not at all. 



A fact not without interest is the entire absence, so far as I 

 know, of any patch even of rocks of the Copper period south 

 of the great Keweenaw belt. If the two systems were conforma- 

 ble and of the same age, it is difl&cult to suppose it possible that 

 erosion should have entirely denuded all the Huronian area 

 which must have been covered by the Copper series of the 

 rocks of that period. One would expect that somewhere a mass 

 of these supposed younger Huronian beds would have been 

 embraced in some one of the numerous sharp, deep synclinals, 

 and have been found by those indefatigable mineral prospectors 

 who have so thoroughly searched this region. On the hypoth- 

 esis of non-conformability, it is much easier to conceive how it 

 was possible for Silurian breakers coming from the south, slow- 

 ly advanced by a subsidence from the same direction, to have 

 done their work in completely uncovering the present Huronian 

 area and leaving the great Copper range escarpment one of the 

 most striking topographical features as well as the most diflicult 

 geological problems in the Northwest. It is easy to suppose for 

 example, thehorizontal Silurian rocks being entirely eroded from 

 any Archaean terrains, but not of the Huronian rocks being en- 

 tirely eroded from a Laurentian area, for the reason already 

 given. Lastly, Logan states. Geology of Canada, 1863, p. 77, 

 that " certain conglomerates of the Lower Copper-bearing rocks 

 north of Lake Superior repose non-conformably on the upturned 

 chloritic schists of the Huronian." 



We are therefore justified, I think, in regarding the Copper- 

 bearing rocks of Lake Superior as a distinct and independent 

 series, marking a definite geological period which separates the 

 Silurian from the Huronian ages. Should future observations 

 confirm this view, it would be advisable to have some more 

 convenient and geologically acceptable name for the series than 

 that now in use. Since Keweenaw Peninsula forms one of the 

 most striking geographical features in Lake Superior and is the 

 locality where the Copper series are best exposed and were first 

 studied, I suggest the name Keweenawian for this period. 



