28 E. W. ELLS ON THE POTSDAM AND CALCIFEROUS 



" III a deep ravine on the south side, about 180 feet of a coarse grained sandstone are visible, 

 in some parts constituting a conglomerate, with rounded pebbles of white quartz, varying in 

 diameter from an eighth to three-fourths of an inch, while in most parts of the rocks there 

 are thinly disseminated pieces of lilack or green shale, one to two inches in diameter b}* an 

 eighth of an inch thick." On the following page Logan says, " the upper part of the forma- 

 tion is in general a tine grained white siliceous sandstone, some parts of which are suthcicntly 

 pure to yield an excellent material for glass making." 



The strata thus described form a well deiined area of the ty[iical Potsdam sandstone, 

 extending northward for several miles into the province. The arenaceous beds gradually 

 become calcareovis and pass without any break into the Calciferous, which is well seen in the 

 Chateauguaj' river near Huntingdon village. This gradual upward passage of beds is 

 noted by Logan for this area, where he states that ' " at the summit the sandstone becomes 

 by. degrees interstratified with beds of magnesian limestone, and presents a passage into the 

 succeeding formation." 



The pebbles found in the basal conglomerates of the Hemmingford mountain area 

 present features which are found in the I'ocks of the underlying Georgia slate series and 

 granular quartz from which they have probably been derived. 



While we have seen that there is no stratigraphical break between the Potsdam sandstone 

 and the Calciferous, the fossil evidence, in so far as developed, leads to the same conclusion. 

 Thus not only the basal portion, but in fact the whole of the sandstone formation proper, is 

 entirely destitute of organic remains in so far as yet known, with the exception of the peculiar 

 marking called scoUtkus concerning the origin of which nothing has yet been definitely 

 ascertained, and certain tracks or impressions regarded as produced by some species of 

 crustacean, the remains of which have, however, never as yet been found in the rock mass. 

 Li the upper portion the scolithus markings are rather better defined, and as the calcareous 

 layers of the transition beds into the Calciferous formation are reached, certain well defined 

 fossil forms appear such as Lingula acuminata, Ophileta compacta and an orthoceras, which 

 with a few allied forms becomes more abundant as we ascend in the succession of strata till 

 these appear to merge into the overlying Cliazy. No Primordial forms, as we know these in 

 Canada, have yet been recognized in the Potsdam or Calciferous beds. 



In 1859-60 a Calciferous fauna was recognized by Billings in certain strata of limestone 

 associated with slates at Point Levis, which had previously been supposed to belong to a 

 much higher position in the geological scale. Subsequent investigations have confirmed the 

 statement that these rocks, in part, must be assigned to this horizon, though they difler in 

 many respects from the typical Calciferous of the Ottawa basin. Beneath these beds at 

 Point Levis we find a ver}' widely extended series of red and green shales with beds of sand- 

 stone and limestone conglomerate already referred to, into which the upper beds of the 

 Levis appear to graduate at certain points, and from their position in synclinals upon the 

 red slate or Sillery division, are uu(loul)teilly the upper members of the group, which 

 have escaped denudation over a few scattered areas. In the Sillery or lower division, the 

 masses of limestone conglomerate are made up of pebbles of limestones, quartzite and slate, 

 the limestone pebbles being often highly fossiliferous and the whole derived evidently from 

 a lower and older formation. Tlie slates of the upper Sillery formation are, for the most 



' Geology of Canada, 1863, p. 89. 



