NEGATIVE CONTINENTAL ELEMENTS 461 



way from Adirondackia to Newfoundland. Closely adjacent to, or even 

 thrust over on, these faunas are found others, usually graptolites, that are 

 manifestly of the same province as those of northern Europe. These 

 faunas are strikingly different, and as the entire Acadian region is one 

 of extreme crushing and overthrusting, Ulrich and Schuchert 69 have 

 assumed the existence of a land barrier to keep these two faunal provinces 

 distinct. This fold or land barrier between the two seaways came into 

 being at the close of the Cambric, and has been called the "Quebec bar- 

 rier/' To the northwest of this barrier was their Chazy channel, while on 

 the opposite side of the same fold was their Levis channel. The definite 

 Atlantic faunas of the latter may be traced southwesterly as far as New 

 Jersey. These two troughs appear to have remained distinct until about 

 Utica ( ?) time, when the Chazy basin ceased, owing to the folding and 

 elevation in force during the Taconic revolution. 



In late Chazy time the Saint Lawrence sea had a distinct bay-like pro- 

 longation extending along the Ottawa valley north of Adirondackia; this 

 has been named "Ottawa bay" (Ulrich and Schuchert, 1902, 639) . Dur- 

 ing the later Ordovicic this depression was invaded either by the Missis- 

 sippian or the Saint Lawrence sea ; subsequently it appears to have been 

 land, yet may again have been beneath the sea in Siluric time. 



The connection of the Saint Lawrence sea with the Mississippian sea 

 was of very short duration, and occurred north of Adirondackia during 

 the Middle and Upper Ordovicic. During the late Cambric and much of 

 the Ordovicic, however, there was much communication with the Appa- 

 lachian sea through the Champlain trough (Dana, 1896, 461), but this 

 passage was closed by the Taconic revolution of late Ordovicic time (see 

 Dana, 1890, 43). In the early Ordovicic this channel was narrow and 

 directly continuous with the Chazy channel, but subsequently it appears 

 to have been considerably wider, embracing the Levis channel, its deposits 

 occurring east as far as lake Memphremagog. During the Siluric there 

 was no direct communication between the two seas, but beginning with 

 the New Scotland interchange of faunas was again resumed, but now by 

 way of the Connecticut trough, 70 which extended across the Taconic moun- 

 tains into the New York basin of the Appalachian sea. The interchange 

 of faunas was then continued well into the Onondaga, after which time 

 Acadia was repeatedly compressed and elevated, thus forcing these two 

 seas ever farther apart. The Connecticut trough was bounded on the west 



69 Ulrich and Schuchert : Rep. New York State Paleontologist, 1902, pp. 630-639. 



70 Dana : Bull. Geological Society of America, vol. 1, 1890, p. 38. American Journal of 

 Science, vol. 39, 1890, p. 380. Manual of Geology, 1895, p. 461. Schuchert : American 

 Geologist, 1903, p. 151. Clarke : Memoir no. 9, New York State Museum, pt. 1, 1908 ; 

 pt. 2, 1909. 



