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Maps, plates, charts, etc., may be filmed at different reduction ratios. Those too large to be entirely included in one exposure are ffilmed 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: Un des symboles suivants apparaitra sur la dernidre image de cheque microffiche, selon le cas: le symbols —► signifie "A SUIVRE", le symbols y signifie "FIN ". Les cartes, planches, tableaux, etc., peuvent dtre filmte d des taux de r6duction diffdrents. Lorsque le document est trop grand pour dtre reproduit en un seul clich6, il est ffilmd A partir de Tangle supirieur gauche, de gauche d droite, et de haut en bas, en prenant le nombre d'images ndcessaire. Les diagrammes suivants illustrent la m6thode. 1 2 3 1 2 3 4 5 6 2:^ ! I ! ! t X ni ; f I » x BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA Vol. 10, pp. 193-198, pl. 2t b v^. 'M / iiLACIAL PHENOMENA IN THE CANADIAN YUKON DISTRICT BY J. B. TYRRELL M ROCHESTER PUBLISHED BY THE SOCIETY April, 1899 .4r..it: ii*^ vsjiJOt-. w*»' wm^m^ "i^P" VJ-. - ll'll"ll""'"» ^^^ 1^ I! ^ I ' I l> £1 i i BULL. GEOL. SOC. AM. VOL. 10, 189H, PI . GLACl Introdn Area trii I'livKioj? (ilacial 1 Kxt The 8tri Mo) Ten Int Tiast Houthw ern par for ohs occur t .some 01 deep ai My r what is the Chi or Chil( being oc XXI CANADIAN YUKON DISTRICT iH. PI . ;m bi> BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA Vol. 10, pp. 193-198, PL. 21 April 3, 1899 GLACIAL PHENOMENA IN THE CANADIAN YUKON DISTRICT '64 -63 -62 BY ,r. H. TYHHELT. {Raid before the Sociclj/ December SO, JS.'>S) CONTENTS Introduction ]();> A roa tru versed !<);{ I'liyKiof,'raj)liic feiituroK 194 (ilacial features 105 Kxtent of the snow and ice 1!),") Tiie till ' 195 iStriation I9(; Moraines 19(1 Terrace.s 197 Tlie classes 1 97 Stream terraces 197 Lake terraces 197 In tlie Dawson district .. . 198 -60 -59 IXTRODUCTrON Last .suiniuer, while traveling on ]i()rsel)aek and on foot througli the Houthwestern ]>ortion of the Yukon district and the extreme nortliwest- ern parts of British Columbia, many opportunities presented them.selves for observing glacial i)henomena- oi)portunities such as would hardly occur to those wlio were i)assing through tlie same country in boats on some of the many streams which flow along the bottoms of the many deep and wide valleys. Area Travkrskd My route lay to .the west of the Lewis river, on antl in the vicinity of what is generally knoAvn as the Dalton trail — tliat is, up the valleys of the Chilcat and Klaliina or Tleliini rivers, over the summit of the Coast or Chilcat range, and down a wide and continuous valley which, after being occupied in succession by parts of several streams, forks, the easterly XXIX-Bui.!,. Okoi.. Soc. Aji., Vol. 10, I8»8 (193) II ! I lUl ,1. i!. I'YUK'KI.I, — (il.At lAI. 1'III:N(».MI:NA in YIKON DISI'K l( 'I' jxirtion lonninif the Viillcy of the N()i'(U'ii>ki(tl(l river, which joins the Vulasses northward l»y Aishihik lake to Nislinj: river, down tlmt rivt-r to White river, and thence down tin- White to the point where it tlows into th(^ Yukon river. In addition to tlie trip outlined, a short time was spent farther north on the Klondike river and its trihutaries. N I'nVsKKiKAIMlIC FKArrUKS 'I'oward tlu; south this country is a mass of stes of Indians on the .Maskan coast. 'riiis ranife is hounded on the south and southwest hy the I'aeilic ocean and toward tin; nortli and northeast l)y the j;reat t'hihiat-Alsek valley, which extends inland from the western arm of the fjynn canal, lollowint? more or less closely the line of contact of the granite to the northeast and tlu! schists and limestones to the soutliwcst. 'I'he aver- aire widtli of the range is Ix'tween SO and KHi miles. Much of the range is hurled in extensive snowlields. from which gla- ciers radiate in all directions, ])oth toward tiie coast and toward the in- terior. A magnificent view of this country was obtained last siunnier from thesuniinit of Farview mountain, a high peak southwest of Aishihik lake, and itpresentepearance of a vast white plain, througli which the higher peaks rose in dark relief, mount Saint FLias appciaring for a few moments from beneath the clouds. It is thus a vast snow-clad pla- teau, lying close to tlu; Pacific coast, in one of the regions of greatest precipitation on the American continent. Farther north the country is also mountainous, hut the mountains are much more rounded, tli<>ir slopes are easiiM-. and their sides show com- parativeh' few broken, ungraded dill's. .\s a rule, they rise from ;!,0()(l to 4,000 feet above the bottoms of the deeper interveniijg valleys. Stand- ing on one of the summits, a great numlier of similar mountains may be seen on every side, all about the same height and prol)ably cut out oi the same extensive pre-Tertiary i)eneplain. Lakes, In some cases of large size, lie in the l)ottoms of the valleys ; ,,.,. ins iiic •<'stcriy ■n Hint lirrc it l'IIVSl()(ii;.\l'lllC AM) (il,.\( lAI, I'KA'l'lKKS lit." I»ut, MS fiir MS my obscrvMlioiis went, tlicy mik (•(•nllncd exclusively to tliusc parts (»r the (MMiiitry wliicli Iimvc Ween inoro or less coniplelely covered l>y ^^laciers during' tin; IMeistocene eiioeli. Ueyond the limits ol' the ghiciiited region no lake.s were seen. (iLAciAi, Kkatiiui;s • KXTI'XT OF THE S^(lW AM) UK While the ChilcMt mountains are almost liiiried in snow throutrhonl the year, very little snow is to l)e seen in summer on this " int(;rior pla- teau," and any small glaciers that do exist are in some of the higher mountains close to the Chileat range. Though the iee-tields of the present (Imv are eoidliied almost entiri'ly to the Chileat mountMins, the iee-lields of the (ilneial per' xl were much more e.xtensive, for they spreal.sll{ It T more or loMM rounded in sliMpc. some of wliicli i\r«' strint«'d while the greiil niiijority iire sniootii iind without ^diu-iid iiuirkin^'s. In ;;ener;il chanii'ter it is very similur to tlie till which underlies so niueh (»!' the |tl;iins ol" northwestern ('aiiiula lietweeii the edue of the? Andiean nueleiis and th(! IJoeky mountains. Similar till was found It) undeilic! the hottoms anti siiles of mt)st of the valleys everywhere thrt)Ujrhout the j;lat'iateil area in tht^ Yukon distriet, havinjj; evitleiitly heeii formeil as a ground mt»raine heneath the yfreat sheets of iee. v ,s/7i'/.l77o.V Striat(!tl roek surfaees were in/l very t)ften st'en, for wluM'e the rt)ek is exposetl 't has usually heeome rt)U,u;li thrt)U,<;h weatheriiijx, hut they were re{'t)f ice-movenient motion from tlu' coast tt»wartl the interior t)r essentially simply a wider extension of the ti,lacial eon- ditioUH which exist in the region at the present time, in this extension toward the interit)r tlu! ice for the mtist part ft)llt)wetl the ^n^at valleys which trench tlu; surface t)f the country in a the I'acilic ocean. In the Skagway valley the White I'ass railrt)ail while constructiutr it.« line has cut a nt)tch along a rocky hillside which has heen heautifully .smoothetl and scoretl hy such a glacier. • ■: i MO HA I Mis Lateral moraines occasionally form ct)nspicuous features along the siiles of the mountains, often runinng as long, narrow lines of hoidtlers or transportetl material, swaying slightly up ami ilown with the irregu- larities of the surface, ami in jilaces runiung into water-worn terraces whert^ some small stream has thrown its loatl of gravel against the side of the glacier. A very well marketl moraim; of this character extends along the west side of the valley of .\ishihik lake at ahout 1,.')()() feet ahove the wat(;r. It is a fairly regular ridge of houlders, along the crest of wliich, ill some places, runs the horse trail from Fort Selkirk south- ward to Pyramid harhor. Ahove it the surface of the mountain con sists of a fairly even, regular incline of deco!ni»osed rock, while helow it is a. till-coveretl slope, often hroken into very lumpy, irregular hills. Lateral moraines were also traced down the side of a deep valley iiorlii- west of Aisluhik lake as well us in some other places. .\|(>i;aini:s and tkI!I!A(i:s |'.»7 'I'criiiiiiiil inoniiiii's wtTf rccogiiizi'd in m lew plMccs, hut they sciircfly torincd iih ('()iis|iicii(»us fciilurcs as one would luivc liecii incliiit'd to ex- pect. Krom lake Aisliili'k iiortliwiird for mImmU I'-' nnles in the liottoui of the vMJh'V is m tei'MiinMl nioraiiu' areii, rt'|ireseiit<'d in places l)y irreg- ular hills of houlders, which was l'ornu;d at the foot of the' Aishihik lolx; of tlu; ji;reat icie-sheet wlieii it had reacheil its cxtreii . uortheni limit. '/•/•'A- A' .If ■/•;>■ T/ic fhisst's. — -'riie terraces occurrin,' t.: m lOS J. IJ. TYKRKLL — fiLACIAf, IMIICNOMKXA IN Vr'KON DISTHK'T no evidence whatever of marine conditions or of recent submergence of the land. Any regularity in heij?ht of the highest terraces is easily ac- counted for by the moderately regular average thickness of the ice-sheet when the lakes were in existence. IN THE DAWSOy DlHTlilCT As small glaciers now exist in the valleys of the mountains north of the Chilcat range, so small glaciers formerly existed in some of the mountain valleys north of the main ice-sheet of the Glacial period. Such glaciers existed in the valleys of Eldorado and Bonanza creeks, near Dawson, and flowed down these valleys at least to some point below the confluence of the two creeks. Beautiful glacial stria« were seen on the hard quartzose rocks at the mouth of Big Skookum gulch, on the west side of Bonanza creek, which had been made by this glacier, furnishing indisputable evidence of its presence. A lateral moraine of this glacier, often containing pebldes and small boulders of distinct glacial shapes, extends along the side of the valley from 150 to 200 feet above the creek, and in it are some of the rich bench claims on Eldorado hill and at French gulch, and the sand and gravel in the bottom of the valley is well rounded, but roughly assorted material, such as is constantly washed down and distributed by glacial streams. I