BLUE EARTH COUNTY. 429 



bhakopec limestone.] 



whole bluff being 50 to 75 feet high. The Shakopee limestone, next in geological order above this 

 sandstone, was not found in place on this part of the river, but about six rods northwest from the 

 sandstone outcrop on O. Halberg's land, large blocks of this limestone lie at the base of the bluff 

 beside the river, and have probably fallen from a ledge above; yet the steep, wooded face of 

 the bluff now exhibits only drift. 



Xo fossils have been detected in the St. Lawrence limestone or Jordan sandstone in Blue 

 Earth county. 



Shakopee limestone. This member of the Lower Magnesian series, and 

 the sandstone just described, which it,conformably overlies, both having a 

 very nearly level stratification, together make the rock-bluff's of the Min- 

 nesota and Blue Earth rivers in the townships of South Bend, Mankato, 

 and Lime. Other outcrops of the Shakopee limestone, without exposures 

 of the underlying formation, occur on the Watonwan river at and close 

 below Garden City, and on the Maple and Big Cobb rivers within their last 

 two miles. This limestone has been quarried at many places, and has a 

 high value for building purposes and for the manufacture of lime and hy- 

 draulic cement.* It is mainly a compact and hard, thick-bedded, some- 

 what siliceous dolomite or magnesian limestone, of light buff color, often 

 mottled with slightly contrasted reddish and yellowish tints. The layer 

 which is burnt for lime at Mankato, situated in the upper part of this for- 

 mation, is sparingly fossiliferous.f Professor Winchell, from an examina- 

 tion of the Mankato quarries and of the river bluffs for several miles below, 

 gives the following general section, in descending order::}: 



Section of the Shakopee limestone in Mankato and Lime. 



1 . Porous magnesian limestone, not used 4-6 ft. 



2. Loose, friable sandstone 2-4 ft. 



3. Magnesiau limestone burned for lime 2 ft. 



4. Calciferous sandstone, in heavy beds, of various grain and texture, sometimes 



mottled, quarried for building 30 ft. 



5. Upper shale bed, arenaceous and mottled with red 2-3 ft. 



6. Calciferous sandstone, generally used as a cut stone, compact and even grained, 4 ft. 



7. Rough and irregular magnesisn limestone, somewhat arenaceous, but unfit for 



cutting 10 ft. 



8. Lower shale bed; very much the same as the upper 2 ft. 



9. One heavy bed, generally good for cut-stone, becoming light blue on deep quar- 



rying , 3 ft. 



Id. Irregular and sandy bed; more or less cavernous and porous, with lenticular strati- 

 fication, its lower three or four inches apparently broken; fine-grained, and 

 stained with iron 3 ft. 



11. Jordan sandstone, seen about 45 ft. 



Total of the Shakopee limestone, about 65 ft. 



See the chapter on building stones, p. 166. The quarries of this stone, and analyses of it, are noted in a later part 

 of the present chapter. 



tin the quarries ut Mankato. and e-tpecially in that of the Standard Cement company, which is in the lower part of 

 the formation, a handsome Lingula is occasionally found. This shall is about half an Inch long, of acuminate-ubovalc 

 outline, with concentric striae. 



tSecond annual report, p. 115. 



