128 THE GEOLOGY OF MINNESOTA. 



[Soils and subsoils. 



latitude, by the black pine (Pinus Banksiana), and in the plains of modified 

 drift isolated from the rivers, as well as in the rolling gravelly (and stony) 

 parts of the Leaf hills moraine. The same subsoils, but more fine, may be 

 said to exist where the loess-loam of the southeastern part of the state 

 becomes so sandy as to show very little clay, as in the upper part of the 

 high terrace below St. Paul, and the terrace flat on which Minneapolis is 

 situated. This is also seen in much of eastern Dakota county, in northern 

 Ramsey and in Anoka counties. 



Subsoils of clay or clay-loam are found, especially, in the lacustrine areas 

 of the Red river of the North, and of the Mississippi below Red Wing, also 

 in some of the flats of the lower St. Louis and upper Mississippi. In south- 

 ern and western Rock county, also, the subsoil passes from a blue till to 

 pebbly and finely stratified clays, and these constitute a subsoil of this class. 

 The soils based on these subsoils, possess the characteristics of the till upon 

 which the clays lie, and from which they may be derived, but in a modified 

 and much lessened degree. The alkaline till of the Red river region is 

 due to the immediate disintegration of the marine Cretaceous, but the clays 

 forming these subsoils are a fresh-water deposit; and in the act of deposi- 

 tion a considerable part of the soluble alkaline ingredients of the country 

 till were carried by drainage to the ocean. The pebbly clay subsoil, how- 

 ever, of Rock county, is not so markedly different from the till subsoils 

 of the region, in these chemical qualities. In the northwestern part of the 

 state these subsoils spread eastwardly to the lake of the Woods, and along 

 Rainy river to Rainy lake, including very much of the Red lake and Pembina 

 Indian reservations; but toward the south the distinctive characters of the 

 clay subsoil are confined to a narrow belt on the east side of the Red river of 

 of the North, and disappear entirely at Traverse lake. The clay subsoils can 

 easily be distinguished from the blue till subsoils of the same valley, ^ince 

 where they prevail no stones or boulders appear on the surface. These are seen 

 scatteringly in passing eastwardly upon the subsoils of till. Subsoils of this 

 class in the northeastern part of the state are found in the St. Louis valley, 

 below Fond du Lac, and above Knife falls. The flats of the East Savannah 

 river, and of Leech Lake river are based on a clay subsoil. In the south- 

 eastern part of the state the soils of the loess-loam are based on a clay 

 subsoil, though sometimes this is too sandy to be styled clay. Such are 



