Eolian Loess. 201 



resisted the erosion of the stream, the valley is narrow and as 

 a consequence high bluffs rise conspicuously on the east side of 

 the valley just south of the wide areas first mentioned. Be- 

 cause of the relations described above, such projections of the 

 east bluffs are apt to grow in height till they rise considerably 

 above the upland level further east. 



A typical case of this sort is found four or five miles south 

 of Pacific Junction, in southwestern Mills county, Iowa. 



Another is north of Council Bluffs and south of Crescent 

 City, and another lies east of the Little Sioux, in southern 

 INIonona county. The gathering ground for this last was a 

 bottom land twelve to fifteen miles wide; consequently the 

 bluffs are unusually high. 



4. A somewhat different case is found in southern Ply- 

 mouth county, east of the Big Sioux river, and of a broad 

 bottom land between that stream and the Missouri further 

 west, and of the bend in the latter stream, where it changes 

 from an easterly direction to the south-southeast. 



Dr. H. F. Bain, in his report on Plj^mouth county, called 

 attention to the peculiarities of this area. (Iowa Geol. Rept., 

 vol. viii, p. 322.) The region shows the divides rising 250 

 to 300 above the streams and 60 to 100 above the upland level 

 on the east and north. This extra height seems to be due to 

 recent deposition over the whole surface. The valleys are so 

 narrowed that the streams can barely keep their courses. 

 The boundary on the northeast is a line running from West- 

 field to Millinerville. He thinks it may be plausibly referred 

 to the sweeping of dust from the broad flood plain west by the 

 wind. The writer approved that view in his report on part of 

 the same area in the Elk Point Folio, of the U. S. Geological 

 Survey, 



5. Crowning the highlands in northern Nebraska, which 

 constitute the divide a few miles south of the Missouri river, 

 are high ridges of loess, beginning as conspicuous headlands 

 at the northwest ends, and running southeast and widening 

 till they coalesce in a general sheet, it may be th^t they are 

 remnants of an area similar to that just described, which 

 formerly accumulated south of the Missouri and lower lands 

 of South Dakota, as the former did on the east. The gathering 

 ground for that older deposit was the surface succeeding the 

 Kansan stage of the ice age, while that for the Plymouth 

 •'lunty area was succeeding the Wisconsin stage. 



