302 H. M. AMI — KNOYDART FORMATION OF NOVA SCOTIA 



resented a lozenge-shaped area of so-called Upper Devonian strata ad- 

 jacent to the Silurian of the Arisaig Coast region and extending from 

 the headwaters of Arisaig brook on the east to those of Baileys brook 

 on the west, and from " The Hollow," or " Bruin's Highway," on the 

 south, to the line of contact and overlap of Carboniferous strata to the 

 north and w^est. 



This area is described as " Upper Devonian " on page 69 P of the 

 "Annual Report " of the Geological Survey of Canada for 1886. Here the 

 first mention of the occurrence of organic remains found in this series is 

 given in what appears to be the lowest portion of the series. These 

 include " plants, fish teeth, and Protichnites." A number of small 

 streams cross this area of Devonian rocks and afford many interesting 

 outcrops, of wiiich one of the two photo-sections rei)roduced in the 

 plate opposite this page, occurs near the bridge over McArras brook, 

 along the shore or postroad from Merigomnish to Arisaig and cape 

 George. These streams include the headwaters of McAdam brook, 

 Joseph jNIcDonald brook, Stonehouse brook, McArras brook, Knoydart* 

 brook (giving the name to the formation discussed), Vamey brook, 

 and of one of the southeastern brandies of Baile^^s brook. 



Contact of Silurian and Devonian Strata 



The line of contact between this area and tlie adjacent Silurian aj)- 

 pears to mark an unconformity, the precise amount and significance of 

 which has not 3'et been fully determined. According to the dips and 

 strikes given by Mr Hugh Fletcher and Mr J. A. Robert on the map just 

 cited, it would follow that, on the whole, the general trend and be- 

 havior of the strata referred to the Silurian and Devonian systems are 

 fairly uniform and generally identical, both having evidently been sub- 

 jected to the same physical forces and disturbing agencies since they 

 were deposited (see plate 26, figures 1 and 2). 



The actual dips of the Devonian strata vary from 16 degrees to 80 

 degrees, and those of the Silurian from 7 degrees to 70 degrees, with 

 local variations in both. The number of post-Silurian and j)Ost-Devo- 

 nian eruptive masses of amygdaloidal trap present in the vicinity have 

 done much to disturb the rocks of the two sedimentary series, not to 

 speak of the older and the newer sedimentaries of the district (see map, 

 figure 1). 



Classification and Views of Various Writers 



Touching the McArras brook area in question, the conclusion cited 

 below was reached by Mr Hugh Fletcher by correlating the same with 



* Pronounced Krodiart. 



