DEVELOPMENT OF THE ACADIAN CxEOSYCLIXE 179' 



ern 'New York and perhaps all the way to N'ewfonndlancl, where there are 

 also known crnstal movements of late Ordovician time. Furthermore, 

 as we shall see later on, the whole of the Acadian trongh on the other 

 side of the New Brunswick geanticline was dry land during the middle 

 and late Ordovician. Other local details might be mentioned, all of which; 

 point to a time of folding and elevation of the eastern portion of the 

 Saint Lawrence geosyncline extending clearly from New Jersey to Ver- 

 mont and possibly all the way to Gaspe, Quebec. 



Before leaving the Saint Lawrence geosyncline, it should be stated that 

 the Canadian shield was the northwestern lowland of this trough. Its 

 other shore was the periodically rising New Brunswick geanticline, a. 

 narrow highland tract described earlier (page 166). To the southeast of 

 this geanticline lies another geosyncline, the Acadian trough, next to be 

 described. 



Development of tile Acadian Geosyncline 



(See Maps, Figures 3 to 8) 

 GENERAL DISCUSSION 



Across the southeastern margin of the New England States and' 

 through the central parts of the Maritime Provinces of Canada and 

 southeastern Newfoundland, a geosyncline developed during Cambrian, 

 Ordovician, Silurian, and Devonian times. Dana in 1890^^ called it the 

 Acadian trough, and its southwestern end, of longest endurance, the 

 Fundy hasin. During its earlier history it extended from at least south- 

 eastern Newfoundland southwestward across Cape Breton, northwestern 

 Nova Scotia, southern New Brunswick, southern Maine, and eastern 

 Massachusetts. Like the Appalachian geosyncline, it appears to have- 

 been in continuance as a trough since early Proterozoic time (see map, 

 figure 1). To the southeast of the Acadian trough lay the borderland 

 Novascotica, of unknown width, while its northwestern shore was made 

 by the New Brunswick geanticline, which separated it completely from, 

 the greater Saint Lawrence geosyncline. 



The Acadian trough was present in Lower Cambrian time, and is seen 

 in better development during the Middle Cambrian, with its Paradoxides 

 faunas of European affinities, extending from southeastern Newfound- 

 land to Boston. Then there is no evidence of this trough until early 

 Ordovician time (Bretonian), when again it has decided European 

 faunas. During all the rest of the Ordovician the trough appears to have 



32 Dana : Archaean axes of eastern North America. Amer. Jour. Sci. (3), vol. 30, p.. 

 380. Also Manual of Geology, 4th ed., 1895, pp. 444, 461, 536. 



