BORDERLANDS OF NORTH AMERICA 161 



lantic. Since this estimate is based on elastics alone, it is probable that 

 Appalachia extended eastward even farther than 250 miles. This land 

 began to founder into the depths of the Atlantic (Poseidon) seemingly 

 as early as the Jurassic period. 



Was Appalachia during Paleozoic and Mesozoic times continuous with 

 Antillia and the Bahamas ? Our knowledge of dated geologic formations 

 in Antillia does not go back of the Jurassic, and so we are left to guess 

 what the earlier relations were. From the maps already shown, it has 

 been seen what shape my guessing has taken. The extent of these 

 lands is, however, circumscribed by the depths of the present oceans and 

 the nature and distribution of the Paleozoic faunas. In any event, what- 

 ever the area and the outward form of iippalachia, it was not an inde- 

 pendent continent; rather was it an integral part of North America. The 

 importance of this conclusion will become apparent when we contrast 

 geosynclines with mediterraneans (see page 194). 



Later on it will be shown that to the southeast of the Saint Lawrence 

 geosyncline lay another one, the Acadian trough (page 179). The ques- 

 tion must now be asked. Was there also a geosyncline to the east of the 

 Appalachian one ? Our answer is that there is nothing in what remains 

 of the western part of xlppalachia to show that such a trough ever existed 

 in this borderland. Much further than this we can not go, but from 

 Barren's physiographic studies of Appalachia in Devonian times it is 

 clear that if another geosyncline was present it must have lain upward 

 of 200 miles east of the eastern shore of the Appalachian geosyncline. 

 Keeping in mind the present depths of the Atlantic Ocean, however, we 

 are disposed to believe that Appalachia was throughout a highland and 

 of the nature of a geanticline. 



As Appalachia furnished nearly all of the sediments of the geosyncline 

 that lay along its western side, we must now try to find out how often 

 this land was reelevated. It is clearly evident that southwestern Appa- 

 lachia was mountainous in earliest Cambrian time. This is seen in the 

 immensely thick, and at first very coarse. Lower Cambrian formations 

 of the Appalachian trough, extending from Tennessee into Alabama. 

 Other thick clastic deposits extend northeastward in decreasing volume 

 to ISTew Jersey. 



On the other hand, elastics in thick deposits of late Ordovician and 

 early Silurian age increase in volume from Virginia to southeastern Xew 

 York. The Silurian is also very thick and in coarse deposits in the 

 Maritime Provinces of eastern Canada, indicating that early in the 

 Silurian Acadia was also in highland condition. 



