598 GEOLOGY 



East of the Cincinnati arch, which was probably an island in 

 the Osage epoch, the deposition of clastic sediments continued. 

 Those of eastern Ohio constitute a part of the Waverly scries. 

 Farther east, the accumulation of the sand and gravel of the first 

 stage (Pocono) either continued, or had been succeeded by the 

 deposition of the mud which now constitutes the Mauch Chunk 

 formation. The sediments of at least a part of this formation seem 

 to have accumulated on land, rather than in the sea. In Maryland 

 and elsewhere farther south, a formation of limestone (Greenbrirr) 

 lies between the Pocono below and the Mauch Chunk above, and 

 the Newman limestone of other regions 1 is perhaps its equiva- 

 lent. 



The St. Louis stage. This stage (including the Salem or 

 Spergen, St. Louis, and St. Genevieve limestones) marks the time 

 of maximum Mississippian submergence, so far as the western in- 

 terior is concerned (Fig. 426). Limestone deposition continued in 

 the Mississippi basin, but the fauna which it contains is so unlike 

 that of the Osage stage as to indicate that geographic changes of 

 consequence to the marine life of the interior had taken place. 

 One of these changes seems to have involved the removal of a barrier 

 somewhere in the west, permitting the fauna of the Great Basin, 

 heretofore shut off from the interior, to migrate eastward, and 

 mingle with that of the Mississippi basin. 



It was during this epoch that the Bedford limestone 2 of Indiana 

 (Salem or Spergen formation), famous as a building stone, was 

 deposited. Much of this limestone, long mistaken for oolite, is 

 foraminiferal. Many of the great limestone caves- in Kentucky and 

 southern Indiana are in the beds of this epoch. In Michigan, beds 

 containing salt (brine) and gypsum were in process of deposition 

 also earlier in the period. 



In the northern part of the Appalachians the Mauch Chunk 

 shales were doubtless in process of deposition, while other names 

 are applied to the contemporaneous deposits in the mountains 



1 Sec Tennessee folios. 



2 The name Bedford, as applied to their linn-stone, is really :i 1 nule name. 

 As a geological term, Bedford is applied to a, member of the Waverly aei 

 farther east. 



