122 



IOWA ACADEMY OF SCIENCES 



statement of the sections appears to present the facts 

 most clearly. 



*Not the same as Poteau of Indian Territory. 



The thickness of the coal measures of the Mississippi 

 valley is greater than anywhere else in the United States. 

 If two east and west cross-sections, one on the north side 

 of the Ozark dome and the other through the Arkansas 

 valley, are contrasted, the Carboniferous series present 

 about the following measurements: 



From the foregoing it will be seen that the Lower Car- 

 boniferous, or Mississippian series, with its minor divisions, 

 is well defined in northern Arkansas. The Kaskaskia 



Figure 3. 



Relations of tlie Mississippi valley members of Carbonifer 

 represents Arkansan. 



