802 Mah WKOOHIN AVE, (OVP (CIROIL OG, 
The mining district of Amasa is of quite recent development, 
and as far as | am aware no attempt has thus far been made to 
refer the deposits to any definite geological horizon. 
During 1892, Messrs. W. N. Merriam and H. L. Smyth, with 
their assistants, were engaged in tracing out the iron-bearing for- 
mation in this region. Smyth worked in the northeast along the 
Michigamme River, and Merriam west of the Michigamme River 
and southwest of the Deer River. When their work was finished 
the two areas were not connected in the north by about twelve 
miles, and a narrow belt separated the mapped areas to the south. 
During the season of 1894, I was engaged, with the assistance 
of G. E. Culver and S. Weidman, in completing this area, pre- 
paratory to extending the work into the Menominee iron district, 
Many of the facts of the field occurrence mentioned in the fol- 
lowing article were observed and recorded by Merriam and assis- 
tants, and were subsequently verified by my own observations of 
last season ina different portion of the area, and by visits to 
localities in the areas previously surveyed. 
Successton.—A résumé of the ascending succession is as follows: 
The area considered is oval in outline, about twenty-five miles 
long and twelve miles wide, extending in a N.W.-S.E. direction 
(Pl. I.) The center of this oval is occupied by an elliptical area 
thirteen miles long by three miles wide, of the oldest rocks of the 
district, consisting of granite and gneiss, cut by numerous basic 
dikes. This is surrounded by a quartzose limestone formation, 
with an estimated thickness of 1500 to 2000 feet.*. In places the 
quartz almost disappears and we get a limestone. In other places 
we have an almost pure quartzite. The formation disintegrates 
very rapidly, and to this fact can probably be attributed the lack 
of outcrops over the greater portion of the area which it is sup- 
posed to underlie. Overlying the limestone we find, both to the 
east and west of the ellipse described, a great series of volcanics 
with an average thickness of about 3000 feet. Their greatest 
development is to the west of the ellipse, where the average 
thickness is 4000 feet. It appears probable that these two areas 
tH. L. SMyTH: Relations of the Lower Menominee and Lower Marquette 
Series in Michigan. Am. Jour. Sci., 3d Ser., Vol. XLVII., p. 217, January 1894. 
