POSSIBLE PRE-CAMBKIAN SEDIMENTS 507 



Section 



Feet 



1. Black mica-schist 100 



2. Gray mica-schist 1,320 



3. Black limestone 2,800 



4. Gray mica-schist '. . 4,590 



5. Micaceous dolomite 300 



6. Black mica-schist 600 



7. Quartzite 180 



8. Micaceous dolomite 60 



9. Gray mica-schist 7,360 



Total sediments 17,310 



10. Amygdaloidal trap . 12,540 



Total igneous 12,540 



Their distribution can be seen by the accompanying map (figure 1). 



The contacts of the sedimentary rocks with one another in this section 

 are of the nature of transitions, suggesting that no marked dislocation 

 or important time-break occurs between them. The graphitic limestone 

 passes upward into mica-chist by an almost insensible gradation, as can 

 be well seen along either bank of Saint Francis river. Still better evi- 

 dence is to be found in the banks of Eddy brook, a small stream in the 

 village of Melbourne, which has cut a postglacial gorge near its outlet 

 into the Saint Francis river. Here in a height of about 30 feet the rock 

 passes from typical black limestone in the bed of the stream to dark 

 mica-schist at the top of the northern bank. The mica-schist can be seen 

 in several places to pass gradually into micaceous dolomite, and the latter 

 into quartzite. It accordingly seems justifiable to conclude that the sedi- 

 mentary rocks of this section belong to a single cycle of deposition. 



The igneous rocks are older than the sediments. All the rocks north 

 of the black limestone, number 4 to number 9, dip toward the northwest, 

 and those on the south side of the limestone, numbers 1 and 2, dip in the 

 opposite direction, or about southeast. The limestone thus apparently 

 forms the axis of an anticline, and so must be the oldest of the stratified 

 of the section. This is the view of the structure that was held by Logan, 

 while Ells considers the limestone to be of much more recent formation 

 than the other rocks of the section, and to have been brought into its 

 present position by "an intricate system of folding and faults." The 

 former placed all these rocks in the Quebec group of Calciferous-Chazy, 

 while the latter regards the limestone as lower Trenton and all the other 

 rocks as pre-Cambrian. 



It is an apparent fact that the dolomite schists do not belong to the 

 pre-Cambrian, for they carry crinoid stems and other fossil evidences of 



