200 Kansas Academy of Science. 



EOLIAN LOESS. 



J. E. Todd. 



OF LATE YEARS numerous writers have supported the 

 view that the mass of the yellow loam of the Missouri 

 and Mississippi river valleys is of eolian origin. Some text- 

 books define loess as an eolian deposit without qualification. 

 While the writer cannot harmonize this extreme view with the 

 facts known to him, he would enumerate several cases which 

 are unquestionably the work of the wind. 



He would first call attention to the conditions productive of 

 sand dunes in certain localities; secondly, show that the ac- 

 cumulation of dust is often to be explained in similar ways ; 

 thirdly, note one locality which can be explained in no other 

 way; and fourthly, explain the modus operandi of such de- 

 posits generally. 



1. South of the Platte river, near Kearney, Neb., is a strip 

 of conspicuous dunes crowning the bluffs and rising above the 

 upland level further south. The sand apparently has been 

 raised by the northwest wind from the river channel just north. 

 Moreover, the greater accumulation there may be accounted 

 for by the fact that the river above this point has a south- 

 easterly course for several miles and there changes to due 

 east. 



2. Another cluster of dunes, rising above the general level 

 around, occurs east of West Point, Neb., where the Elkhorn 

 changes sharply from a long southeasterly course to a south- 

 erly. In both of these cases the northwest wind is considered 

 particularly instrumental, because it prevails at a time when 

 the river is low, the bars extensively uncovered and the vege- 

 tation elsewhere scanty. 



3. We now call attention to accumulations of finer material 

 — in other words, loess — in analogous situations along the 

 Missouri river. In these cases there is very little sand avail- 

 able, and only of a fine grain, and the bluffs are much higher 

 than those already considered. The general course of the 

 river is south-southeast from Sioux City to northern Mis- 

 souri. The bottom lands on the east of the river are in places 

 very wide. These occur where soft rocks lie at the level of the 

 river. On the contrary, where harder strata at that level have 



