400 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



deep road or valley sections where the two drift sheets are con- 

 tiguous and, (3) the small relative value of well logs. Investiga- 

 tion was carried on some distance back from the Wisconsin border, 

 well within the Wisconsin, drift plain. Well logs were examined 

 carefully, where possible to secure them, public road sections, rail- 

 way cuts and river valley sections were studied, with the result that 

 not a single instance was obtained where it can be affirmed posi- 

 tively that lowan drift exists beneath Wisconsin drift. 



The eastern line of demarcation between the lowan and Wis- 

 consin drift sheets was studied carefully and, where possible, all 

 evidence was applied to determine any errors. For great distances 

 the margin can be detected by the striking difference in the topog- 

 raphy of the two drift sheets. From the northern border of Worth 

 county, to Hanlantown, Danville township, the line between the 

 two drift sheets is not pronounced except to the northwest, west 

 and southwest of Northwood. In this vicinity, the Wisconsin bor- 

 der is characterized by a prominent terminal moraine, which meets 

 the level lowan drift plain very sharply. This sharpness is em- 

 phasized by the absence of any outwash. Elsewhere in the county 

 the Wisconsin drift margin meets the lowan drift plain in a greatly 

 softened topography so that it becomes more difficult to outline 

 definitely the border of the Wisconsin drift. The lack of reliable 

 well logs and drift sections of sufficient depth, makes the location 

 of the margin difficult. Many well logs were examined, some to the 

 east of the mapped margin, and others to the west of the margin. 

 Many of the wells to the west of the Wisconsin margin are shal- 

 low and are of no value. The following well log was secured west 

 of Kensett, Kensett township, and is quite typical of many others 

 examined east of the Wisconsin margin. 



Feet Inches 



1. Black soil 1 to 2 



2. Clay, yellow, noncalcareous , . . 8 .... 



3. Clay, blue, calcareous 23 .... 



4. Sand and gravel 4 to 6 



5. Clay, blue, highly calcareous 30 .... 



6. Sand and gravel 6 



7. Bed rock. 



The well records reveal two drift sheets to the east of the Wis- 

 consin border. The upper drift sheet is unquestionably lowan, and 

 the lower is probably Kansan. 



In the vicinity of Hanlantown, the Wisconsin border should be 

 extended eastward as shown in figure 117. 



Here may be found good evidences of outwash and lake deposits 

 which are unquestionably of Wisconsin age. The upper terrace 



