8 THE DEVONIAN OF MISSOURI. 



Devonian, but Devonian formations are absent in many places 

 and in such areas the Sylamore rests on Ordovician formations. 



The Sylamore sandstone and its equivalent, the Phelps 

 sandstone and the Eureka shales are the only formations south 

 of Pettis County that have been referred to the Devonian and in 

 this work they are considered as basal Mississippian. 



Grabau 1 notes the similarity of conditions in the origin of 

 the Grassy Creek shales and the Noel shales of southwestern 

 Missouri, but considers the Noel much younger than the Grassy 

 Creek. However, he reached that conclusion from incomplete 

 data on the relationships of the shales and he was not aware of 

 the wide extent- of the Sylamore sandstone of the same age as 

 the shales. He says: "Whatever the age of the Sylamore, the rela- 

 tionship of the Black shale (Eureka or Noel) to the overlying 

 and underlying formations is clear. It represents a basal bed 

 of an advancing sea, and progressively rises in the scale south- 

 ward from middle Kinderhook to uppermost Kinderhook or 

 lowest Burlington. That this basal bed is such a fine grained 

 rock can only be explained by the assumption that the land 

 was very low, and that the residual soil covering it was clay 

 mixed with much carbonaceous material. In other words, the 

 Noel shale can only represent the reworked residual soil of an 

 old peneplain surface which was slowly submerged beneath the 

 advancing Mississippian sea. Taken in connection with the 

 position of the Black shale at the base of the Louisiana lime- 

 stone in northeastern Missouri, we see that the transgression 

 went on through the entire Kinderhook." 



The Sylamore in central Missouri, in Warren, Montgomery 

 and Callaway counties, is immediately below the Burlington 

 limestone, but is overlapped by Chouteau in patches in the same 

 general area, and the Chouteau comes in between the Burlington 

 and Sylamore from Boone County to near the Arkansas line. 

 In Arkansas the Chouteau is absent and the same relationships 

 exist as in the central district. No general rise in horizon of the 

 black shale is indicated as postulated by Grabau, and the age of 

 Noel shale, Sylamore sandstone, and Grassy Creek shale seems 

 to be practically the same. 



COOPER LIMESTONE 



Historical — The Cooper limestone was first described by 

 Swallow 2 in 1855 under the name or Cooper marble, as follows: 



iBulletin, Geol. Soc. Am., 17, 1906, pp. 598 and 599. 

 •Geol. Surv. Mo., Reports I and II, p. 196. 



