118 S. CALVIN lOWAX DKIKT 



ing an average width of less than 3 miles begins at Dyersville and extends 

 to a point 5 miles southeast of Farley. The total length of this lobe is 

 about 13 miles, and it shows a number of distinct lobulations, particu- 

 larly at its southeastern extremity. A moderately high ridge of Kansan 

 overlain with loess, less than 3 miles wide, separates the lobe described 

 from another and more slender lowan area which begins near Worthing- 

 ton and continues southeast for a distance of nearly 20 miles. This last 

 area is constricted at one or two points to very narrow dimensions. Rocky 

 cliffs encroach upon the low plain that afforded the opportunity for the 

 extension of the thin ice-lobe, and in passing them the ice-stream was 

 reduced in width to a few hundred j'ards, after which it broadened out 

 again where the surface configuration rendered such broadening possible. 

 Both of the lobes noted blend into the general lowan plain west of the 

 Dubuque county line. 



A short distance north of Dyersville the lowan boundary crosses into 

 Delaware count}^ and follows a very sinuous line to the middle of the 

 north line of the county named, whence it passes with similar windings 

 through the southwest part of Clayton into Fayette, and maintains the 

 same sinuous characteristics through Winneshiek count}^ to the state line. 



RELATION TO MARGIN OF KANSAN ALONG EDGE OF DRIFTLESS AREA 



Along its eastern and northeastern border the lowan ice failed to reach 

 the limit attained by the Kansan, and so a belt of loess-covered Kansan, 

 varying from 1 to 15 miles in width, occurs between the edge of the lowan 

 plain and the Driftless area. The main body of the lowan ice, for ex- 

 ample, halted near the west line of Dubuque county ; only a narrow lobe 

 pushed out in the Dyersville-Farley area, and it stopped just west of 

 Epworth ; but east of Peosta there is a railway cut 35 feet in de^jth in a 

 ridge of typical Kansan drift. 



RELATION TO DISTRIBUTION OF LOESS 



The geographical distribution and physical characteristics of the t^'pical 

 loess of northeastern Iowa suggest genetic relationship with the lowan 

 till. That it was in some way derived from the till when the lowan ice 

 invasion was at its maximum is indicated by many lines of evidence. 

 The main body of the loess is all extra-marginal. Over no considerable 

 area is typical loess ever found resting on lowan drift. It is thickest just 

 at the margin of the region occupied b}^ lowan ice at the time of its 

 maximum development, and is spread widely, but not uniforml}^ over 

 the extra-marginal space to distances at present undetermined. Loess, 

 or a product resembling loess, was developed in connection with more 

 than one drift-sheet, and it is possible that the lowan loess blends into 



