CHAPTER XVIII. 



THE GEOLOGY OF PIPESTONE AND ROCK COUNTIES. 



BY N. H. WINCHELL.* 



Situation and area. These counties are in the extreme southwest cor- 

 ner of the state, Pipestone county lying north of Rock. They are named 

 from the appearance of the Potsdam quartzyte, the former containing the 

 famed region of the "red pipestone quarry," and the latter an extensive 

 area in which the same quartzyte appears at the surface, and constitutes 

 its most marked topographic feature, in "the mound" near Luverne. Rock 

 county contains 308,910.15 acres, of which 1,174.04 are covered by water ; 

 and Pipestone has 296,493.51 acres-, including 611.76 covered by water. 



SURFACE FEATURES. 



Natural drainage. With, the exception of a small area in the north- 

 eastern corner of Pipestone county, on the east slope of the Coteau, mostly 

 drained by the Redwood river, in which also is found the ultimate source 

 of the Des Moines river, the whole of these two counties and portions of 

 Nobles and Jackson are drained by streams that reach the Missouri river, 

 these being the only waters in the state that take that course to the sea. 

 The Rock river is the main stream, and runs from north to south through 

 both counties, receiving several tributaries from the east, but none of 

 importance from the west. Several streams, rising not far west of the 

 valley of Rock river, flow westward and southwestward and finally reach 

 the Missouri by way of the Big Sioux river, near Sioux City, in Iowa. These 

 are the Flandreau, Pipestone, Split Rock, Beaver and Mud creeks. These 

 streams are all small, and in the summer some of them are rather valleys, 

 with occasional pools of standing water, than living streams. They furnish 



'Including copious notes by Mr. Upham. Compare, also the sixth annual report. 



