THE FLORA OF THE ST. PETER SAND- 

 STONE IN WINNESHIEK 

 COUNTY, IOWA 



By B. Shimek 



Read before the A. A. A. S. at St. Louis, Mo., Dec. 20, /903 



The exposures of St. Peter sandstone in Iowa are limited 

 to Winneshiek, Allamakee, Clayton and the extreme north- 

 eastern part of Dubuque counties. They are found in large 

 part along the bluffs which border the deep, narrow valleys 

 of the streams of this part of the state, but in some portions 

 of the area they are remote from streams, being then found 

 along the borders of depressions which were evidently formed 

 by the erosion of large quantities of the sandstone. 



In Winneshiek county this sandstone is exposed only in 

 interrupted areas along the Oneota river below Decorah, and 

 along Canoe creek, where it forms portions of the bordering 

 bluffs, and in several localities in the extreme northeastern 

 part of the county, notably near the state line, where the 

 exposures are evidently remnants of formerly extensive de- 

 posits, or the visible margins of sandstone strata now buried 

 under geest, or drift, or loess. 



The St. Peter sandstone of Allamakee county, which lies 

 east of Winneshiek, has been described as follows: * 



"The formation is made up almost entirely of water-worn 

 grains of quartz. ***** ^^ e 5 a { n t Peter sandstone 

 is in some places practically as incoherent as when the beds 

 were first laid down in the Ordovician sea. In portions 

 exposed to the weather for some time the constituent sand 



* Calvin, S. , Iowa Geol. Sur. , vol. IV, p. 69 ; 1895. 



