THE LOESS AND THE LANSING MAN. 34 1 



less merged into one. With onr present knowledge it is cer- 

 tainly impossible to correlate southern loess, or any part of it, 

 with any particular drift-sheet. 



The seventh proposition, that loess and drift intergrade, is 

 emphasized by Winchell* for the purpose of showing that the 

 loess was deposited under glacial conditions. To judge from 

 his statement there is no clear distinction between the two 

 deposits, yet the statement that loess can be "in most cases cer- 

 tainly identified by student and layman alike 1 ' is just as true 

 as it was when McGee wrote it. It is true that at some 

 points, especially along the border of the Iowan drift, sand is 

 more or less mingled with the base of the loess and that us- 

 ually the line between the loess and the drift is not absolute- 

 ly sharp, but this is precisely what would be expected under 

 the aeolian hypothesis. The recession of the glaciers left the 

 surface covered with till, boulders and sand. Along the drift- 

 borders, and especially along the streams near the Iowan bor- 

 der, there were ridges of overwashed sand presenting sand- 

 dune conditions perhaps not unlike those which now prevail 

 along the Missouri, near Missouri Valley and Modale, la., and 

 Blair, Neb., or along the Platte river near Fremont, Neb. As 

 soon as a vegetation, at first scant, gained a foothold, dust was 

 retained more or less, but for a time stronger winds, perhaps in 

 drier seasons, would occasionally sweep sand over the plant-cov- 

 ered areas, and a mingling of sand of different degrees of fine- 

 ness, and of dust, was the result. As vegetation gained a bet- 

 ter foothold over larger areas these incursions of sand became 

 less frequent, and finally ceased. Such mingling of sand and 

 fine soils may be observed today at the localities named, and 

 fine illustrations may be seen along the road leading east from 

 West Point, Neb., where sand and loess, evidently wind- 

 blown, are interstratified in various ways. At one point along 

 this road fossiliferous loess has been covered by wind-blown 

 sand in comparatively recent years. That the fine sands at 



*Bull. Geol. Soc. of Am., vol. 14, pp. 141 -J; Am. Geol., vol. xxxi, 



pp. 279-282. 



