34 Tilt; LAUKENTIAN. 



limestones would seem to indicate that the lower member of the 

 series alone is represented. The same remark applies to the continua- 

 tion of the formation in the south of the island, with the exception 

 that indications of graphitic limestone and of magnetic iron-ore have 

 been found in two places.* 



It is to be noted here that the great uplift in Pre-Cambrian times 

 of the Laurentian nucleus of Newfoundland seems to have acted as an 

 outwork to the formations to the westward, protecting the area of the 

 Gulf of St Lawrence from those thrusts from the eastward which 

 have piled up in gigantic earth-waves the older formations of other 

 parts of Eastern Canada and the Appalachian region. In consequence 

 of this the area of the Gulf of St Lawrence has throughout Palseozoic 

 time remained undisturbed, and has conformed in its conditions of 

 deposit rather to the internal plateau than to the maritime districts. 



In Cape Breton the isolated mass of St Ann's Mountain seems to 

 be a representative of the Lower Laurentian of Newfoundland, and 

 Mr Fletcher's observations render it probable that rocks of this kind 

 exist in the northern extremity of the island. In Nova Scotia proper 

 I have not as yet been able to recognise any true Laurentian, the 

 rocks attributed by some other observers to this age being, in my 

 judgment, intrusive granite masses of much later date associated with 

 altered rocks. -f- 



In southern New Brunswick, however, the Laurentian reappears. 

 As seen near St John, the lower part consists of red and gray gneiss 

 with chloritic gneiss and diorite. The occurrence of hydrated silicates 

 in some parts of these old gneisses may be attributed to changes sub- 

 sequent to their original formation. The upper member contains 

 much limestone, with graphite and serpentine,:j: gray quartzites and 

 diorite. This last series, which I hold to be really Laurentian, as 

 it certainly underlies, and probably unconformably, the Huronian 

 system, must belong to the upper member of the series. There is, 

 indeed, nothing in its mineral character to exclude it from the Upper 

 Laurentian as developed further west except the absence of certain 

 igneous rocks. 



The resemblance of this interrupted belt of Laurentian along the 

 Atlantic coast of America to that which extends southward from 

 Scandinavia along the west of Europe is patent to every observer. 

 The relation to the next succeeding formations is also identical, and 



* Murray's Geol. Survey of Newfoundland, 1881. 

 t Supplement to Acadian Geology, 1878, p. 89. 



i In this limestone there occur fragments of Eozoon, and the graphite shows 

 obscure fibrous structures. 



