DESCRIPTION OF THE FORMATION 



295 



The specimens for the most part are considerably worn, but a few have 

 been collected which show scarcely any wear. 



At a number of localities the pebbles are cemented into a conglomerate 

 by manganiferous limonite, and at Waukon, Iowa, the linionite is suffi- 



FiGUEE 1. — Map of parts of Ioiva, Illinois, Wisconsin, and Minnesota, showing 

 Distribution of the Windrow Formation 



Sparta-Tomah quadrangles shown by heavy black line. Windrow gravels shown by 

 black spots. Cretaceous areas shown by cross-lining. Distribution of the gravels sug- 

 gests that they were deposited by streams which flowed southwest into the Cretaceous 

 sea. Boundary of driftless area shown by dashed line. 



ciently free from pebbles to be mined for iron ore. The sands which 

 constitute a part of the deposit are mainly coarse grained, poorly assorted, 

 and imperfectly rounded. Wherever bedding has been observed, it is 

 rude and imperfect. Current ripple-marks were seen at one locality. 



