244 Will in ins — Geology of Arisaig-Antigonish District. 



Glaciation. — Throughout the region mounds of unsorted 

 clay and gravel are common, and in places are capped by sorted 

 sands. On the plateau the ice of glacial times moved, as 

 inferred from the direction of strife on the rock surfaces, in a 

 direction 10° east of south, but on the lower lands its course 

 was somewhat varied as a result of the diversity of the topog- 

 raphy at that time. 



Recent movements. — Post-glacial rejuvenation is thought to 

 be indicated by the presence of elevated terraces along the 

 Northumberland Strait between 10 and 145 feet above the 

 present sea-level. These terraces appear to be old sea beaches 

 which have been modified only by the agents of erosion at work 

 at the present time. 



The geological record. 



The geological history of the district is written in sedimen- 

 tary records representing, with interruptions, the time from 

 Upper Cambrian to Pennsylvanian. The following table will 

 help to make the sequence clear. 



Sedimentary formations. 



Cenozoic. 

 Quaternary. 



1. Recent.— Stream gravels and residual soils, 



modified glacial gravels. 



2. Pleistocene or Glacial. — Unstratified clay-gravel 



deposits, red clayey marl. 



Paleozoic. 



? Pennsylvanian or Upper Carboniferous. 



1. Listmore formation (Millstone Grit of Fletch- 

 er). — Light gray and red-brown sandstones, 

 thin argillaceous shale, thin green conglomer- 

 ate, etc. Thickness (Fletcher), 982 feet. 



Mississippian or Lower Carboniferous. 



1. Ardness formation (Carboniferous Limestone of 



Fletcher). — Brown and green sandy shale, 

 ripple-marked sandstone and shale, gypsum 

 (along the I. C. R.), and a compact bed of gray 

 limestone. Thickness (Fletcher and corrected), 2045 " 



2. McAra's Brook formation (Carboniferous Con- 



glomerate of Fletcher). — Limy gray shale, 

 green shale, cross bedded conglomerate, brec- 

 cia and basal conglomerate. Cut by intrusive 

 diabase sheets and dikes. Thickness (Fletcher), 1145 " 



