R. D. Irving—Divisibility of the Archean. 245 
5. In the discordant laminations of the two sets of rocks 
when seen in contact or close proximity 
6. In the occurrence in the upper series, not only at horizons 
above the base, but also at points on the contact line, of abund- 
ant detrital material derived from the lower series. 
The succession of formations in this region is, then, as I see 
the matter, as follows, beginning with the southernmost or old- 
est: (1) gnetss-granite-green-schist formation ; great unconform- 
Ity ; (2) tron-bearing slate formation; unconformity; Keweenaw 
Series. 
Turning next our attention to the Marquette Region of 
Michigan, we note at once, that, while the slaty iron-bearing 
formation here displayed is manifestly and by common consent 
the same as that of the Penokee-Gogebic region just described, 
regarding certain greenish schists, which ie ig intervene 
? 
whose present crumpled and trough-like arrangement he con- 
nects with the subsequent protrusion of the granite masses on 
