GRAPTOLITES OF NEW YORK, PART 2 65 



in the geosynclines. As such deposits are named the graptolite shales, the 

 Posidonomya shales, the Dentalium clays, and the argillaceous and cal- 

 careous Ammonite shales and compact or nodulous Ammonite limestones, 

 etc. The absence of organic life over vast regions on the argillaceous 

 bottom of the " zone bathyale " is also a feature well illustrated by the bar- 

 renness of the greater part of our graptolite shales and the remarkable 

 absence of other fossils in these beds. 



As to the relation of the depth of the sea and the constancy of the 

 deposition, Mr Haug states [p.624] : 



A une certaine profondeur, des oscillations qui maintiendront le fond 

 dans les limites de la zone bathyale n'ameneront aucune modification clans 

 la nature des sediments deposes, aussi les depots n'offriront-ils que de faibles 

 variations dans le sens vertical et cela sur des epaisseurs souvent tres con- 

 siderables. C'est la encore une raison de plus pour attribuer a un grand 

 nombre de geosynclinaux une profondeur relativement grande. 



This general independence of the deposition from oscillations in the 

 northern Appalachian geosyncline during Champlainic time is strikingly 

 illustrated by a comparison of the series of graptolite shales in the Levis 

 basin with that of the varying synchronous rocks deposited to the west of it. 



The Appalachian trough is the classic example from which Hall's con- 

 ception of a geosyncline took its origin. But in size, importance and length 

 of existence it is not comparable with the geosynclines which encircle the 

 Pacific and Indian oceans and which according to Haul's lucid discussions 

 persisted as the mobile parts of the earth crust through all geologic ages, 

 giving rise to the large mountain systems of the earth. But it seems to us 

 that this smaller geosyncline gains greater importance and interest if con- 

 sidered as a member of a system of very ancient geosynclines which stand 

 in some relation to the Baltic and Canadian shields. If we turn again to 

 the principal Champlainic graptolite regions of Europe, viz, Scotland, 

 Wales, Bretagne and Scania, we find that they are the sites of the very 

 ancient geosynclines which surround the " Baltic shield " of Europe and 

 have given origin to the ancient mountain systems of Great Britain and the 

 Bretagne. In America we find the graptolite zones in the Appalachian 



