600 GEOLOGY 



farther south. 1 Locally, deposits of this time contain both coal 

 and iron ore. 



The Chester stage. The fourth stage of the Mississippian 

 period (Chester), according to the classification adopted for the 

 Mississippi basin, seems to have been marked by more restricted 

 waters and more varied sedimentation, for sandstone and shale 

 are prominent members of this series. The deposits of this stage 

 resemble in a general way those of the Kinderhook stage. Those 

 were made while the sea was advancing on the land, these while it 

 was retreating. Both are more restricted in their distribution 

 than the beds of the intermediate epochs. In Illinois, the Chester 

 sandstone bears oil locally. 2 



In summation it may be said that the Mississippian beds are 

 predominantly clastic east of the Cincinnati arch, and predom- 

 inantly calcareous west of it. In many places the limestone of 

 the system carries great quantities of chert. 



In Nova Scotia, the Mississippian system rests, locally, on 

 Cambrian and pre-Cambrian terranes, and contains beds of red 

 sandstone and gypsum. 



In the Great Plains 



In the Great Plains, the Mississippian system is known in Okla- 

 homa and South Dakota, where deformation and erosion have 

 brought the strata to the surface (Fig. 426). In Oklahoma there 

 was some deformation at about the close of the period. The up- 

 warped beds suffered erosion, and an extensive chert-conglom- 

 erate, the conditions for which were prepared by the interval 

 of erosion, marks the first stage of Pennsylvanian deposition. 



West of the Great Plains 



West of the Great Plains the Lower Carboniferous is so widely 

 distributed as to show that the present mountain region, as far 

 west as the 117th meridian, was mostly submerged, though their 



1 The name Mauch Chunk is applied as far south as Maryland; see Jour. 

 Geol., Vol. IX, pp. 422-424. 



2 Bain, Econ. Geol. Vol. Ill, and Bull. 2, 111. Geol. Surv. 



