THE Universlty of CALGARY
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THE UNIVERSlTY OF CALGARY Three-dimensional Geometry and Evolution of the Lovett River Triangle Zone, central Alberta Foothills Janice LeDrew A THESIS SUBh4ITTED TO THE FACULTY OF GRADUATE STuDIES IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE DEPARTMENT OF GEOLOGY AND GEOPHYSICS CALGARY, ALBERTA MAY, 1997 O Janice LeDrew 1997 National Library Bibliothèque nationale I*I of Canada du Canada Acquisitions and Acquisitions et Bibliographic Services services bibliographiques 395 Wellington Street 395. rue Weltington Ottawa ON KIA ON4 Ottawa ON KIA ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distnie or sell reproduire, prêter, distribuer ou copies of this thesis in microfoq vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/nIm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propiété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts from it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Abstract Four detachments separate rocks with different structural styles and arnounts of shortening in the study area within the central Alberta Foothills. The intensely deformed, shaie-dominated Alberta Group is characterized by foreland-verging duplexes, fault- propagation folds, and pop-ups; whereas the deeper, older, more competent rocks are deformed into larger fault-bend folded thrust sheets with fewer faults. Deep structures in the Lovett River Triangle Zone are en échelon to those in the Brazeau River Triangle Zone dong-strike to the southeast. The Pedley Thnist, upper bounding backthrust of the Lovett River Triangle Zone, terminates in a fold to the southeast and a new upper bounding backthrust at a higher stratigraphic level is interpreted in the Brazeau River Triangle Zone, where the foreland-verging Ancona Thrust has ovemden the previous upper bounding backthrust. A relict triangle zone is interpreted in the Pembina River area in the hinterland. The Elk River area, in the foreland, contains structures that represent initiation stages of triangle zone evolution. There are many people and organizations who have helped me in various ways throughout the course of this project and 1thank them dl. I would like to th& my advisor, Don Lawton, for taking me on as a graduate saident and allowing me to do rny own thing. He provided immense guidance and encouragement during this project for which f am gratefd. Thanks to Willem Langenberg, Debbie Spratt and Daniel Lebel, for their assistance in the field, especially WiIlem for sharing his work with me and Debbie for her input to this project My appreciation is extended to many people in the Department of GeoIogy and Geophysics: Foothills Research Project, CREWES, main office, Gdagher Library. Conoco Canada Limited provided me with much of the invaluable seisrnic data used in this thesis and 1am grateful to many people there for their support and helpful discussions: Peter Maas, Mike Folger, Mike Chalis, and JoeI Guttorrnsen. I would also like to thanks the sponsors of the Foothills Research Project for their financial support and interest in the project. This research was also funded in part by two consecutive Atlantic Accord Career Development Awards. My family and friends not only supported my efforts during this project but helped me keep my sanity. My sister Michelle and her family created a wondemil balance in my life that 1greatly appreciate. I would also like to th& my parents Scott and Gloria LeDrew for king proud of me and telling me so. There are many fiends that I should acknowledge but I'rn sure 1 wouId forget some crucial person if I try so please accept my thanks, you know who you are. Dave and Eric 1have to mention because they have been my partners in crime and 1couldn't have done it without hem, or should I Say without knowing they were suffering the same fate as me. To Andy 1owe many thanks not ody for puning up with me but for his advice, patience and encouragement. Thanks also to Mrs. Evans for her sound advice: "Shut up and do it". .. Approvai Page ...................... ..... ................................................................................ ...11 Abstract ......................................................................................................................... iii Acknowledgements.................... .... ............................................................................... iv of vi Table Contents.......................................................................................................... .. List of Tables................................................................................................................ vri... List of Figures............... .. ........................................................................................ viii CHAPTER ONE: INTRODUCTION AND PREVIOUS W0R.K 11 Introduction ....................................................... .............................. -1 1.2 Literature Review ................................................................................4 1.2.1 Structural geologv of the triangle zone .................... ,..,.. ....... -4 1 .2.2 Evolution of the triangle zone ............................. ....... ............... -6 1.2.3 ai on^-stdce variation in the triande zone ................................11 1.2.4 Regionai stratigra~hy. .............................................................. -12 1.2.5 Previous work in study area ............................ .........................-17 Data and software .................................,,,, ...................................... 21 1.3.1 Surface geolom ......................................................................... 24 1.3.2. Well data .......................... .,, .. .-. .......................................... 25 1.3.3. Seismic data ............................................................................ 26 CHAPTER TWO: SEISMIC IMAGING 2.1 Introduction ..........................................................................~............ -27 2.2 Seismic data acquisition .................................................................... 28 2.3 Seismic data processing .................. ... ........................................... 31 2.4 Aniso tropy and lateral velocity variation ................... .. .............. -33 2.5 Affects of 3D structure on 2D data .................................................... -34 CHAPTER THREE: INTEGRA'IXD STRUCTURAL IN'IERPRETATIONS 3.1 Introduction ........................................... ........................................ 36 3.2 Weii geology tie to seismic data ........................................................ 36 3.3 Lovett River Triangle Zone ................................................................. 41 3.3.1 Surface geolom in Lovett River area ......................... .....,.... .......41 3.3.2 Subsurface intemretation in the Lovett River area ..................... 46 3.3.2.1 Seismic section descriptions in the Lovett River area ..... 47 3.3.2.2 Detachments ................................................................... 61 3.3.2.3 Pedley Backthrust (Wapiabi Detachment) Brazeau to Paskapoo strata ............................................. 61 3.3.2.4 Alberta Group duplexes ................................................. -63 3.3.2.5 Blackstone Detachment .................................................. 67 3.3.2.6 Mississippian through Luscar Group rocks ..................... 67 3.3.2.7 Lower Bounding Thnrst and Autochthonous strata ......... 68 Pembina River Relict Triangle Zone .................................................... 69 3.4.1 Surface geology in the Pembina River area ..................... ,., ...... 70 3.4.2 Subsurface intemretation in the Pembina River area ....................72 35 Brazeau River Triangle Zone ...................... .... ................................. 73 3S.1 Surface geo10~in the Brazeau River area .................................. 75 3.5.2 Subsurface intemretation. in the Brazeau River area .................... 79 3 S.2.1 New upper bounding backthrurt ....................................79 3.5.2.2 Brazeau tu Paskpoo rocks ............................................ 80 3.5.2.3 Previous upper bounding backthrust .............................. 80 3.5 .2.4 Alberta Group structure ............................................. 8 1 3.5 .2.5 Deeper Lower Mesozoic and Paleozoic structure ......... -82 3.5.2.6 Lower bounding th^ ................................... ............ 82 EL River Pre-triangle Zone ............................. ... .............................. 83 3.6.1 Surface geolow in the Elk River area ......................................... 83 3.6.2 Subsurface interpretation in the EIk River area ........................... 85 CHAPTER FOUR: PALINSPASTIC RESTORATION AND DEFORMATTONAL HISTORY 4.1 Introduction.......................................................................................... 88 4.1.1 Cross section descrbtions ........................................................... 89 4.2 PalinspasticRestomti~m............... .. .................................................