336 



NOTES UPON THE GEOLOGY OF SOME PORTIONS OF MINNESOTA, 



is a concretionary limestone of peculiar character, cropping out about fifty feet above the 

 river level, and abutting directly against the outcropping edges of the quartzite, as shown 

 in the section. 



a. Gray and reddish -gray quartzites, with 

 obscure lines of bedding, and numerous 

 vertical joints. 



b. Purplish or reddish quartzites, becoming 

 brick-red, and thinly laminated below. 



c. Concretionary limestone, horizontally 

 stratified, and lying against the uplifted 

 edges of the quartzites. 



d. Red and variegated marls. 

 R. River level. 



On the west side of the Minnesota, below or south of the mouth of the Cottonwood, I 

 found a horizontally stratified red and variegated marl, with thin interrupted layers of con- 

 cretionary limestone. 



1. Soil of bottom prairie ; 2 to 4 ft. 



2. Red clay with calcareous concretions ; 4 ft. 



3. Rod marly sandstone with calcareous concretions in continuous layers ; 10 ft. 



Half a mile below this point, on the farm of Mr. Winkleman, I obtained the following 

 section : 



1. Soil of bottom prairie; 2 to 4 ft. 



2. Concretionary limestone in irregular layers, with seams of clay or marl; 10 ft. 



3. Greenish or red marl ; I ft. 



4. Heavy-bedded concretionary limestone ; 2 ft. 



5. Marl, green and reddish, with concretionary layers to river level. 



C. Continuation of red marls and concretionary limestone layers to the depth of 05 feet from the surface, as deter- 

 mined in the digging of a well. 



A well dug at a little distance from the margin of the river, sixty-five feet deep, pene- 

 trates the limestone and ends in the red marl and sandstone below the level of the river. 



The plateau or river bottom is about three-fourths of a mile wide, and comparatively 

 very level. Beyond this the country rises in a pretty abrupt slope to the level of the 

 high prairie. About five miles west of New Ulm, and seven or eight miles above the 

 mouth of the Cottonwood, and where the river flows in a depression considerably below 

 the level of the high prairie, I found the ferruginous sandstone,* with coaly matter in the 



* This locality was pointed out to mo by Mr. Back, who has proved himself a good observer of the country over 

 which he has travelled. 



