S/. Peter's Sandstone. 



face of the Lower Magnesian, and to be an almost pure quart- 

 zose sandstone. The greatest thickness observed was 212 

 feet, but its average is hardly over eighty. Traces of life are 

 rare. The method of formation is considered due to me- 

 chanical action, rather than to chemical solution. In dis- 

 cussing its history it is stated that the sand was probably 

 derived from the Archean nucleus or the Potsdam sandstone 

 toward the north, which was then exposed above the surface, 

 or at least subject to the mechanical action of the waves. 

 The distribution is given, the Saccharoidal sandstone in 

 Missouri and the Chazy limestone of New York being con- 

 sidered its equivalents. He says: "We have felt somewhat 

 inclined to refer its main deposition to the closing Caleiferous 

 or early Quebec, and to suppose that it was rewrought by 

 the advancing sea in the Chazy or early Trenton epoch, the 

 remainder of the interval between the Calciferous and the 

 Trenton being unrepresented in our series, because the 

 water had retired."* 



As known in New York, the Chazy formation is essentially 

 a limestone, and therefore differs greatly in lithological 

 features from the St. Peter's. But in Canada the limestone 

 is associated with sandstones and shales. At Greenville the 

 calcareous strata are succeeded by about fifty feet of whitish 

 sandstone, in beds from two or three to twelve inches, inter- 

 stratified with bands of green shale, holding great numbers 

 of fucoids.t A sandstone, in beds of from four to twelve 

 inches thick, interstratified with green arenaceous shales is 

 found resting on the Laurentian, and immediately underlying 

 the Trenton. This is found near the mouth of the Coldwater 

 on Lake Huron. + 



The beds of sandstone here mentioned form, however, only 

 a small portion of the formation, while in the west the cal- 

 careous feature is almost entirely absent. This difference in 

 lithological features, and the scarcity of fossils combined, has 

 made it difficult to say positively, but the facts all point to 

 the conclusion that in the St. Peter's sandstone we have the 

 western equivalent of the Chazy limestone of the New York 

 system. The correlation rests almost entirely upon the strati- 

 graphic position. 



•Ibid, p. 150. 



tGeology of Canada, from the commencement to 1863. 1863, pp. 123-124. 

 Ilbid, p. 192. 



