GEOLOGY OF THE PEILIPSBURG REGION OF QUEBEC 323 



has correlated A partly on the basis of its own lithological makeup, 

 but largely on the faunal evidence of the overlying B strata. 



It is possible that even if organisms were living in the waters 

 which gave rise to the A beds, clastic deposition was so slow that 

 the calcareous shells were dissolved and reprecipitated as normal 

 lime rock before they could be buried and preserved as fossils. It is 

 a striking fact that the few fossils found in A were but faint shadows 

 of the original organisms. The state of preservation of these fossils 

 strongly suggests that dissolution was active before the rocks were 

 lithified, and only those individuals whose shells were thick and 

 resistent, succeeded in being preserved. 



Strike faults and Minor folds. — ^At the international boundary 

 the beds of A can be followed down the dip with almost no conceal- 

 ment. To the casual observer, the beds would seem to be dipping 

 to the southeast at a gentle and fairly constant angle. The rock 

 is peculiarly massive and unbedded, and it is only with careful 

 study that the true dip can be ascertained. In the section cited, 

 between the lake shore and the road, the Ai beds are turned up 

 practically on edge, possibly overturned in places. The pure, 

 dove-grey beds of A2 show no good criteria for correct measurement 

 of dip, except that they conform generally to the normal southeast 

 dip of the whole series. A3, on the other hand, being made up of 

 less pure, reddish-grey granular limestone, with magnesian beds, 

 and shaly black limestones, shows the effect of compressive forces. 

 At the international boundary the A3 beds, near their contact with 

 those of A2, fold under a synclinal axis. One bed of A^a is promi- 

 nently exposed where the strike can be followed without break around 

 the nose of the trough. Other beds of A7,a, which would not bend, 

 are seen in a much faulted condition nearby, lying at various angles. 

 This undulation in A3 appears to have been effected by a thrust 

 from the southeast, causing a steeper dip on the east limb of the 

 syncline and a gentler dip on the west limb.^ 



The folding in Ai on the lake shore was probably localized in 

 horizons of the more thinly bedded strata of the grey facies. With 

 the exception of these folds, seen and traceable on the surface, the 

 mass of A as a whole is distorted more by faulting than folding. 



' Sir William Logan, op. cit., 1863, pp. 846, 847. See also Fig. 2. 



