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The original copy was borrowed from, and filmed with, the kind consent of the following institution: Library of the Public Archives of Canada Maps or plates too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: L'exemplaire film6 fut reproduit grdce 6 la g6n6rosit6 de I'dtablissement prdteur suivant : La bibliothdque des Archives publiques du Canada Les cartes ou les planches trop grandes pour dtre reproduites en un seul clich6 sont filmdes 6 partir de Tangle supdrieure gauche, de gauche 6 droite et de haut en bas, en prenant le nombre d'images ndcessaire. Le diagramme suivant illustre la m6thode : 1 2 3 1 2 3 4 5 6 A. M. CAMPB£L1- Section IV, 1801. [ 67 ] Trans. Roy. Soo. Canada. VI. — On tlie Geology of the St. Clair Tunnel. By Frank D. Adams, Lecturer in Geology, McGill University. (CommunicHted by Sir William Dawsou and read, May 27, 1891.) The St. Clair Tuunel, one of the most useful and important engineering works of recent years, runs under the St. Clair River from Saruia, Ontario, to Port Huron, Michigan, and joins the Chicago & Grand Trunk Eailway in Michigan with the Great Western Branch of the Grand Trunk Railway in Canada. These points had formerly been con- nected by a steam car ferry, but owing to the great annual expense and the uncertainty of this means of communication, especially in winter, when the ice from Lake Huron is passing down the St. Clair, as well as to the steady increase of trallic over the line, it was decided to tunnel the river at this point, so that a continuous track might be laid. The tunnel proper was commenced in August, 1889, and finished in August, 1890, the work being thus completed within about one year, the time I .?ing the fastest yet made in tunnel construction. The work was begun by opening horizontal mattings to the required depth on either side of the river, and on each of the headings thus formed a tunnel was commenced by means of Beach hydraulic shields, the tunnels finally meeting under the river and thus completing the work. The tunnel is 6,000 feet long and 21 feet in diameter, the walls being constructed of cast iron segments bolted together. As the tunnel passes through the heavy deposits of drift which cover this portion of the boundary of Canada and the United States, it seemed probable that an examination of the material ex<'avated might prove of interest. Sir Joseph Hickson kindly consented, on request of Sir William Dawson, to secure specimens of the material passed through as the work proceeded, and this was arranged for through the kindness of Mr. James Hobson, the chief engineer of the tunnel ; eight samples, taken from, different points between the Canadian and American ends of the tunnel, being forwarded to the Peter Redpath Museum of this University and placed in the hands of the writer for examination. General Geology of the District. Resting on the Laurentian axis, whose southern edge forms the eastern shore of the Georgian Bay, 180 miles northeast of Sarnia, there is, as is well known, a regular succes- sion of Palieozoic strata, having a general southwesterly dip and forming an almost con- tinuous series from the horizon of the Black River beds to that of the Chemung. These underlie what is known as the peninsula portion of the province of Ontario. Passing over the St. Clair River, into the state of Michigan, we find these highest beds succeeded 68 FRANK I). ADAMS ON TlIK by the siimlsf'>in's, t'tc, oi tin- " Waverly Group," whi h murks the base of the Ciirhonifer- ous, and which in its lurn is overlaid by the carbon ilorous linn'stoni' and coa! uioasuns occupying the central portion of the state. - . The distribution of these formations is shown in the accompanying geological map. The entire area, however, both in Ontario and Michigan is heavily drifted, so that over long stretches of country no outcrop can ])e seen. This drift in Ontario has not been as yet carefully studied. In the early years of the Canadian Geolog. "al survey it was examined in a general way, and in the 'Geology of Canada,' published i.^ 1863, was classilicd as follows, in descending order: — Recent Alluvia. Artemisia Gravel and Algomu Sand. Saugeeu Clay and Sand. Erie Clay. Boulder Clay. There is reason to believe, however, that the Saugeen clay and, perhai)S. some of the other members of the series are secondary deposits whose material was derived from the underlying boulder clay. The Ibllowing extract from a report prepared by J)r. liidl, of the Canadian (icological survey, for the Royal Commission on the Mineral Resources of Ontario, gives a general description of the Saugeen and Erie days : — • " West of the points above mentioned, south of the height of the land, the marine deposits are replaced by others which appear to be in part, at least, of fresh water origin. One of the most important of these is an extensive blue clay deposit which we have called the Erie clay, and which has as yet yielded no organic remains of any kind. It burns to white bricks, while the marine clays to the east burn red. The Erie clay is often very calcareous, and is seldom or never entirely free from pebbles and stones, more or less thickly disseminated through it. Indeed, it often seems to merge into the underlying boulder clay. It covers the whole of the southwestern part of the western peninsula, and is locally developed in many other parts of the province, as far east as the line of rail- way from Brockville to Ottawa. Its greatest known depth is about 200 feet, but it is found at ditferences of levels amounting to 500 f(>et. When seen in fresh sections it pre- sents lines of stratiHcatiou, and often a transversely jointed structure. In some localities its upper parts have been unevenly denuded before the deposition of the next higher formation, which consists of brownish clay yielding red bricks. This unconformable formation is well developed in the valley of the Saugeen River, and hence it has received the name of the Saugeen clay. Its thickness appears to be less than that of the Erie clay, but it is found in broken areas in all parts of the province, except the most easterly and northerly. When seen in fresh sections it is usually found to be very distinctly stratified in thin layers; sometimes with partings of fine sand between them. Beds of sand and gravel are occasionally I'ound between the Erie and Saugeen clays, and these are of im- portance as afibrding good wells of water. Fresh water shells have been detected in a few instances in the Saugeen clay." The "marine clays " above mentioned are those found in the valley of the St. Law- rence east of Brockville and known as the Leda clays, beinj probably the eastern equiva- (^ / Cr i<» O / tm 4 I GKOLOGY OF TIIK ST. CLAIR TUNNEL. 69 lent of thi' Erio and Sauireon days laid down under diU'crcnf t-onditioiiN. This Loda clay will bo referred to again later on. Character ok thk Strata penetrated hy the Tunnel. Judging from the character of the deposit there is reason to believe that the St. Clair tunnel passes through boulder clay, though biingin places very sandy, and having in some places a certain stratifiealion, i1 pnrtakes of the character of the Erie clay, which, as above mentioned, gradu.ites into the l)ould(>r clay, and may really prove to be n peculiar development of it. The material o])tained from the tunnel is a stilf clay, in places, as above mentioned, very sandy, and elsewhere very gravelly, while occasionally large gneiss boulders an^ found embedded in it. When dry it i.s grey in colour, but assumes a pule reddish yellow tint on burning. Judging from the samples received it is entirely destitute of fossils. This clay rests on a dark bituminous shale, with iil>uudance of Frotosalcinia Huron- ensU, characteristics of the so-cnlled "Huron shale" of Chemung age, which is well ex- posed in Ontario at Kettle Point on Lake Huron, and is extensively developed on the Michigan peninsula. This Huron shale was struck at the bottom of a shaft which was sunk for drainage purposes close to the Canadian end of the tunnel and, as seen in the accompany; lower. " Boulders weri occasiouiiUy struck, some of them eontnining two or three cubic yards. " The large boulders were not numerous ; perhaps there were not more than half a dozen of them. I am now speaking of boulders too large to pass through the com- partments of the shields ; of small boulders there were a considerable rumber. They were all, so far as I know, coarse granite. The woikni"n used to call them 'bastard granite.' " The bed of the river consists of sand and gravel, varying in thickness Irom a few inches to several feet." In order to ascei-tain the proportion of sand and gravel present, weighed portions of the several samples were submitted to a process of washing or elutriation, being repeat- edly stirred with successive portions of water and allowed each time to settle for ten seconds ; in this way only the clay and the exceedingly fine sand were remced. The gravel and the rest of the sand remaining behind were then weighed. The amount of carbonic dioxide present in the several samples was also kindly determined by Mr. A. Klock, under Dr. Harrington's supervision, in the chemical laboratory of this University. These results, together with the amount of carbonate of lime represented by the carbonic acid in each case, are given in the following table : — Nnniber of Siieciiiieo. Pi>int from wliich Specimen wn.H*r:iUeii. PorcpntiiKo of Sand ami Urnvol. Porcentaite of Ciirhnnio Dioxide. PerccntiiRO of Calcium Carbonate. I. 11. III. IV. V. vr. VII. VIII. / Canadian side, l,fiOO feet ea»t of river 1 , and 70 feet below surface j ■ American Hide, l.OfK) fc*t wprI of" river and 00 feet lielow tlie surface. .' I ,„ ,„„ ( n-0 12'2 3-2 40-8 (Sand ct Gravel) 54-0 (Sand & Gravel) 04-4 (Sandy) 81-4 (Gravelly) 73-8 (Sandy) 6-238 c-7n(> 6-987 f.-225 5 872 4-440 5' 981 3-387 14 180 15-241 15-880 11-875 13-347 10-1(KI 13-00 8 80O /Canadian side, 1,643 feet in and 801 \ feet below the surface ... j' Canadian end of tunnel It may here be mentioned, however, that a certain amount of magnesia is probably present in combination with lime and carbonic acid, forming adolomitic limestone rather than a pure carbonate of lime Nos. 1 and 2 when boiled with concentrated hydrochloric acid for an hoar left 68-3 per cent, and 688 per cent, of insoluble residue respectively. The following figures showing the amount of calcium carbonate in brick clays from (JEOLOGY OF TUB ST. GLAIR TUNNEL. 71 other parts of Ontario may bo of interest for comparison. The determinations were made by Dr. B. J. Harrington and have not hitherto been published : — liOCALITY Per cent, of Ctloium Carbonate. 2-77 26-72 •008 20-72 11-30 53-05 York ville Ont (* <* , ^ , , ,, Petrooeaphicai. Character of the Gravel. The gravel in these clays is generally small, passing into saud, but in No. VII. some of it was quite coarse, the largest fragments measuring as much as two inches across. It is composed principally of worn fragments of soft brownish-black earthy looking bituminous shale. When struck with a hammer this readily splits up into thin fragments parallel to the lamination, and when held in the llame )f a Bunsen burner decrepitates and takes fire, burning for a second or two and giving ofi' a strong tarry odour. In almost every case where a broken fragment of the shale is examined by means of a lens it is seen to be thickly strewed with the minute sporocarps of Prutosatvinia Huronensis, characteristic of the Chemung (Huron) shales, from exposures of which the fragments were evidently derived. In addition to the fragments of Huron shale, a number of fragments, more or less worn, of a soft line grained, somewhat doloraitic, and micaceous sandstone, are found in the gravel, as well as some much smaller fragments of brownish or yellowish limestone, often highly magnesi>.u. These latter are sometimes pure, and at other times contain a very large amount of siliceous and argillaceous insoluble residue. Occasionally a few rounded fragments of whitt; or greenish quartzite are also found. A number of fragments of the sandstone referred to above were crushed and treated with warm dilute hydrochloric acid. A slight effervescence took place, and small amounts of iron, lime and magnesia passed into solution. The dolomite being thus removed, the insoluble residue was mounted and examined with the microscope. A thin section of one fragment was also prepared. The sandstone was found to consist of the following miner- ala: — quartz, orthoclase, microcline, plagioclase, rauscovite, biotite, hornblende (?), tour- maline, zircon, sphene (?) together with some opaque dark grains, possibly of some carbon- aceous material. In the thin section, which was not treated with dilute hydrochloric acid before examination, dolomite and ferric hydrate could also be recognized. The little crys- tals and grains of tourmaline and sphene (?) closely resembled those which, as mentioned below, were found in the sand occurring with the clay. One large well laminated fragment of this sandstone had a structure resembling false bedding and showed what Sir William Dawson believes to be obscure worm burrows or fucoid markings. 72 FRANK ]). ADAMS ON THE In nil ilH chiiractoristics it closely roNerabli's thi« sandstonos ol' th(! " Wiivorly Group," which, ill Michigan, ovcrli*! the Huron shales. (Sec report of the Geological survey of Michigan, 1873-70, Vol. Ill, pp. (i!»-101.) The limestone I'ragments were small and (iontained no fossils visible to the naked eye, or with the help of a lens. Some of the minute grains mixed in with the sand, how- ever, when properly mounted and examined under the microscope, were Ibund to possess an organic structure ; some of them n-sembling I'ragmeiUs of crinoids, while others had a minutely punctate character and were probably fragments of brachiopods)iells. There is nothing, therefore, to indicate th(! age of the beds from whi.h these limestone frag- ments have been derived. They may have come, from the thin beds of limestone inter- stratified with the sandstones of the " Waverly (Iroui)," or they may be from older strata of Cornifevous, or even Niagara age. The very few fragments of quartzite have no dis- tinctive characters by which their origin can be determined ; some of them resemble the quartzite of the more compact beds of the Oriskany formation. PETBOdBAl'niCAI. ChABACTKB OF THE SaND. As will be seen by referring to the table, Nos. VI. and VIII. consist very largely of saud : No.VIII, in fact, is a nearly pure sand, but a portion of it being extremely flue was washed away during the process of elntriation. Another portion of No.VIII was carefully riutriated, and the material of various degrees of coarseness being thus separati'd, speci- mens of each were mounted in Canada balsam for microscopic examination, while others were prepared in almond oil and in water. The constituents found in this sand are the same as those found in the sands separated from the other samples, although all the minerals here mentioned were not found in evt.'ry case. A brief description of this sand, therefore, will serve to indicate the <;haracter of the whole. The coarse portions separated by the washing were ibund to be composed of the following minerals :— quartz, orthodase, microdiue, plagioclase, hornblende, epidote, tourmaline, garnet, calcite, pyrite, magnetite, spheue (?). A few small pieces of the shale and sandstone before mentioned were also present. The quartz o<-curs principally in partially rounded fragments, but also as angular chips, while a number of grains are perfectly rounded with a surface like ground glass. They are generally clear and colourless, but some few have the surface stained red by oxide of iron. Some of them hold the minute black hair-like bodies often seen in the quartz of the crystalline schists. Some of the quartz grains in the sand in No. I. show the peculiar crushed or broken character so often seen in the quartz of gneiss. The orthoclase is not nearly so abundant as the quartz and occurs usually in much decomposed grains. It shows a biaxial figure in convergent light. Microcline and plagioclase in well characterized grains occur in every slide. Horn- blende occurs in green transparent anisotropic grains, often strongly pleochroic in tints of green. Generally in oblong grains with slightly inclined extinction and absorption (£>a Tourmaline was found in the sands of aU degrees of fineness. It occurs in short, stout prisms, terminated at one extremity by a Hat pyramid ; the other end is sometimes simi- larly terminated, but is generally irregular. One of the largest of these little prisms was Mm f GKOLOGY OK TIIK ST. (ILAIU TlINNrij. 78 round to inoiuuiH) Ofj x '027 mm. Thoy have a high index of rcfrHction and strong douhlo rtil'raction, with i)iinill(il L-xtiiiction, and nhow Htiong plt'ochroism in tintn running Iroiii light brown, yoilowiHli or grofniwh brown to deep brown or ntiarly Macii. Tho gr<'iitt'(s( iibK()ri)tion in in u diroition at right iingloc? to thi^ length of thu i;ryNtal. It is uniaxial and negative and HhowH uo cloavago. These chttractcrs loavi; but little doubt that th(f mineral is really tourmaline. The f^nrnet is pink in color and isotropir with high index of rel'raction. Tho calcite i8 present in considerable amount, the sand elferveseing readily when treated with dilute hydroehloric acid, and oreurs principally as cleavage Iragments. It is uniaxial and negative, and between cro.ssed Nieols shows the characteristic white of the higher orders. Although here reft'pred to as ealeite, an some of tne grains at least are attracted by the electro-magnet showing that they contain some iron, it may really be dolomite in part. Pyrite occurs in numerous little yellow grains with crystalline faces. Some of these are very minute but perfect octahedra. In No. IV, in addition to little rounded grains resembliu^ liuute concn^tions. a number of little octahedra were found often in groups. One vt -y perfect little octahedron, showing also planes of the nentagonal dodecahedron, measured 07 mm. in diameter. On ac(;ouut of the good form and sharp angles usually possessed by this pyrite it seems probable that it has crystallized ia the drift. The mineral referred to as sphene (i) occurs in small rounded grains with high index of refraclion and high double refraction, and is either sphene or zircon, but I was unable to lind any grain in which an axial figure could be obtained. The fine material deposited from the first washing was found to be made up alto- gether of minute grains of dilFerenl minerals. In addition to those already mentioned biotite and a (iolourlcss mica resembling muscovite, but probably belonging to some hydratcd species, were also present. A very small amount of a fine grained aggregate, probably kaolin, was also seen in the slides. I'ETROtJRAPHIOAIj OhABACTER OK THE ClaY. A careful microscopical examination of the clay separated by washing from Nos. I. and VI. was also made. These clays were found to be almost identical in character, and may be taken as representing the clays of the whole deposit. The material is exceedingly fine and requires a very high power for its examination. Minute fragments of calcite, c^hoclase and little mica shreds can always be recognized, as well as in tome cases little grains of plagioclase, hornblende and quartz. Kaolin is also present, and in No. I. occurs in large amount. Mixed with these minerals in No. I. and in No. IV., constituting a very large proportion of the clay, are dark fragments, which are opaque, except on the thinnest edges, where they are seen to be composed of a kaolin-like aggregate holding opaque grains. This is in part at least the Huron shale in a finely comminuted condition, while a portion of it seems to be a decomposition product of orthoclase. 8«c. IV, 1891. 10. •m FIJANK D. ADAMS ON TilE Orioin ok the Drikt penetrated by the Tunnel. It is evident from the character of the drift as above describid, that with the excep- tion of the comparatively few boulders of Laureiitiau gneiss embedded in it. it has not Laen brought from the I'ar north, but has been derived very largely, if not exclusively, from the wear and tear of the Huron shales and rocks of the " Waverly Group " which occur in the ' nraediate vicinity. This is indicated by the character of the gravel which is present in almost every sample of the clay, sometimes constituting a large proportion of the whole. Although ''13 peculiar character of the sand shows that it has been derived origin- ally from the gneisses of the Laureutian, it seems pretty certain that its proximate origin is to be found in the " Waverly "' sandstones, since not only are fragments of sandstone, which, as shown above, there is every reason to believe belong to this group, scattered through the drift and occur even in these very beds of sand, but the sandstone itself con- tains nearly all the minerals found in the sand, and among them some of the rarer and more characteristic species. The characte» of the clays also points to a similar origin. Since the general movement of the drilt in this district was from north to south, the material constituting the drift penetrated by the tunnel must have come from some por- tion of the area now occupied by Lake Huron. This conclusion, as will be seen by consulting the accompanying geological map, is in perfect accord with that indicated by the composition of the drift itself, namely, that it is derived from the wear and tear of the Huron ch U's and beds of the "Waverly Group," seeing that a considerable portion of the southern u-\lf of Lake Huron lies in a depression scooped out of these formations. A great part of Lake Michigan also must be underlain by rocks of this age. The Leda Clay. As above mentioned, the Erie and Saugeen clays do not extend down the valley of the St. Lawrence below Brockville. East of this point their place is taken by a deposit of clay quite different in character and known as the Leda clay. This clay is in places highly fossiliferous, and, as indicated by its fos-sils, is of truly marine origin. For comparison with the clays above described a typical specimen of this Leda clay was examined microscopically. The sample, which was given to me by Sir William Dawson, was taken from an excavation on Sherbrooke street, in the city of Montreal. It is an impalpably fine clay with no admixture of sand and gravel. When powdered and carefully washed a minute residue remains, which, when examined under the microscope, is seen to consist of little angular fragments quite clear and fresh of the following min- erals :— quartz, microcline, orthoclase, plagioclase, hornblende, garnet, calcite, apatite (?), tourmaline (?)• The quartz sometimes shows the uneven extinction t,o often seen in gneiss. Under the microscope th.; rest of the clay is seen to consist of exceedingly finely divided kaolin, with here aid there a fev. minute brilliantly polarizing fragments of one or other of the above mentioned mineral species. Thin diiFerence in the character of the Leda clay and the clays from the St. Clair GKOLOCIY OF THE ST. flLAlR TUNNEL. 78 tunnel is in all probability due to the fact that the Leda clay was deposited far from land in what was th(>n a great westward extension of the Atlantic. In closin"' I desire to thank th<' various gentlemen to whom I am indebted for assist- ance in carrying out this investigation. My thanks are due more especially to Sir Joseph Hickson and Mr.. Joseph Hobson for having the samples carefully collected and forwarded, as well as for notes on their mode of occurrence, and to Sir William Dawson, at whose request I undertook the examination of the same, for aid more particularly in the deter- mination of the fossils. ' it ioatm ;v c -< "/ Trans. \\. S. C, iH'.ll. Sec. IV. I'latr IV a 1 ,•* 2 u. O a. <-> X 1- u. o a 2 Q < Z O u o UJ o a Q. C/5 I 3 X < o o a: S S a: < z a OQ 6 to i O cc q: o >- cc O I 2 3: i?- «*- -^ i-^ ct I- CO s 2 < To illustrate Mr. I\ I). .\,l:„ns- j'apcr on the St. Clair Tunnel. i; v^