Artesian Well Boring in Southeastern Minnesota — Hall. 133 



limestone* at Shakopee and Louisville, where a terrace is made by 

 the upper part of the Shakopee limestone, and between Kasota anc! 

 Mankato. The three divisions may be called, in descending order: 



1. Shakopee or Lower Magnesian limestone A. 



2. Elevator B sandstone. 



8. Shakopee or Lower Magnesian limestone B." 

 Well-borers have not found the Elevator B sandstone in other 

 wells bored in this valley, although from Mr. Upham's statements 

 we may suppose it to be spread very widely through this Upper 

 Cambrian dolomite. 



8. The Shakopee B. — It need only be mentioned here that 

 this layer is essentially the same in lithologic characters as number 

 six and has already been described in Mr. Upham's own words. 



9. The Jordan Sandstone. — Beneath Upham's Shakopee 

 B layer which at Elevator B is a ''buff magnesian limestone, 55 

 feet in thickness," lies the Jordan sandstone. This formation is 

 almost identical with the St. Peter and Elevator B sandstones in 

 lithologic characters. "It is 116 feet thick at East Minneapolis, 

 103 feet at Elevator B, and 95 feet at Hastings. It has a wide dis- 

 tribution in the Mississippi valley, occurring in Missouri as the 

 Second sandstone of Swallow, 115 feet thick, and in Wisconsin as 

 the Madison sandstone of Irving, in thickness from 35 to 60 feet. 

 The white, evenly granular, medium textured, easily crumbling 

 Jordan sandstone is found at Jordan, St. Peter, Kasota, Mankato 



*Mr. Upham calls this rock a limestone in conformity with the usage of 

 Keveral other geologists. Analyses by Professor Dodge and Mr. Sidener 

 give from 54.78 per cent, calcium carbonate and 42.53 per cent, magnesium 

 (carbonate in the building stone at Frontenac to 50.68 per cent, and 33.61 per 

 cent, respectively, in the Red Wing stone. As a mean between those two 

 extremes the following analysis of the rock at Ottawa made for the writer 

 by Professor Dodge in January 1886. is given: 



Carbonate of lime. Ca CO, 50.-J6 percent. 



Carbonate of magnesia, Mg CO, 36.26 " 



silica, Si O2 8.58 "■ 



Alumina, AL O3 3.18 " 



Peroxide of iron, Fe2 O3 1.72 '* 



Soda and potassa traces 



Chlorides, Sulphates and phosphates traces 



Total 100.20 



Amount of the stone not soluble in hydrochloric acid, 10.61 per cent. 



Consisting of Si Oj 8.50 percent, 



" AlgOj... 2.00 



*' Fe^ O3 traces 



Since a typical dolomite has the proportion of 54.35 per cent, calcium 

 carbonate and 45.65 per cent, magnesium carbonate, and Dana's list of analy- 

 ses of the mineral dolomite (System of Mineralogy, 5th edition, p. 683) shows 

 a greater variation from the type than do the analyses of Professor Dodge 

 and Mr. Sidener, there can be no serious objection to calling these beds 

 dolomites or dolomitic limestones. 



