yl Jidft'oiKif \'ietr of the KeinciKiira II. — ]V i iifhcll . 155- 
Affei' the A iiimikie rerolnfio/i ira.s a Ihikj erosion interval. 
This interval is emphasized by the siliceous conglomerates that 
have already been referred to — first at the base of Grand 
Portage island, second, in the valley of the St. Louis river, 
and third, west of Agogebic lake, as described recently by 
Van Hise.* This conglomerate we are disposed to consider as 
pre-Keweenawan, notwithstanding the argument of Van Hise 
that it is post-Keweenawan. Its readiness to disintegrate on 
exposure to the atmosphere is perhaps its strongest evidence 
of post-Keweenawan age. So far as observed all ]u-e-Kewee- 
nawan conglomerates are much indurated. 
In addition to these localities Sweet has described it in T. 
32, R. 6 W., Wisconsin, on the Chippewa river, but without 
apprehending its age, except that he found it underlying a 
massive quartzyte. The conglomerate here reaches 300 feet 
in thickness. I It has been fully described by the Wisconsin 
Geological Survey. J This conglomerate and the overlying 
(juartzj^te have been found in Minnesota associated as in Wis- 
consin. At New Ulm this conglomerate lies on a coarse red 
granite and has a thickness exposed of about 25 feet. As a 
conglomerate this formation is not known further southwest,, 
but as a (luartzyte it appears conspicuously in Cottonwood 
county, where it forms a long characteristic ridge. It reappears 
in Pipestone county, and is well known at Sioux Falls, in 
South Dakota. Red felsytes, probabl}^ connected with it, have 
been described by S. W. Beyer,§ and certain diabases appar- 
ently cutting it in South Dakota have been described by G. E. 
Culver and W. H. Hobbs. II 
This red quartzyte has had various names, and has l)een as- 
signed to various ages. The authors of the Wisconsin geolog- 
ical report, 1873-1879, referred it tf> the Huronian, and they 
have since so considered it, though, later. Van Hise has char- 
itably covered the whole (juestion with the convenient non- 
committal ti^rm A I (JO It k- inn. The writer originally, in 1872, 
*The Penokee Iron-Vjcarinf^ series of Michigan and Wisconsin, Men. 
XIX, U. S. Geol. Sur., p. 461. 
IE. T. Sweet, Notes on the Geology of Northern Wisconsin. Wis- 
consin Acad. Sci. and Arts, vol. iii, p. 4."j. 
J Vol. IV, p. .575. 
§Iowa Geological Survey, vol. i, 1892, p. 165. 
II Wisconsin Acad. Sciences, vol. viii, j). 206. 
