PRE-CAMBRIAN ROCKS OF NEWFOUNDLAND 451 



unconformity existing between them. He was followed by Murray 

 (1881), who gives accurate descriptions of the pre-Cambrian sedi- 

 ments and classes them as the intermediate series, possibly equiva- 

 lent to the Huronian of Canada. Walcott (1899, p. 219) proposed 

 the name Avalon for the terrane lying between the basal beds of 

 the Cambrian and the Archean gneisses of Newfoundland . Walcott 

 (1900) described a new pre-Cambrian terrane conformable above 

 the Signal Hill series, which he called the Random and included in 

 the Avalon terrane. Howley (1907) published a map in which he 

 outlined the distribution of the Avalonian series and also distin- 

 guished a formation composed of interbedded volcanics and aqueous 

 deposits, which he separated from the base of the Avalonian terrane 

 and called Lower Huronian. The succession worked out by Murray 

 and Howley, the addition by Walcott, and the modification pro- 

 posed by Howley are given below. 



Feet 



Random Sandstones, quartzitic sandstones, and sandy shales 1,000 



[■ Red conglomerate 500 



Signal Hill I Dark- red sandstones 1,320 



\ Greenish or gray fine-grained sandstones 1,300 



Momable slates Dark -brown or blackish slates 2,000 



Torbay slates Green, purple, pinkish, or red slates 3,3°° 



Conception slates Greenish slates 



Lower Huronian Mixed igneous and aqueous deposits in a highly meta- 

 morphosed condition 



PHYSIOGRAPHY 



In general, the striking features of the Avalon Peninsula are the 

 parallel lineaments of the topography; the ever-present, bold, 

 rocky cliffs of the coast ; the flat-topped uplands with innumerable 

 lakes and ponds (Jukes counted 153 from the top of Powder Horn 

 Mountain); and the fiord bays with their deep interiors and 

 shallower thresholds. 



The topography is that of a much-dissected plateau at an 

 altitude of from 500 to 700 feet, with monadnocks rising to heights 

 of 1,000 to 1,100 feet, and submerged river valleys deeply gouged by 

 glaciers and invaded by the sea, constituting fiord bays and their 

 arms. The remnants of two definable peneplains may be repre- 

 sented in the present topography: one on the highland peneplain 



