Lawson.] 



The Eparthcean Interval. 



series, we might reasonably expect similar characters in its sup- 

 posed correlative north of Lake Huron, only 140 miles distant. 

 There is, however, no resemblance between these upper series of 

 the south shore and the (Upper) Huronian, and it is exceedingly 

 difficult to get at the evidence upon which that correlation is 

 based. The correlative of the Penokee, Upper Menominee and 

 Upper Marquette seems to be entirely kicking in the region 

 north of Lake Huron. The (Upper) Huronian of Lake Huron, 

 on the contrary, bears a striking resemblance in its stratigraphic 

 make up to the Lower Menominee and Lower Marquette, and is 

 much more probably their equivalent, as has been recently 

 suggested by Willmott.* 



if this latter correlation be sustained, as I believe it xilti- 

 mately will be, it would of course effectually dispose of the 

 current correlation of the Animikie and its south shore equiva- 

 lents with the ( Upper) Huronian. But if it be denied, or even 

 eventually disproved, that will not support the correlation of the 

 Animikie and (Upper) Huronian, for in the Lake Huron region 

 there appears to be nothing with which the Animikie may be 

 correlated either on the basis of petrographic and stratigraphic 

 similarity or on the basis of sequence of series. 



A profound erosion interval is recognized everywhere on the 

 south shore below the Penokee, Upfper Menominee and Upper 

 Marquette, just as there is below the Animikie of Thunder Bay, 

 and since all these rock series are correlated without question, 

 this erosion interval must also be correlated. The Eparchaean 

 Interval, therefore, separates the Upper and Lower Marquette. 

 We may place the Upper series in the Algonkian, but we must 

 place the Lower in the Archaean of Dana. This leaves the (Upper) 

 Huronian where it belongs, on the far side of the Eparchaean 

 Interval . 



If now we turn our attention to the sequence of rock series 

 within Dana's Archaean, we And a rather remarkable parallelism, 

 not only as regards sequence, but also as regards the petrographic 

 character of the different members of the sequence and their 

 relation to the granite-gneisses, in western Ontario, in Minne- 

 sota, on the south shore of Lake Superior and on the north shore 



*Journal of Geology, Vol. X.. No. 1. 



