Handbook of Paleontology 217 



est deposits of Paleozoic time were laid down and in the 

 Appalachian Mountains area, which is the type region 

 for geosynclines, the Paleozoic sediments reached a total 

 thickness of over 60,000 feet. In all cases deposition in 

 the geosynclines was terminated by foldings of the strata 

 deposited and both during and at the close of the Paleo- 

 zoic they were the sites of the principal mountain folds. 

 It was the positive elements or dominant land masses 

 which were the source of the bulk of the clastic material 

 that was deposited in the geosynclines and continental 

 seas and upon the lowlands. Certain of these land 

 masses should be mentioned here. Most prominent in 

 eastern North America is the one to which the general 

 name of Appalachia has been given. This land area in 

 general was situated along the eastern border of the con- 

 tinent and extended for an unknown distance into the 

 present Atlantic ocean. Its western limit was the present 

 Piedmont belt of the southern Appalachians, the Florida 

 platform covered by younger deposits and part of the 

 New England and Newfoundland uplands in the north. 

 It extended continuously from Newfoundland on the 

 north to the Brazilian oldland of South America and 

 beyond on the south. The central axis of Appalachia 

 was probably located somewhere near to or outside the 

 present eastern margin of the continent, and that it was 

 of mountainous heights is indicated by the amount of 

 sediments derived from it. Appalachia was the source 

 of practically all the clastic materials which make up the 

 Paleozoic deposits of eastern North America. On its 

 western border was a narrow arm of the sea or seaway, 

 the Appalachian geosynclinal trough, which received the 

 bulk of the clastic material derived from Appalachia and 

 whose sediments toward the close of the Paleozoic were 



