UNCONFORMITIES 107 



^o the Meguma series and present certain strong contrasts with it in 

 lithology and history. 



In the east, contacts with the Ordovician and Silurian can not be had 

 because of intervening rocks of Devonian and Carboniferous age. In the 

 valley of Salmon river, at the eastern end of the province, Middle De- 

 vonian adjoins the Meguma on the north, but the low topography gives 

 no opportunities for visible contacts. As rocks containing Cambrian fos- 

 sils are absent from the mainland portion of the province, it is impossible 

 to work out relations between the Cambrian and the Meguma anywhere. 

 Most of the remainder of the northern contact, as far west as the line of 

 the Intercolonial railway, is with the Lower Carboniferous. 



This contact is best seen in the artificial exposures at Coldstream (or 

 Gays Eiver mines), Colchester county, where an auriferous conglomerate 

 has been worked intermittently for many years, the only fossil gold placer 

 in the province. The upper strata are conglomerates and sandstones 

 forming the southern edge of a large body of Lower Carboniferous rocks 

 and composed chiefly of detritus from the Meguma series. The boulders 

 include quartzite, slate, and quartz, the last perhaps 10 per cent of the 

 whole. The difference between the composition of the boulders and the 

 matrix is very marked, the latter being largely quartz. The cements are 

 carbonate of lime, carbonate of iron, and iron hydroxide. 



Gold of clastic origin is present in the conglomerate. The folding of 

 the Meguma long preceded the erosion which gave the basal conglom- 

 erates above, and cleavage and jointing, well developed in the older series, 

 stop short at the contact. The interbedded quartz veins characteristic of 

 the Goldenville formation are present and their detritus furnishes much 

 of the matrix of the conglomerate. The facet made by the plane of the 

 floor of the Carboniferous and that made by the present erosion surface 

 of the Meguma south of the margin form an angle of only a few degrees, 

 indicating comparatively slight distortion and erosion since Lower Car- 

 boniferous time. 



It will thus be seen that all the great events in the history of the series 

 had been enacted before the deposition of this conglomerate. 



COMPOSITION OF YOUNGER ROCKS 



The testimony of sediments younger than the Meguma is inconclusive. 

 The Carboniferous conglomerate contains much material from it, both 

 igneous and sedimentary, showing that it was then in much the same con- 

 dition as at present. At Salmon river the Devonian conglomerate holds 

 pebbles of quartzite, often gneissoid, but no granite, according to Fari- 

 bault (1887). In other places, however, the Devonian has much granite 

 in its basal members. The supposed Ordovician conglomerate at Liv- 



