Reconnaissance Turnagain and Upper Kechika Rivers
Total Page:16
File Type:pdf, Size:1020Kb
BRITISH COLUMBIA DEPARTMENT OF MINES Hon. W.J. ASSELSTINE, Minister JOHN F. WALKER, Deputy Minister BULLETIN No. 12 Reconnaissance IN THE AREA OF Turnagain and Upper Kechika Rivers Northern British Columbia by M. S. HEDLEY and STUART S. HOLLAND 1941 VICTORIA. B.C.: Photwffset by CHARLES F. BANFISLD,Printer to the King's Moat Excellent Majesty. 1941. ..J ILLUSTRATION> Page Keymap showing position of r'egion in northernBritish in Columbia 3 Plate I* h Looking south along Rocky Mountain Trench fromPassSifton near 4 B Lookingnorth-westward along Rocky MountainTrench from near Sifton Pass 4 Plate11* A Lookingsouth-eastward up Kechika River from Valemonk Mountain -. 9 B Lookingnorthward across the Trench from Valem ont Mountain Valemont ._ 9 Plate III* A Looking north across the Trench towards Gataga Mountain ..................................................................................................................... 10 Lookingnorth-east across the Trench near TerminusMountain ............................................................ 10 Plate IV View looking north-eastward across the continuation of the Rocky Mountains13 KechikaRiver, looking towards Terminus Mountain 1 13 Plate V Lookingtowards granite ranges at head of Dall Lake 14 TurnagainRiver valley, looking north .- 14 Plate VI Lookingsouth-eastward along the through-valleytowardsDall Lake 17 Lookingsouth-east across the head of M osquito Creek valley Creek Mosquito 17 Plate VI1 Lookingsouth-westward up the valley of theupper Turnagain from the head of M osquito Creek 18 Creek Mosquito * The photographs on Plates I, I1 and I11 arereproduced throughthe courtesy of the Department of Lands. (ii) Page Plate VI1 B Lookingnorth-eastward down the valley of theupper Turnagain from 'Kheaton Creek ........................................................................................................................................... 18 Geological map of the Turnagain and upper Kechika Rivers ._.....I._....I._.................................................. In 'pocket RECONNAISSANCE IN THE AREA OF TURNAGAIN AND UPPER KECHIKA RIVERS """"""" 1. Kechikaand Turnagain Rivers drain an extensive region of the northern Cassiar and Rocky Mounta,ins in northern British Columbia. 2. The RockyMountain Trench* separates the Rocky Mountains on the east fromthe Cassiar Mountains on thewest. The high, deeply incised Rocky Mountains of thesouth dwindle in elevation to low wooded ridges and lose their identity north ofTerminus Mountain. The Cassiar Mountainsare more irregular and much higher than the Rockies and ex- tend north'nrardbeyond the limits of the region. 3. The termination of the northern Rocky Mountains was not caused by greater erosion in that section but by lackof Tertiary elevation. 4. The highcentral granite range of theCassiar Mountains hasbeen sculptured by intensealpine glaciation, whem- as the Rocky Mountainshave been only slightly affecte,i. The Cassiar Niountains show theeffects of alpine glacii3- tion with cirque basins formed. and some valleys'modified. However, the distribution of erraticsindicates an east- ward movement of continental ice from the Cassiar Moun- tains across the Trench and over the Rocky Mountains. S. The drainagepattern in part is normal,and partly ex- hibits a trellis pattern reflecting bed-rockstructura:!. control. Over much of theregion the drainage system has resulted from stream piracy on a major scale. 6. A highflanking rock bench on the upper Kechika is the result of pre-glacial stream rejuvenation. 7. The Rocky Mountains are composed of longranges made U;I of a great variety of tightly folded sedimentary rocks. 8. The centralcore of theCassiar Mountains is a granitic batholith 20 to 30 mileswide and mapped for a length of 100 miles. The flankingmountains are composed largely of sedimentaryrocks and a minoramount of volcanics.For * Rereafter the Trench refers to the Rocky MountainTrench. (iv) 20 miles north of Sifton Pass the Trench is underlain by Upper Cretaceous or earlyTertiary conglomerate, north of which the Trench is floored with glacial drift and allu- vium. South of Dall Lake theCassiar batholith is flanked by schists acdgneisses formed b.~the action of numerous pegmatites,elsewhere there is little or no contactmeta- morphism. 9. All thesoft argillaceous rocks are highly cleaved, and contorted by drag-folding. 10. The Trench is a boundary across which it hasbeen impossible to make lithologic correlation between the two different mountainsystems. The Rocky Mountain structurecomprises regular,steeply-dipping, tightly compressed folds.Folding inthe Cassiar Mountains is more irregulsr,the structural trend is different from the Rocky Mountains,and the folds are interrupted by cross-warpsand are complicated by drag- folding,thrusting and some overturning to theeast. The core of the system is theCassiar batholith, some 20 to 30 miles wide. 11. Placer-golddeposits have been worked on "neatonand 'Walker Creeks. The countryhas not been thoroughly pros- pectedbut exploration on othercreeks should begoverned by the knowledge already gained. 12. h fewlode-deposits are known butnone has undergone any development. A sectionnear Dall Lake radialto a bulge in the eastern contact of the batholith is considered the mostfavourable lode prospecting area. IMTRODUCTION The upper Kechikaand Turnagain Rivers together draitn a region greater than 6,000 squaremiles in extent in northern British Columbia (seekey map). They unite,as the Kechika, to form a majortributary of theLiard River. Kechika River heads at Sifton Pass, latitude 58 degreesnorth, and flows north-westward in the Rocky MountainTrench along the flank of the northernmost Rocky Mountains.Turnagain River heads on the west flank of theCassiar Mountains and cuts across them. in a general north-easterly direction to join the Kechika at Chee House, an abandoned tradingpost, about 70 miles from LiardKiver and 60 miles due south of the Yukon boundary. During1939 topographic mapping of the Trench by the Department of Lands was completedfrom Finlay Forks to S3.fton Pass, and in addition triangulation was al.mostcompleted from Sifton Pass to Lower Post on Liard River, a few miles south, of the Yukon boundary. This work was continued, at a reduced rate, in 1940; the Trench was mapped as far north-west a8 Gatagaand Terminus Mountains. Triangulation was completed to the Yukon boundaryand extended up Turnagain River to within 25 miles of an existing network to the east of DeaseLake. The authors travelled with the two survey parties from Prince George, using their base camps as headquarters from which fly trips were made during the greater part of the season. hi. S. Hedley so travelledwith the topographic party underthe direction of ?I. C. Stewart, as far as the mouth of GatagaRiver. In September he and his assistant weretra.ns- ported up Frog River by boat to the first main fork andfrom there they proceeded on foot by way of Jackstone Creek an.d Dall River to the upper TurnagainRiver. S. S. Holland started with the triangulation party under the direction of H. Pattinson, comnenced work at the mouth of GatagaRiver, and progressed down river to Chee House and thenwestward by way of the MosquitoCreek trail to 'Nheaton Creek. The authorsre- turned to the coast byway ofDease Lake and TelegraphCreek. Topography of a' strip 10 miles wide, centering on Kechika River, was obtainedfrom vertioal aerial photographs taken duringthe season. These, together with horizontal photo.- graphs of the strip between SiftonPass and Gataga Mountain, were furnished through thecourtesy of the Department of Lands and greatly facilitated work both in the field and in theoffice. Topography lateralto the photographed strip was sketched in the field and controlled by the triangulation network. fill topography on TurnagainRiver was mapped in this -1- fashion. Elevations of most peaks other than those occupied by triangulation stations have been calculatedby photo- topographic methods. N. C. Stewart was consistently helpful during the course of the office work. The topography at the head of the Turnagain is compi1,ed from: (1) Map 381-A of the Department of Xine's and Resources, Ottawa: (2) a sketch map published in 1933 by Mandy*; (3) a map published in Bulletin No. 2, 1940 of the Department of Mines, British Columbia. The writers wish to express theirthanks to Messrs. Stewart and Pattinsonfor assistance in the field, especially the former,who altered his plans in the latter part of the season to make the overland trip more feasible.S. D. Town- send and R.G. McEachern gave admirable assistance throughout the season. Acoess and Means of Travel The region isso large that only the established routes into it may be mentioned, particularly as littleor nothing is known of other possible routes. That followedon the journey in 1940, is from PrinceGeorge. Regular travel is over the waterways from Summit Lake,32 miles northof Prince George via Crooked, Pack, Parsnip and Finlay Rivers to Ware. The distance to Ware, the Hudson's Bay Companyon postFinlay River, is 350 miles and the trip can be made by carry-boats ing a pay load of 2 1/2 tons. The only hazardous seotion on the Pinlay is Geserters Canyon; it cannot be navigatedin high water and is halfa milelong. From Ware a pack-trail follows the Fox River44 miles northward to Sifton Pass.Fox River is navigable with difficulty; for a distance of 23 miles in a straight line, from abovea short portage close to the mouth. The,other principal route is from Telegraph Creek, the head of navigation on Stikine