394 The Arnerican Geologist. December, I8ii7 
distributed above tlie Hood plain of the river and upon the 
slopes. It is a loose sand made up of rounded quartz grains 
and some impurities, and shows no bedding, except where 
runsliavt^ waslied across it duringits accumulation. Tiie sand 
has been derived from the Saint Peter sandstone evident]}^ in 
this valley. The river has cut a wide valley through the Ma- 
quoketa shales and Galena limestones, through the Saint Peter 
into the Shakopee formation and in many places into promi- 
nences of the Oneota dolomite, so that the Saint Peter sand- 
stone borders the valley on both sides for 80 miles. We have 
no reason to doubt that the loose sand has been derived chiefly 
from the Saint Peter, especially since no other probable or 
possible source is known. I do not know that anyone has 
ever distinguished this sand from the Saint Peter, heretofore. 
When it rests upon that formation it is distinguished by its 
entirely loose structure and by impurities, and by polished 
concretions of iron, and polished blocks of Saint Peter sand- 
stone or b}^ chert fragments that lie upon the once denuded 
surface of sandstone upon which the sand now rests. That 
the loose sand is not mere residuum of the Saint Peter is 
proved by the fact that it often extends upwards over the 
Beloit and Galena formations which overlie the Saint Peter. 
This is seen well near Argyle, LaFayette county. Again loess 
loam instead of the sand often covers areas of St. Peter sand- 
stone. 
It is a wind driven sand deposit contemporaneous with tli<* 
loess from which the loess loam resulted, and into which the 
sand graduates in many places on the slopes of hills. I can 
not otherwise explain it, than as wind driven sand because 
the sand grains have been driven up hill in many cases, and 
up the valley, or north instead of down it; because the sand 
shows general lack of sorting; and because it includes here 
and there assorted sand where small temporary streams have 
crossed it during its accumulation, showingthatit was aland 
area. The gradation from sand into loess ascending the 
slopes, without any stratification reminds one not at all of 
water action. Where the valley is open to southwestern 
winds, there especially the upward trans])ortation of this sand 
has obtained. 
The thickness of the sand is from to 20 feet. The loess 
