DALY: PHYSIOGRAPHY OF ACADIA. 85 



Island, while the surface of the Southern Plateau across St. Mary's 

 Bay similarly falls toward the southwest. Apart from these note- 

 worthy correlations, there are several arguments going to show that 

 the trap ridge has been once peneplained. These will be best appre- 

 ciated after a short account of the Fundy trough has been given. 



The Bay of Fundy Trough in Geological Time. — The rocks now 

 exposed between the Southern Plateau and the New Brunswick High- 

 land are chiefly of Triassic (Newark) age. There is little doubt that 

 the original extent and detailed structures of these beds cannot be de- 

 termined with anything like the completeness that characterizes our 

 knowledge of the New England Trias. It is highly probable that rocks 

 of this age underlie the bay; but just what relation they bear to the 

 exposed members on the shore-belts has, of course, not been made out. 

 Even there our interpretation must be limited because of the drift- 

 covering about the Minas Basin and in the Annapolis Valley. I have 

 not been able to find a definite statement of what correlation can be 

 made of possible observations or of those already published. The facts 

 regarding the structures and history of these rocks may be noted. The 

 scarcity of these facts will indicate the evident need of careful field-work 

 in addition to that already done by Dawson, Bailey, and others. 



The trough now occupied by the Bay of Fundy seems to have been 

 first delimited on the south during the late Devonian, the northern rim 

 having been defined at the beginning of the Cambrian (Bailey, '97, 

 p. 107). The estuary was filled with Lower Carboniferous sediments; 

 these were disturbed by folding in pre-Triassic times, denudation trun- 

 cated, the new structures, depression ensued, and thick Triassic sands 

 and gravels were laid unconformably on the Carboniferous. Observa- 

 tions on the most northerly and most southerly outcrops of the Tri- 

 assic show that these rocks (there chiefly of conglomeratic nature) mark 

 old shore-zones. The consensus of opinion is that the Trias never ex- 

 tended much farther than the present limits of that system. 



One of the youngest, if not the youngest, accessible member of the 

 Triassic series is also one of the most important from the physiographic 

 standpoint. I refer to the lava-flows and volcanic breccias of North 

 Mountain and the adjacent islands including Partridge Island and the 

 prominent Isle Haute isolated in the bay. The lowest bed is an 

 amygdaloid conformable with the red sandstones and supposed by Daw- 

 son ('68, p. 93) to have been deposited beneath the sea. Above it is 

 the massive compact trap which crowns the ridge throughout its ex- 

 tent. Whether or not this thick flow was overlain by sediments in 



