LEGEND TERTIARY AND QUATERNARY [on | Basalt; minor pyroclastic rocks TERTIARY KASTBERG INTRUSIONS Feldspar and feldspar-quartz porphyries; porphyritic granodiorite and quartz diorite | CRETACEOUS AND TERTIARY | UPPER CRETACEOUS AND PALEOCENE CENOZOIC SUSTUT GROUP 9A. Sandstones, conglomerates, and shales; minor dacitic tuff and coal; 9a, interlayered dacitic tuff 9B. Mainly conglomerate JURASSIC AND/OR CRETACEOUS UPPER JURASSIC AND/OR LOWER CRETACEOUS _____ OMINECA INTRUSIONS Granodiorite, quartz diorite, and allied rocks JURASSIC (?) 6.Peridotite pyroxenite dunite and serpentine. May be in part or entirely of pre-Takla age 7. Olivine gabbro JURASSIC TAKLA GROUP (3,4,5) 5A. Greywacke, pebble-conglomerate, shale, and argillite; minor limestone and coal 5B.Probably includes undifferentiated voleanic rocks (4) Andesitic, basaltic, and dacitic tuffs, agglomerates, and lavas; in part interbedded with 5 TRIASSIC AND(?) JURASSIC UPPER TRIASSIC AND@) LATER ale 3A. Andesitic and basaltic tuffs, agglomerates, lavas, and minor tuffaceous argillite; meta-andesite, meta-basalt, greenstone, and hornblende schist and gneiss 3B. Limestone, tuff, and argillite. May include some undifferentiated older rocks MESOZOIC PENNSYLVANIAN(?) AND PERMIAN CACHE CREEK GROUP Slate, argillite, phyllite, argillaceous quartzite, and ribbon chert; chlorite and amphibole schist and gneiss; minor limestone ; Rhyolitic lavas, andesitic lavas, tuffs, and breccias, and derived greenstones, slaty tuffs, phyllites, and schists; argillite, slate, phyllite, and chert; limestone, minor dolomite. May include some undifferentiated pre-Pennsylvanian rocks PALAEOZOIC ASITKA GROUP Heavilisatitt. COVered (areata an tate sig gy ee een Matec ha ede Bedding (horizontal, inclined, vertical), .......0.0.0.0 ccc ccc eevee eee Schistosity, gneissosity (inclined, vertical) Fault or shear zone ADCICHNAN GZIS ii Os hee he ott oaths SE Ta Re PTE kame et COTS AES = + en RSs aed UTS eat foi retire i Gr Gt SB ACG OLE EPI Te REID Dean nn ire she om aka Ca AOL ALLSEI BD Teen nT Ie ries Te ce Pee Re NG SU SPE TE hed eters eee: Wage Perey HHA feted 1] Aiea SPN AAC EAA DL | Bical Aeon te aA EEE eae amy eT © Fossil collection (1-12,Asitka group; 13-3, Jurassic, Takla rocks; 4-39, Upper Cretaceous, Sustut rocks; 40-42, Paleocene, Sustut rocks). .........6.00.20 cess ® MineralhOccurrence oa parc rene seals Pie eee Bree cea aa Ree hes ic eR Rd erate a, x Minerals properey.cnavcinccnceahiien ACCU Ieee eT eRe Rees e Beryillarm Sones sor trans cee eee Be CRrOraUnt nut ensenan meee Cr Coal ane rs aise mine ak satan oes Cc COpper nave an Weng eee coats its Cu Gold placer* irncsen sions Au(P) Gold tlodesnn mse hoarse rae tar Au YN Yo By Mes he acre ne pont Sale ten Bd es Pb MERCURY Rene eich eee one He MOLY DGenturr at cnacenns dene cee Mo Placinuimion = te ee eee ele Pt SHUVOT Ie aers Hole vata ett RO ERR Ag VENACIUNIT anak ecient ate tae Va WAT Pott Eek win th oh pails Oat Gye eI nl Zn MINERAL PROPERTIES 1. King George group (pyrite) 2. Quyzvhx group (gold) 3. Solo group (gold) AL. Bruce group (gold) 5. Ginger group (gold) 6G. Shell group (gold, copper) 7. Motase group (copper, silver) Geology by C.S.Lord, 1941, 1944, and 1945. TRAN ARG: CADIN was tlacat ae Headache CH ee het yee fests Passable pack-train route (position approximate) ............ GHURCHE ON ALORENN GEO eT A AMT aT CMI EG Ne nna eT) ua eda Lake and stream (position approximate)....................... GA CIO Nien d= a Uertatde ete Sky t beech URIN Feteieca ont Ponts, ag pe ote aA Contours (interval 500 feet)....... 0.0 cece cece cece cece ee ese ee 5050 Contours (position approximate )........6. 6.0... c eee ce lev eee aces = 000 Height in feet above mean sea-level Base-map from surveys by the Topographical Survey, 193Z Cartography by the Geological Mapping Division,/948. Approximate magnetic declination, 27°to 31 East. fo] SCALE, 1INCH TO 200 MILES CANADA DEPARTMENT OF MINES AND RESOURCES MINES, FORESTS AND SCIENTIFIC SERVICES BRANCH GEOLOGICAL SURVEY OF CANADA SIKANNI RANGE 4 Quenada Cr. Diagrammatic structure-section along line A-B na x °° : 10000’ — & CONNELLY A kK RANGE ; Q o> 5000 — SEA-LEVEL — -5000' : -190000' : | 12700" 5700 45° 30° 15 A 5600’ 12700° 45, hs PUBLISHED, 1949 McCONNELL CREEK Dortatelle Cr. (Miller cr. MAP 962A CASSIAR_ DISTRICT BRITISH COLUMBIA Scale: One Inch to Four Miles = '/253,440 Miles 4 3 2 1 i) 4 8 12 5000’ 10000" SEA-LEVEL -5000' -10000° DESCRIPTIVE NOTES The centre of the map-area is about 165 miles north-northwest of Fort St. James, whence a good gravelled road leads to Vanderhoof, a Canadian National Railways station 41 miles to the south. Access from Fort St. James during the summer is provided by aircraft on floats, or by motor launches and scows as far as Bulkley House at the head of Takla Lake and thence by pack-horse over about 105 miles of fair trail that leads to McConnell Creek placer camp. Elevations range from 2,600 to 8,100 feet above sea-level, but the local relief rarely exceeds 4,000 feet. Particularly rugged mountains occupy areas underlain by volcanic rocks of the Takla group (3, 4). An ice-sheet, which in Pleistocene time covered most or all of the map-area, moved easterly and southeasterly. Remnants, as alpine glaciers, are far more numerous than those mapped, and some have receded noticeably within recent years. Unconsolidated Pleistocene and Recent deposits conceal much bedrock, particularly on the bottoms and lower slopes of the main valleys. Timber-line is about 5,000 feet above sea-level, and the densest stands of timber occur in the southern and southwestern parts of the area where precipitation is relatively abundant. The base of the oldest, ASITKA group (1) has not been recognized. These rocks comprise probably more than 8,500 feet of variously metamorphosed volcanic and sedimentary strata, the most characteristic of which are hard, dense, red, green, or buff, massive, streaked, and spherulitic rhyolitic lavas; varicoloured, bedded cherts; and scattered bands of massive to bedded, crystalline, commonly impure limestone. The upper members of the assemblage contain abundant Lower Permian foraminifera, and Pennsylvanian or-even older strata may occur elsewhere. The dominant members of the CACHE CREEK group (2) are black, platy, argillaceous rocks and grey cherts; these are accompanied by minor interlayered limestone, and by chlorite and amphibole schist and gneiss derived from andesitic lavas and tuffs. Ribbon cherts are common: they are composed of platy or crumpled layers of grey chert, commonly less than one-quarter inch thick, separated by thin partings of lustrous, black, partly graphitic argillite or slate, in places altered to mica schist. The assemblage was not seen in contact with Asitka strata. The TAKLA strata (3, 4, 5) occupy a broad, northwesterly trending synclinorium greatly complicated by faults and subsidiary folds. The approximate axial part of this structure extends northerly and northwesterly from Scallop Mountain to beyond the mouth of Asitka River. The members of the lower division (3) rest on Asitka rocks without apparent angular discordance despite the long interval of erosion that must have intervened. Southwest of a line extending from the southeast corner of the map-area northwesterly through Sustut and Thutade Lakes they comprise about 10,000 feet of relatively fresh, mainly dark green, andesitic and basaltic tuffs, coarse agglomerates, and pillow lavas, all charac- terized by prominent, black, blocky pyroxene grains and phenocrysts. Other members of the lower division, lying to the northeast, are probably the meta- morphosed equivalents of these rocks: they are mainly greenish meta-andesites and meta-basalts, with numerous, black, stubby hornblende and pyroxene grains and phenocrysts, and here and there display bedding, fragmental textures, amygdules, and other internal structural features common in their less altered equivalents. The upper Takla rocks (4, 5) overlie those of the lower division (3) without. recognized angular discordance and without known evidence of widespread intervening erosion. Nevertheless, a basal conglomerate 4 miles south of Sustut Lake contains detritus apparently derived from underlying basaltic lava and agglomerate (3A) and is interpreted as evidence of local erosion prior to the deposition of the upper Takla assemblage. This assemblage (4, 5) comprises more than 23,000 feet of volcanic and sedimentary rocks. The oldest part (4) includes more than 18,000 feet of mainly reddish, andesitic, basaltic, and dacitic lavas and pyroclastic rocks, commonly with conspicuous white feldspar pheno- crysts and grains. These are overlain by more than 5,000 feet of shallow water, marine, fossiliferous sedimentary beds (5) interlayered with minor volcanic rocks, carbonaceous strata, and coal. Conglomerate beds, with chert pebbles apparently derived from Asitka rocks, are common. Scattered dykes, sills, and other ultrabasic bodies (6) cut Cache Creek forma- tions and in places probably cut the lower Takla rocks (3); they were not found in contact with the upper part of the Takla group (4, 5). Most of the olivine gabbro (7) is a medium-grained, fresh, conspicuously banded rock, with individual layers ranging from less than 1 foot to 5 feet in thickness. The OMINECA INTRUSIONS (8) are not known to represent more than one general period of emplacement. They cut fossiliferous Lower Jurassic strata in the nearby Takla map-area, and contributed abundant detritus to upper Lower Cretaceous formations of the adjacent Aiken Lake map-area. More than 3,000 feet of conspicuously bedded and banded continental SUSTUT strata (9) were laid down on an erosion surface that truncated folded Takla and older rocks and Omineca intrusions. The strata are mainly interlayered, buff to grey, impure, crossbedded sandstones, conglomerates containing pebbles and cobbles derived in part from the Omineca batholith, and red, green, and grey shales. Fossil plant remains are common. The most diagnostic collections from the lower part of the group are of early Upper Cretaceous age, whereas others, from thin bands of dacitic tuff in the upper part, are of Paleocene age. The strata southwest of Saiya and Red Creek faults occupy mainly rather open folds, but near the latter fault are overturned towards the northeast as if thrust from the southwest. North- east of the Omineca fault they are horizontal or gently inclined. Chalky weathering, grey, buff, rarely pink, fine- to medium-grained, porphyritic rocks (10) form one principal stock (Nep Peak to Comb Peak) and numerous dykes and sills. They may be a late phase of an early Tertiary period of mountain building that deformed the Sustut strata, which they intrude. The youngest consolidated rocks (11) are fresh, dark grey to black basalts, and occur mainly as necks, dykes, and lavas. Probable KASTBERG porphyries (10) are cut by a few of the dykes. None of the basalts is known to have been folded or faulted. They range in age from about Middle Tertiary to, in the case of a few, related, cone-like, pyroclastic deposits, Recent. Most of the known major faults lie within a northwesterly trending belt, about 12 miles wide, bordering the Omineca fault on the southwest. The fault zones probably dip steeply, and range from about 25 feet to possibly 1,000 feet or more in width. They are marked by various combinations of schistose, fractured, crumpled, or carbonatized and otherwise altered rocks. Directions and magni- tudes of the lateral displacements are not known. The apparent vertical displace- ments may be greatest in the northeast half of the faulted belt, along the Omineca, Carruthers, and Ominicetla faults, where in places as much as 10,000 feet of strata appear to be missing. Available evidence suggests that the strata on the southwest side of the Omineca fault have moved upwards relative to those on the northeast side, whereas the relative movement on the other northwesterly trending faults of the belt is probably in the opposite direction. Major, although not necessarily the greatest, displacements took place in post-Paleocene, probably early Tertiary time. Fine, apparently erratically distributed, placer gold was found in gravel resting on lacustrine silts along McConnell Creek in 1899, and a little has been recovered each year since, affording the only known mineral production of the map-area. The annual recovery, now insignificant, probably never exceeded a few hundred ounces. No lode deposit in the map-area is known to be of commercial size or grade, but none has received more than a little stripping and trenching, and only a very casual, intermittent search was made for such deposits prior to 1946. In view of the number and distribution of mineral deposits, including gold, copper, silver, and other metals, found by prospectors during this brief period, and by the Geological Survey, the area undoubtedly warrants further examination. The most promising host rocks appear to be volcanic members (3A, 4) of the Takla group. The numerous coal seams, found mainly in Jurassic strata (5A), will require trenching and stripping before much is known of their size and quality.