t 



110 J. E. WOODMAN PROBABLE AGE OF THE MEGUMA SERIES 



marginal diorites are known in the Megnma strata, all abyssal and ex- 

 hibiting no tendency to become rhyolitic. None of the younger rocks are 

 thus characterized. The lavas of the Cambrian in Cape Breton are 

 basaltic. The Ordovician has much contemporaneous volcanic material, 

 largely basic, the most acid being a few syenites and aporhyolites and not 

 granites. The Silurian in the eastern part of the province has a noticeable 

 lack of intrusives, the chief ones being a narrow coast belt west of Malig- 

 nant cove, and in the west the so-called diorites, regarded as originating 

 in the great western bysmalith of Meguma granite. In the east the intru- 

 sives of the Devonian are chiefly basic. The Carboniferous is relatively 

 free from igneous rocks, most of those that do occur lying near the mar- 

 gin of Silurian, Devonian, and Ordovician areas and possibly associated 

 with the igneous masses in those strata. 



Thus it appears that none of the rocks of known Paleozoic age in the 

 province have passed through the same or a comparable history of inva- 

 sion from molten matter as the Meguma. The pre-Cambrian of southern 

 Cape Breton contains an abundance of rhyolitic material, affording the 

 nearest approach to the igneous history of the Meguma shown by any of 

 the Nova Scotian series. 



COERELATIQjSr WITH OTHER GROUPS 



Correlation of the Meguma series, direct or implied, has been made 

 with the Saint John Eiver slates of New Brunswick and eastern Maine, 

 with several other unfossiliferous slate and sandstone belts of Maine and 

 New Hampshire, with the Taconic of the Green mountains in New Eng- 

 land and New York, with the gold-bearing slates of North Carolina, with 

 the gold-bearing pre-Cambrian of Newfoundland, with similar slates and 

 sandstones in the eastern townships of Canada, and with several British 

 formations. 



It may appear presumptuous to criticise such correlations without hav- 

 ing seen in the field all the rocks compared, but certain safe conclusions 

 can be drawn from general principles. In the first place, the age of some 

 of the series has not yet been determined, through the absence of just 

 such evidence as is needed in the Meguma; others have been classed as 

 young as the Carboniferous. In the second place, thus far all correlation 

 has been on two bases, neither of which can be regarded as adequate — 

 similar position with reference to rocks of known age and similar litho- 

 logical character. The first has no force, from the indefinite position of 

 the Meguma itself. The second is invalid because of the great distances 

 over which it has been obliged to do duty. The conditions under which 

 strata similar to those of the Meguma might form are so easily repeated 



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