Glacial Deposits in Driftless Area. — Sardesoii. 393 
glacial drift, have been apparently often passed by lightly as 
drift deposits or modified drift, and also, as it would appear, 
the glacial phenomena of the " driftless area " have scarcely 
been considered, and a study of certain ph<Mi()uiena of the 
drifted and driftless areas together will, it is hoped, reveal 
them both more clearly. 
The Loess and Dime Sands. In this " driftless area " the 
uppermost deposit is the loess formation, consisting chietly of 
loess loam. The deposit has been describetl from several 
counties of Minnesota, Iowa and Wisconsin, and is well known 
to be continuous with loess that covers the more ancient gla- 
cial drift surrounding the area. It is not a local deposit. It 
covers nearly the entire " driftless area," although much of its 
extent has been described as residuarj' clay of the disinte- 
grated Paleozoic rocks.* It differs fiom this residuary clay 
structurally, and is separated from it. Outside the '"drift- 
less area," drift intervenes between them. For example, at 
Freeport, Illinois, at the west side of the city in quarries, one 
sees : — 
Loess loam 6 feet 
Loess to (5 feet 
Northern drift thin 
Residuary clay 1 to 2 feet 
Galena limestone 20-|- feet 
Farther north the unchanged loess and the '' northern drift " 
become more and more frequently absent until in the " drift- 
less area " the residuary clay of the loess, loess loam, rests 
upon that of the limestones, as a rule, but the same are always 
distinct. No one has doubted that the residuary clay of the 
loess above the drift is continuous with that described here as 
loess loam of the •' driftless area," although there has been 
confusion as to the origin of the latter. In places where the 
loess loam without loess occurs it is understood that the loess 
has been entirely reduced to loam, and only where a greater 
depth of loess existed does any of it remain. I observed this 
formation particularly in the Peccatonica river basin in south- 
western Wisconsin, where it is associated with some wind- 
driven sands that aid in explaining its origin. 
This sand deposit is abundant in the valley, irregularly 
• *J. D. Whitney, Geo!. Wisconsin, vol. 1 (18G1): Chanihcrlin and Sal- 
isbury, Gth Ann. Rep. U. B. (ieol. Survey, p. 2.'}9. (1885). 
