BORDERLANDS OF NORTH AMERICA 163 



but the submerged portion of this borderland. The width of Novascotica. 

 is unknown, but it seemingly was not less than 150 miles and may well 

 have been of the order of 250 miles. 



Novascotica appears to have been reelevated during the first half of the 

 Paleozoic at least five times : first, decidedly toward the close of the 

 Cambrian, as is shown in the thick and coarse elastics of earliest Ordo- 

 vician time; secondly, during the last half of the Ordovician, when the 

 Acadian trough was dry; thirdly, at the close of the Ordovician, as is 

 attested by the thick deposits of the Silurian ; fourthly, toward the close 

 of the Silurian, when the reelevation was not decided, as seen from the- 

 thin but coarse materials of the Lower Devonian ; fifthly, toward the 

 close of the Devonian, as attested by the coarse elastics of the younger 

 Perry and Horton series. Finally, it seems probable that Acadia during 

 Pennsylvanian time was elevated four times more, as is clearly the case 

 for the Northumberland basin. In all, then, this or that portion of 

 Acadia rose nine times during the Paleozoic. 



CA8CAD1A 



It«appears probable that Paleozoic Cascadia extended from southern' 

 California far into the north, even beyond the Queen Charlotte Islands. 

 On the other hand, it must also have extended many hundreds of miles 

 to the west of the present shoreline of the Pacific Ocean, since it fur- 

 nished the thick deposits of the Cordilleran geosyncline. There is, how- 

 ever, from time to time much uncertainty as to the exact position of the 

 eastern shorelines of Cascadia. These uncertainties are due to the fact 

 that but little of this vast area has been studied in detail and geologically 

 mapped, and our knowledge is still in the main that of reconnaissance 

 work. 



Dana included in the borderland Cascadia the Sierra Nevada, Coast, 

 and Vancouver mountains, and the ranges of western British Columbia; 

 in fact, this entire region exhibits but rarely any sediments of Paleozoic 

 age previous to the Pennsylvanian. This and the further fact that the 

 sediments of the Cordilleran geosyncline thicken and become coarser to 

 the west are the basis for postulating the long borderland Cascadia. 



It is generally assumed that Cascadia was a long north-south trending 

 continuous land, and it may have been so throughout the Proterozoic and 

 up to the close of the Ordovician and even the Silurian. With the De- 

 vonian, but more especially in the Carboniferous, the occurrences of" 

 marine strata across parts of Cascadia are such as to indicate that even 

 as early as these times this borderland consisted of at least two parts, the 



