DISCUSSION OP EVIDENCE 209 



sandstone cliff with a small talus at the base. The apparent downward 

 drag of the beds at the contact between the breccia and the diabase is 

 precisely similar to the soil drag found on steep faces of escarpments or 

 slopes where the edges of thin beds containing shale members are exposed. 



The writer is thus inclined to regard the breccias found only along the 

 base of the hill as old soil breccias and the unconformity at this point 

 as evidence of extensive erosion previous to the incursion of the trap. 



An almost precisely similar breccia, in which many of the fragments 

 are distinctly rounded, occurs near the post-office about 1% miles east of 

 Ouimet station (between mileposts 87 and 88), where it is also asso- 

 ciated with, but only partially concealed by, a trap sheet — both at the 

 foot of a slope and at its summit. 



Again, at mileage 97%, is a mass of very similar material consisting 

 of fragments of red arenaceous dolomites lying in a hollow in granite 

 and not now associated with any trap sheet. 



The breccia found at the base of Red Rock, on the east side of the ridge, 

 is in immediate contact with diabase and is only a small fragment of 

 material similar to that which is found in several other localities not 

 always associated with diabase sheets at the present time and not neces- 

 sarily occurring at points where an intrusive mass has forced its way 

 across strata. Under any other circumstances these fragments of waste 

 rocks would unhesitatingly be regarded as remnants of an old soil cover. 

 Except for the fact that they are recemented, they are almost precisely 

 similar to the waste masses found in many other places associated with 

 these same rocks today. 



Discussion of the Evidence 



surface. flows versus intrusions 



Obviously the "capping" sheets of diabase, the group under consider- 

 ation here, must have been either surface flows or intrusions. Were the 

 original upper surface of the sheets preserved, it is extremely probabie 

 that there would be no difficulty in determining to which group they be- 

 longed. If they were surface flows we would expect to find the upper 

 layers glassy, amygdaloidal, with traces of flow structure, occasionally 

 perhaps associated with lava breccias or other pyroclastics. If intrusions, 

 we could expect to find traces of the overlying sediments, or, internally, 

 at or close to the former upper contact, the diabase would at times con- 

 tain fragments derived from the old cover/ and would always show a 

 progressive diminution in the size of the grains of the constituent min- 

 erals as the contact was approached, precisely the same as is shown in ail 

 cases where both upper and lower contacts are known. Unfortunately 



