Drift of Nortlnvesteni loiva. — Bain. 169 
belong to the earlier ice sheet and the loess-loam was be- 
lieved to belong in age with this earlier drift rather than with 
the moraines.* The loess was mapped as approximately 
bounded by the 1500 feet contour; though with reservations. 
When later, finer discriminations came into vogue, Chamberlin 
considered both the lowan and Kansan to be displayed in the 
region.t The Iowa survey has been disposed to refer the 
whole to the lowant though recognizing that the Kansan is 
present in the region. § 
At its southern extremity the Des Moines lobe of the 
Wisconsin rests on the Kansan. || Along its eastern front as 
far sovith as Hardin county the drift immediately outside the 
moraine is lowan. ^ The over-lap by which the Wisconsin is 
brought to rest on the Kansan is quite extensive and the rela- 
tions between the Kansan and Wisconsin are characteristically 
displayed as far north as Carroll county. In the region north- 
west of that county the relations along the border are not al- 
ways clear and the drift has been considered too young in 
appearance to be correlated with Kansan. So far no Illinoian 
drift has been recognized in the region. The previous ref- 
erences of the drift to lowan seem now unadvisable as a result 
of the observations, yet unpublished, of professor Macbride in 
Humboldt and Dr. Beyer in Story counties. The drift must 
accordingly be Kansan, Illinoian or early Wisconsin. It may 
belong in part to any two of these or indeed all these mav 
be present though the latter is' considered improbable. In the 
course of the last field season certain exposures of apparently 
young drift in Carroll county have been proven to be Kansan 
and it lias been found that many of the criteria which in south- 
ern Iowa and in Illinois allow the ready and secure recognition 
of that drift sheet, partially fail when applied to the region 
in question. 
The Kansan drift, where typically displayed, exhibits a ma- 
*See Winchell, Loc. cit., p. 545. 
tSee plate IV, Geikie's Ice Age (3rd Ed.) 1895. 
JCalvin: Iowa Geol. Surv., vol. VII, p. 20; Bain, Ibid. vol. VI, pp. 
462-463, vol. VIII, pp. 341-351- 
§ Iowa Geol. Surv., vol. V, p. 279, et seq. 
IIRel. Wisconsin and Kansan Drift .Sheets in Central Iowa; Iowa 
Geol. Surv., vol. VI, pp. 433-476. 
•[Iowa Geol. Surv., vol. VII, pp. 174-176. 
