REVIEW OF GEOLOGICAL STEUCTIJEE. 25 



acters and fossils are identical with those of the Maxville and Logan 

 limestones, such as have apparently resulted from the destruction of 

 thpse limestones by the forces which, at a later date, spread the Con- 

 glomerate. Hence, we must conclude that the Conglomerate of Northern 

 Ohio is more recent than that of the Hocking Valley, and that Coal No. 

 1 of Mahoning county is not, as formerly supposed, identical with the 

 Jackson shaft coal. 



In the Sub-Carboniferous coals of Southern Ohio, we have additional 

 evidence that the submergence which resulted in the formation of the 

 Lower Caibonilerous limestone was progressive from the south toward 

 the north. They show that the Waverly shore of the Carboniferous sea 

 was for a time marshy, and sustained a luxuriant vegetatioa that pro- 

 duced the accumulation of peat, and that, by subsequent subsidence, the 

 sea water flowed in over this shore, covering the peat beds with tbin 

 sheets of orginic sediment derived from the hard parts of the moUusks 

 which inhabited the Carboniferous ocean. At a later date continued 



t 



sinking of the surface resulted in the formation of other peat beds, lime- 

 stones, etc., but the water which buried or doposited these was not that 

 which formed the Maxvilie limestone, but came from a different source, 

 and was, perhaps, fresh. 



THE CONGLOMERATE. 



In the description of the development of the Conglomerate in Ohio 

 contained in the first and second volumes of this report, nearly all we 

 have learned about it is told. It seems necessary, however, to refer to 

 one or two errors which have become current in regard to this rock, and 

 which require correction. 



First. It is believed by some that the Conglomerate nowhere extends 

 under the Coal Measures, but forms a bank or rim around the margin of 

 the basin. 



Abundant evidence of the falsity of this theory is, however, fur- 

 nished in the reports and maps descriptive of the geology of Mahoning, 

 Trumbull, Portage, Summit, Medina, Wayne, Holmes, and Licking 

 counties, contained in this or the preceding volumes of our report. In 

 all these the Conglomerate is shown to pass under Coal No. 1. It is true 

 that the greatest development of the Conglomerate is north of the coal 

 field, and that it is rarely struck in borings made towards the cenffral 

 portion of the basin. It is reported, however, in a number of localities, 

 and has been missed in many others, simply because it was not reached. 

 There are sometimes forty or fifty feet of light shales interposed between 

 the Conglomerate and Coal No. 1, and as these have been considered 

 " bottom rock," the borings have not been carried deeper. The Conglom- 



