EXPOSURES OF IOWAN AND KANSAN ( ?) DRIFT, EAST OF 
THE USUALLY ACCEPTED WEST BOUNDARY 
LINE OF THE DRIFTLESS AREA. 
BY ELLISON ORR. 
McGhee, in the map accompanying his Pleistocene History of 
Northeastern Iowa, makes the “Upper Till” overlap the “Lower 
Till.” And the eastern boundary line of the “Upper Till” (Iowan), 
as shown by the same, and consequent western boundary line of the 
Driftless Area, in the counties of Winneshiek, Allamakee and Clay- 
ton, the three northeastern counties of Iowa, begins at the boundary 
line of Clayton County about six miles south of the mouth of the 
Turkey River, and runs thence northwesterly at about that distance 
south of the Turkey, to West Union in Fayette County, and from 
there runs nearly due north at about an average distance of six 
miles from the west boundary line of Winneshiek County, to the 
state line. Leaving all of Clayton but about half of the southwest 
township, all of Allamakee, and the eastern three-fourths of Winne- 
shiek in the Driftless Area. 
On The Preliminary Outline Map of the Drift Sheets of Iowa, 
1900, opposite page 372 of Grasses of Iowa, a Supplementary Re- 
port of the Iowa Geological Survey, this boundary line is given ap- 
proximately the same as by McGee. A little more of the south- 
west part of Clayton,— about equal to four townships, — is repre- 
sented as being covered by the Iowan, and instead of covering 
the west one-fourth of Winneshiek County the Iowa Report makes 
the same formation cover only the southwest corner. 
During the past few years the writer’s business has made it nec- 
essary for him to drive over most of the main roads north of the 
Turkey river in the three counties named. The country is. rolling 
and in places rough. Owing to the rapid erosion of the hillsides 
where not grassed over, roadside ditches of great depth are com- 
mon in the more hilly portions, affording excellent opportunities 
to study the Pleistocene formations. Our observations show that 
modified and apparently unmodified deposits and other evidences 
of drift occur over nearly all of Clayton and Winneshiek counties, 
and over about one-fourth of Allamakee. The deposits noted were 
almost without exception originally buried under a heavy mantle of 
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