2 6o SIDNEY POWERS 



filling of the basin with sediments. This fault is supposed to have 

 been initiated after sedimentation commenced, and to have increased 

 in displacement with the accumulation of the sediments. 



In the Acadian area a corresponding fault is found on the north 

 and west, but there is no evidence that this fault developed until 

 sedimentation ceased. No completely satisfactory theory to account 

 for the structure has yet been presented. 



IGNEOUS ROCKS 

 DISTRIBUTION 



A description of the igneous rocks in each locality has been 

 given in the description of the general stratigraphy of the region, 

 and therefore merely a summary is attempted here. The flows 

 at Cape d'Or have been especially studied, and will be considered 

 in a separate paper by Professor Alfred C. Lane and the writer. 



All of the igneous rocks associated with the Acadian Triassic 

 are of a basaltic composition. From the form of occurrence, they 

 are grouped into dikes and flows. According to the time of forma- 

 tion, they are classified as the Five Islands volcanics and the North 

 Mountain basalts. Dikes are so rarely exposed that it is necessary 

 to consider the rocks from the point of age, rather than form. 



In Nova Scotia, outside of the Triassic area there are some dia- 

 bases and basalts which are probably of Triassic age. At Cheverie, 

 near the Avon River, there is a sill of diabase intruding Pennsyl- 

 vanian strata. 1 Again, in Guysborough County, near Guys- 

 borough, Fletcher has mapped on the sheets of the Geological 

 Survey of Canada masses of diabase cutting the Union-Riversdale 

 series. The nature of these masses is described by Fletcher 2 as 

 partly amygdaloidal, partly dioritic. 



Dikes of Triassic age occur in a number of places between Nova 

 Scotia and the Connecticut Valley. The large majority of them 

 are of diabase composition. 



1 Verbal communication from Mr. W. A. Bell, of the Geological Survey of Canada. 



2 H. Fletcher, Geol. Surv. of Canada, Annual Report, 1886, pp. 101-3 P; also 

 Gcol. Surv. Canada, Maps, Nova Scotia, Nos. 30, 31, 35, 36. 



