W. H. Twenhofel — Physiography of Newfoundland. 21 



carved, is the older, while the lower portion may be immediately 

 pre-glacial or even younger, thus explaining its well preserved 

 character. This hypothesis gives to the foreland surface and 

 that of the upraised peneplain a community of origin — both 

 formed when the land was a peneplain and since separated by 

 the faulting up of the Long Range. 



Physiographic History. 



The present physiography probably took its birth at the 

 close of the period of folding in which the Pennsylvanian 

 sediments were the latest involved. Then was initiated that 

 cycle of erosion resulting in the peneplain, the numerous rem- 

 nants of which are so well preserved on the flat-topped uplands 

 of the west coast. On the lowland thus created, made almost 

 perfect by the end of the Cretaceous, the rivers, free to wander, 

 ploughed their channels across the site of the present moun- 

 tains. The close of Cretaceous time is thought to have witnessed 

 the uplift of the highlands of the west coast to an amount 

 equal to about 800 feet, in which movement it is not believed 

 that the foreland participated to a great extent. That it was 

 below the wide upper valleys appears certain, otherwise they 

 should be found engraved on its surface. This uplift inaugu- 

 rated a new cycle in which these valleys were carved and the 

 rivers once more became adjusted to the structure and assumed 

 their northeast-southwest alignment. Before the completion 

 of this cycle it was interrupted by renewed uplift ; but suffi- 

 cient time had elapsed to bring the topography well on the 

 way toward maturity. When the movement had reached com- 

 pletion, the highlands of the west coast stood about 600 feet 

 above their present altitude, this figure being derived from 

 the depth of the drowned valleys :* and the distance between 

 their summits and the surface of the foreland was increased by 

 an average of about 1000 feet, the latter not participating to a 

 great extent in the elevation. To what extent the east side was 

 aifected is not known but that it once was much higher appears 

 certain. Following the elevation the deeply submerged val- 

 leys of the west coast were cut. The striking U-shape of 

 the. upper valleys and the presence of striae on the foreland 

 fix the time of uplift as pre-glacial. 



. Glacial time saw the island under a sheet of ice and then 

 were developed the U-shapes to the upper valleys and the 

 flaring out of the small valleys cut in the cliff face. The 

 topography was softened by the chiseling exerted by the ice 

 on its salients, and many rock basins — the beds of existing 

 lakes — were carved. 



* It is possible that a part of this depth may be due to ice cutting below 

 sea-level, although more than 100 feet has been allowed. 



