PKOCEEDINGS OF THE SAINT LOUIS MEETING 



ing of Prionocyclas wyomingensis* a Benton fossil, above the so-called Niobrara, 

 near Hawarden, Iowa, and also by the discovery of marine fossils far below the 

 top of the supposed Dakota, near Woonsocket, South Dakota. 



Original Missouri River Section Reexamined 



The writer has repeatedly visited scattered exposures along the Missouri river 

 and has hitherto accepted without much question the interpretations of Meek and 



Hayden, who first classified the Creta- 

 ceous rocks of the region and named 

 them. He had extended those inter- 

 pretations to areas in the James River 

 valley, which he has studied more care- 

 fully. 



Last July, at the request of Mr Darton, 

 he spent several days in company with 

 Mr G. E. Condra, of Nebraska Univer- 

 sity, in making a comprehensive review 

 of the section along the Missouri river 

 from near Homer, Nebraska, to the 

 mouth of the Bow river, in Cedar county, 

 Nebraska. We found the only difficulty, 

 and that not a great one, near the old 

 site of Ionia, in Dixon county. There 

 the chalky limestone, which is promi- 

 nent on the top of the bluffs near Ponca, 

 steals beneath the river in a talused 

 bluff; so that, like others, we at first 

 overlooked it and had to return to dis- 

 cover what had become of it. Its top 

 was nearly hidden at the water's edge 

 at the Ionia ferry. With this exception 

 the whole section seemed clear, the only 

 uncertainty being in the thickness of the 

 formation, which appears to increase ir- 

 regularly toward the northwest. 



Besides this the writer has since re- 

 connoitered the Minnesota valley from 

 Marshall, Minnesota, to Sisseton, South 

 Dakota, and studied with some care all 

 the Cretaceous exposures along the Mis- 



Figuke y— Extent of Benton under Drift in eastern souri and Big Sioux rivers and Brule 

 South Da/iota. , . ,, -r^n ^ • , j i 



creek in the Elk Point quadrangle. 



We will first give our results concerning the general section, then compare it 



with the interpretations of previous students of the region, and afterward give the 



distribution of the Benton throughout the eastern part of South Dakota. 



Results 



A. The three members of the Benton found along the Rocky mountains appear 

 also on the Missouri river, as the following combined section shows. 



♦IowaGeol. Survey, vol.10, p. 114, 1899, 



