252 J. Barrett — Upper Devonian Delta of the 



out since the Jurassic and extending the platform toward limits 

 set by the resistance of the crust. The normal slope from the 

 Appalachians to the ocean basin would in the present period 

 be a much smoother and more gently sloping curve, although 

 quite probably above the present level of the crystalline floor, 

 if surface agencies had not planed across the piedmont on the 

 one side and built out the shelf on the other. The surface of 

 the latter holds then no relation to the limits of Paleozoic 

 Appalachia. 



The Ocean Basins widened by Continental Fragmentation. 



The preceding arguments lead to the conclusion that the 

 ocean basin has advanced inland since the close of the 

 Paleozoic and that the seat of a part of the ancient land is 

 now deep ocean. 



This is in accord with the views of Suess, who holds that the 

 Atlantic and Indian oceans cut across the Paleozoic structures 

 and indicate a breaking down of the continental platforms since 

 those structures were made. It is known also that close faunal 

 relationships have existed in the past between northwestern 

 Europe and northeastern America, implying some path of 

 migration. On the maps by American geologists such a bridge has 

 been shown as a more or less narrow connection circling Davis 

 Strait and utilizing Greenland and Iceland as piers supporting a 

 narrow causeway between North America and Europe. The 

 structural evidence which has been considered would seem to 

 show that such connecting lands may have been broader and more 

 like the areas of the adjacent continental platforms, of which 

 they in fact formed then a portion : at times, flooded in part by 

 shallow sea; at times, in part the seat of ancient mountains. 



Conclusion on Appalachia. in the later Paleozoic. 



The old-land of Appalachia during the Paleozoic tended to 

 be a broad and mountainous upland. West of it was the trough 

 into which much of its waste was poured. As in the Eurasian 

 mountain system, when this trough collapsed it was underthrust. 

 Appalachia was overthrust against it. The eastward-dipping 

 folds and faults and the greater uplift and consequent erosion 

 on the eastern side of the geosyncline were in response to this 

 relation of anticlinorium and synclinorium and not to a thrust 

 from the ocean. The ocean in fact need have had no more direct 

 connection than it had in the Laramide overthrusting of the 

 front ranges of the Rocky Mountains upon the Great Plains in 

 the center of the North American continent, or the Neocene 

 overthrusting of the Himalaya upon the plains of India. 



The general conclusion to this article which perhaps is most 

 impressive is that regarding the magnitude in breadth and in 

 vertical relations of the ancient orographic elements and the 



