STRATIGRAPHY AND smInmmmy mms ON THE BULL- I(OUNTAIN-PEACE RIVERCANYON, CARBON CREEK AREA NORTHEASTERN BRITISH COLUMBIA (930/15, 16; 94B/1, 2)

INTRODUCTION

As the new District Geologist at Charlie lake, 1982 fieldwork was orientedtoward gaining a grasp of theregional and loc,slstratigraphy andsedimentology of thecoal-bearing sequences in the Northeast Coal- field. In thisregard I am indebted to Dave Gibsonand Con Stott of the GeologicalSurvey of Canada, Paul Cowley and NormanDuncan of Utah Mines Ltd.,and Charlie Williams of Gulf Canada ResourcesInc. for informative discussions.

Fieldwork was concentrated in the area betweenBullhead Mountain on the east andPardonet Creek on the west (Fig.27). lhis areaincludes coal licences of Utah Mines Ltd.,Gulf Canada Resources Inc.., Shell Canada ResourcesLimited, andCinnabar Peak Mines Ltd.Recently published paperson the area includethose of Gibson(19781, St.ott and(Gibson (1980), andAnderson (1980).

There are two coal-bearingformations in the area, theGething Formation of theBullhead Groupand theBickford Formation of thme Minnes ,:roup. The GethingFormation overlies the Bickford Formation and is sepsrated from it by the Cadomin Formation,which is variablypebbly sandstone to conglomerate (see stratigraphic column, Table 1). Regionallythe Cadomin Formation may rest on unitslower in the succession than the Bickford.According toStott (1973) this is due to an unconformitywhich progressivelytruncates underlying strata in a southwest-northeast direction.

TABLE 1. SIWLIFIED STRATIGRPPHY OF THEMiNNES ANDBULLHEAD GROUPS (UPPERJWASSIC+CWER CRETACEOUS) IN THE BULLHEADMOUNTAIKPARDONET CREEK AREA

BuIGething Formationlhead bal measures &CUD Cadomin Formation Pebblysandstone, quartzitic sandstone,conglomerate

Mlnnes BickfordFormation Carbonaceousmeasures Grou p Monach FormtionFeldspathic sandstone, minor mounts of quartzite

battle Peaks Formation Interbedded sandstone and shale

bnteith Formatlon @per quartzites Lower greysandstones,, teldspathlc sandstones

93 ?he stratigraphy of thearea is notyet satisfactorily resolved (D. F. Stott,personal communication). Problems include:

(1) Identifyingthe Cadomin Formation in places where it is a sandstone ratherthan a pebblysandstone or a conglomerate. It is difficult todistinguish the Cadomin Formationwhere it overliessandstone of formationssuch as the Monach. (2) Iateralfacies variations within formations of the MinnesGroup. (3) lbe natureof the unconformity at thebase of the Cadomin Formation. Does it haverelief and hence control the thickness and distribution ofthe Cadomin?

The CarbonCreek basincontinues to be a focusof these stratigraphic difficulties. Forexample, coal measures initially identified as Gething Formation were temporarilyre-interpreted to beBickford Formation by Stott andGibson (1980).

STRATIGRAPHIC SETTINGOF THE CADOMIN POPJWTION

A number of sections were examined inorder to establishthe strati- graphicsetting theof Cadomin Formation in the area. These are summarized as follows (see Fig. 21 forlocation): RidgeSouthwest of MountMonach C oa l measures Gethinq Formation Gethinq measures Coal Thickunits of pebbly quartzitic Cadomin Formation sandstone;local siltstone and recessivebeds Gradationalcontact ? Salt-and-peppersandstone, siltstone Bickford Formation (calcareous),mudstone, carbonaceous shale,coal M a ssive flaggy sandstoneflaggy Massive Monach Formation BattleshipMountain (tributary to CarbonCreek on west side) C oa l measures Gethinq Formation Gethinq measures Coal Thickunits ofsandstone to pebble Cadomin Formation sandstone,local recessive interbeds Contactcovered Massivequartzitic sandstone, salt- Monach Formation and-peppersandstone East of CarbonCreek Road andCarbon Lake C oa l measures Gething Formation Gething measures Coal Pebblyquartzitic sandstones, Cadomin Formation quartzitelocally at base, coal Contact sharp Salt-and-pepperto quartzitic Monach Formation sandstone, minoramounts of burrowed siltstone

94 (4) BullheadMountain - west side P ebb ly sandstone,Pebblyconglomerate Cadomin Formation Contactsharp Feldspathicsandstone (flaggy), salt- Monach Formation and-peppersandstone, kaolinitic quartzite bed neartop Interbeddedfeldspathic sandstone, Beattie PeaksForma.tion burrowed siltstone,black mudstone plartzite, minoramounts of black MonteithFormation mudstone,feldspathic sandstone, dark greysandstone

The Monach, Bickford, Cadomin, andGething Formations are exposed .in the 'Whiterabbit'licence area of Gulf Canada ResourcesInc,. and inridges extendingsouthwest and west of buntbnach. They comprisethe e,?mtern limbof a major syncline. The BickfordFormation is severalhundred metres thick andgrades into the Cadomin over a width of about 5 metres. An interbed of salt-and-peppersandstone, typical of the Bickford Forma- tion, lies abovethe 10-metre thick basal, sparsely pebbly quartzitic sandstoneof the Cadomin Formation.Nineteen kilometres to thenorth- east, on the east sideof the CarbonCreek syncline, theBickford Forma- tion is missing. mere the pebbly Cadomin Formationabruptly overlies a burrowed siltstone (marine ?). Off CarbonCreek Road, cm the west side ofBattleship Wuntain, it rests on flaggymassive sandstone units (Monach Formation ? ) .

Eitherthe Bickford Formation develops a marinesandy facies eastward or it is truncated by theregional unconformity described by Stott (1973). Rocks inthe anticlinal structure near bunt Rochfort arid bunt Wrigley may holdthe key. Just west ofthe core of the anticline on the west sides of the two mountains, a thin zoneofBickford Fsrmation may be exposed. On a ridgenorthwest ofbunt Wrigley, Paul Cowley OE Utah MinesLtd. (personalcommunication) describes a carbonaceousmudstone, siltstone, andsandstone sequence that underlies salt-and-pepper (to quartzitic)sandstones of the Cadomin Formation. HoWeVE!r, pebblysand- stone belowand withinthe sequence makes it unclearwt.ether it is all Cadomin or whetherboth Cadomin andBickford Formations are present..

East of the CarbonCreek basin at Bullheadbuntain the Cadomin is separated fromunderlying mottled (bioturbated ?) quart.zite by s,everal centimetres of coal(the contact is exposedonly on thesouth side of the mountainalong the hydro line). Below this are feldspathicsandstones, a shalytransition zone, and quartzite. The feldspathicsandstones correspondto either the Monach Formation or a sandyupper facies of the BeattiePeaks Fbrmation. The transitionalsequence below consists of interbeddedquartzite, black shale, burrowed mudstone, feldspathic sand- tone,and ferruginous shale. It is probablythe Beattie Peaks Formation. Thissequence grades downward into thickquartzite beds of the Mclnteith Formationwhich are in rathersharp contact with underlying dark grey

95 sandstones(also Monteith Formation). These darksandstones crop out at the base ofBullhead Mountain on both its west andsouth sides.

At BullheadMountain the Cadomin Formation is in part conglomeraticand locally more than 200 metres thick(Stott, 1973). Stott alsodescribed 30 metres ofconglomerate at the mouth ofCarbon Creek. At Rattleship Mountain,however, only one 10-metre bed was pebblyand the total thick- nessof the formation is at most 200 metres. Inthe Mount Rochfort-Mount Wrigley area the Cadomin is predominantlysandstone. Its appearance is notdistinctive and it wasmapped as part of the Monach sandstone. As a consequence,pebbly sandstones that are stratigraphically much higher(in theGething Formation), were mislabelled as Cadomin. Southwest of Mount Monach the Cadomin is apparentlythick (400 metres ?) butonly sparsely pebbly (maximum clastsize 2 to 3 centimetres). Clearlythe Cadomin Formation is not a simple westwardthickening and coarsening fan of fluvialsediment. A local isopach map, distribution of paleocurrentflow directions, and maximum clastsize are requireddetermineto what controls its thickness and lithology in theBullhead Mountain-Pardonet Creekarea.

TRACE F'OSSILS

Some ratherspectacular examples of tracefossils are evident in the Beattie PeaksFormation along Carbon Lake Road. Abundant verticalpipe- like burrowsup to 3 centimetres in diameter are present as well as vertical20-centimetre-deep U-shapedand steeplyinclined rhizocorallium burrows(U-shaped and spreite-filled). They are particularly well developedin a number of regressive,coarsening upsequences (shale- sandstone). The structures correspond to theSkolithos facies of Seilacher(1967) and represent suspension feeders found in the shallowest parts of thesea.

PEACE RIVER CANYON

A section was examined starting at the toe of the dam and continuing alongthe north shoreto Gething Creek. It hasbeen previously described by Stott(1973), McLearn (1923), and others. The first 57 metres of the sequence atthe toe of the dam includes three thicksandstone units and is assignedto the Cadomin Formation by Stott. These unitsare gritty at thebase, fine upward,and are ripple cross-laminated at thetop. The middlezone has extensive convoluted bedding. The units all have a sharp flat base and two of thethree are marked by inclinedinterbedding of sandstoneand shale at thetop and coal at thebase. These features sugqestthe sandstone bodies may represent distributaries of thelower or transitionaldelta plain rather than fluvial channels of theupper delta plain. Foraminiferaindicating marine influence were collected by Chamney (in Stott, 1973)from finersedimentary rocks between the sandstoneunits but according to Gibson (personal communication) the work requires re-examination. The overlyingGething Formation sediments are

96 predominantly a monotonous,repeated sequence of sandstone, horizontally interbeddedshale, and coal. Interestingfeatures do include some channelstructures, lateral accretionbedding (indicative ofmeandering), minor upward coarseningburrowed sequences (bay fills ?), andCoal- boundedcrevasse splay deposits.

Variousfloral and faunal collections have been made from theGething Formation inthe Peace River Canyon.They includedinosaur bones and trackways,pelecypods, foraminifera, spores, andremains ferns,of cycads,and conifers. The writer recentlycollected a Well-pKeSeKVed silicified tree trunkin the east side of thecanyon in .view of the dam. The trunkmeasures about a metre indiameter and a mt?tre inheight. Growth rings are well preservedand alternating thin

REPERWCES

Anderson, R. B. (1980): CarbonCreek - Geologyand Coal :Resources,Paper presented at Symposium on Northeast Coal, February 1'380, 27 pp. Gibson, D. W. (1978) : Stratigraphy andSedimentology theof Iawer CretaceousGething Formation, 'Carbon Creek Coal Basin, Northeastern British Columbia, Inst. Sed. & Pet. Geol., internalcept. McLearn, F. H. (1923) : Peace River Canyon Coal Area, Geol. Surv., Canada, Summ. Rept., 1922,Pt. B, pp. 1-46. Seilacher, A. (1967):Bathymetry of Trace Fossils,Marine Geology, Vol. 5, pp. 413-429. Stott, D. F. (1973) : Lower CretaceousBullhead Group bt?tween Bullmoose Mountainand Tetsa River, Fbcky WuntainFoothills, Northeastern British Columbia, Geol. Srv., Canada, Bull. 219, 228 pp. Stott, D. F. andGibson, D. W. (1980): Minnes Coal, NortheasternBritish Columbia, Currentin Research, Pt. C, Geol. .%rv., Canada, Paper 80-1C. pp.135-137.

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