TRENTON CONGLOMERATE OF RYSEDORPH HILL ' 100 



end of the Trenton, is represented by Freeh on his chart 1 drawn 

 to explain the complete faunistic differentiation of the American 

 continental and North Atlantic basins from the beginning of the 

 lower Siluric to the end of the Black river limestone period. 

 Freeh there assumes an oceanic transgression in the Appalach- 

 ian regions to connect the Trenton with the European faunas, 

 while Dana has the barrier migrate westward at the end of the 

 Trenton period to explain the transition to clastic accumulations. 

 The writer in the foregoing chapters, has brought more evidence 

 to demonstrate the ingress of Atlantic forms into the eastern 

 part of the Trenton basin at the beginning of the Trenton period, 

 and has elsewhere shown that, in this part of eastern New 

 York or in those parts of the Appalachian area where the 

 Normans kill shale is found, the transition to the deposition of 

 clastic sediment began in the early Trenton period and not 

 toward its end. 



If we attempt to apply to our investigation into the origin of 

 the conglomerate the theories set forth by these authors, we may 

 infer that at the beginning of the Trenton period the deposition 

 of limestone continued for a short period in this region, and 

 the material of the gray limestone pebbles of lowest Trenton 

 aspect was formed; that at this time, by the incipient transgres- 

 sion of the ocean over the eastern barrier, the influence of north 

 Atlantic forms began, becoming more pronounced at the time of 

 the deposition of the black limestone; that, at the same time, 

 the gradual rising of the more westerly parallel barrier in the 

 Appalachian region, together with the numerous Archaean is- 

 lands assumed by Dana, furnished the material for the long belt 

 of Normans kill shale and the conglomerate bed. The very exten- 

 sion of the Normans kill shale from north to south would indi- 

 cate the direction of this barrier and of the intercalated conglom- 

 erate bed as that of a probable coast line. 



This attempt to account for the presence and the peculiarities 

 of the conglomerate bed is partly supported by a view advanced 

 by Walcott to explain the origin of intraformational conglomer- 

 ate beds of Cambric and earliest lower Siluric age observed 



i Roemer & Freeh. Letbaea palaeozica. 1897. v. 3, Karte 2. 



