Williams — Geology of Arisaig- Antigonish District. 247 



action and their sedimentation characters, together with their 

 general red color, suggest for these poorly sorted but well-worn 

 deposits a continental origin. 



Because of the orogenic disturbances suggested and because 

 of the silicified character of its rocks, which are similar to those 

 of the Brown's Mountain group, the Malignant Cove formation 

 is thought to be a remnant of early Ordovician sedimentation. 



Silurian deposits. — On the shore about one mile west of 

 Malignant Cove, rocks of Silurian age rest unconformably 

 upon an old rhyolite flow. As the Malignant Cove conglom- 

 erate contains fragments similar to, if not identical with, this 

 rhyolite, it seems probable that the rhyolite flow was earlier 

 than the conglomerate deposition and may have been at one 

 time covered by the Malignant Cove formation. Be this as it 

 may, but small isolated deposits of conglomerate now remain 

 between the rhyolite flow-breccia and the sandy shales at the 

 base of the Arisaig series. 



The Silurian formations occupy an area about 1^ miles wide, 

 extending from Malignant Cove about 6 miles to the southwest 

 along the shore. The 3,500 feet of sediments here represented 

 consist in a generalized ascending order of argillaceous sand- 

 stone, black carbonaceous shales, arenaceous and argillaceous 

 shales, a 2^ foot bed of fossiliferous hematite, argillaceous 

 limestones, and red shales. As previously shown by Schuchert 

 and Twenhofel, the Arisaig series represent a period of time in 

 Europe between the lower Llandovery and the Ludlow, and so 

 far as they can be correlated with other American occurrences 

 they represent the time interval between the Clinton of eastern 

 JSTew York and the Guelph of interior America. The sedi- 

 ments are thought to be the deposits of a shallow sea during 

 varying conditions of clear and muddy waters. For the detailed 

 description of the formations and list of their fossils the reader 

 is referred to the work of Twenhofel and Schuchert cited 

 above. 



The Silurian formations are separated from the older rocks 

 by a great fault having a probable throw of 3000-4000 feet. 

 During the down-faulting, readjustment within the younger 

 strata took place, resulting in crumpling, overturning, and 

 many small faults which have divided the area into a number 

 of blocks. Because of the soft, yielding nature of the strata the 

 structure is but poorly expressed in the surface exposures. 



Devonian deposits. — Bed sandy slates containing some gray 

 impure sandstone rest unconformably upon the Silurian strata to 

 the southwest. They, too, have been downfaulted to the north- 

 westward by the major dislocation of the region, and have suf- 

 fered readjustment in the form of a synclinal flexure and 

 minor faulting. Ami, who gave these the name of Knoydart 



