23 



cycle has been upwarped and dissected. Nor does this 

 complete its history; for subsequently to its dissection, 

 probably during the Pleistocene, the lowland has subsided, 

 letting the sea up over the lower portions and drowning 

 the broad trunk valleys to form tidal "basins". 



It is more than probable that other changes of level 

 have taken place along the coast since the beginning of 

 the Glacial period. The evidence of these later oscillations, 

 however, have not yet been fully gathered and correlated. 

 Extensive plains of stratified sand and clay which cover 

 the lower ioo feet (30 m.) or so of the coast, more especially 

 where rivers formerly entered the sea, appear to be marine 

 or estuarine deposits formed during a period of greater sub- 

 mergence than the present. Wave carved cliffs and wave 

 built beaches, however, if present, are too obscure to justify 

 any statement as to the altitude of the upper limit of 

 post-Glacial submergence. The extreme range of tide 

 complicates the problem. More interesting still is the 

 question of the modern stability or instability of the 

 coast. The salt marshes at Sackville and Dorchester 

 furnish suggestive material for study of this problem. 

 At Fort Lawrence, near Amherst, a buried forest is exposed 

 at low tide beneath 30 feet (9 m.) of marsh mud, and 

 8 feet (2-4 m.) below mean tide level. While this is 

 indisputable evidence of coastal subsidence, it may date 

 from early post-Glacial time, and proves nothing about 

 modern stability or instability. 



Cape Breton. — Separated as it is from Nova Scotia by 

 hardly a mile of water, at the Straits of Canso, the Island 

 of Cape Breton is a part of the province just described. 

 Both the Cretaceous upland and the Tertiary lowland ex- 

 tend over from the peninsula; but the harder and the 

 softer rock structures on which these two physiographic 

 facets are respectively developed are so irregularly dis- 

 tributed over the island that the upland and lowland 

 districts interrupt each other very strongly. 



Two areas particularly in which metamorphosed strata 

 and granitic stocks prevail are upland districts; the wide 

 northern arm of the island including most of Victoria 

 county, and the southeastern border of the island east of 

 Bras d'Or lake and south of Sydney. The central portion 

 of the island, on the other hand, from the Sydney district 

 across Bras d'Or lake and northwestward to the gulf, 

 in which soft Carboniferous sediments prevail, is an 



