.».,. IMAGE EVALUATION TEST TARGET (MT-3) A % .% 1.0 I.I 11.25 -Sis ^ 1^ 12.0 U IIIIII.6 III V qv :1>^ :\ \ V 4^ CIHM/ICMH Microfiche Series. CIHM/ICIVIH Collection de microfiches. Canadian institute for Historical lyAicroreproductions Institut Canadian da microraproductions historiquas 1980 Technical Notes / Notes techniques The Institute has attempted to obtain the best original copy available for filming. Physical features of this copy which may alter any of the images in the reproduction are checked below. L'Institut a microfilm* le meilleur exemplaire qu'il lui a At« possible de se procurer. 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Las images suivantes ont At* reproduites avec le plus grand soin, compte tenu de la condition at de la nettett de I'exemplaire film*, et en conformit6 avec les conditions du contrat de filmage. The last recorded frame on each microfiche shall contain the symbol — ► (meaning CONTINUED"), or the symbol y (meaning "END"), whichever applies. Un dee symboles sulvants apparattra sur la der- niiro image de cheque microfiche, selon le cas: le symbols — ► signlfie "A SUIVRE", le symbols V signlfie "FIN". The original copy was borrowed from, and filmed with, the kind consent of the following institution: National Library of Canada L'exemplaire film* fut reproduit grAce A la gAnirosit* de I'Atablissement prAteur suivant : Bibiiothique natlonale du Canada Maps or plates too large to be entirely Included In one exposure are filmed beginning In the upper l«ft hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: Les cartes ou les planches trop grandes pour Atre reproduites en un seul cilch* sont fllmies A partir de I'angle supArieure gauche, de gauche A droite et de haut en bas, en prenant le nombre d'Images nicessaire. Le diagramme suivant illustre la mithode : 1 2 3 1 2 3 4 S 6 BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA Vol. 6, pp. 357-366, pls. 15, 16 PRE-PALEOZOIC DECAY OF CRYSTALLINE ROCKS NORTH OF LAKE HURON BV ROBERT BELL ASSISTANT DIRECTOR OF THE GEOLOGICAL SURVEY OP CANADA ROCHESTER rUBLISHED BY THE SOCIETY . March, 1894 aammmmfi- BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA Vol. 5, pp. 357-366, PLS. 15, 16 MARCH 24, 1894. PRE-PAr.EOZOrc DECAY OF CRYSTALLINE UOCKS XOHTH OF LAKE irURON j HY IIOHKHT BKLL I ASSI.SIA.NT DlllKCI'OH Ol" THE OKOIAMUtA I, SritVKY <)l' ( ANADA I (Ei'dd hefoir the Soc.ietij Decemhcr iS, JSO.l) , j COXTKXTS • . j Relation of Arclu'iin to I'iiloozoic liocks ,'{.>7 ! I'Aidonce of i)r('-I'iileozi)io Decay 1558 j Wlit-re ln'Mt 8 i UocUk of the lluronian 15elt ;!.")() j Ancient Erosion ;!")(l Typical Krosion Surface :{.')!) ("onditions alfectin^r l"-i'osion .'ifil Contacts of Arcliean with I'aleo/.oic llocks ;i(i2 River and Lake (Miannels due to Hock Decay ;)((4 Ahsence of I'aieo/.oic Deposition and its Sii;nilicance .'[(id Krt"ect of ylaciai Denudation ."!(>(! IvKI. ATION OK AkcIIKAN TO 1*AI.K()Z<)I(; HoCKS. Li all parts of Canada wbei'o tlio Paleozoic strata coiiie in contact with the underlying Archoan rocks the latter appear to pass i)eneath them with very luiicli the same <'ontour or slo[tc as that of tlieir modern sur- face. It appears evident that those ancient stratified or laminated rocks have been tilted to their present lii«;h angles, and that their included in- trusive masses, whether of granite or green.stone, and even most of th(>ir dikes, have occupied their pnjsent positions relatively to each other before the commencement of Paleozoic time, excepting in cnses where faulting has taken place. Not only is this so, l)ut at that early date they appear to have lieen worn down l)y denudation to sotnething like their present superticiai aspect. What has become of the vast amount of debris resulting from thi.« denudation ? Tliis is a prol)lem t)f .Vmericau geology wliich has not L-BvLL. Gkol. Soc. Am., Vol. 5, 1893, (357) 358 R.BELL — PRE-PALEOZOIC DECAY OF CRYSTALLINE ROCKS. yet received much explanation. Between the time of the folding of the Huronian rooks and the deposition of the earhcst fossihferous beds there must have been an interval much "greater than is commonly suppo.sed. Throughout the vast region of Canada occupied by the Archean rocks the attitude of the Huronian and Laurentian strata generally approaches the vertical, and their surface has generally b(;en cut down to nearly a horizontal outline, which is only slightly raised above the scalevel. Lower Silurian strata, csi)ccially limestone, unaltered and full of fossils, may be seen in many places, resting almost horizontally upon the up- turned and denuded edges of the crystalline rocks, and yet the former contain but few fragments of the older terrancs, and they occur only at the very contact, showing that the latter had a hartl and naked surface when the Paleozoic rocks were l)eing deposited upon them. Evidence of pre-Paleozoic Decay. MHiere bed displayed. — The evidence of pre-Palcozoic decay of the an- cient surface is more discernible upon the surfaces of ma.sses of intrusive granite than upon gneiss or other foliated rocks. The reason of this seems to be that in the bottom of the deep sea, where the eating away of the rocks appears to have taken place, the granite was more susceptible to disintegration than the others. Possibly this susceptibility nuiy have been increased by a somewhat higher temi)erature in the intrusive granite. "Of^H.«" or Pits of Decay. — The northwestern jxirtion of George island and the greater part of the township of Rutherford, at the northwest ex- tremity of Georgian bay, consist of red granite. Wherever the surface of this rock has been protected from glacial action it is found to be eaten into hollows in the form of round and sack-like pits and small caverns. The latter generally occur on steep slopes or in per|)endicular faces of the rock, which, however, do not rise to any great height in this vicinity. The floors of these caverns are usually flat, as they are formed by the lower sides of horizontal joints, while the roofs are arched like ovens. Whatever may have been tiie agency which excavated these ovens, it always worked inward from the granite face and ui)ward from the floor formed by a joint, the rock of the latter not being afl'ected, but remaining as sound here as elsewhere along the joint-plane. One of these caverns, which occurs in the western part of Killarncy village, opposite to George island above mentioned, and which is shown in figure 1 of plate 15, the rei)roduction of a photograph, has almost the form and dimensions of the clay ovens used by the French Canadians for baking bread, while other caverns in the neighborhood bear more or less resemblance to this one; hence they have received the local name of BULL. GEOL. SOC. AM. VOL. 5, 1893, PL. 15. Kli.lllK 1. — " <.)VKN " IN GkAMTK, WKST EnH Kll.I.ARSEV VlI.LAHE. Kkuhi; :i.— F.KuiiF.ii iiuamtk s-i ihace ai' Kii.lahnkv Villaue. PRE-PALEOZOIC ROCK DECAY. KVIDENCES OV THE DECAY. 359 " ovens," whioli may also be adopted for convenience as their peoloj^fic desijiniition. Tlu! ovon shown in tliis (il'AI,K()Z()IC DKCAY OF CK YSTA M,IXK KOCKS. {(hu't.'s (»n this island, wliuie the rock surface has l)een sheltered from ^hicial action, wlictlicr level, sli>|»in^ or pi^'pendicular, it is ertxlcd into pits, hollows, humniocks and knobs and has a wvy rou AMINO .loiNTS IN liRANITK TllANSVK.IlSK T(i IIIK ('(llll.SK ipK ( il.AII ATlllN. ROCK DECAY, DEPOSITION AND GLACIATION. EROSION. stirfac 861 n.iKO an, ,,,t|„,,. !!„„,■ ,„.„i,u,l than tl,. s„lToun,ii,« ,„,s, Tl |.nreiltly .>! M)luTctioii„ry origin. '" '"■" "l'" .•n«„n ab.,v.. .i„«,.iboits and ovens of iJenjiunin island, in one case in the face of a perpendicular bluff, as well as of the nearly horizontal beds of greater extent upon the sound though uneven surface of the granite, such as might exist at great depths in the sea, but not upon the land, shows that t!;-*UI*J^'''^P^ ^lJ^ ' 'B^l' Jl-^ ' *''^ ^^^^'^ '^^^ become thus eroded 'm>S^'^*mmJ^^^^'/^i m''' : .1,^1 was destitute of other cov- ering when the limestone began to be deposited upon it. The sea bottom then rose to a more moderate dei)th, so that an abundant fauna found a suita- ble hal)itat and the formation of the limestone commenced. The area now occupied by the North channel of lake Huron might at that time have formed a (juiet arm of the sea, with hills of Huronian rocks to the north, as at present, and similar hills to the south, which have since sunk to lower levels, but of which traces remain. Fr(iniK ^.— Low, circular liklrie, four Feel in Diameter, im weathered Surface of Granite. I'oNTAcrs OF Akchkan with Palkozoig Rocks. Along the junction of the Arcliean and Paleozoic rocks occurring be- tween the foot of lake Ontario and tlie head o{ Georgian bay the actual contact of the Potsdam sandstone and Black river limestone with the Laureniian gneiss may l)e seen in a great number of places. The surface of the gneiss, which can be observed to pass under the nearly horizontal beds of the newer rocks, is generally rough or angular, quite hard and fresh looking, as if it had never been exposed to weathering on land. The points and promontories of these flat-lying strata which stretch northward from the general line of the basal geographic boundary of the Sihirian rocks in this region lie on the lowest ground or in the oro- graphic depressions of the southern margin of the Archean area, where they found shelter from glacial erosion or preglacial decay. It is doubtful if either these or higher formations ever extended over a large part of the Archean area to the northward, as is commonly supposed, although judging from the vast amount of their ruins which have been carried si)Uth they must have been much more extensive before the glacial epoch CONTACTS OF ARCHEAN WITH PALEOZOIC ROCKS. o()o than at present. The middle Sihirian inlier in the great orographic de- pression of lake Teniiscaming on the Ottawa, whicli will he again referred to, is {mother* example of these newer and undisturbed strata oecupying ground much below the general level of the surrounding country. On the north shore of lake Huron, between Killarney village and Spanish river, and again on Grand Manitoulin island, in the vicinity of Sheguenda and westward of that village, the Lower Silurian strata rest almost horizontally upon the flanks of hold l)are ridges of (i[uartzite, the stratification of which stands nearly vertically. The angh's of slope of the ancient rock-surfaces exposed to the weather along the crests of these ridges are continued, as far as can be observed in sections, under the newer rocks forming their flanks, so that the former represent only the upper })arts of ridges, once much higher, but now ]>artly buried under the strata which accumulated around them in Silurian times. A high ridge of (|uartzite runs along the north side of Frazer l)ay. and a similar ridge, but less elevated, forms the northwest side of Killarney bay. The summits and sides of these ridges are, for the most ])art, thoroughly smoothed and striated by glaciation, but near their southern bases occa- sional spots are found which have escaped the action of tiie ice and wiiich show evidence of great anti(iuity, the flinty rock being worn into pits and hollows, but with no sign of granular or textural disintegration. A broken fringe of Black river limestone skirts the base of the (juartzite range on the northwest side of Killarney bay, and the erosion of the spots referred to may be of pre-Paleozoic date, having been preserved till now by a thin limestone covering, or they may rei)resent portions of the surface as it existed immediately before the glacial epoch which have escaped the smoothing action of the ice, hut this is not so likely. In the neighborhood of the quartzite ridges only those beds of the newer rock which are in contact with the old formation contain angular fragments of the rocks on which they lie. The layers containing this debris are usually of no great thickness and the fragments themselves are of small size; but close to Sheguenda, to the uortii and south of the village, are pretty thick strata composed of sharply angular pieces of (piartzite of all sizes packed closely and confusedly togetlier, with only enough calcareous cement to consolidate them. Tliis locality is about twenty miles south of the main Huronian area left uncovered by Silurian strata and the water of laki; Huron. On La Cloche island and elsewhen> in the vicinity numerous ridges and domes of Huronian (piartzite protrude throu'j;h the flat-lying Silu- rian limestones and shales, so that the former n'scmljle masses which have been forced up through them from below, whereas they are only higher portions of the old sea bottom, around which the horizontal beds o()4 R. BKLL — rUE-PALE07,0IC DICrAV OF CUYST.VrLIXE ROCKS. of the much newer rocks were dc|)OHite(l. Tlie quartzites appear to have iindorfronc no change in texture, structural attitucK- or even surface (!<)n- tour since a period vastly antedating Silurian time. Such facts as these indicate pretty clearly that the jdiysical features of the older parts of our continent had their origin at a very remote ]teriod. RiVKH AND LakK ("haNNRLS nUK TO RoCK Dkc'AV. \ The writer has elsewhere* shown that many of the long, straight val- leys in the Archean regions of Canada, now often occupied l»y straight I river stretches, by long, narrow lakes, and by inlets of the larger lakes, ' are due to the decay and removal of wide greenstones dikes or of paral- lel dikes, together with the belts of rock between them. Wlien the depressions along these decayed dikes are not overspread by water they form valleys, more or less filled up with drift, so that the greenstone in the bottom may be only exceptionally exposed to view. Copious si)rings fre(][uently issue from the drift in these valleys. The long, narrow and straight inlets of the northern part of ( Jeorgian ; bay have had their origin along the courses of dikes of this class. The contiimation of each of these channels out into the l)ed of the lake in ' front of it is distinctly marked by a straight line of deeper soundings, having the same direction as the fiord itscilf. Collins, Key, Henvey and Byng inlets, each about twelve miles long, but averaging oid}' 200 or 800 yards in width, are good examples of these fiords. Among the more con- spicuous of the long, narrow and nearly straight valleys of the Archean region which have been formed in the manner just (lescril)ed may be mentioned that of Onaping lake, 30 miles long, north of lake Huron ; Long lake, 02 miles long, north of lake Superior, and Sei)iwesk lake and Nelson river below it, 96 miles long, north of lake Winnipeg. The green- stone of the dike or dikes along the course of these channels may be seen only on islets and points or in patches adhering to the country rock on either side. In the case of fjong lake an immense greenstone dike , emerges from its southern extremity and runs into the hills in the same j bearing as the central line of the lake. i The course of the Mattagami river, the central branch of the Moose, is I guided in its northward trend for a distance of 100 miles from the head of lake Kenogamisse by a number of long dikes of greenstone from 200 to 1,000 feet wide, all having nearly the same direction. f In a typical sec- tion of this part of the river we find that the central portion of the dike i is coarsely crystalline and more deeply eroded than at the sides and * Repoi'tn Geol. Survey Canada, 1870, p. ;i31 ; 1875, p. 315; 1878, p. 15 CO; Report Bureau of Mines Ontario, 1891, p. 7(1: Bull. Geol. Soc. Am., 1890, p. 300. t Report of R. Bell : Geol. Survey of Canada for 1875, p. 315. KIVKR AXU r>AKF CHANNELS Dl'K TO KOCK DECAY. 365 that it lias fjiven rise to tlic main channel of the stream. The fjnoiss has l)een altered and shattered for some distance from the wallw of tlie dike, and this has also suffered decay and erosion and now forms a parallel channel on either side of the ceritral one. Between them the finer f^rained, hard and undecayed greenstone constituting the outer portions of the dike rises up in the shape of ridges and chains of Islands, so that the river Hows as a main central channel more or less separated from the smaller lateral ones. fjake Temiscaming, on the Ottawa, like the Montreal river, which enters its southern extremity, appears to follow the course of a great decayed dike or set of ]»arallel dikes. It lies in a narrow depression which cuts across the general strike of the Archean rocks of the region, and its surface is probably 500 feet below the average elevation of the surrounding country. Its width is only from a mile to two miles, and it has a length of thirty-five miles, but the channel is continued in Deep river, the name given to the section of the Ottawa immediately below" it. Temiscaming is an Ojibwe word meaning " deep lake." and it is well named, for in one part it measures, according to Mr A. K. Barlow, 1,800 feet in depth. The bottom is covered very uneijually with drift, which has l)een pushed into it by glaciers at different times, and the deepest part of the bottom may still be a con.siderable height above the sound greenstone ])elow this filling. If we suppose this height to be 300 feet, then we have a total of 2,()00 feet as representing the average height of the surrounding country al)ove the bottom of the excavation. The sur- face of the lake is 612 feet above the sea, so that the bottom of the water is about 1,200 feet, and that of the whole rock excavation may be 1,')0() feet or more below this level. This may, therefore, be regarded as a very deep cutting across a country, the general aspect of which is that of a mammillated plateau with few great inecjualities. The islands toward the north end of the lake consist of limestone of the Niagara formation, which also rises in cliffs at its extremity and extends northward a consideral^le distance beyond the lake in the same orogra]ibic depression, while the Upper Ottawa river falls over the side of this valley by a rapid descent from the plateau to the eastward. This valley therefore existed before the date of the Niagara formation, an