332 



NOTES UPON THE GEOLOGY OF SOME PORTIONS OF MINNESOTA, 



the Big Cottonwood River, there is an exposure of rock in the hank of the stream ; and 

 at a short distance further on, some explorations had been made for coal, and a shaft had 

 been sunk to the depth of more than one hundred feet. The materials thrown out of this 

 shaft consisted of a dull greenish argillaceous sand, with calcareous nodules, together with 

 irregularly laminated sandstone containing vegetable remains. The order of deposits, as 

 given to me by Mr. Morin, who superintended a part of the working, was as follows : 



t $*^ 





is=m 



1. Ironstone; 1 ft. inches. 



— 2. Sand, clay, etc. ; 40 ft. 



3. Earthy coal ;* 1 ft. 8 inches. 

 I Sand, clay, etc. ; 3 ft. 



5. Sandstonem irregular and diagonally laminated layers, with sometimes calcareous concretions, 



and containing plant remains ; - r > ft. 



6. A calcareous sandy clay of variable color and character ; 20 ft. 



7. Sandstone in loose thin layers of threo or four inches ; 4 ft. 



8. Clay with coaly seams near tho bottom ; 10 ft. 



9. Clay ; 13 ft. 



10. Loose quicksand to bottom of shaft. 



In the river bank, at a quarter of a mile distant, and at a level 30 or 40 feet below the 

 ground where the shaft began, there is the following exposure : 



1. Loose ironstonef in nodules and irregular concretions, more or Less mixed with drift and pebbles ; 1-2 ft. 



2. Calcareous clay ; 6-8 ft. 

 8. Earthy coal ; 8 inches. 



4. Clay as above coal ; 4 inches. 



5. Yellow or ferruginous sand and clay; 3-3^ ft. 



6. Ferruginous sandstone in irregular layers and diagonally laminated, to level of river; thickness unknown. 



This sandstone appears to be the same as that containing plant remains met with in 

 the shaft ; and though I did not find plants in it at this point, I was informed that speci- 



* An analysis of this coal, by Prof. T. Stcrry Hunt, gave the following results: 



Fixed carbon, . 26.1 



Volatile matters, ..... 25.7 



Ash, . 48.2 100.0 



In the sections of strata near the mouth of the Redwood River, there is a stratum of similar earthy coal throe 

 feet thick. • 



f This ferruginous layer docs not appear to belong to the regularly stratified deposits, as it overlies, irregularly, 

 the edges of the successive beds, and has been deposited after the denudation had taken place. 





