PALYNOLOGICAL ZONATION AND CORRELATION OF THE PEACE RIVER COALFIELD NORTHEASTERN BRITISH COLUMBIA By Jane Broatch

INTRODUCTION BurntRiver, however, the chzlractcr of the formationchanses enough to allow four distinct m8:mben to be identified and for the Strataofthe Peace Ri\erCoalfield formcd along the Southwestern Minnes Formation to become a targel. for coal exploration. edge of the Jurassic/Crclaceous (:learwntct Sed. The rocks were deposited during a series of m:tjar and minor transgressive- Cadomin Formation: The Ckidomin conglomerate lies uncon regressive cycles and reflect a conlplex depositional setting. Map- mably on the Minnes Formation. Although quite variable in 1hi:k- ping and correlation of economic cwal deposlts are difficult. but the ness (3 to 200 metres). a general trcnd of thinning eastward :and task is made more so by numerous thrusts and folds which occurred northward is evident(Stott. 196x1. Within the study are;, the when the region underwent comp:ession. A diverse body of geo- CadominFormation is predominantly conglomerate, but the logiral information from a variely of disciplines is required to northwest it becomes a pebbly sandstrlne containing silty, shaly, ;lad unravel the structure and stratigrallhy. coaly lenses. Where this occurs it is mapped as the Dresser Fortr a- tion, after the nomenclature of Hughes. PREVIOUS WORK Gething Formation: The G,:thzng Formation is a domin:mly terrestrial sequence of interbedded conglomerate, sandstone, silt- Stratigraphic work in the area (Flg. 49-1 i was carried out by Stott Stone, and mudstone. Coal occu.s in tne upper halfof the form:h,n (1968, 1973, 1974, 19x1) andHughes (1964, 1967).Extensive but is only of economic importance in the central regions 01 the drilling by coal companiesha!, provided core samples and coalfield. The conglomerates, which occur toward the base of the geophysicaldata for a number 0' morerecent studies aimed at formation, are thickest in the soltheas1 and are commonly cnnfu;:d locating.identifying. and interpr:ting environmentalindicators, with the Cadomin Formation. Although it has been noted that the rock-stratigraphic and time-stratigraphic horizons. and subtle dis- Cadomin conglomerate exhibit! a clcan matrix sand response con tinctions between similar lithologics contained within and between geophysicallogs (Duff andGilchrisr, 1981) and that the pebtmle formations(Duff and Ciilchrist, 19x1; Leckie, IYXI: Leckie and content is more quartzitic, the congl~~mcratcsare rarely drillcc to wdlker, 1982; McLean. 1977. 1932: Carmichael.1983). Paleon- allow comparison. Furthermore, the #differences are not consistrnt tological work has been attemptc,d by Bell (1956) with leaves. or easily recognizable in surface outcrop. In many places the Gcth- McL,ean and Wall (1981) with fo.aminifer;l, Chamney (report in ing Formationresembles both thr Minnes andcates Formations. :ut Stott. 196X) also with foraminifer;^, and Duff and Cilchrisl (19811 its overall texture is somewhal comer and average bedding is with marine macrofossils: but the usefulness of these studies has thicker. been limited by a paucit!, of specimens and generallypoor preserva- tion. Regular symposiums sponsor:d by the British Columbia Min- Moosebar Formation: The Gething Formation passes abruptly istry of Energy. Mines and Petmle~~mResources have encouraged a into black marine shales of the Nlooselm Formation. At its base t?e cooperative attitude amongst the c~mpaniesholding coal licenucs, formation is similar in appcarance to the marine Hulcross shale!, ti at and the many workers cc,nducting rssearchin the area. The resultant overlie the Gates Formation,however. the upper third of the unit :,a transitional sequence of interbed,led siltstones. mudstones, and t ?in exchange of information has led to B bcttcl- understanding of the complex structure, strat gaphy, artd depusitianal setting. sandstones. This sequence, althrtugh not recngnired everywhen in the field. is identifiable on geophysical logs and is now mapped Ihy The present palynological study was undertaken with the support most workers as a separate member of thc Mooscbar Formxion. of the Ministry in the hrpc of providing anorhcr tool for accurately Southeast of thc study area this lransilional unit has been pmpx,ed identifying rack units, particularly where faulting has displaccd or asaformal memberofthcGates iForm;nion (McLean, 1982). Unfw thickened them: for correlating units or horirons within units and tunately the gradational nature of thi:; unit and the uncertainty in ultimately the coal seams themselves; and for identifytng minor locating the sandstone bed which marks the base of the Gatis marine incursions and tracing theil extent. In addition, the palynu- Formation in the coalfield incrcace the confusion regarding hc morphs will provide information lor dating the rock units and for actual location of the Moosebar~Catcacontact. locating the JurassicICmaccous boundary In the undifferentiated Minnes Formation. Gates Formation: The FatesFormation consists of both marine and nun-marine sandstones. sil:stones, and mudstones: thin cx- STRATIGRAPHY glomeratesare present. Coal occurs throughout, but minrat'le seams are more common in the southeast whcrc the marine inllu- The btratigraphy of the Peace Rlver Coaltield is summarized on ence is less pronounced. Recognition of the marine componenl of Figure 49-2.The following bric' description of the rock units the formation has been the focu:; of st:veral recent studies (Lcckie. sampled for this study i!, intended :o provide: insight into prublcms 1981; Carmichael, 1983). particularly since it is thought top a) a specrfic to the region and into the interpretation of results. ma.ior role in truncating the coal in many areas Minnes Formation:The Mime', Formation south of Burnt River Although fdmiliarity with thc rock units locally allows fairly is a sequence of interfingering marine and non-marinc rocks com- accuratemapping of theformations. structural complexity oftkn posed of thin to thick-bedded mutlstonc. siltstone, conplomcratic confusesinterpretation. The n:gion is dominated by imbrcatc sandjtone. and coal beds. that r;mge from thin partings in the thrusting and associated folding which have greatly shortenci t?e southern extremes to medium th ck beds in thc northwcst: thc section in a wesf to cast direction. Idmtification of formations ;,Id sequencecannot be dif-crentiated intomappable units. North of thrust faults at surface does not g,ual.anteewhat will be encounlerzd

~ Elritish Columbia Miniatry of Enelgy, Mine? and Pelmieum Resource,. Cculogical Fieldwurk. 198s. Paper IYX6-I 32 I 322 - Northcast British Columhia North of Burnt Kiver South of Burnt River

Boulder Creek Formation

Hulcross Formation /'Mocntain Wrk

Gates Formation

- -Transition - - - Memhcr - - - - Mooschar Formation Moosebar Formation (Sukunkd Member)

Gething Glad\tone Formation Frrrmation

Cadomin Formation

Mimes Formation indrill holes. Units often appear unusually thick mare faultcdaffto 49-41; identification and correlation of marine facies are in pro- be replaced by uncxpccted. and occasionally unidentifiable, units. gress. hut still subject to revision. Eleven ofthe X9 surface samplcs Complex structures and rapidly changing facies present a need for were selected for processing. based an results obtained from ap- highly specific information where correlation from onc drill hole to proxlmately equivalent drill-hole samples. Slides from the surface another is required. particularly if the decision to mine a cwal seam samples havc not yet been examincd. rests on the accuracy of that correlation. RESULTS CURRENT STUDY 01 the 204 samples examined to date X0 per cent haw yiclded In an attempt to identify and correlate horizons in the coal mea- palynomorphs. A species list containing approximately 370 spores sures, a study of fossil spores and marinedinocysts was undertaken. and I15 dinocysts was compiled. Although same of thespecies Two hundred thirty-eightcore samples were collected rrom I3 drill- identifications are subject to review, it is expected that this list will hole locations between Burnt River in the northwest and Narrawdy be slightly larger on completionbecause half the slides have not yet River in thesoutheast (Fig. 49-11, Thecores represent approx- been examined and these represent a section of the Minnes Fortna~ imately 3 600 metres of section, from the upper Minnes through tion which is expected to yield exclusively Jurassic palyntlmorphs. Gates Formations. sampled at 15-metre intervals on average. 'The Thc gcncralixd zonation shownon Fipre49-4 includes 2s of the drill holes have hecn pieced togethcr to obtain composite sections 43 dmocyst species and 30 of thc X5 pollen and spore species which from the regions shown on Figure 49-3. An additional XY samples are rsstrictcd to specific formations.The original plotuf spccics was were collected from surface sections adjacentto the drill-hole Inca- done on a formation basis, u,hich does not allow for easy rccogni- tions (Fig. 49-1) to determine theusefulness of surface 'grab' tion of zones within the formations. The exception is thc Minnes samplescompared to the unweathered, relatively fresh core Formation where distinct zonation is apparent at the JurassiclCre- samples. taccous boundary (dotted line). Thc division (~ccurs between 2x0 Processing andexamination of the core samples are nearcomple- and 294 metres from the tapofthc Minnes Formationin the Bclcourt tion. A preliminary zonation schemehas been workcd out (Fip. section,

Mt Nerrick Wolverine Crk-Triad Belcourt- duintette Antler Rdg Mt -Sukunka 2" M t Secus Bullmoose Nonkman SE NW Mt Pass

Scale Horizontal-1.5 cm = 10 km Vertical- 1 mrn = 10 m A plot of the age range of spccics has heen completed lor the and, commonly. from one forr,ation to thcncxt within a sin1:le Gcthing asscmhlagc only. Initial data suggest a Middle Alhian agc section. TAI values also vary considcrcrhly and suggest that, at le 1st for this formation. Plats of rhc sp:cies ranges for the remaining on thescale of this study. TAI is r8:lated more to depositiotlal formations, couplcd wit11 information from other palcontalogical environment than to depth of burial(SYP Manum. erd.. 1976). 'This studics, will establish the accuracy dthis dating. Ifa Middlc Alhian relationship may he unique to coal measures where humic acids age is confirmed for the &thing h.mation. and only thc uppcr 300 increase the oxidation rate of organic matter.hut at thetim: 19 metres of the MinneL hrmation is Early Crctaccnus in agc. a writing no attempt has heen matlc to ~cstahlishthis through a lit:r- considerable time gap ('! Middle B(:rriasian through Early Alhian) aturc seirch. can he inlerred at the MinneKadcmin unconformity. Interpretation of dcpositianal cnvirrmments is currently in PI'<'- Despite this apc diffcvcc of approximately 30 milliun years. grcss. The original mudstonc s.rmp1r.s can. after processing and examination of slidcs and.lnl moun 5 indicates a degree ofpreserw examination, he grouped by palyno~ncmrph contentinto four catq II- tion in reverse OS what nlipht he expected. The Minncs Formation ries: marine. marine influenced. lerre!.trial. and harrcn. It is hqcd exhibits good prescrvatiunof palyn,morphs ;and a TAl value in the thatthe marine-influenced samples. containing hoth terrestrial pale ycllow through ambu ycllow ( I .5-2.25) range. Preservationin spores and marine dinocysts. wi I provide a time-stratigraphic link the overlying units is hi1:hly variable Srom one section to thc ncxt betwccn thc marine and Don-ma-in? f,rcies.

FORNAlION NAME FM CETHINC FM MOOSEBAR FM GATES FM ..DINOCYSTS MINNES Chytroeisphaeridia variabilir; Frorneaamphora ConyaulacystahyalodPrma Tenua hystrix Tenua riaulti canningia reticu1ata -I- Cribroperidiniumintcicatum Deflandrea Derlucida Pseudoceratium regiun Tenuacapitata Cyclonephelium distincturn var. brevispinatu? CaSSieuloSrhaeridiaPeticulata Cleistosphaeridium diversispinosum Hystrichokrlpoma ferox Hystrichosrhaeridiumcooksoni Pareodiniaaphelia Hystrichosrhaeracinqulata Hystrichosghaeridiumstellaturn Oligasphaeridium pulcherrimum I " Muderongiatetracantha Ascotomocys,tis maxima convau1acv:taeretacea I I

Ischympoeitesmarburgensis Ischyospori tes "radiatus" Lygodiosporitesperverrucatul; Rugulatisp'lriteschamiornatul; CiCatriCOsjsporiteS1udbraok.r Leptolepidites major Pilosisporjtestrichopapil1o:;us Triletes tllberculifcrmis Cicatricosjeporitespotomaeensie Reticulisp<,rites senireticulatus stap1inisporites caninus Trilobosporitestritotrys cicatricosisporitesauritus Clavatipo1l.enitesccuperii Cooksoniteareticulatus Inaperturol,ollenite dubivs M"F-OSpOr-8 I.P""csta Reticulisooriteselcncatue Schizospori :i rugulatui Schizospori 5 cooksarii Spheripolltlnitesscabratus Cicatricosisporitesimbricatus Appendicisparitesdentimarginatus I I Appendicisparitesuricus Cicatricosisporites dorogensis Distaltria,,g"latisp~=i~~~-foss"lat"5- I I Foraminisporisasymnetricus Foveotrile-:essUbtrianmlaPi,s COMMENTS Leckic, D. A. (1981): Shallow-marine Transitional to Non-marine Sedimentation in the Upper Moosebar-Lower Gates Member. The results to date from this study have been encouraging. The Fort St. JohnGroup. N.E. British Columbia:Storm and detail of information indicates that the formations present in the Tidally Influenced Shorelines, Tech-Memo 81-1, McMosrer Peace River Coalfield can he identified and dated by their palyno- Universih. Hamilton. 57 pp. morph assemblages. Furthcr plats of the spore and dinocyst species by location(that is, as continu~ussections) may revcal further Leckie, D. A. andWalker, R. G. (1982):StormandTlde-dominated zonationand the specific relationship of thetransition member Shorelines in Cretaceous Moosebar-Lower Gates Interval - occurring between the Moosebar shales and the coal-bearing Gates Outcrop Equivalents of Deep Basin Gas Trap in Western Can- Formation. Correlation of the marine and non-marinc facies may ada. Alfa. Asroc. Per. GPO/.,Bull., Val. 66, pp. 138-157. reveal time-stratigraphic horizons, in addition to those provided by Manum, S. 8.. Bjaerke. T., Throndsen, T., and Ein, M. (1976): tonstein and bentonite layers already recognized. Presemation and Abundance of Palvnomorohs. and Obscrva- lions on Thermal Alteration in Svaibard, NkkPolrrrinsrirurr In the future it is hoped that coal companies will use the palyno- Arhok, Oslo, 1977, ..DD. 121-130. logical result5 of this study for the more refined task of drill-hole Mclxan. R. (1977): The Cadomin Formation: Stratieraohv. Sedi- J. I., correlation of coal seams using the palynomorph assemblagesfound rnentohgy. andTcctonic Implications, Cdn. Per. Gml.,Bull., in roof shales. Thc groundworkhas also been laid for furtherstudies Vol. 25. PD. 7Y2-827. of the rocks to the northwest and southeast of the study area whcrc .. the application ofa different nomenclature reflects the uncertainty ~ ( 1982): Lithostratigraphy of the Lowcr Cretaceous Coal- of stratigraphic relationships. bearing Sequence. Foothills of Alberta. Geol. Surv., Canudu, Paper 80-29, 31 pp. Mcl.ean, J. R. and Wall, J. H. (1981): The Early Cretaceous Moos- REFERENCES ebarSea in Alberta, Cdn. Per. Geol., Bull., Vol. 29, pp. Bell, W. A. ( 1956): Lower Cretaceous Flora5 of Westem Canada, 334-377. Geol. Sum. Cunrrdn, Mem. 285, 153 pp. Stott, D. F. (1968): Lower Cretaceous Bullhead and Fort St. John G~~uDs.between Smokev and Peace Rivers. Rockv Mountain Carmichael, S. (1983): SedimentologyoftheLowerCretaceaus M. Foothills, Alhertaand BrkshColumbia. Geol.Sur;.. Cunuda, British GatesandMoosebarFormations,NorthedstCoalfields. Bull. 152. 279 Columbia. unpub. Ph.D. Thesis, Univercir? ofBritish Colum- ..DD. bin, 2x5 pp. -( 1973):Lower Cretaceous Bullhead Group between Bull- moose Mountain and Tetsa Kiver, Rocky Mountain Foothills, Duff. P. McL. D. andGilchrist. R. D. (1981): Correlation of Lower Northeastern British Columbia, Geol. Surv.. Canada, Bull. CretaceousCoal Measures, Peace Rivcr Coalfield. British 219, 228 pp. Columbia. B.C. Ministry ofEnerg?. Mines & Per. Res., Paper ~ ( 1974): Lower Cretaceous Coal Measuresof the Foothills 1981-3, 31 pp. of West-central Alberta and Northeastern British Columbia, Hughes,J.E.(1964):JurdssicandCretaceousStrafaoftheBullhead C.I.M.,Bull.. Vol. 67, pp. 87-101. Succession in the Pedce and Pine River Foothills, B.C. Minir- ~ (1981): Bickford and Gorman Creek. Two New Forma- If? qf€nergy, Mines & Per. Res., Bull. 51, 73 pp. lions of the Jurassic-Cretaceous Minnes Group. Alberta and ___ (1967): Geology of thePine Valley. B.C. Minisrv q/ British Columbia, in Scientific and Technical Reports, Geol. Energy, Mines & Per. Res., Bull. 52, 137 pp. Surv., Cunada, Fhper81-IB, pp. 1-9.

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