Abstract Ongoing and Future Research Detrital Zircon Age Data: At least one detrital zircon sample was taken he Lower Cretaceous Jackass Mountain Group (JMG), exposed Sedimentology, Stratigraphy, and Reservoir Potential of the Lower Cretaceous Jackass Mountain Group, from each measured section. A total of six “high-priority” samples were Talong the southern margin of the (south-central selected for processing from the and are currently being ), is a >2 km-thick succession of marine and non- prepared for analysis in Spring 2008 at the University of Arizona. marine siliciclastic sandstone, minor mudstone, and lesser Southern Nechako Basin, Camelsfoot Range, B.C. - Preliminary Observations conglomerate, ranging in age from Hauterivian/Barremian to Albian or Geochemistry: Twelve fine-grained geochemistry sample have been younger. The JMG was deposited in the Jura-Cretaceous Methow J. Russell Goodin Peter S. Mustard J. Brian Mahoney James W. Haggart analyzed using an XRF at the University of Wisconsin - Eau Claire. Results are currently pending. Basin, and appears to trend northward, beneath Cenozoic Department of Earth Sciences Department of Earth Sciences Department of Geology Geological Survey of Canada - Pacific Division into the Nechako Basin, which is currently the focus of renewed Simon Fraser University Simon Fraser University University of Wisconsin - Eau Claire Natural Resources Canada Fossil Age Data: The Jackass Mountain Group in the Camelsfoot Range interest for hydrocarbon potential. Previous studies have suggested contains a notable lack of fossils. Several fossils were collected from this that the JMG is comprised dominantly of turbidites deposited in year’s study area and are awaiting analysis. However, one belemnoid fossil submarine fan complexes. The southern part of the study area does 51o 09’ from the basal Madson Creek section has been identified by James W. Introduction and Geologic Setting Fraser 2 51’ 121 Interpretation contain very thick (>1500 m), repeated, massive sandstone turbidite Haggart as Acroteuthis, suggesting a pre-Albian age. Nine Mile Ridge Facies Associations N i n e M i l e R i d g e 3: Cross-bedded Sandstone Facies Association o o Dominant, green, cross-bedded, litho-feldspathic, medium- successions, which are interpreted as being deposited in sub- “Central Ridge” During summer 2007, detailed examination of well exposed sections of the JMG Simplified Stratigraphy As generalised on the right, Jackass Mountain Group rk Petrography: Approximately thirty-five petrographic thin sections have 122S 40’ C R Non-Marine hu n i grained sandstone, interbedded with laminar or cross-stratified wavebase marine fan complexes. North of this, turbidites, while in the Camelsfoot Range were conduted. The JMG is well exposed on several o v strata in the Camelsfoot Range can be susbdivided into laps Yalakom Hogback er been prepared for analysis using a polarized petrographic microscope. of the Chilcotin Mountains 92O2 mudstones. Sandstones range in thickness from <10m to <70m and present, commonly show evidence of reworking in environments ridges in this area and volumetrically the most significant unit in the central and R Mtn Mtn Mads 92O1 92P4 are overlain by coarsening-upwards mudstone successions. Only six are currently ready. three major facies. It should be noted, however, that an 92J16 92I13 above storm wavebase. The central and northern areas are eastern Camelsfoot Range ( Hickson et al, 1994, Schiarizza et al., 1997, ge Yal C a m e Quaternary the geographic constraints of these facies are relatively ak Ichnology: Trace fossils will be analysed under the supervision of Dr. dominated by extensive non-marine, fluvial trough cross-bedded Mahoney et al., in review). It forms the central part of a ~150 km long, southward- om l s 2: Interbedded Sandstone/Siltstone Facies Association R f o Marine Neogene Chilcotin Gp LEGEND ive r o t James MacEachern at Simon Fraser University. This should assist in the sandstone and floodplain siltstone. The precise age of these tapering wedge of mainly medium- to coarse-grained sandstone and polymictic ambiguous. This problem is a general result of poor R Shoreface Distinct “striped” sandstone/siltstone, commonly cross-stratified, a n g Sub-Marine Fan/Delta determination of appropriate facies designations. Tertiary 92P4 couplets. Striped succession are interbedded with massive or locally nonmarine facies is presently unknown, but detrital zircon samples conglomerate exposed between the Yalakom and Fraser fault systems. Ootsa Lake Group exposure, remote access, the preliminary nature of this NTS e 1:50 000 map cross-bedded medium-grained sandstones and range in thickness from fluvial sandstones in this facies will at least provide a maximum strata study, and the probability that the facies are laterally and Study Area from <10m to >125m. Stratigraphy: The aforementioned analyses will be used to gain a better Boundary Brid At and near Yalakom Mountain, northwest-trending JMG strata dip steeply and g understanding of the stratigraphy and paleogeography of this part of the age, and palynology samples will hopefully provide more specific age Late K Powell Creek Group internally variable across the 35 km strike of the this Topographic e R Late iver are slightly overturned towards the north in some areas. JMG units in this area Contours 1: Green Massive Lithic Coarse Sandstone Facies Association Cretaceous Methow Basin. constraints and other biostratigraphic information. These Cretaceous Marine study area. Primary Lower Shoreface/Shelf overlie middle Jurassic rocks of the Ladner Group (Mahoney, 1994; Schiarizza et Silverquick conglomerate Sub-marine Fan Dominantly thick (< 20m) massive, lithic, medium- to coarse- observations suggest that a continuous, nonmarine to marine Roads km grained sandstone, interbedded with laminar and cross-stratified Hydrocarbon Potential: Facies, porosity/permeability, and total organic al., 1997). These basal JMG rocks are dominated by massive, green, medium- to Taylor Creek Gp Rivers N succession is preserved in this area, which possibly spans Barremian 0 5 10 mudstones. carbon analyses are currently underway. coarse-grained, lithofeldspathic sandstones and interbedded siltstones. These Albian F Lizard Fm Jackass 50o 38’ to Albian-Cenomanian time. Thick and moderately well-sorted cross- Yalakom Mountain Dash Fm Mt. North Hogback Aptian form a >1500m thick unit on Yalakom Mountain that is correlative with the Paradise Fm F Gp stratified fluvial sandstone packages in the northern Camelsfoot Mountain volcanic sandstone unit described by Schiarizza et al. (1997). JMG strata Early Range represent a new potential hydrocarbon reservoir system, Cretaceous Facies Association 2 Succession - Madson Creek Typical Facies Association 3 Outcrops - Nine Mile Ridge which may have had better original porosity and permeability containing fossils of probable Barremian age are present about 200m below the F Neocomian 130 characteristics than the less well-sorted massive sandstone base of this section, but above the basal unconformity with the underlying Lower F Relay to Middle Jurassic Dewdney Creek Formation, (GSC Loc. 74815; Poulton et al. in 125 turbidites common in the southern Camelsfoot Range. Extensive Nine Mile Ridge Upper Mountain Gp fluvial and shallow marine facies associations in the JMG also support Schiarizza et al., 1997). New fossil collections from the upper part of the Jurassic F base 120 of stratigraphic section north of Yalakom Mountain are of Albian age (Brewericeras section the interpretation that the JMG continues northward into the Early to v v v hulenense zone). Thus, the full stratigraphic section of the JMG in the Yalakom F subsurface and may comprise the strata previously termed “Skeena Middle v v v Last Creek Fm 115 Jurassic assemblage,” which have been interpreted as containing “the most Mountain area appears to range in age from Barremian to Albian. F 110 significant petroleum plays…” in the Nechako Basin. Ongoing Upper Cadwallader, Tyaughton Gps From JMG strata in the Camelsfoot Range, five detailed stratigraphic sections Triassic geochronologic, geochemical, paleontologic, and 105 were measured, 45 petrologic, 10 detrital zircon, 12 fine-grained geochemistry, Late Gp porosity/permeability analyses will constrain basin evolution and Paleozoic 11 micro-, and 3 macrofossil samples were recovered. Section locations and 100 48.9 reservoir suitability. thicknesses include approximately 1500 m on Yalakom Mountain (A on measured section map), 130 m on eastern Nine Mile Ridge (B), 130 m on western 90 48.8

Purpose for Investigation Nine Mile Ridge (C), 125 m on Madson Creek, north of Hogsback Mountain (D), 48.7 85 References and 70 m on a low-lying ridge in the central study area (E), between Beaverdam Typical Facies Association 2 Outcrop - Madson Creek B.C. Ministry of Energy, Mines and Petroleum Resources, 2002. Nechako Basin: Oil and Gas Opportunities in Central British Columbia. This MSc study is a subset of a regional multi-year project funded by Geoscience BC (active project 2006-014) and NSERC (Grant 611258), with 48.6 principal investigators Peter S. Mustard and J. Brian Mahoney. and Watson Bar Creeks. Several additional traverses were also conducted in 80 BC Ministry of Energy, Mines and Petroleum Resources, Information Brochure. order to collect general rock type, structural, and fossil information. Simplified Regional Geology Bouma, A.H, 2000. Fine-grained, mud-rich turbidite systems: model and comparisons with coarse-grained, sand-rich systems. In: Bouma, A.H., 75 48.5 and Stone, C.G. (Eds.), Fine-grained turbidite systems. American Association of Petroleum Geologists Memoir 72 / SEPM Special Publication The principle focus of this investigation is the assessment of hydrocarbon potential in the subsurface of the -capped “Nechako Basin”. 68, pages 9-68. Pinchi F Exposed strata of the Jackass Mountain Group in the Camelsfoot range are the closest and most volumetric sedimentary packages in the region. F N 97 48.4 Ferri. F. and Riddell, J. 2006. The Nechako Basin project: new insights from the southern Nechako Basin in Summary of Activities 2006, BC aw e 70 Analysis of this strata, along with seismic data and investigation of core from industry drill holes should shed some light on hydrocarbon possibilities n cha Ministry of Energy, Mines and Petroleum Resources, pages 89-124. ie k au in the region. Ra o 48.3 Garver, J. I., 1992. Provenance of Albian-Cenomanian rocks of the Methow and Tyaughton basins, southern British Columbia: a mid-Cretaceous R lt 65 Regional Tectonic Elements nge a link between North America and the Insular terranes, Canadian Journal of Earth Science, Volume 29, pages 1274-1295. nge Quesnel Aside from industry interest in oil and gas, there is some acedemic interest in the reconstruction and paleogeography of the Cretaceous Methow 48.2 Hannigan, P. Lee, P.J., Osadetz, K., J., Dietrich, J.R. and K. Olsen-Heise, K. 1994. Oil and Gas Resource Potential of the Nechako-Chilcotin ST Insular superterrane 60 93 B Area of British Columbia. Geological Survey of Canada, Geofile 2001-6. and Tyaughton basins. These basins, initially discussed by Kleinspehn (1982) and Garver (1992), are not well understood. CD Wrangellia (WR)*

QN/ST? eek r 48.1 Hickson, C.J., Mahoney, J.B., and Read, P., 1994, Geology of Big Bar map area: facies distribution in the Jackass Mountain Group; in Current Na C 55

o zk Research, Part A; Geological Survey of Canada, Paper 94-1A, pages 143-150. sbak Cli o

Imbricated terranes Ri Thickness (metres)

v (linked with Wrangella by 90 Ma) e k r 48.0 Hunt, J.A. 1992. Stratigraphy, maturation, and source rock potential of Cretaceous strata in the Chilcotin-Nechako region of British Columbia. ee 50

Cr Unpublished M.Sc. thesis, University of British Columbia, Vancouver, B.C., 447 pages. i

BC Location Location of Measured Sections r Bridge River terrane (BR)* ut

CC QN a T BR 51o 09’ Jackass Mtn Group Williams 45 47.9 Kleinspehn, K.L. 1982. Cretaceous sedimentation and tectonics, Tyaughton-Methow Basin, southwestern British Columbia. Ph.D. thesis, F Cadwallader terrane (CD)* (known or probable) Princeton University, Princeton, N.J., 184 p. ra 51’ 121 Lake ser known Cretaceous 20 B Thickness (metres) N i n e M i l e R i d g e Methow terrane (MT)* 40 47.8 Kleinspehn, K.L. 1982. Cretaceous sedimentation and tectonics, Tyaughton-Methow Basin, southwestern British Columbia. Ph.D. thesis, o sedimentary rocks

o Princeton University, Princeton, N.J., 184 p. Kleinspehn, K.L. 1985. Cretaceous sedimentation and tectonics, Tyaughton-Methow Basin, of “Nechako basin” O southwest British Columbia. Canadian Journal of Earth Science, Volume 22, pages 154-174 rk 92 N 92 C Parks or F Typical Facies Association 1 Outcrops - Yalakom Mountain 122 40’ A C R Intermontane superterrane Y 47.7 S E Protected Areas a r 35 hu D n i lako a Mahoney, J.B., Hickson, C.J., and Schiarizza, P. in review. Geology, Taseko Lakes, British Columbia. Geological Survey of Canada, Open File o v s l Yalakom e Quesnellia (QN) m F er Map, scale 1:250 000. 1 sheet. a Hogback ds r Measured Section Legend p a Primary Areas a F s 92O2 Mtn M 92O1 92P4 B u 30 47.6 R Mtn of Study lt ault pebble/gravel bed lenticular bedding a Stikinia (ST) Schiarizza, P., and Riddell, J., 1997. Geology of the Tatlayoko Lake – Beece Creek area. in Geoscience Project: Summary of n 92J16 92I13 A Camelsfoot Range sandstone flaser bedding Geological, Geochemical and Geophysical Studies; BC Ministry of Employment and Investment, Energy and Minerals Division, Geological g Ya C a m WR Survey Branch paper 1997-2 and Geological Survey of Canada Open File 3448, pages 63-101. 47.5 sandstone-siltstone normal grading e l Ch 25 couplet ak Chilko Lake - ilc om e l B o silty mudstone inverse grading s f o o NWC MT Terranes of uncertain affiliation Nemaia Valley tin Schiarizza, P., Gaba, R.G., Glover, J.K., Garver, J.I., and Umhoefer, P.J., 1997. Geology and mineral occurrences of the Taseko-Bridge River LEGEND Riv M siltstone-mudstone loaded basal area: BC Ministry of Employment and Investment, Energy and Minerals Division, Geological Survey Branch, Bulletin 100, 291 pages. o A 47.4 interbeds t untains 20 contact Measured er R a n Northwest Cascades System (NWC) 75 km mudstone scoured base A sill Schiarizza, P. Riddell, J., Gaba, R.G., Melville, D.M., Umhoefer, P.J., Robinson, M.J., Jennings B.K., and Hick, D. 2002. Geology of the Beece Sections g e ripup clast horizon Creek-Nuit Mountain Area, B.C. (NTS 92N/8, 9, 10; 92O/5, 6, 12) BC Ministry of Energy, Mines and Petroleum Resources, Geoscience Map Western and Eastern Melange Belts 15 47.3 horizontal planar parallel strata ripup clasts 2002-3, 1 sheet Quaternary Cadwallader terrane and overlying NTS 92P4 Tyaughton-Methow basin Jura- Cretaceous sediments (except JMG) low angle truncations pebble/gravel lag 1:50 000 map Anahim Volcanics; Miocene Riddell, J.M. (compiler) 2006. Geology of the Southern Nechako Basin, NTS 92N, 92O, 93B, 93C, 93F, 93G. BC Ministry of Energy, Mines and Bri Stikine Terrane; Late Triassic to mid- 10 47.2 trough x-strata dewatering structures Petroleum Resources, Resource Development and Geoscience Branch, Petroleum Geology Map 2006-1, 3 sheets. dg Miocene-Pliocene flood basalts Jurassic volcanics and sediments; Topographic e Crystalline Rocks includes Hazelton Gp ripple x-lamination wood fragments R Tertiary volcanics and sediments Contours ive Cache Creek Terrane; mid to Late 47.1 wavy lamination/bedding concretion Acknowledgments r Cascade Metamorphic Core Spences Bridge volcanic arc (K) Paleozoic and Mesozoic ocean floor 5 Nechako Basin basalts, sediments, and intrusions trace fossils Primary Cretaceous Sediments hummocky cross-strata Special thanks goes to Pete Mustard for letting me take a whack at completing an MSc at Simon Fraser University...and not tossing Slide Mountain, Kootenay/Cassiar Roads Coast Plutonic Complex Nechako Basin and Quesnel terranes swaley cross-strata bivalves me out the door a long time ago. Thanks to Geoscience BC and NSERC for funding this project. Brian Mahoney’s enthusiasm for Quaternary deposits Jurassic Sediments 47.0 km 0 r f m c g p c

Lillooet t silt ammonite field work, the Canadian Cordillera, geology, and everything else, really helped get this project off the ground. Thanks to Jim

Powell Creek and/or Spences Bridge ve Post-Acretionary Intrusions and clay convolute bedding Rivers N ss J-K plutonic rocks Gps, Late Cretaceous volcanics metamorphic rocks 0 5 10 co belemnite Haggart for the fossil calls...wish we could have found more. Thanks to my lab mate Kate MacLaurin for pretending to listen to me o syn-sedimentary 50 38’ Gambier Gp; Early Cret. volcanics Pre-mid Jurassic Intrusions deformed strata rant about random bits of nonsense. A huge thanks to Scott Taylor at CC Helicopters in Lillooet, BC for getting us in and out safely f m c g p c

silt every time. Our field assistants Alexandra Guy, Elizabeth Balgord, and Michelle Forgette did a great job...I couldn’t be doing this

t ver

clay o *includes overlying Jurassic-Cretaceous clastic succession ss c without you!