THE SOUTHERN TEFWlNATION OF THE MAIN RANGES AND WESTERN RANGES OF THE SOUTHERN CANADIAN ROCKY MOUNTAINS: STRATIGRAPHY, STRUCTURAL GEOLOGY, AND TECTONIC IMPLICATIONS by GORDON W. STRETCH A thesis submitted to the Department of GeoIogicai Sciences in conformity with the requirements for the degree of Master of Science Queen's University Kingston, Ontario, Canada April, 1997 copyright O Gordon W. Stretch, 1997 National Library Bibliothhue nationale du Canada Acquisitions and Acquisitions et Bibliographic Services services bibliographiques 395 Wellington Sweet 395. rue Wellington OttawaON KtAON4 Ottawa ON KIA ON4 Canada Canada The author has granted a non- L'auteur a accordk une licence non exclusive licence allowing the exclusive pennettant a 12 National Library of Canada to Biblioth@e natiode du Canada de reproduce, loan, or sell reproduire, prgter, dis6nibuer ou copies of Merthesis by any means vendre des copies de sa hkse de and in any form or format, making quelque manibe et sous quelque this thesis available to interested foxme que ce soit pour mettre des persons. exemplaires de cette these a la disposition des personnes int6ressees. The author retains ownership of the L'auteur conserve la proprikte du copyright in hidher thesis. Neither droit d'auteur qui protkge sa these. Ni the thesis nor substantial extracts la these ni des extraits substantiels de fiom it may be printed or otherwise celle-ci ne doivent Etre imprimcis ou reproduced with the author's autrement reproduits sans son pemission. autorisation. ABSTRACT The Tanglefoot area straddles the southern termination of the Main Ranges and Western Ranges geologic sub-provinces of the Foreland Fold and Thrust Belt of the Canadian Cordillera. The map-area also straddles a regional, east-west. cross-strike discontinuity, across which there are profound changes in the stratigraphy, sedimentary facies, and the style and orientation of the structures of the Rocky Mountains. The stratigraphy of the Tanglefoot area is subdivided into three distinct. unconformity-bounded assemblages: the Mesoproterozoic straw the Lower Palaeozoic strata, and the Upper Palaeozoic strata. There is a profound change in the Palaeozoic stratigraphy across the Dibble Creek fault. On the south side of the fault, the Lower Palaeozoic strata comprise a thin (1 18 m - 337 m), condensed succession of Middle Cambrian cratonic platform facies rocks, which unconformably overlie Mesoproterozoic strata, and are unconformably overlain by Upper Devonian cratonic platform facies strata. On the north side of the Dibble Creek fault, shaly equivalents of the Upper Devonian Fairholme Group (?), Palliser, Exshaw, and Banff Formations overlie approximately 7 km of shaly Lower Palaeozoic rocks. The structures within the maparea are dominantly northeast-trending, and verge to the southeast, in marked contrast to the regional structurai trend of the Foreland Fo!d and Thrust Belt. The Tanglefoot area has been subdivided into three structural domains: the Montania domain, the Tanglefoot domain, and the Hughes domain. The "Fisher block", which forms the stratigraphic base of the shaly Tanglefoot domain, is a steeply- dipping, east-northeast- facing, relatively undeformed panel of Mesoproterozoic and basal Cambrian strata It is separated £kom the shale-dominated Tanglefoot domain by an important dkcollement within the Eager Formation. Above the decollement, shaly Lower Palaeozoic strata are tightly folded, with a penetrative, northwest-dipping solution cleavage. The south-trending axis cf the fan-shaped Porcupine Creek anticlinoriurn swings to southwest in the Tangiefoot area, and the fan structure terminates above the dicollement in the Eager Formation. The conspicuous southeast-verging deformation in the Tangiefoot area is the result of tectonic inversion, which involved thickening and elevation of the Tanglefoot shale basin, followed by lateral gravitational spreading to the southeast. The Mount Haley syenitoid stock, which occurs in the footwall of the Lussier River fault, appears to be deformed, and therefore is older than regional deformation. "ArP9A.r geochronology completed as part of this study gives a date of 1 1 1 Ma for the Mount Haley stock. On the west side of the Rocky Mountain trench, the Reade Lake granitoid stock plugs the St. Mary-Lussier River fault, which cuts through the Tanglefoot area. Previous work has reported a U-Pb zircon date of 94 Ma for the Reade Lake stock. Hence, upper and lower constraints are placed on the age of deformation, at 94 Ma and 11 1 Ma respectively. "...thedescription of the highlands that surround that veritable sinkhole ofdisappearing fads, the Bull Valley in the Dibble-Lime-Iron Creek section. " -G.B.Leech. 1962 ACKNOWLEDGEMENTS It is a pleasure to acknowledge Dr. Raymond A. Price for his generous support. patient criticism, and guidance throughout all stages of this project. I am also indebted to Dr. Doug Archibald for guiding and supervising the geochronological work on the Mount Hdey stock, for providing me with geochronological results fiom the Central Hughes Range, for many insightfid conversations about the geology of the study area and Cordilleran tectonics, and lastly, for being a great fiend. Dr. Geoff Leech of the Geological Survey of Canada continues to provide fiesh and thoughtfid insight into the geology of the southeast Cordillera, and I thank him for his interest in this project. and for providing me with copies of his geological maps and field notes. Fossils collected during the field work for the study were identified by Dr. W.H. Fritz of the Geological Survey of Canada. At Queen's University, Dr. Hamish Sandeman assisted with the geochronological work on the Mount Haley stock, and Drs. Frank Brunton and Guy Narbonne provided assistance with certain samples. My thanks also go out to Dr. Dugald Carmichael for making his petrographic equipment available to me. I am also very gratefd to Derek Brown of the British Columbia Geological Survey for providing digitized TRIM maps of the Tanglefoot area. Assistance in the field was provided by P. Twa in 1994 and S. Bertels in 1995. In addition, visits to the Tanglefoot area by Ray Price in 1994 and 1995 and Doug Archibald in 1995 are gratemy acknowledged. A specid thank-you goes out to my father, Gord C. Stretch, for helping with the logistics of my field work, and for the cheefi companionship and outstanding camp food provided during a visit to the area in the summer of 1995. My thanks are also extended to Art, Linda, Rudy, and Frieda of the Kootenay Country Comfort Inn in Cranbrook, for their down-home generosity, hospitality, and for putting up with a certain pugnacious field assistant! Field work was hded by an NSERC research grant to Dr. R.A. Price. and personal financial support was provided by a Carl Reinhart Fellowship and a Queen's Graduate Scholarship in 1994, and by an Amoco Fellowship in 1995 and 1996. I owe a big thank you to dl the staff and graduate students at Queen's geology department for countless geological discussions and much assistance. My closest partners in crime, Mike "Ooley" Cooley, Clark Darner, Dave Gale. Brian Martin. Ian Russell, and Karen-Jane Wright: a 'uge-big thank you for everything, and thanks for helping me relax with an occasional pop at the Grad Club. Finally, my very sincere and profound thanks are extended to Pat and Gord Stretch of Edmonton for their support, assistance, confidence and encouragement throughout all stages of this project. TABLE OF CONTENTS Page Abstract I ... Acknowledgements U1 Table of contents v .. List of Figures VIlI List of Plates x Chapter 1 - INTRODUCTION................................................................................. 1 General Statement 1 Location Access Relief and Exposure Methodology Previous work Chapter 2 - REGIONAL BASEMENT TECTONICS......... ............ ... .. ..... .. .. ... .. .. -6 Introduction 6 Basement tectonics and the Tanglefoot area 7 Chapter 3 - REGIONAL TECTONIC SETTTNG ..................................................... 10 Chapter 4 - STRATIGRAPHY................................................................................. 18 Introduction 18 Mesoproterozoic strata 25 Fort Steele and Aldridge Formatons 25 Creston Formation 27 Kitchener Formation 28 Van Creek Formation 29 Nicol Creek Formation 30 Sheppard Formation 32 Gateway Formation 32 Phillips Formation 33 Lower Palaeozoic strata 34 Flathead, Gordon, and Elko Formations 34 Cranbrook Formation 37 Eager Formation 38 "Tanglefoot unit" McKay Group Glenogle Formation Mount Wilson Formation Beaverfoot Formation Upper Palaeozoic strata "basal Devonian unit" Buraais. Cedared, and Harrogate Formations Fairholme Group Palliser Fonnation "Devono-Mississippian shale unit" Cretaceous Intrusive Rocks Chapter 5 - STRUCTURE................................. Introduction The Montania domain Moyie-Dibble Creek fault The Tanglefoot domain The "Fisher block" Faulting Boulder Creek fault Porcupine Creek anticlinorium St. Mary-Lussier River fault The Hughes domain Chapter 6 - INTRUSIVE ROCKS: SIGNIFICANCE AND GEOCHRONOLOGY......................... .. ..... 87 Introduction 87 The Reade Lake and Kiakho stocks 88 The Mount Haley stock 91 Petrography 91 Structures 92 Geochronology results Conclusions Chapter 7 - DISCUSSION ......................................................................................... 96 The "Tanglefoot unit": Interpretations 96 Conclusions 97 REFERENCES CITED.. .. .. .. .. .. 1 00 vii Page APPENDICES ................................................... .........