138 



SOUTHERN PLATEAU. 



The particular area to be described is an embayment 

 of the Carboniferous lowland bordering the Southern 

 plateau to the south and west, but merging into the 

 Triassic basin of the Bay of Fundy to the north. It is 

 drained by the Avon river and its tributaries. The 

 prominent characters of the three physiographic divisions 

 may be read within the district. The Southern plateau 

 is seen rising abruptly on the south to a smoothly curving, 

 timbered skyline at an average elevation of about 500 

 feet (152-4 m.). This plateau is marked by a gently 

 rolling old-age surface interrupted only by occasional 

 residual hills rising several hundred feet above the general 

 level of the plain, and by the narrow, young gorges of 

 the northerly flowing streams. The irregular veneer of 

 glacial debris has so modified the pre-Glacial drainage that 

 abundant lakes as well as large areas of marsh are now 

 present on the divides. The underlying rocks are a 

 thick series of slates and quartzites, known as the Gold- 

 bearing series, and generally assigned to the Pre-Cambrian ; 

 they are closely folded, and intruded by granitic masses. 

 A plateau extension also limits the district on the west, 

 but, whereas the descent to the lowland in the south is 

 abrupt, here on the west it is eased by rolling foothills. 

 In the former case the slope is from hard resistant rock 

 to soft marls and gypsum, whilst in the latter a stronger 

 development of the more competent Horton series inter- 

 venes. 



NORTH MOUNTAIN. 



An outlying remnant of this plateau surface forms the 

 crest of the trap ridge of North mountain, which extends 

 in a very even line a distance of some 120 miles (193 km.) 

 at an average elevation of about 550 feet (167-6 m.). 

 This ridge is uniformly carved on a sheet of massive, 

 compact trap, roughly 200 feet (61 m.) thick, of which 

 the lowermost bed is an amygdaloid conformable with 

 Triassic red sandstone. To the south it terminates in 

 an abrupt escarpment. To the north the dip is gently 

 towards the bay. 



