82 GEOLOGICAL FORMATIONS. 



tricts to the south assume somewhat different lines from those 

 which have been commonly recognized. 



The geological cross-sections recently made in central Iowa 

 show clearly that the great limestone of Winterset may be re- 

 garded as the base of the "upper" Coal Measures. Coastal 

 sediments carrying workable seams continue up to this line. 

 Above it, open-sea deposits abruptly replace the former, and 

 the coal veins are wanting almost entirely. The great Winter- 

 set limestone is known to extend a considerable distance north- 

 westward from its typical locality, probably soon passing be- 

 neath the Cretaceous. It has been traced to the south nearly 

 to the south boundary line of Iowa. In Missouri it appears 

 to be continued by what is known as the Bethany Falls lime- 

 stone, which sweeps southward and westward in a broad arc, 

 and seems to be represented at Kansas City by one of the 

 leading beds exposed in the bluffs at that place. 



It is proposed, therefore, to divide the "upper" Carbonifer- 

 ous series, or Coal Measures, into : 



(2) The Missouri formation, and 



(1) The Des Moines formation. 



The Des Moines represents the lower Coal Measures, or 

 the marginal deposits of the upper Carboniferous. It takes its 

 name from the Des Moines river, which flows for more than 

 200 miles directly through the beds of this terrane. It extends 

 into Missouri and follows the northern and western boundaries 

 of the Ozark uplift into Kansas and Indian territory. 



T/^elfmoim corresponds essentially with the "upper" Coal 

 Measures, representing the more strictly marine beds. It is 

 the formation typically developed in the northwestern part of 

 the State of Missouri. The Missouri river also winds its way 

 for more than 400 miles through the beds of this stage, expos- 

 ing numberless fine sections on both sides of the stream 

 throughout the entire distance. 



In lithological characters the Lower Coal Measures are con- 

 trasted rather sharply with the great underlying limestone 

 basement, on account of being chiefly argillaceous and arena- 

 ceous sediments. No less striking is the relative thickness of 



