18 THE DEVONIAN OF MISSOURI. 



tion more than four or five miles in diameter and many patches 

 are only a few hundred feet in extent. It was deposited on an 

 eroded surface and was deeply eroded before the Callaway lime- 

 stone was deposited on it, though the greater part of the removal 

 by erosion was accomplished in post Devonian, pre-Mississippian 

 time. 



The Mineola rests on Jefferson City dolomite, St. Peter 

 sandstone, Joachim dolomite, Plattin limestone, Kimmswick lime- 

 stone and Maquoketa shale. The absence of Silurian and lower 

 Devonian rocks in the area where it occurs indicates a long period 

 of erosion. In the main the underlying rocks are only slightly 

 folded though in some places the Jefferson City is crushed and 

 crumpled into small folds. Wherever the Mineola rests on 

 Jefferson City the nonconformity between the formations is easily 

 made out but where it rests on Kimmswick or Joachim the 

 structural relations are obscure. 



At location 5 south of Montgomery City, on Smith's Branch, 

 the Mineola rests on the Plattin on a slightly irregular surface. 

 Here it is less than 5 feet thick and occurs in patches. At loca- 

 tion 6, southeast of New Florence it also rests on Kimmswick. 



At the mouth of Cow Creek in Callaway County, the 

 Mineola rests on dipping Jefferson City. (See Plate D, figure 

 a.) About one mile west of Mineola, Montgomery County, it 

 also immediately overlies Jefferson City. 



On Whetstone Creek about half way between Montgomery 

 City and Williamsburg, St. Peter is the underlying rock in a 

 few places. Both St. Peter and Mineola are very patchy in this 

 district and come in contact in only a few places. At several 

 places near the Callaway-Montgomery County line, St. Peter 

 and Mineola are in contact. 



Nearly everywhere in eastern Montgomery County, where 

 the Mineola occurs, it rests on Joachim. At location 7, three 

 miles northwest of Big Springs in Montgomery County, it rests 

 on Joachim less than half a mile from an area where a good 

 section of Plattin overlies the Joachim. 



The Mineola is overlain by Callaway limestone, Sylamore 

 sandstone, and Chouteau limestone, though the Callaway is the 

 commonest overlying formation. The disconformity between 

 the Mineola and Callaway is much less distinct than between the 

 Cooper and Callaway and the final determination of uncon- 

 formity rests on the thickening and thinning of the Mineola and 

 the overlap of the Callaway. Next to the Callaway the Syla- 



