50 



Tremadoc 

 fossils on Me- 

 Leod brook. 



"General up- 

 ward succes- 

 sion from 

 George river 

 station to 

 head of Mc- 

 Leod brcok. 



Differential 

 uplift of the 

 north-eastern 

 nd of the 

 Barachois 

 basin. 



About half a mile below the Boisdale road bridge, McMullins little 

 brook enters the main brook on the right. On this brook a short dis- 

 tance above its outlet are gray shales containing Monobolina refulgens, 

 Schizambon prisons and parts of trilobites. At the bridge the same 

 fossils and others occur in a shale bank on the right side. At Mc- 

 Mullin's brook the dip is S. mag. and S. 40 E. mag. < 70 acd 80. 

 About a quarter of a mile above the bridge is another shale bank on 

 the right side having limestone lentiles with Monobolina refulgens 

 and a Lingulella ; here the dip is S. mag. < 60. About a furlong 

 below the bridge in the left bank a thin fossiliferous band crops 

 out, dipping at a high angle, and carrying AsapJiellus cf Homfrayi, a 

 Triarthrus, a Parabolinella and other f^rms of the Tremadoc faunal 

 Other exposures with fossils are found in this bank of the stream, 

 further up. 



It will be observed that the dip in this part of the valley is 

 quite variable, but the rocks are not strongly cleaved, as they are at 

 the Barachois. Notwithstanding the confusing dips and faults in some 

 parts of the Cambrian terranes in the basin extending from George 

 river station to the head of McLeod brook, one can note a general 

 succession of the parts of the Cambrian system from the former to the 

 latter place. 



From the station named, where the oldest Cambrian sedi- 

 ments of this basin rest on the Coldbrook felsites and pre-Cambrian 

 syenite, to Young point at the entrance of the Long Island passage, 

 the rocks are Etcheminian. Behind this point the first division (Aca- 

 dian) of the St. John group is cut out by a fault, but the middle 

 division (Johannian) holds the shore of the eastern side of Long Island 

 passage, to the head of Barachois harbour. Here it disappears beneath 

 the upper, or Bretonian division, which extends thence to the narrow 

 deep gorge at the French Vale read, near the source of McLeod 

 brook. This arrangement would imply a differential uplift of the 

 north-eastern end of the basin since Cambrian time, through which 

 the whole of the terranes at this end of the basin have been eroded 

 to the basal conglomerates. Complementary to this there has been a 

 depression at the south-western end with the production of heavy 

 faults on both sides of the Cambrian valley, by which the terranes 

 have been let down between the bordering pre-Cambrian ranges for 

 the whole thickness of the three terranes which constitute this system 

 in Cape Breton. 



Yery different conditions and structure prevailed in Indian brook 

 valley, which is a nearly direct continuation of the Barachois basin. 



