Driftless Area in Minnesota. — Grant. yj'j 
A POSSIBLY DRIFTLESS AREA IN NORTHEAST- 
ERN MINNESOTA. 
By U. S. Grant, North vve.>::tt)rn University, Evanston, 111. 
In the reports of field work by the Geological and Natural 
History Survey of Minnesota mention has been made of an 
area, in the northeastern part of the state, in which the glacial 
drift is scant or lacking, and which possesses some of the other 
distinctive characters of non-glaciated districts.* Because the 
chief object of this field work was the investigation of the 
crystalline and associated rocks, this area — in common with 
other areas and questions of interest from a glacial standpoint 
— was not studied in detail. Moreover, as it lies well within a 
region which is underlain by a monotonous mass of gabbro 
(the great Keweenawan gabbro mass), it was not visited ex- 
cept in a few points. Still, sufficient is known to demonstrate 
that this area is an anomalous one, and that it has exceptional 
features when compared with the immediately adjacent coun- 
try which is markedly glaciated and more or less drift-covered. 
The area under consideration is situated in the northeastern 
part of Lake county, thirty-five miles north of lake Superior. 
xA.s far as known it is somewhat elliptical in outline, the major 
axis, which runs northeast and southwest, being twelve miles 
in length and the minor axis eight miles. The surface is un- 
dulating with elevations that usually rise no more than thirty 
feet above the general level. In common with the surrounding- 
glaciated country this area has many small lakes and the drain- 
age system is very recent and poorly developed. In fact the 
topographic features are very similar to, or identical with, those 
of much of the gabbro-covered district of northeastern Min- 
nesota. This underlying rock is a coarse grained aggregate of 
plagioclase (near labradorite), augite (diallage), olivine and 
magnetite (titaniferous). The plagioclase is the most abundant 
mineral and at times so predominates over the others that the 
rock may be termed an anorthosyte. 
Lying within the area described are three lakes — Wilder, 
Alice and Pollyf — of larger size than the majority of those in 
*N. H. Winchell: Geol. and Nat. Hist. Survey of Minn., 15th Ann- 
Rept., p. 350, 1887. U. S. Grant: Ibid., Final Rept., vol. 4, pp. 421, 437, 
i8Qq. 
tThe k)cations of these lakes can be seen bv consulting late 68, or 
plates 7Q and 80, of vol. 4 of the Final Rept. of 'the Geol. and Nat. Hist. 
Survey of Minn. 
