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EVOLUTION AND SUBSIDENCE MECHANISMS OF THE NORTHERN CORDILLERAN FORELAND BASIN DURING THE MIDDLE CRETACEOUS by Yongtai Yang A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Graduate Department of Geology In the University of Toronto © copyright by Yongtai Yang (2008) Library and Bibliotheque et 1*1 Archives Canada Archives Canada Published Heritage Direction du Branch Patrimoine de I'edition 395 Wellington Street 395, rue Wellington Ottawa ON K1A0N4 Ottawa ON K1A0N4 Canada Canada Your file Votre reference ISBN: 978-0-494-44730-7 Our file Notre reference ISBN: 978-0-494-44730-7 NOTICE: AVIS: The author has granted a non L'auteur a accorde une licence non exclusive exclusive license allowing Library permettant a la Bibliotheque et Archives and Archives Canada to reproduce, Canada de reproduire, publier, archiver, publish, archive, preserve, conserve, sauvegarder, conserver, transmettre au public communicate to the public by par telecommunication ou par Plntemet, prefer, telecommunication or on the Internet, distribuer et vendre des theses partout dans loan, distribute and sell theses le monde, a des fins commerciales ou autres, worldwide, for commercial or non sur support microforme, papier, electronique commercial purposes, in microform, et/ou autres formats. paper, electronic and/or any other formats. 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Canada EVOLUTION AND SUBSIDENCE MECHANISMS OF THE NORTHERN CORDILLERAN FORELAND BASIN DURING THE MIDDLE CRETACEOUS A Doctor of Philosophy thesis, 2008 by Yongtai Yang Department of Geology University of Toronto ABSTRACT Mainly based on detailed allostratigraphic and sedimentologic study of the Early Cenomanian Fish Scales Formation and the mid-late Cenomanian Belle Fourche Formation in southern Alberta, this study reconstructs the evolution and explores the subsidence mechanisms of the Cordilleran foreland basin during the mid-Cretaceous. The middle Cretaceous succession consists of tectonically-driven cycles containing strata deposited in an underfilled basin during the orogenic loading and early unloading periods, and strata deposited in an overfilled basin during the late orogenic unloading period. High-frequency tectonism (106-year time scale) and sediment distribution in the basin are the main causes of the tectonic cyclicity. The positions of the proximal foredeep, forebulge and backbulge depozones from the Late Albian to Early Coniacian time are defined in northern Cordilleran foreland basin. During the Late Albian-Middle Cenomanian, the forebulge extended northwest through the northwest corner of Wyoming and curved northeastward through the present-day location of Calgary. At the end of the mid-Cenomanian, the forebulge retreated westward within Alberta, reflecting the change of convergence vectors along the western margin of North America during the mid- n Cretaceous. The mid-late Cenomanian forebulge zones controlled the deposition of the upper and lower Belle Fourche sandstones in southern Alberta, southwestern Saskatchewan and northern Montana. This study suggests that the forebulge setting needs to be emphasized as an important regional control in any basin-scale model for offshore sandstones in the Cordilleran foreland basin. During the late orogenic unloading period, a peripheral sag was formed in front of the uplifted orogenic belt and with a depocenter located in the forebulge zone of the preceding orogenic loading period and early unloading period. The Fish Scales and Second White Specks formations, formed during marine transgressions in the latest Albian-earliest Cenomanian and the Early Turonian, are interpreted to have been deposited in wide shallow interior seaways during late orogenic unloading periods. This study calls into question the general significance of units such as the Mowry Shale and the Greenhorn Formation as indicators of eustatic high-stands of sea level, and suggests regional tectonism as an alternative or additional control on basin evolution. iii ACKNOWLEDGMENTS I am grateful to my supervisor Professor Andrew Miall, for providing me a great opportunity to study at the U. of T., professional guidance and advice, and financial support. His course "Seminars in Basin Analysis" shown me how to do basin analysis professionally, and is and will be an asset for my professional career. I am also grateful to my Ph.D. committee members, Sandy Cruden, Nick Eyles, Russell Pyaklywec, and Uli Wormian in the Geology Department for their effort to keep me on track. I thank the external appraiser Peter DeCelles and reviewers of our papers: Octavian Catuneanu, Brian Currie, Paul Heller, Terry Jordan, Brendan Murphy, James Schmitt, Glen S. Stockmal, Brian Turner, and Tim White, for their critical review and much help in improving this thesis. I thank Guy Plint, Bogdan Varban, Aditya Tyagi and other members in Basin Analysis Group, University of Western Ontario, for their many good suggestions and much help in well- log selection and core measurement. I would like to thank my wife Meng and my mother-in-law Xiuying for taking care of my daughter Victoria, so I could concentrate on this Ph.D. thesis. IV TABLE OF CONTENTS CHAPTER 1. INTRODUCTION 1 CHAPTER 2. EVOLUTION OF THE NORTHERN CORDILLERAN FORELAND BASIN DURING THE MIDDLE CRETACEOUS 8 ABSTRACT INTRODUCTION STRATIGRAPHY ALLOSTRATIGRAPHY COLORADO GROUP IN ALBERTA AND MONTANA Upper Albian Lower Cenomanian Middle-Upper Cenomanian RECONSTRUCTION OF THE MID-CRETACEOUS FORELAND BASIN Late Albian Early Cenomanian Middle Cenomanian Late Cenomanian DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES CHAPTER 3. MIGRATION AND STRATIGRAPHIC FILL OF A FORELAND BASIN SYSTEM: MID-LATE CENOMANIAN BELLE FOURCHE FORMATION IN THE NORTHERN CORDILLERAN FORELAND BASIN 59 v ABSTRACT INTRODUCTION ALLOSTRATIGRAPHY SEDIMENTOLOGY A QUALITATIVE MODEL DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES CHAPTER 4. MARINE TRANSGRESSIONS IN THE MID-CRETACEOUS OF THE CORDILLERAN FORELAND BASIN RE-INTERPRETED AS OROGENIC UNLOADING DEPOSITS 93 ABSTRACT INTRODUCTION ALLOSTRATIGRAPHY Typical fades successions Regional distribution of allomembers BASIN ANALYSIS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES CHAPTER 5. TECTONIC CYCLES OF FORELAND BASINS 133 ABSTRACT vi INTRODUCTION STRATIGRAPHIC CYCLE DRIVEN BY OROGENIC LOAD AND SEDIMENT LOAD TECTONIC CYCLES IN THE NORTHERN CORDILLERAN FORELAND BASIN CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES vn LIST OF FIGURES Figure 1.1. The two-phase stratigraphic model for foreland basins, (A) orogenic loading period; (B) orogenic unloading period. Figure 2.1. Location of study area. (A) Thickness of the Late Albian to Santonian Colorado Group in the northern Cordilleran foreland basin. (B) Location of 1480 well logs in southern Alberta and 35 well logs in northwestern Montana. Figure 2.2. Stratigraphic nomenclature and microfaunal zones of the Late Albian to Turonian strata in the northern Cordilleran foreland basin. Figure 2.3. The distribution of the time equivalent Belle Fourche Formation in southern Alberta and western Montana. Figure 2.4. Allostratigraphy of the Belle Fourche Formation in Well 6-4-17-13 W4. Figure 2.5. A west-east cross section of the Belle Fourche Formation in southern Alberta. Figure 2.6. A south-north cross section of the Belle Fourche Formation in southern Alberta. Figure 2.7. Isopach maps of five allomembers of the Belle Fourche Formation in southern Alberta. Figure 2.8. Cross Section of the Cenomanian strata in the northern Cordilleran foreland basin. Figure 2.9. (A) The Late Albian foreland basin system in southern Canada. (B) The latest Albian foreland basin system in southern Canada. (C) The Late Albian foreland basin system in northern US. Figure 2.10. The reconstructed Middle Cenomanian foreland basin system in western North America. Figure 2.11. The reconstructed Late Cenomanian foreland basin system in western North America. viii Figure 3.1. (A) Restored Middle and Late Cenomanian foreland basin systems in western North America (Chapter 2), mainly showing the forebulge zones. (B) Isopach map of the Late Cenomanian Upper Belle Fourche Formation in southern Alberta (Chapter 2), showing location of 1480 well logs in southern Alberta and 35 well logs in northwestern Montana. Figure 3.2. Stratigraphic nomenclature of the Early Cenomanian -Early Coniacian strata in the northern Cordilleran foreland basin. Figure 3.3. Allostratigraphy of the Belle Fourche Formation in Well 9-13-15-12W4. Figure 3.4 A cross section of the Belle Fourche Formation in southern Alberta. Figure 3.5 A cross section of the Belle Fourche Formation in southern Alberta. Figure 3.6 A cross section of the Belle Fourche Formation in southern Alberta.

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