BRITISHCOLUMBIA DEPARTMENT OF MINES AND PETROLEUMRESOURCES HoN. D.L. BROTHERS,Minister K. B. BLAKEY,Deputy Minister ~~ BULLETIN No. 52 GEOLOGY of the PINE VALLEY Mount Wabi to Solitude Mountain Northeastern British Columbia by J. E. HUGHES GEOLOGY OF THE PINE .VALLEY Mount Wabi to Solitude Mountain Northeastern British Columbia SUMMARY 1. The map-area covers the Pine Valley, in the Rocky Mountain Foothills of northeastern British Columbia, from latitude 55 degrees 30 minutes to latitude 55 degrees 45 minutes north. 2. The exposed rocks are Triassic, Jurassic, and Cretaceous in age. The suc- cession (Ladinian to Cenomanian) is between 10,000 and 20,000 feet thick, and mostly of marine deposition. Most stratigraphic units thicken westward. 3. In the Triassic, the Grey Beds contain limestones, dolomites, siltstones, and sandstones; and the overlying PardonetFormation, argillaceous limestones with fossil shell beds of Halobia and Monotis. 4. The Fernie Group of Jurassic age consists of: thin limestone, interbedded shales and siltstones with cherty banding, the Nordegg Beds; followed by the Middle Shales; and in the upper part, interbedded shales, siltstones, and sandstone:;, the Transition Beds, which mark the change to Beaudette deposition. 5. The Beaudette Group of late Jurassic to early Cretaceous age has three formations: the Monteith, thick sandstones mostly, and with quartzites in the 'upper third part; the BeattiePeaks, interbedded shales, siltstones, andsandstones; and the Monach Formation,sandstones, with or without quartzite beds at the top. Facies changes and incomplete outcrops make it advisable to map Beaudette strata as an undivided unit to the west. 6. Coal measures overlying Beaudette strata are described by the term Crassier Group. The group is a continuous sequence of deposits in the field. They have a complex lithology: shales, mudstones, siltstones, sandstones, grits, conglome:rates, and coals, laid down in cyclic repetition. The sequence is undivided to the west. Eastwardit can be divided intothe Brenot, Dresser, and Gething Formations, according to their sand/shale ratios, the nature of the cyclothems, and the dirtribu- tion of the coarser clastics. 7. TheFort St. John Group contains alternations of shaleformations, the Moosebar in the lower part, the Hasler, and theCruiser, with sandstone formations, the Commotion, and the Goodrich. These units are marine, except for thin non- marine beds and coal measures in the Commotion Formation. 8. The Dunvegan strata are mostly non-marine, and they form the youngest formation of the Cretaceous in the map-area. 9. The sedimentary rocks were deformed and uplifted in the Rocky Mountain orogeny, one phase of the Laramide revolution. 10. The Rocky Mountain Foothills in the Pine area are in two parts: the Inner (or Western)Foothills and the Outer (or Eastern) Foothills. The structures of the Inner and Outer Foothills represent different tectonic styles. 11. Close folding and thrusting prevailed in the Inner Foothills, and t:he de- formation resembles that of the Rocky Mountains on the west. 12. The Outer Foothills contain long anticlines separated by wide synclimes, andhere the deformation was restricted tothe anticlinal folding,and fmlting 7 along the anticlines. The Outer FoothiUs belong to the orogenic foreland, Their structures can beascribed to block faulting inthe basement, though positive evidence is lacking. 13. Foldingin the Foothills is of parallel type. The fold forms are con- centric, or angular. The angularfolds (that is, parallel folds of non-concentric form) include those of cuspate and lamhdate forms, in the writer's classification. Two types of concentric folds are distinguished-those of low and high fold ampli- tude respectively. 14. Concentric anticlines of low fold amplitude occur in the Outer Foothills. The Commotion anticline is the only example that has been drilled to depth. Its surface and subsurface structures differ considerably, and they are separated by a low angle thrust, or dtcollement, or a zone of complex folding and shearing. 15. High-amplitude concentric anticlines have fold centres at shallow levels, and may be underlain by cuspate and angular folds, as well as dkcollements. Con- centric folds of high amplitude, cuspate, and angular folds occur together in the Inner Foothills. 16. According to the writer's view, cuspate anticlines developed by replacing concentric anticlines during the folding compression. Lambdate folds are not spe- cially related to concentric folds, and the few examples noted lie close to fault planes. 17. The structures of the Pine Valley area form part of a larger tectonic frame- work, which includes: the junction of the northern and southern parts of the Rocky Mountains; and in the Plains, the junctions of three tectonic units of the foreland, the Halfway block, the Fort St. John arch, and theAlberta syncline. The junction of tectonic units of the foreland now occupy the site of the Peace River emhayment, a palzotectonic basin of differential subsidence and sedimentation lying transversely to the former miogeosyncline along the site of the Rocky Mountains and Foothills. 18. Observations, and analyses of structural geology presented here, are of use in exploring for petroleumand natural gas. Natural gas has been discovered in the Pine River anticline. Important reserves of coal occur in the Pine Valley. 8 CHAPTER1.-INTRODUCTION LOCATION 1954; K. Falconer and C. Wright, 1955; Y. Kamachi, 1956; R. M. Luning, 1957; and A. Jellinek, 1958. The writer is grateful to them for their work, and to the residents of the Pine Valley for their interest and many courtesies. Dr. J. A. Jeletzky identified the Upper Jurassic and Cretaceous faunas, and Dr. D. C. McGregor, the Cretaceous floras, at the GeologicalSurvey of Canada, Ottawa. Parts of the manuscript and its presentation were discussed by Drs. S. S. Hol- land and G. E. P. Eastwood. Full acknowledgments are due to Piofessors C. W. Stearn and P. Eakinsof McGill University for their advice, reading, and supervision of part of this work as a thesis. PREVIOUSGEOLOGICAL WORK The first reconnaissances of the Pine Valley were made by G. M. Dawson (1881)and R. G. McConnell (1893). Later, geological work was directedto explorations for petroleum by J. C. Gwillim (1920), J. A. Dresser (1920, 1921), E. M. Spieker (1921,1922), M. Y. Williams (1939); toexplorations of coal deposits by 3. Spivak (1944), W. H. Mathews (1947), N. D. McKechnie (1955); and to reconnaissanceby M. Y. Williams and J. B. Bocock (1932), and C. R. Stelck (1942). The geology of parts of the Pine Valley, the Mount Hulcross-Commotion Creek area, was mapped by R. T. D. Wickenden and G. Shaw at a scale of 1 inch to 1 mile, and the Mount Bickford area by W. H. Mathews at a scale of 1 inch to 2 miles. The preliminary geological maps, Sheet 93-0 Pine Pass by J. E. Muller (1961), and Sheet 93-P Dawson Creek by D. F. Stott (196181, at scales of 1 inch to 4 miles, also include the Pine Valley. In stratigraphic work completed in the Pine area, G. E. G. Westermann (1962) zoned the Monotis beds of the Triassic; J. E. Hughes (1964) describedJurassic and Cretaceous strata of the Bullhead succession; R. T. D. Wickenden and G. Shaw (1943) classified the Fort St. John Group, and later D. F. Stott (1961~)redescribed the group. References in the bibliographymark the debt to F. H. McLearn(1918 to 1960) for hispioneer studiesof Mesozoic fossils andstratigraphy in northeasternBritish Columbia. McLearnlaid the basis forlater geological work,and his studiesapply tothe geology of the Pine Valley. BIBLIOGRAPHY Ager, D. V., and Westermann, G. E. G. (1963) : New Mesozoic Brachiopods from Canada, Jour. Pal., Vol. 37, pp. 595-610. Arkell, W. J. (1956): Jurassic Geology of the World, Hafner Publishing Co. Inc. Armitage, J. H. (1962) : Triassic Oil and Gas Occurrences in Northeastern British Columbia, Canada, Alta. SOC.Pet. Geol., Jour., Vol. 10, pp, 35-56. Auhert, D. (1949) : Le Jura-Orogen. und Vorland, Zeif. fur A&. Geol., Band 37, pp. 2-17. Barnwell, G.: See Lees, G. M. (1952). Barton, D. C. (1925): Discussion-"Upthrust Salt Masses of Germany," by H. Stille, Am. Assn. Pet. Geol., Bull., Vol. 9, pp. 439-441, Beach. H. H.. and Soivak. J. f 1944) : Dunlevv-Portage- Mountain Mao-area. Brit- ish Columbia, Geol. Surv., Canada, Paper 44-19. Beckwith, R. H. (1938) : Structure of the Southwest Margin of the Laramie Basin, Wyoming, Geol. SOC. Am., Bull., Vol. 49, pp. 1519-1544. __ (1942): Strncture of theUpper Laramie River Valley, Colorado- Wyoming, Geol. Soc. Am., Bull., Vol. 53, pp. 1491-1532. Bell,W. A. (1956): Lower Cretaceous Floras of WesternCanada, Geol. Surv., Canada, Mem. 285. __ (1963) : Upper Cretaceous Floras of the Dunvegan, Bad Heart, and Milk River Formations of Western Canada, Geol. Surv., Canada, Bull. 94. 10 Berg, R. (1962): MountainFlank Thrusting in Rocky MountainForeland, Wyoming and Colorado, Am. Assn. Pet. Geol., Bull., Vol. 46, pp. 2019-2032. Billings, M. (1942) : Structural Geology, Prenlice-Hall Inc. Biot, M. A. (1961): Theory of Folding of Stratified Viscoelastic Media and Its Implications in Tectonics and Orogenesis, Geol. Soc. Am., Bull., Vol. 72, pp. 1595-1620. Biot, M. A.; Od6, H.; and Rower, W. L. (1961): Experimental Verification of the Theory of Folding of Stratified Viscoelastic Media, Geol. SOC.Am., Bull., Vol. 72, pp. 1621-1632. Bocock, J. B. (1929): Peace River Block, Pacific Great Eastern Railway La!lds, Survey of Resources. Bohm, J. (1903):tiber dieObertriadische Fauna der Bareninsel, K. Svenska Vetensk., Akad. Handl., Band 37, No. 3. British Columbia, Department of Mines and Petroleum Resources (1874 et seq.): Annual Reports. British Columbia, Department of Mines and Petroleum Resources (1960 et seq.) : Schedule of Wells Drilled for Oil and Gas in British Columbia. Burk, C. F. (1963): Structure,Isopach, and Facies Maps of Upper Cretaceous Marine Succession, West CentralAlberta and Adjacent British Columbia, Geol. Surv., Canada, Paper, 62-31.