EAGLE RIVER SECTION. it 
reddish brown in color, with sometimes red crystals of feldspar porphy- 
ritically imbedded in it" In some of the harder amygdaloids the base is 
often greenish in color. In the intermediate pseud-amygdaloids a pinkish 
radiated prehnite is the chief pseud-amyedule. 
Interstratified with the diabases and amy gdaloids of this portion of the 
section are eleven beds of sandstone,’ running from 3 to 63 feet in thick- 
ness, with a total thickness of some 860 feet, and increasing in thickness 
and coarseness towards the north. They consist of the same materials as 
already described, and are all of a dark-reddish color. They all contain 
more or less infiltrated calcite. The section of one of these sandstones, 
the first below the Great Conglomerate, is figured on Plate XVI, Fig. 3. 
It shows subangular particles worn from the several kinds of porphyry, 
chiefly from their matrices. A few of the single quartzes and feldspars of 
the porphyry are included. Very abundant secondary calcite fills up the 
spaces between the fragments. 
Next below these layers there succeeds a group (Marvine’s “b”, in- 
cluding beds 45 to 66 of his detailed section) 618 feet in thickness, extend- 
ing from the upper falls of Eagle River southeastward to the so-called and 
well-known ‘“Ashbed,” whose name may not inappropriately be given to 
the whole group. At both summit and base of this group are diabases of 
peculiar character.’ The lower portion of each of these two beds is a hard, 
brittle, elastic rock, of specific gravity 2.93, with a very fine-grained light- 
colored purplish matrix, in which are porphyritically imbedded numerous 
minute plagioclases. The upper portion of each of these beds is a scoria- 
ceous amygdaloid, separated from the main part of the bed by rather a sharp 
line of demarkation. This peculiar amygdaloid is 
composed of irregular bunches or “bomb-like” masses of calcitic amygdaloid, 1.5 
feet to .5 inch diameter, filled in with a very fine-grained to compact brick-red mate- 
rial, which often shows fine but irregular bands or lines, apparently of stratification. 
This material increases in amount toward the top of the bed, where it quite often 
incloses and surrounds the smaller irregularly round amygdaloidal balls. The strata- 
like bands are more evident when the material is in larger amounts, and they often 
Geological Survey of Michigan, Vol. I, Part II, p. 103. 
?One more than counted by Marvine. This additional bed was pointed out to me by M. L. G. 
Emerson, who aided Marvine in preparing his section. 
’ Beds 45 and 66 of Maryine. 
