132 ROYAL SOCIETY OF CANADA 



The Cambro-Ordovician Cycle. 



As an example of a series of strata which in this area of the 

 Maritime Provinces has been more fully exploited than most others, 

 and which is a good example of a complete geological cycle, may be 

 mentioned the Cambrian, or, more properly, Cambro-Ordovician. 



In this cycle we include the Etcheminian deposits which underlie 

 what was formerly recognized as Cambrian, and apparently underlie 

 the Olonellus Zone. The meagre faunas that are contained in these 

 rocks are essentially Paheozoic, and so there seems good reason for con- 

 necting them with the Cambrian. 



In this range of deposits there arc presented the following foraia- 

 tions, and we attempt their interpretation: — 



Coldbrook — Volcanic effusions over a region that for a long time 



had been above the sea; and so continued during this term. 



Etcheminian — Land below sea level, deposits mostly of levigated 



effusives, red and green colours prevalent in the elastics. 

 St. John Group : 



Division 1. — Clast'ics of various kinds, the faunas those of 



sheltered bays and shallow basins. 

 Division 2. — Sands and muds of ocoan-shoal character, current 

 swept and ripple marked. Depth less than 100 fathoms. 

 Division 3a-d. — Dark gray and black muds of deeper water, jjro- 

 tected from currents. Depth about 100-300 fathoms. 

 e. — Eetum to shallow conditions (in the band 3e). Fine 

 sands, now mostly eroded. 

 The division probably ended with a complete emergence, as there 

 is no continuous sedimentation into the next terrane. 



The geological text-books tell us that a limestone formation should 

 come in the middle of a geological cycle, but this is not the case in 

 northern regions where cold and deep waters prevent the growth of 

 corals and other lime secreting organisms. So in this cycle the division 

 3 of the St. John group takes the place of the usual calcareous member 

 of deposits in the warmer seas. 



Another peculiarity in the geological cycles of this region, and 

 which does not seem to be noticed as marking geological cycles else- 

 where, is the intercalation of a member of comparatively barren sands 

 (and muds) between the shore deposits and those of deep water origin. 

 Such a member, the Goldenville terrane, is enormously developed in the 

 great Huronian cycle below the Cambrian, and is also a marked feature 

 of the latter cycle. This member, it appears to me, to be due to the 

 exposure of the sea bottom by the continuous sinking of the earth's 



