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'!,„, •■^ ,7:61 482 - j<00 - Chon, -^ ^S ("f) 288 - 5989 - fo. c'c^u- y^'^ X()Ti:s ox Till-: i-i.A< I K .\ii.\i:s oi- c vkibuo MRITI- LL'MBIA J B. TvRitfxj.. EcnnoMir GinLot-t fuiLnaiNG Crvi-AiiT TH4^aT3H Ctbrar^ KINOSTON. ONTARIO I (Kfpntiled froo- Econhmic Geouioy, Vol. XIV., No 4, Jun«, 1919 ] NOTES ON TIIK I'LACER MINKS OF CARIBOO. liRITISH COLUMBIA. J. U. TVKKI.U.. In a brief trip made to tlie placer mines of the Cariboo district. British Columbia, in the summer of 1918, .M,me data were gath- ered pertaining to the distribution and geolojjical features of the auriferous gravels, particularly in regard to the existence of ex- tensive beds of pre-glacial gravcLs below Cilacial deposits, and the greater influence of stream piracy over glaciation in changing the courses of streams. They are here presented in the form of brief notes. It is not my intention to describe the configuration of the coun- try, the details of its geolog\-, or the extent to which it is being mined. The Geological Survey of Canada began a survey of the area last summer, and intends to continue it until it is able to publish a complete report with detailed maps of the geolog)' and structure of the country, not only of the older rocks which under- lie it, but also of the later formations and of the influences to which it hns been subjected to form its mountains and valleys, and to deposit the gold in the bottoms of these valleys. Mr. Bowman, of the Geological Survey of Canada, made an examination of the countrj- some years ago and published a num- ber of gO(xi maps of the whole district, and of several of the gold-bearing creeks. With these he published a report on the older rocks underlying the country. Possibly the material per- taining to the gravels collected by Mr. Bowman may he incor- porated in the report which is now to be published by the Geo- logical Survey. HISTORIC.\L DEVELOPMEXT. For many years the country was surrounded with a halo of glory and mystery. Discovered in the winter of 1860-61 by prospectors travelling overland through the rugged mountains to \ 2AHr>i) .rv> }. U. IVKHIU.L. ilu- -until. ..^^.r nl,:.l, u ua^ .ilni.-.t inii.,sMl,le to tran>|..>rt Mip- |'!ii>. .-111,1 . It uliicl, ihe lianly tr iiticTMiien were .,Wij,a.,l t , .U- '"■'"' ''•"■ ' ' "" ''"■• '•.->r!l..'M that fanifd ilir..ii^'Ii the f..rc-i>. it ua, hi.lce.l a .liffinilt c..nn'ry !■• read., hut alter it was readied the leuanN f. ilie iM..,urr, uta- ;;rcat. Writin-; in the autiniin Mt i.Vf.i (.Mvcrnor |;n„.ln, -ay, tliai he ha,l met a lar-c niitiiher ■'t men wh.. ha.l reinriie.I frMin the new -.M camp, .-md withmit eNceptt.n tliey lia.l all I.t-ni Miae-stul. a statement whidi cannot he made lor m.-iny camp*. Alter j;nl,l h;id heen ,lisc.,\ ere.l at the Canon on Williams J reck hy Wdh.nu Hict. , Dutd, Ihlh word was quicklv pas-ed hack to the prospector, >cattered alonj; the I-raser River and iliey >onn ma.le llieir way to the new I'.ldora.Io. I„ ,x,,.. and i-^'-.? many parties came in fr..m the s,.nth and also across the plains and m-.,m,ain, fr..,, the east until a few years later Kar- kervdle. the center of the new district, was second unlv to \ic- t'Tia in i...p„lation i„ ^-liat is now the I'r nince of Itr'itish Co- liimhi;i. Since i8.:,S up to the end .,f n,,; the Government Rep,rts sh.ny that Hritish Colu,nh,a produced alxnit $7S.fJOo.ooo wurth ot placer -old. ( )t this amount the Carilx.., coinitry. net includ- ing the Qtiesnd district, pro.juced s'W to the value of $41- = ei|iiciitIy w.,ter wa> usually present in great nuantity. ihe unwaleruig of the deei)er mine> was therefore a serious and exijcnsive pn.ljleMi and with greater increase in the dei.th of the ovcrhurden, water tinally rendered the deep ground unworkable. 1 could not learn of any individual instance where miners were actually driven out of rich pay gravel which they were mining, hy water, hut exploration and development of deep ground have undoubtedly Ix-en stopjK-d by water, even where rich prosiiects were obtaineti. The ques- ti..n therefore at once arises, how nnich valuable gold-bearmg ground is there still in the ,'her above the sea than the Dome, but the Ixttoms of the .surroundmg valleys are also ahnil 2,0(X} feet higher than the valleys that radiate from the Dome and as hnh sets of valleys are of alMiut the same deiuh. with shijiing wooded sides, the general sim- ilarity of the natural features of the two districts is (juite striking. Williams (.V.cA-.— While the valleys were k-ing formed the streams did not always follmv their present water c^tur-es. l-"or instance, the valley of Conchlir Gulch which comes fnun the southeast, crosses Williams Creek, and is c ]. K. TYKkELI.. IVniii tliat lime ..nunrds 0>ncliliii Creek discharged into this newer i.nrt of \\illianis Creek, and Stoin Creek developed a -nri,re ( I'late X., o) in tiie upper part of the ahamlnned Stuut- l.-uliee \alley in wliich it tluucd eastward into \\illiam< Creek. instead <<\ nMrihwe-tward ;i, liefMre. Hut stream piracy did n.)t end in the rohbinj^ of the water of G,nchlin-Si..m-I.ouIiee Creek by Williams Creek. Slough (.reek I .r >..nie reason (leei)ened its cliannel and fMrmed a gre'rit ui.le valley ( Plate X.. b !. the ll.Mjr of which was about a third of a mile acmx. It must have cut back and robbed the water from the \\illiain<-\\illuw river, f-r Jack-nf-Clul)s lake, which lies in its valley, is reported to be J(X) feet deep, and the bedrock in its valley a little farther we>t was found by drilling to be -'S- feet below the surface, while the louest part of the bedrock in tlie ^alley of WUInw Kiver wa< only 102 feet below the surface. which was probably a little higher than the surface at the drill iK.Ie near .^longh Creek. Thus the original be.lr.,ck bott..m of the valley of Slough Creek is nearly joo feet deeper than that of Uillow River, anrl cnnH-.|uently it undoubtedly robbed the water from the latter stream. In excavating its great valley the old Slough Creek, which had donl>tless become a large and important river through the adilition f.f Williams Creek, and probably also of \'alley and Downie-l'ass Creeks, cut away the lower portion of the almost abandoned valley of Lowhee Creek, and of the wide valley of Jack-of-Clubs Creek, reducing them to hanging valleys on the side of the master valley. The original courses of the lower parts of the streams that occupied these two old hanging valleys was not apparent, but it is possible that they turned westward and then somhwestward in what is now the valley of Chisholm Creek, and thus flowed into Lightning Creek, for the upper por- tion of Chisholm Creek valley was also cut away by Slough Creek. Luihtning C/rr/.'.— Lightning Creek valley is narrow and \ -shaped as far down as Stanley, the narrow channel in its rock door being often not more than 20 or 30 feet in width. At Stan- Plate X, Economic Geologv. Vol. X(V. i ./. M..ii!li ,,f St.iif- (.iiVli irMMi \\illi.,in ( mk ~h,.«iim miliim, ir,,m livdraiilu- ..mrali..ti- ii; tiii' I.Ti i;r. iiiii.l. aii.l ^.Ty. in ihv IimiImiti ,.t tin- ..lil inanin \all<> ir, tin li.uk iiiitir /'. Wi.k- \^]\^ .,i <.\..nuh ( r, < k I..,.kin,i; n. .nliu<-M«;;i d n,,m M. .-,,11111,, ( r. J llitf ,,f li,,;ilcle(I .lley of Chishnlni Creek joins it from the ncrth. and thence downward^ ilie wh.de valley is wider than l)efnre, and maintains a L'-shapcd character. At a place known a- the P.eavcr I'as^ the main \alley s\\ in;,'^ off to the north, and (I'liibtless the drainai,'e ran fcir a Innj; time in that direction, but the present stream turns s, luhwe.-tward into a narrow S'^rpe be- tween p'cky walls, and continues in it past \\':nf,'s I'eters Creek fVnvs int > Li.L;litninf,r River from the south, and whether the narrow valley of Lightning,' Creek below the continence of these two streams was once the con- tinuation of it^ valley, or was the valley of a tributary in which the drainage has been reversed, is uncertain, though the latter -upi)osition is probably the correct one. I was not able to learn the dei)ih of bedrock bcl'>w the >urf:ice ;it Heaver Pas<, but it is pnibably several hundred feet, fur according to information re- ceived froin Mr. M. liaik-y. the depth from the surface to bed- rock alxiut four miles farther up Lightning Creek is 205 feet, and while the grade of the surface between tlie two places is \ery light, tlie grade of the bedrock is probably much steeper. This will indicate the conditions of drainage, and the char- acters of the valleys that had been formed l)y it at the end of the Pliocene Period, and it will be seen that in pre-Glacial times wide mature valleys had been ff>rmed, but streant piracy had been taking place and the streams thaf formed these valleys were robbed by other streams that flowed in deeper valleys. Accnmulation of Gold. — During this time gold was being con- centrated into the bottoms of some of these vallevs in larger or smaller quantities, according to the alnmdance of th supjjly. the excellence of the bedrock for forming riffier. or tin. length of time through which the concentration was operative. If similar conditions had continued down to the present there would have been several wide valley . in the district with lieds of gravel cov- ering their bottom lands, through which paystreaks would run. Deep narrow \'-shai)ed valleys and gidches would discharge into them, sometimes from hanging valleys, while in eml)avments 342 J. II. TYKHELL. alMiif; tlifir si(le> wduld i)rMl)aI)ly (.cciir gravel-covered erosion terraces. Tlie continuity of conilitions of erosion was suddenly broken by tlie advent of the Glacial Period. There was no general Cor- dillcran glacier in this district with a motion southeastward or northwestward parallel to the trend of the mountains, but the Country was heavily glaciated by local glaciers that flowed down from the mountains into the great valleys. On the side of the mountain nTth of the valley of Lightning Creek near Stanley, and 1,000 feet above the stream, a quartz ledge was seen to lie scored by glacial markings trending northwestward parallel to the course of the vallev.' After existing for a long time, and in some cases extending far out over the plateau, even to the banks of the Fraser River itself, the local glaciers retired and disappeared, leaving behind them extensive sheets and deposits of boulder-clay, and large moraines : the latter dammed many valleys and diverted streams into other channels, thus adding to the intricacies of a drainage system which was already quite complicated in pre-Glacial tiines. Most, if not all of the valleys had beds of pre-Glacial gravel of varying thickness co\ ering their rocky floors. As the glaciers moved down the valleys they in many cases rode over this gravel and left it, with its cargo of gold, comparatively undisturbed, and at the same time they brought down a certain quantity of material from the hills on each side and formed ground moraines of hard massive impervious boulder-clay, which, on the retire- ment of the glaciers remained as watertight covers of varying thicknr-s over the underhing gravel. Existing streams usually flow on the top of this bed of boulder-clay. In some narrower and swifter places in the upper reaches of valleys they have doubtless cut through it to the underlying gravel or bedrock, and many of the earlier mining operations were probably carried on in places where this had occurred. In these places all the gravel down to bedrock, as well as the upper part of bedrock 1 " Was tlur-> a Cordilleran Glacier in P.ritisli Columbia." by J. B. Tyrrell, Jour, (if Cii-o!.. \'ol. J-. No. I. 1019. pp. 55-60. I «» PLACER MIXES or CARIBOO. BRITISH COLUMBIA. 343 itself, was shovelled into the sliiice-lx)xes. and washed to re- cover the gold. In those parts of the bottoms of valleys where boulder-clay was st.ll lying undisturbed on the gravel the miners sank shafts through the boulder-clay and gravels to bedrock, drove tunnels on or in bedrock, pumped the water from them with Cornish pumps, and extracted the gold-bearing gravel from the shafts. As the gravel was usually porous, the How of water was often large and r'-flficult to handle with the pumps. In fact, in long stretches oi s. ,eral of the valleys, where the pre-G'.acial gravels have been bu.ied to a great depth it has been found impossible to mme. or even to explore them on account of the heavy flow and heavy pressure of water encountered. Further attempts will doubtless be made to explore these deep gravels, but if such enterprises should be undertaken there should be made careful physiographic surveys of the district in order to determine the particular valleys or parts of valleys into which most gold was discharged, and the localities in which it probably lodged. An interesting feature was observed on some of the gulches tributary to the larger valleys, as for instance on those of Mos- quito and Last^-hance Creeks. Both these streams flow in chan- nels bounded by rock on their western or down-stream sides, and boulder-clay on their eastern or upstream sides. In searching for a paystreak in each case the old miners found that the pre- Glacial channel was buried beneath the boulder-clay on the east- ern side of. and at considerably lower level than, the present stream for the glaciers, as they descended the main valleys, had filled the upper sides of the gulches with boulder-clay, and when drainage was re-established in post-Glacial times, the new chan- nels were formed above and to the west of the old ones At the Caiion on Williams Creek, where two narrow gorges have been cut on opposite sides of a rocky knoll, the direction of movement of the glacier would appear to have been more or less transverse to the course of the stream at this point, and the glacier completely filled and covered up the eastern of the two gorges with boulder clay, so that it was not until some little time 344 /. /(. TVHkELL. afiLT niiniii},^ was be^iin on tlie ircck tliat tliis ^'Tge \\a> f.iunJ and iiiRii\L'rc(l. The valley* so far referred to lia\e had beds of pre-Glacial gravel remaining in them, Init two valleys, or ]><)s>il)ly parts of one valley, which came under my notice, namely, Stout-Lowhee and Chisliolm Creek valleys, were different from the rest in this particular, for either mo>t of ihe gravels which had originally covered their lloors had been remo\ed Ijefore the advent of the glacier, or possibly the glacier it>ell may have displaced what re- mained of the gravel, and may have kneaded it up with material brought from elsewhere to form the Iwulder-clay which is now either resting directly on Ijedrock, or is separated from it by a thin layer of poorly aborted material ( IM.ite X., o This ab- sence of gravel beiueen the lx)ul(ler clay and the underlying rock is well shown in a 1 mg luiiiiel into the we-tcrn siile tif the \ alley of C'hisholm Creek. .\lso the hydraulic o[)erations which were being carried on in -Stout Gulch at the titne of my visit exposed an excclleiu sectii'U of boulder clay, which seeme from top to bottom. Some of it was slightly aurif- erous. On A'osquito (iulch, where hxdraulic operations were also being conducted, and where boulder-clay along with botli overl\ing and underlying gravel was being broken down ami washed through sluice ixixes, some of it was decidedly auriferous. In addition to forming a blanket over the earlier gold-bearing gravels the boulder-clay would a[)jiear to have l)een deix)sited in some places of sufficient thickness to divert streams into new channels, as for instance at Beaver Pass House, Lightning Creek has l>een diverted to a narrow western froin a »»'ide northern channel, probably on account of the deposition of a thick l)ed of boulder-clay in the latter. In addition lo the deposition of a Ijed of boulder-clay over most of the surface of the lower land the glacier formed terminal moraines across the b(. toms of the valleys. One of the most conspicuous of these is in Slough Creek valley, and extends from the west end of Jack-of-Clubs lake for several miles westward to a point some little distance Ijehnv the mouth of Devils' Creek. J I'L.ICER MIXES or C.IKIBOO. IIRITISH COLUMBIA. 345 This niuntine blocks the drainage of tlie valley, ami forces the water issuiiifj from Jack-of-Chihs lake to How down the valley of Willow River. Another hilly and sti>iiy moraine lies in the b-Jttom of the valley of Lightning Creek between the mouths of Chishohn and Davis Creeks, but it had no intluence on the general drainage except temporarily to dam back the water into a small lake. Altogether the diversion of drainage from one valley to an- other would seem to have been affected much more by stream piracy in pre-Glacial times than by moraines or other dams in Glacial or post-Glacial times.