DEVONIAN PROBLEMS 269 



there are very good reasons for the lack of exact information concerning 

 the Devonian of the region. 



Devonian Problems presented 



Irrespective of the actual geological age of the several parts of the 

 interval deposits represented in the Mississippi valley, there arise a num- 

 ber of questions which must find answer before the stratigraphy of the 

 region can be considered as even approximately understood. The state- 

 ment of some of these propositions may be given here. In the present 

 connection many others which have been formulated are passed over. 



The main proposition is whether or not the deposits tying between the 

 " Niagara " and the Mississippian series are all to be regarded as belong- 

 ing to the same geological system. 



A second important problem has to do with the harmonizing of the 

 northern sections, where more than 500 feet of Devonian strata are repre- 

 sented, with the central sections, where little or no sediments exist be- 

 tween the Silurian and the Mississippian, and with the southern sections, 

 where, as in Arkansas, for example, the Interval beds have a thickness 

 of 100 feet or more. 



In the so-called transition beds lying immediately beneath the Bur- 

 lington limestone another group of problems is presented. Of first im- 

 portance is the query whether there are here any beds which can be ad- 

 vantageously denominated Devono-Carboniferous. 



Not of least significance is the real taxonomic value of the original 

 Kinderhook, the classificatory reference of its several members, and its 

 stratigraphical equivalency in other localities. 



A fifth great problem deals with the unconformities as indicative of 

 important changes influencing sedimentation. 



General geological Cross-section of the Region 

 main features 



The direction of the general cross-section is indicated on the small 

 sketch map accompanying the drawing (plate 44). A supplementary 

 section may be considered as extending around the eastern end of the 

 Ozark uplift. 



The most notable feature is the great shale bed at the top of the se- 

 quence. This thickens enormously in northern Missouri, where, in 

 its middle, it completely envelops the great calcareous lense known as 

 the Louisiana limestone. The most typical formations of the Upper 

 Devonian, which are so thick in the north, successively thin out south- 



