Art. V. — The Geology of Cape Breton — The Lower Silu- 

 rian. — By Edwin Gilpin, Jr., Ll. D., F. R. S. C, 

 Etc., Inspector of Mines. 



(Rtad 9th May, 1892.) 



In my last paper I gave a brief sketch of the Devonian 

 Measures of Cape Breton and now come to the Lower Sikirian 

 rocks. I have ah'eady drawn attention to the remarkably 

 limited developments of geological horizons in this island. 

 Between the basal conglomerate of the Carboniferous and 

 the Pre-Cambrian there intervene only a few limited areas 

 referred to the Devonian and the Lower Silurian. The Lauren- 

 tian hills of the island may have borne on their crests much 

 fuller representations of the geological sequence than are now 

 presented, but evidence is not wanting to show that for long 

 periods they must have stood as now, bare and patriarchal. 



The Lower Silurian of Cape Breton rests frequently upon the 

 Laurentian, and its conglomerates include pebbles of its felsites, 

 gneisses, etc. It is in turn overlaid at many points by Lower 

 Carboniferous strata, and has yielded its fragments to form the 

 basal conglomerates of the latter formation. The fact that 

 hitherto the Lower Carboniferous conglomerates have failed to 

 yield pebbles differing from the Lower Silurian and Laurentian 

 rocks, forms an argument in favor of the view that the Lower 

 Silurian an<I Devonian alone in Cape Breton mark the gap 

 already alluded to. This argument is the stronger because the 

 Carboniferous conglomerates are composed of material derived 

 from strata close to the point of formation. They do not, as in 

 several cases in Nova Scotia, contain boulders and pebbles that 

 have been carried many miles. 



The extent of these Silurian strata is observed at many points 

 by the overlying Carboniferous conglomerates, and at other 

 localities they appear to have been preserved by the protection 

 against denudation afforded by the Laurentian ridges. These 

 strata are not found in the counties of Richmond or Inverness, 



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