THE BARITE DEPOSITS OF MISSOURI 9 



eastern part of the state it is about an equal distance to Creta- 

 ceous outcrops to the southeast. When Cretaceous seas covered 

 the region to the northwest and an embayment extended up the 

 Mississippi River to southern IlUnois, it would seem that the Mis- 

 souri region might also have been submerged, at least in part. 

 The region had been land, so far as it known, since late Pennsyl- 

 vanian times, and even during that period the Ozark Plateau was 

 perhaps only partly submerged. It would seem, therefore, that 

 erosion may have leveled the surface so that due to the Creta- 

 ceous subsidence a considerable part of the state would have been 

 submerged. If Cretaceous deposits were laid down, however, 

 they have been entirely removed from northwestern Missouri, 

 and probably also from southeastern Missouri. So far as now 

 known, it is possible that in some places in southeastern Missouri 

 faulting has carried Cretaceous beds down so that Tertiary beds 

 bury them. 



The oldest Tertiary beds to the south of this area are the 

 Lower Eocene. Had this region been elevated at the close of the 

 Cretaceous period the Lower Eocene to the south of the Ozark 

 Plateau would be expected to contain materials derived from 

 that region. The present streams are transporting a great deal 

 of chert derived from the various formations of the Cambrian 

 and Ordovician, so, unless the surface of the Ozark Plateau was 

 at one time covered by formations later than the Cambrian and 

 the Ordovician formations, streams, cutting into a recently ele- 

 vated area in this region, would probably have found an abund- 

 ance of chert to transport, much as do the present streams. This 

 material would have become a part of the Eocene, but such is not 

 the case. 



There is not much doubt that during Tertiary times the en- 

 tire Ozark Plateau was undergoing erosion. The Missouri River 

 was largely developed after Cretaceous times, and it received the 

 major part of the drainage from the northern slope of the pla- 

 teau. The Tertiary sea to the south received the drainage of the 

 southern slope. Thruout the period, the region was being re- 

 duced until probably near the later part of the Pliocene period. 

 This was a period of uplift over much of the United States, and 



