276 C. R. KEYES — DEVONIAN- INTERVAL IN MISSOURI 



the Argillo-calcareous group of Burlington and Hannibal he fancied 

 that he recognized the Chemung of the east.* He had already traced 

 the Devonian formations westward from New York to the Mississippi 

 river. 



The determination of the Devonian age of the shales at the base of the 

 section at Burlington and at Hannibal did not rest on observations at 

 these points alone. There was a correlation of these beds with litho- 

 logically similar beds farther to the northward, at Muscatine and in 

 northern Iowa, where there was obvious association with undoubted 

 Devonian limestones. Singularly enough, after 40 years of discussion, 

 Hall's correlation and assignment of Devonian age to the strata are 

 again beginning to be demonstrated to be correct. At no time in all 

 this prolix controversy did Hall himself abandon his early views regard- 

 ing the Devonian age of these shales which have until lately been gen- 

 erally called the median member of the Kinderhook. 



SWALLOWS VIEWS 



With the aid of Meek and Shumard, the first state geologist of Mis- 

 souri recognized in his state, immediately beneath the great Encrinital 

 limestone, a three-fold terrane which he referred to the Chemung divi- 

 sion of the Devonian. f 



Swallow introduced a new member into the succession as reported 

 from the Mississippi river, calling it the Chouteau limestone. In cen- 

 tral Missouri this limestone attains a maximum thickness of more than 

 100 feet. No one would suspect from examinations along the Missis- 

 sippi river that such an important formation existed at the base of the 

 Burlington limestone ; hence it is not very strange that the geologists 

 who had only seen the river sections gave the dozen feet of earthy 

 limestone at the bottom of the Burlington so little consideration. 



Meek found the Chouteau limestone in the original locality to contain 

 many Carboniferous types of fossils. Their great resemblance to those 

 in the limestones above had from the first a tendency to shake his faith 

 in the Devonian age of the so-called Chemung beds. X In his later re- 

 port^ on Saline county, the next year (though not published until seven 

 years later) he is fully convinced that the Chouteau limestone should be 

 associated with the Carboniferous rather than with the Devonian. It 



* Geology of Iowa, vol. i, 1858, p. 88. 



Trans. Assoc. American Geol. and Nat., 1843, p. 267. 

 f Missouri Geol. Survey, 1st and 2d Ann. Repts., 1855, pt. i, p. 103. 

 % Missouri Geol. Survey, 1st and 2d Ann. Repts., 1855, pt. ii, p. 103. 

 I Ibid., \&tt--"l\, 1873, p. 160. 



