STRAND-LINE DISPLACEMENTS 483 



the Cordilleran sea also appeared on the inner side of Cascadia, but in the 

 earlier transgressive stages did not connect the Pacific with the Arctic 

 ocean. While no secular changes of this time are known in the lands 

 bounding these seas, yet from their very position and character it might 

 be asserted that during the close of the Proterozoic Acadia, Appalachian 

 and Cascadia had been thrust away from the oceans, developing synclinal 

 seas along their inner sides. It was these synclines that the transgressive 

 seas invaded. These bordering lands were then still high, and in the 

 earlier stages furnished much clastic material in formations of great 

 thickness. The lands of the interior, however, appear to have been low 

 and featureless. The synclinal seas were the beginnings of the Saint 

 Lawrence, Appalachian, and Cordilleran transgressive seas. 



The maximum inundation of the Xorth American continent apparently 

 did not exceed 18 per cent, and that of the United States 12 per cent. 113 

 This inundation was also slow in spreading, first appearing in the Great 

 Basin and gradually moving northward. In the east the Appalachian sea 

 may have first shown itself in the northern Appalachian trough, from 

 Pennsylvania to northern Vermont and thence northeast to Labrador and 

 south to Alabama. 



Toward the close of the Georgic the eastern lands are known to have 

 moved, and apparently this elevation drained the entire trough from Lab- 

 rador to Alabama. This movement is of great significance in the subse- 

 quent distribution of the faunas, for it is seen that when the seas again 

 invaded the region of this fold the descendants of the former universal 

 Pacific Olenellus faunas were prevented from mixing with those of the 

 northern Atlantic. On the west of this protaxis of "Middle Cambric" 

 time were the Olenoides faunas of the Pacific realm, while to the east are 

 the Atlantic Paradoxides biotas. Here occurred, therefore, the birth of 

 the Appalachian protaxis of Dana and the Chilhowee-Green Mountain 

 barrier of Ulrich and Schuchert. 114 In the Cordilleran region the seas 

 are continuous. 



Accidie period or system 115 — Saint Croix transgression (see map, plate 

 52 ) . — Following upon this eastern movement a great transgression was 

 introduced with fair rapidity, one of the Pacific ocean from the pre- 



113 The estimates given in this chapter are exact calculations based on the writer's 

 paleogeographic maps. It must be understood, however, that in all probability the maps 

 are not accurate and can not be made so for years to come. The figures given, there- 

 fore, are but expressions of present knowledge, yet are believed to represent the rela- 

 tive amount of inundations and emergences. The area here called "United States" 

 embraces more than this country — all the present land between 30° and 50° north lati- 

 tude. Geologically, it is the best-known region. 



114 Ulrich and Schuchert : Rep. New York State Paleontologist, 1902, p. 638. 



115 Middle Cambrian and Acadian of most writers. 



