WIKONA COUNTY. 257 



St. Croix sandstone.] 



side. These could not be detached, but resemble very much the Ophileta 

 already mentioned in the report on Houston county. In the same situation 

 was found also the pygidium of a small trilobite. 



The St. Croix sandstone. The examinations made in Winona county 

 add somewhat to the knowledge of the stratigraphic composition of this 

 sandstone that was obtained in Houston county. Its main divisions only 

 can be made out, owing to the concealment of its beds by the uniformly 

 heavy, turfed talus that skirts along the foot of all the bluffs. As nearly 

 as can be stated the following downward section exhibits the stratification 

 of the St. Croix in this county. Some of these parts, and probably most of 

 them, extend, without much variation, throughout the southeastern^ part 

 of the state where this sandstone appears. 



FIG. 11. THE ST. CROIX SANDSTONE. 



General section of the St. Croix sandstone. 



1. Argillaceous, siliceous dolomitic beds, forming the transition layers between the St. Croix 

 and the St. Lawrence. Generally fine-grained, but embracing some thin strata that consist of 

 coarse, loose quartz sand. These embrace a thickness of about forty to fifty feet. 



2. Concretionary sandstone. This has many nodules, and even continuous layers of concre- 

 tionary rock. These lumps are sometimes very fine, no larger than peas, and sometimes they 

 swell out so as to be a foot or more in thickness, constituting nearly continuous layers, and making 

 a very firm rock, since they consist entirely of cemented grains of silica, the cement itself being 



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