1 853.] 



One of the points to -wliicli it is ray wish to draw attention is 

 the age of the copper-bearing rocks of Lakes Superior and Huron, 

 as determined by tlie evidences collected on the Canadian survey; 

 and another, the diti'erenees chat exist in the structural condition 

 of the western and eastern parts of the Province. 



The rocks on the north shoi'e of Lake Superior consist of red- 

 dish granite and syenite, which in ascending ordei' pass into 

 micaceous and horublendic gneiss and allied forms. These are 

 succeeded by chloritic and partially talcose slates, which become 

 intei'sti'atified with obscure conglomerates, with a slaty base; and 

 upon them rest unconformably bluish slates, with intermingled 

 bands of chert and limestone towards the bottom, and a thick and 

 extensive overflow of greenstone trap at the top. Reposing on 

 these are wldte sandstones, which puss by an alternation of colours 

 into red sandstones and conglomerates, often with jasper pebbles, 

 and these are repeated after the occurrence of an uncertain amount 

 of reddish limestone of an argillaceous qualit}^ The sandstones 

 and conglomerates become interstratified with amygdaloidal trap 

 layers, and an enormous amount of volcanic overthrow divided 

 into beds ci'owns the summit. The sandstones are often argilla- 

 ceous, and display i-ipple-mark and crack casts on their surfaces, 

 while the concentric curves of flow sometimes characterize those 

 of the tra]). Lmumerable dykes cut up the sedimentaiy and 

 volcanic beds; and both the dykes and the oveiflows are almost 

 universall)- marked by a transverse columnar structure. The 

 thickness of the whole from the base of the blue slates cannot be 

 less than 12,000 feet; and the whole formation is intersected by 

 copper lodes of dift'ei-ent characters in difl'erent places, which run 

 in directions both with and transverse to the strike. 



On the north shore of Lake Huron the granite is succeeded by 

 a formation consisting of wdiite, often vitreous sandstone or quartz 

 rock of great thickness, sometimes passing into a beautiful jasper 

 conglomerate, and alternating with great beds of slate and bands 

 of conglomerate with a slaty base, both being interstratified with 

 thick masses of greenstone. A persistent band of limestone of 

 about 150 feet in thickness, and interstratified with thin cherty 

 layers, occupies a place in the series, probably somewhere about 

 the middle. The surfaces of the sandstone often exhibit rip]ile- 

 mark; and the total thickness of all the members of the formation 

 may be about 10,000 feet. Difierent intrusive rocks intersect 

 those of stratification ; and, as related to one another, they display 

 a succession of events in the history of the foi'mation. Thei'e is 

 of coui-se a set of dykes, — greenstone, no doubt, — cutting the 

 sedimentary rocks, and giving o'igin to the greenstone overflows. 

 It is difiicult, however, to identify these ; but another set of 

 greenstone dykes are seen cutting both the sedimentary and igne- 

 ous strata ; intrusive granite, sometimes occuyping considerable 

 areas, thrusts these antecedents aside, sending forth dykes of its 

 own order, intersectnig all, and reaching to considerable distances 

 from the nuclei ; and then another set of greenstone dykes, and 

 all that previous causes had placed. Evidences of disturbances 

 and dislocations accompany all these successive intrusions, — those 

 connected with the granite being the most violent. But there is, 

 in addition, another set of disturbances of still posterior date, and 

 it is to these that is due the presence of those metalliferous veins 

 which give the country its value as a mineral region. 



In respect to the age of the Huron cuprifei'ous formation, the 

 evidence aftbrded by the facts collected by my friend and asso- 

 ciate, Mr. Murray, (pubhshed in our Report of Progress for 

 1847-48,) on the Grand Manitoulin, La Cloche, Snake, Thessalon, 

 Sulphui', and other Islands, points ranging along a line ninety 

 miles out in front of the coast, is clear, satisfactory, and indisput- 

 ably conclusive. On these Islands, the Potsdam sandstone, the 

 Trenton limestone, the Utica slates, and the Loraine shales, — 

 successive formations in the lowest fossiliferous group of North 

 America, were each, in one place ot another, found in exposures 



ON THE ROCKS OF CANADA. 



125 



denuded of all vegetation, resting in uncomformable repose, in a 

 nearly horizontal position, upon the tilted beds and undulating 

 surface of the quartz rock and its strata : filling up valleys ; o^•er- 

 topping mountains; and concealing everv vestige of dykes and 

 copper veins ; and it would appear that some of these mountains 

 have required the aceunnilatiou of the whole thickness of the 

 lowest three and part of the fourth fossiliferous deposit, equal to 

 about 700 feet, to bury their summits. 



The chief difference in the copper-bearing rocks of Lakes 

 Huron and Superior seems to be the great amount of amygda- 

 loidal trap present among the latter, and of white quartz sandstone 

 among the former. But on the Canadian side of Lake Superior 

 there are considerable areas without amygdaloid, while white sand- 

 stone are present in others, as on the south side of 1 hundor Bay, 

 though not in the same vast amount or the same state of vitiiii- 

 cation as those of Huron. But, notwdthstanding these diderences, 

 there are strong points of resemblance in the interstratification of 

 igneous locks, and the general mineralized condition of the whole, 

 as to render their proximate equivalence highly probable ; and 

 the conclusi\'e evidence given of the age of the Huron would thus 

 appear to settle that of the Lake Superior rocks in the position 

 given to them by Di'. Houghton, the late St;ite Geologist of 

 Michigan, as beneath the lowest known American fossiliferous 

 deposits ; and in this sequence those of Lake Huron, if not those 

 of Superior, would apjiear to be contemporaneous with the 

 Cambrian series of the Bi'itish Isles. 



The eastern hmit of this formation on Lake Huron is in the 

 vicinity of Colling's Inlet, opposite the enstei-n extremity of the 

 Great Manitoulin Island, whence it gradually recedes inland, taking 

 a north-eastern course; and farther down the St. Lawrence and 

 its lakes the Lower Silurian appear to rest upon gneissoid rocks, 

 without the intervention of the Cambrian. 



If a line be drawn on the map in continuation of the Hudson 

 Ri\-er and Lake Champlain valleys to the vicinity of Poitneuf, 

 about thirty miles above Quebec, and thence in a north-eastward 

 direction, it will di\'ide the country into two areas ; wdiich, though 

 neai-ly resembling one another in the general formations of which 

 they are composed, yet present important differences in their 

 stiuctural condition. Each area belongs to a great trough of fos- 

 siliferous strata resting in Canada, with the exception of the sup- 

 porting Cambrian formation of Lakes Huron and Superior, on 

 gneissoid rocks, and containing coal measures in the centre; and 

 the conditions, in which the two areas differ, are the general qui- 

 escence and conformable sequence of the formations fiom the base 

 of the Lower Silurian upwards in the western, and the violent 

 contortions and unconformable relations of those of the eastern. 

 The coal measures of the eastern area are those of Rhode Island, 

 and in a metaraorphic state of Massachusetts, and those of Nova 

 Scotia and New Bi-unswick. None of the producti\-e part of the 

 New Brunswick coal measures reaches Canada; but there comes 

 out from beneath it, on the Canada side of the Bay Chaleur, .3000 

 feet of carboniferous red sandstones and conglomerates. These 

 are succeeded by 7000 feet of Devonian sandstones, which rest 

 upon 2000 feet of Upper Silurian rocks, consisting of limestones 

 and slates. The base of the Up]3er Silurian group has been traced 

 a distance of about 700 miles from Gaspe on the Gulf of St.Law- 

 rence, first to Memphramngog Lake in Canada, thence to Halifax 

 on the southern limit of Vermont, and further into Massachusetts, 

 keepiniT in its outcrop at a variable distance from the coal. In 

 the interval, between the Upper Silurian and the carboniferous 

 formations, there can be little doubt the De\onian sandstones will 

 display a cons]iicuous figure in the eastern area, as they are known 

 to be still 2500 feet thick in the eastern portion of the western 

 area, in which they do not die away until reaching the banks of 

 the Mississippi. In the eastern area the Lower Silurian sb-ata 

 sweep round the LTpper, oe^-upying a zone of between 40 and 50 



