284 



WINTHROP P. HAYNES 



Madison limestone: The lower formation has been named by 

 Dr. Peale 1 the Madison formation and was subdivided by him into 

 three members; (1) the Laminated limestones at the base; (2) 

 Massive limestone in the middle, and (3) Jaspery limestone at the 

 top. The thickness of the Madison formation near Logan is about 

 1,300 feet. Although it forms conspicuous gray cliffs along the 

 ridge west of the Missouri River, its best exposures are seen where 



Fig. 10. — Missouri River in canyon in Madison limestone 



the river has cut a deep canyon through it near Lombard, and also 

 in the smaller canyon along Sixteenmile Creek,, east of Lombard 

 (Figs. 10 and n). • 



A large collection of fossils was made by the writer from the 

 Madison formation in all parts of the region. These fossils all 

 pointed to the general Lower Mississippian age of the Madison 

 limestone. 



Quadrant formation: Lying in apparent conformity upon the 

 Madison limestone in this region is the Quadrant formation which 



1 A. C. Peale, op. tit., p. 33. 



