402 



Sources of the Constituents of Minnesota Soils. 



XXIV. Siliceous clay, thought to be Cretaceous iNIankato; 

 Prof. S. R. Peckham. Geol. & Nat. Hist. Survey Minn., Am. 

 Rep., 1880, p. 153. 



XXV. Dark shaly bands Minneapolis building stone, Tren- 

 ton limestone; Prof. W. A. Noyes. 



XXVI. Contact clay between Shakopee limestone and Jor- 

 dan sandstone, mouth of Blue Earth river; Professor C. F. Sid- 

 ener. Geol. & Nat. Hist. Survey Minnesota, nth An. Rep. 1884, 

 p. 181. 



XXVII. Stratum of easily crumbling calcareous rock above 

 the building stone, Minneapolis, Minn., by H. V. Winchell. 



XXV |XXVI |XXVII| Average 



■35 



XXIII XXIV 



Silica SiOa 



Alumina AI2O3 



Ferric oxide FeoO:; 



Ferrous oxide FeO 



Lime CaO 



Magnesia MgO 



Soda NasO 



Potash K2O 



V^ater H^O 



Sulphuric acid SO3 



Calcium carbonate CaCOs . . . 

 Magnesium carbonate MgCO;i 



Organic matter 



MgO with SiO. 



41.71 



34.61 



4.58 



6.88 



1. 16 



0.22 



o.ii 



Trace 



12.69 



70.10 

 16.99 



15.84 

 4.93 

 4.00 



10.69 

 1.98 

 0.23 



56.47 



14.21 



1.26 



0.14 



Total I101.96I 99.99 



96.86 



68.70 



18.04 



1-53 



1.24 

 0.56 

 0.24 

 5.28 

 1.40 



0.09 



97.08 



20.38 

 26.77 



1-57 

 13-74 



0.70 



43- 

 20.27 



2.34 



28.16 

 II. 18 



4.02 



102. 50 j 



The Carbonates. — The last group, or the carbonates, occupy 

 a large area in southeastern Minnesota, and they probably under- 

 lie a considerable area of the Red river valley. At one time, I 

 have no doubt, they covered the entire state as well as Wisconsin 

 and the Dakotas to the right and left, and even Manitoba and 

 Ontario on the north. They are crystalline and firm of texture, 

 and they form an excellent building stone. In composition they 

 contain carbonic acid, lime and magnesia, with small quantities 

 of other plant foods. In the southeastern portion of the state, over 

 some hundreds of square miles, these rocks are not covered by 

 Glacial debris; for there we see a portion of the old Glacial island 

 which lies largely in Wisconsin and Illinois — a tract of land over 

 which the ice did not spread during the period when all the rest 

 of the northwest was buried deep beneath the glacier. In this cor- 

 ner of the state, then, these carbonates by their decay have pro- 

 duced the surface soil ; while by the breaking up of boulders in 

 every other portion of the state they have done their work in soil 



