150 N. H. WINCHELL WAS MAN IN AMERICA IN GLACIAL PERIOD 



occurs broadly about the margin of the ice-sheet when the ice margin is 

 surrounded, or covered, b)^ abundant waters nearly stagnant, the whole 

 drift, and especially the till-producing portions, being then converted into 

 a semi-mobile mass resembling mud. Such a drift is neither loess nor 

 drift, but a " product of the miscegenation of ice and water," a hybrid 

 which has no name, but whose parentage is well known. 



As to the relative date of this deposit at this place, the presumption 

 is that it was the product of the lowan stage of the Glacial period. It 

 is in the valley of the great river where characteristic and long-known 

 bodies of the loess exist, and near the bottom of that deposit. It shows 

 none but the features of the loess — even the pebbly composition having 

 been noted by Udden* in Pottawattamie county, Iowa, which adjoins 

 the Missouri river on the east. Calvin, reporting on the geology of Page 

 county, t bas briefly outlined the method of deposition of the alluvial 

 loess of the Missouri valley during the lowan stage in these words, which 

 apply exactly to the Lansing locality : 



" While the lowan ice-sheet did not come within miany miles of Page county, it 

 may have invaded the upper part of the Missouri valley, and so have contributed 

 volumes of water loaded with a laro^e amount of fine yellow mud which, following 

 the Missouri and backing into the tributary valleys, produced the effects observed." 



It is in this loess sheet that Udden reports, along with numerous 

 species of terrestrial mollusks, two species of Limnea and one of Unio. 



This conclusion is that which is arrived at on the face of the facts. 

 It is a priori the true one, since it involves the facts and accounts for 

 them in accordance with what is known of the Pleistocene geology of 

 Iowa and Kansas and violates none that are known elsewhere. 



A L TERN A TI VE H YPO THESES 



If it be desired to further test this, and to suggest outre h3^potheses 

 more or less plausible, we may consider the following : 



1. That the skeleton was buried by wind deposits, the materials having 

 been brought from the valley of the river by dust storms. It is sufficient 

 to point to the pebbles that are found in the loess, some of them being 

 3 or 4 inches in diameter and arranged in horizontal bands. 



2. That the materials overlying the skeleton were brought to their 

 present position by the joint action of the Missouri river and the small 

 stream which joins the Missouri hard by, during some post-glacial flood 

 stage of the Missouri. This hypothesis will require that since the Wis- 

 consin glacial epoch the Missouri has deposited at this height a sub- 



* Geological Survey of Iowa, vol. 11, p. 260, 19()1, 

 fOp. eit., p. 448. 



