2 ® tA 

 •p. S^^ 



Red shales, ^^a 



Conglomerate, i «a 



CATSKILL-MOCNTAIN GROUP, i5|.S 



INTRODUCTION. ffS 



Section of strata in Ketc-York and Ptnntylvania. Section of strata in th» Mississippi valley. 



Coal measures, Coal jieasures, 



Kaskaskia limestone. 

 Ferruginous sandstone, 

 St. Louis limestone, 

 Warsaw limestone, 

 Keokuk limestone, 

 I, Burlington limestone, 

 Chemung and Portage groups, Chemung and Portage groups, 



Hamilton group. Hamilton group. 



That interval of time, which in the east is marked by the accumu- 

 lation of the Catskill-mountain group (Formations ix and x of the 

 Pennsylvania Survey), and the Hed-shale group (Formation xi), is 

 marked in the west by the great Carboniferous limestone series of the 

 Mississippi valley. These formations are widely different in lithological 

 characters, and nowhere commingling, unless it be in the eastern part 

 of Tennessee or in Alabama ; and at this time it has not been shown 

 which of these has the precedence. A careful examination of the. section 

 on the Mississippi shows such a close sequence between the higher 

 beds of the Chemung group and the lower beds of the Burlington 

 limestone, that we find it difficult to believe that any interval or cessa- 

 tion of deposits has occurred. On the other hand, some beds of coarse 

 material mark the junction of the Chemung group with the base of 

 the Catskill-mountain formation in Eastern New- York ; and though 

 the entire fauna of the Chemung group suddenly ceases, there is no 

 evidence of a long interval between the termination of the one and 

 the commencement of the other. 



Admitting this view, we have to contemplate a wide extent of coun- 

 try, lying between New- York and the most easterly extension of the 

 Carboniferous limestones, as an area over which no sediments were 

 deposited, nor calcareous formations accumulated, during this period. 



It may not be uninteresting in this place to present a few facts 

 relative to this great Carboniferous limestone formation of the Missis- 

 sippi valley ; since, hereafter, in the consideration of the sequence of 



