FORMATIONS OF (^UKHIiC AND FASTFRN ONTAKIO. 27 



other hand the Cak^iferous will contain the remains generally of those animals which inhahit 

 deep water." Emmons further says, " we can find no abrupt discontinuance or commence- 

 ment of either. We may find gradual transitions extend to three or four rocks and in the 

 geographical range of the second district we accordingly find that it actually extends up to 

 the Trenton limestone and the black slates above. In the several members constituting this 

 natural association or group, there are characters in common, but a gradual departure appears 

 as we trace these masses upward." 



Sir William Logan also says, in describing the Calciferous formation,' that "calcareous 

 sandstone beds mark the passage between that formation and the underlying Potsdam sand- 

 stone," showing that in his opinion there did not exist any break between the two, and at 

 other places in the same report the same intimate connection between the two formations is 

 pointed out. The fact that these rocks occur as nearly horizontal strata renders the strati- 

 graphical sequence easy to be determined, and although the Cambro-Silurian beds of the St. 

 Lawrence and Ottawa are aftected by faults at several places, these dislocations are of but 

 small comparative amount and do not complicate the structure to any serious extent. 



It would therefore appear to be well established that no stratigraphical break occurs 

 between the base of the Potsdam sandstone and the Chazy-Trenton grou}) of strata. We 

 may then briefly consider the question, whether any well defined break exists between these 

 sediments and the fossiliferous Cambrian or Primordial strata which underlie these and which 

 by Emmons and Eaton were regarded as constituting a distinctly separate and lower series, 

 while by others they were included in the same division. 



A short distance east of St. Armand station on the Grand Ti'unk railway near the 

 Vermont boundary a ridge of the characteristic red sandrock of Vermont occurs which is 

 the extension northward from that state of that formation into the province of Quebec. 

 The physical characters of the formation are entirely distinct from those of the typical Pots- 

 dam sandstone, and in certain beds Primordial fossils were found which as already stated were 

 described by Billings more than thirty years ago. These rocks consist of whitish and reddish 

 dolomites, some of which are siliceous, grayish limestone, and dark-gray and bluish-l^lack 

 slates. These may be said to constitute, in part at least, the Georgia slate and red sandrock 

 series, and from these, as early as 1847, paradoxides and conocephalites, Primordial forms, 

 were obtained by the American geologists. The relations of this peculiar group of strata to 

 the typical Potsdam sandstone cannot be ascertained at this point. Between this ridge and 

 the Calciferous-Chazy beds near St. Armand a well defined fault exists which can be recognized 

 at St. Armand, Highgate and Swanton and has been pointed out by Logan in the Geology of 

 Canada, 1863, pp. 858-66. On the east side, the red sandrock is overlapped by fossiliferous 

 Chazy sediments. It is difficult therefore, in view of the discordance in character between 

 the beds of the Potsdam proper and those of the series just described, to see how they can 

 be correlated either on stratigraphical, physical or palfeontological grounds, since nowhere 

 in the Potsdam sandstone formation proper do any fossils of Primordial age occur. 



Further west at Hemmingford mountain on the boundary between N"ew York and 

 Quebec, the basal beds of the Potsdam have been so cleaidy described by Sir Wm. Logan ^ as to 

 indicate that a well defined stratigraphical break really does occur between this formation and 

 the underlying Cambrian rocks. Thus Logan says in describing the formation at this place, 



' Geology of Canada, 1863, p. 110. ' Geology of Canada, 1863, p. 88. 



