690 A. C. LANE AND A. E SEAMAN 
the amygdaloids shade into beds of scoria mixed with red mud called 
“‘ashbeds.”’ 
4. ‘Eagle River” group.—Marvine’s (c), characterized by waning 
volcanic activity shown by numerous (10 or more) sandstones and 
conglomerates, while the interbedded flows are more of the normal 
type. In the upper 2,300 feet Marvine estimates 860 feet of sediment. 
On Black River it is given as 1,417 feet; at the Tamarack as 1,700 ft. 
5,6, and 7. Copper Harbor conglomerates.—The conglomerates 
north of the Eagle River Group were grouped together by Douglass 
Houghton, who considered the Lake Shore Traps as intrusive dikes. 
When these were understood to be interbedded flows, the conglom- 
erate was divided into the Great and Outer, respectively, below. and 
above the Lake Shore traps. Hubbard’s studies around Copper 
Harbor have shown that there are at least three heavy conglomerates. 
It is not probable that the lines between the Great Conglomerate, 
Lake Shore Trap, and Outer Conglomerate can be drawn at all 
consistently. Together they cover the period of decadent vulcanism, 
and it is not at all likely that the flows from these last expiring throes 
filled the whole basin but more likely they occur irregularly in the 
conglomerate series. It therefore seems fitting to give a local term 
to the whole assemblage, treating ihe Lake Shore traps as a lentil or 
lentils in the same. 
5. “Great” conglomerate—Its thickness, not allowing for initial 
dips, is say 2,200 feet at Eagle River and Calumet, but apparently 
much less, 340 feet, on Black River. It has a wide variety of pebbles, 
but mainly of Keweenawan rocks. 
6. Lake Shore Traps.—These are apparently thickest near Copper 
Harbor where using Hubbard’s figures, they are about 1,800 feet 
thick. They are near goo feet thick at Calumet, but at Black River 
are only about 4oo feet thick. There is at least one well-marked con- 
glomerate in the group. Above this group is the line between the 
Upper and Lower Keweenawan as drawn by Irving, marked by a 
cessation of volcanic activity. There are also less dips in general, 
and very soon a greater variety in detritus. 
7. Outer conglomerate——With pebbles representing all the Lower 
Keweenawan types, including intrusives, amygdules and agates, 
and also the Huronian jaspilites. Only 1,000 feet are given at 
