CALLAWAY LIMESTONE. 33 



consolidated and on that account was easily eroded. The lack 

 of muds in the botton of the Callaway indicates the erosion of a 

 surface that was very completely weathered or consisted of un- 

 consolidated limestones. 



Over about one-third of its extent the Callaway is overlain 

 unconformably by the Sylamore sandstone of the basal Mississip- 

 pian. In most cases only a slight difference in dip between the 

 Callaway and Sylamore is apparent, but in some cases the 

 difference is as great as six degrees. In some places erosion had 

 completely removed the Callaway before the Sylamore sea 

 advanced, and the latter filled narrow valleys with their sides 

 formed of Callaway and their bottoms of some older formation. 

 On the whole, the surface over which the Sylamore sea advanced 

 was a nearly level plain with shallow narrow young valleys dis- 

 secting it here and there. 



Over perhaps one-fifth of its extent the Callaway is overlain 

 conformably by the Snyder Creek shale. The amount of erosion 

 suffered by the Upper Devonian before the advance of the 

 Mississippian seas is indicated better by the Snyder Creek than 

 by the Callaway. 



In a few places Chouteau limestone is in contact, noncon- 

 formably, with the Callaway. In these places the Sylamore 

 failed to be deposited. This relationship is exceedingly rare. 



More common than the Chouteau-Callaway contact is the 

 Burlington-Callaway contact. A considerable interval of erosion 

 elapsed between Chouteau and Burlington time and in many 

 places the Chouteau and Sylamore were completely removed and 

 Burlington limestone was deposited on Callaway limestone. 



In Sec. 21, T. 46 N., R. 10 W., on Little Murphy Creek, 

 Pennsylvanian conglomerates of Cherokee age rest on Callaway, 

 and this is not the only instance of the kind observed. 



In Ralls County the Grassy Creek shales of the basal 

 Mississippian are disconformable on the Callaway. In Lincoln 

 County the Chouteau limestone rests on the Callaway where the 

 Grassy Creek shales are absent. 



The Callaway was slightly folded and subjected to erosion 



at the close of the Devonian; it was uplifted and those parts 



exposed subject to erosion in the interval between the Chouteau 



and Burlington; it again suffered erosion after the close of the 



Mississippian and before the advance of the Pennsylvanian 



seas; and parts of it have been undergoing erosion from the 



close of the Pennsylvanian to the present. 

 2 



