STRAND-LINE DISPLACEMENTS 495 



pian sea the emergence was due to withdrawal of the waters without ap- 

 parent land movement. This emergence apparently resulted from sub- 

 sidence in the Pacific realm. The next invasion was a small one, and as 

 it had well marked faunas, combined with peculiar physical characters, it 

 is here distinguished under a new systemic term. 



Tennesseic period or system 12 ® — Saint Louis invasion (see maps, plates 

 81, 82). — The Upper Warsaw, a part of the Spergen, of restricted extent, 

 began another invasion that attained its climax in the Saint Louis. This 

 was the smallest inundation of the Paleozoic, and was chiefly confined to 

 the Mississippian and Appalachian seas. There was no Cordilleran sea of 

 this time. The material deposited by these waters in connection with the 

 subsequent emergence — the Kaskaskia emergence — attained a minimum 

 thickness of about 1,100 feet, with a maximum of 1,800 feet. The beds 

 are repeatedly marked by zones of oolite containing a characteristic dwarf 

 fauna known as the Spergen fauna. The invasion is distinguished by 

 limestones and oolites, while in the emergence the oolites occur between 

 sandstones. The sea ended in deposits of limestone, oolites, and shales. 



This small invasion was in harmony with the general and almost contin- 

 uously progressive emergence beginning in the Chemung and terminating 

 with the Tennesseic. However, on the long enduring Onondaga trans- 

 gression were superimposed two smaller accentuated emergences having, 

 it is thought, each the value of a system or period. Finally the entire 

 continent was emergent except a limited area in the Oklahoma basin, 

 which was continuous into Pennsylvanic time. To make these statements 

 more clear, the percentages of marine invasions from the maximum in the 

 Hamilton to the end of the Tennesseic are here given, as follows : 



North America. United States. 



Late Hamilton 35 per cent 32 per cent 



Ithaca-Chemung 33 " " 33 " 



Close of Devonic, estimated 20 " " 23 " " 



Bradfordian 24 " " 30 " 



Fern Glen 25 " " 36 " 



Burlington 20 " " 24 " 



Close of Keokuk, estimated 5 " " 8 " " 



Saint Louis 7 " " 10 " 



Chester 13 " " 12 " " 



Close of Chester, estimated 7 " " 8 " " 



Throughout the close of the Tennesseic, Appalachia must have been in 

 constant elevation, especially in the southern portion, for very thick de- 

 posits of coarse material that are mainly continental in character are seen 



20 The upper half of the Mississippian of stratigraphers and Tennessean of Ulrich. 



