114 IOWA ACADEMY OF SCIENCE 



gradually lost sight of. Whenever reference is made to the up- 

 permost member of the succession it is called the Kinderhook 

 limestone 8 . 



Singularly enough, since Swallow's time, the Chouteau lime- 

 stone in its original locality has never been carefully studied. 

 Few persons have taken the opportunity to inspect the type- 

 sections. The eastward attenuation of the formation, in eastern 

 Missouri, where it again reaches sky after burial in a broad syn- 

 cline, has made the terrane appear to be an unimportant mem- 

 ber of the so-called Kinderhook section. 



In recent years a large number of deep-well records enables 

 the underground extent and thickness of many formations in 

 Missouri and Iowa to be accurately traced and determined far 

 from their lines of outcrop. Among the terranes of this class, is 

 the Chouteau limestone. The data bearing upon its stratigraphic 

 relations permit it to be clearly delimited from Minnesota to 

 Arkansas, a distance of more than 600 miles, As a definite litho- 

 logic unit and a sharply delimited terrane the Chouteau lime- 

 stone presents some features of more than local interest in gen- 

 eral geologic correlation. 



At the original locality, at Chouteau Springs, central Missouri, 

 and at neighboring places in Saline, Cooper and Pettis counties, 

 the interval of 125 feet between the undoubted Devonian Calla- 

 way limestone and the Early Carboniferous Burlington lime- 

 stone is occupied by grey limestones. This circumstance leads 

 Professor Stuart Weller 9 to regard the original Chouteau sec- 

 tion as representing the entire Kinderhook succession of other 

 parts of the Mississippi valley. Swallow 10 from the first recog- 

 nized the fact that the entire section of his "Chemung" (Kinder- 

 hook) group, which in other parts of Missouri is a three-fold 

 division, is in the central portion of the state an unbroken se- 

 quence of limestone layers. Nevertheless?, he considers 11 the lower 

 twenty feet as the Lithographic (Louisiana) limestone division; 

 and the middle part as replacing the Vermicular (Hannibal) 

 shales of elsewhere. 



Recent observations show r that Swallow is mistaken only in a 

 single point. Not finding the Vermicular shales in distinct de- 

 velopment in Cooper county as elsewhere he assumes them to be 



s Iowa Geol. Surv., Vol. I, p. 56, 1893. 

 9 Bull. Geol. Sop. America, Vol. XX, p. 321, 1909. 

 "Missouri Geol. Surv., 1st and 2d Ann. Repts., p. 195, 1855. 

 "Ibid., p. 103. 



