TIMING AND MECHANISMS CONTROLLING EVAPORITE DIAPIRISM ON ELLEF RINGNES ISLAND, CANADIAN ARCTIC ARCHIPELAGO by Jennifer Anne Macauley A thesis submitted in conformity with the requirements for the degree of Master of Applied Science Graduate Department of Geology University of Toronto © Copyright by Jennifer Anne Macauley 2009 Timing and mechanisms controlling evaporite diapirism on Ellef Ringnes Island, Canadian Arctic Archipelago M.A.Sc. thesis by Jennifer Anne Macauley Department of Geology, University of Toronto, 2009 Abstract This thesis investigates the timing and mechanisms involved in the formation of evaporite piercement structures on Ellef Ringnes Island, Canadian Arctic Archipelago. The study includes the interpretation of industry seismic reflection and borehole data to characterize the geometry of the domes, 1D backstripping of wells to investigate the role of tectonic influences on diapirism, and analogue modelling to better understand the mechanisms that drive diapirs with dense anhydrite caps. I propose that basement structures played a significant role in the formation of evaporite domes by triggering and directing salt movement. The domes developed during the Mesozoic by passive growth driven by the differential loading of salt on adjacent fault blocks, which led to their present day asymmetric geometries. Diapir growth rates in the Mesozoic were closely linked to the rate of sedimentation, which was greatly influenced by the amount of accommodation space provided by tectonic subsidence of the basin. ii Acknowledgements I first and foremost would like to thank my supervisor Alexander Cruden for the support and guidance he has provided over the last two years. I am very grateful for the many amazing opportunities this project has given me during my studies at the University of Toronto. I would like to thank Tom Brent, Keith Dewing and Chris Harrison from the Geological Survey of Canada (Calgary) for their helpful insight on the project. Tom Brent, in particular, spent several weeks with me gathering and processing data that was crucial for my project. I enjoyed the many lunches we spent during my visits to Calgary. I would like to thank Randell Stephenson for being a great host in Amsterdam. He was encouraging throughout this process and his support and expertise on the Sverdrup Basin is greatly appreciated. I would also like to thank him for the bike he lent me during my stay in Amsterdam. I acknowledge the members of my supervisory committee, Andrew Miall and Bernd Milkereit, who have been highly supportive throughout my project. I thank Christoph Schrank for being an awesome friend and mentor when Sandy was unavailable. He would always provide help when asked, above and beyond my expectations. I enjoyed all the random nights we spent out in Toronto. Becky Ghent helped me with countless posters and math problems. I most appreciated her company, however, on many de-stressing tea breaks. I thank David Boutelier for reading over multiple drafts of my thesis and always listening whenever I needed to sort out my thoughts. Last but not least, I would like to thank all the friends and family that distracted me from my studies when I needed it most. iii This research was financed with an OGSST (Ontario Graduate Scholarship in Science and Technology) awarded to J. Macauley, and NSERC (Natural Sciences and Engineering Research Council Discovery) and Geological Survey of Canada Unconventional Oil and Gas Research and Development grants awarded to A. Cruden. Access to seismic and borehole data was provided by ConocoPhillips, Imperial Oil Resources and PetroCanada. iv Table of Contents Abstract ii Acknowledgments iii Chapter 1: Introduction 1 1.1 Background on the development of the Sverdrup Basin 1 1.2 Salt tectonics 3 1.2.1 Salt properties 3 1.2.2 Mechanics of salt flow 4 1.2.2.1 Differential loading 7 1.2.2.2 Initiation and growth of diapirs by regional tectonics 8 1.2.3 Allochthonous evaporite structures in the Sverdrup Basin 10 1.2.4 Timing and mechanisms of halokinesis in the Sverdrup Basin 11 1.3 Study Area: Ellef Ringnes Island 14 1.3.1 Stratigraphy 14 1.3.2 Mafic intrusions 16 1.3.3 Structural geology 17 1.3.4 Evaporite piercement structures 17 1.4 Research Objectives 18 1.4.1 Chapter Two: Structural and geometrical characterization of evaporite piercement structures on Ellef Ringnes Island 19 1.4.2 Chapter Three: Basin subsidence modelling 19 1.4.3 Chapter Four: Analogue modelling of diapirism 19 Chapter 2: Structural and geometrical characterization of evaporite piercement structures on Ellef Ringnes Island 20 2.1 Introduction 20 2.2 Methods 21 2.2.1 Data 21 2.2.2 Seismic processing 22 2.2.3 Analysis of borehole data 23 v 2.2.4 Interpretation of formation tops 24 2.2.5 Isopach maps 25 2.3 Results 29 2.3.1 Dome asymmetry 29 2.3.2 Salt canopies at Hoodoo Dome 30 2.3.3 Deformation and unconformities within overburden adjacent to piercement structures 32 2.3.4 Regional variations in formation thicknesses from isopach maps 34 2.4 Discussion 36 2.4.1 Basement fault-initiated and controlled diapirism 36 2.4.2 The timing of diapirism in the Sverdrup Basin 41 2.5 Conclusion 43 Chapter 3: Basin subsidence modelling 45 3.1 Introduction 45 3.2 Methods 48 3.2.1 Backstripping 48 3.2.2 Data 49 3.2.3 Input parameters for backstripping 50 3.3 Results 52 3.3.1 Regional and local changes in tectonic subsidence rates 52 3.3.2 Contour plots of 1-D subsidence curves through time 56 3.3.3 Limitations due to data quality and resolution 56 3.4 Discussion 59 3.4.1 Relation between tectonic subsidence trends and diapir growth 59 3.4.2 Axel Heiberg subsidence 65 3.5 Conclusion 65 vi Chatper 4: Analogue modelling of diapirism 67 4.1 Introduction 67 4.1.1 The role of anhydrite in diapirism and other tectonic settings 67 4.1.2 Anhydrite piercement structures in the Sverdrup Basin 68 4.1.3 Previous analogue and numerical modeling of diapirism involving anhydrite 71 4.2 Methods 73 4.2.1 Model set-up 73 4.2.2 Materials and scaling 75 4.3 Results 79 4.3.1 Limitations due to boundary conditions 79 4.3.2 Problems localizing sheared diapir margins 83 4.4 Discussion 85 4.4.1 The influence of material properties on the development of sheared dome margins 85 4.4.2 Localization of salt flow and the effect of boundary conditions 87 4.4.3 The affect of buoyancy on diapirism within the Sverdrup Basin 89 4.4.4 Insight on the development of Hoodoo Dome canopies 91 4.5 Conclusion 93 Chapter 5: Summary and final remarks 95 5.1 Summary of mechanics and timing of salt growth on Ellef Ringnes Island 95 5.1.1 Initiation of Diapirism 95 5.1.2 Diapirism in the Triassic 96 5.1.3 Diapirism in the Jurassic 97 5.1.4 Diapirism in the Cretaceous and Early Tertiary 98 5.2 Implications for oil and gas exploration 99 5.2.1 Petroleum generation in the Sverdrup Basin 99 5.2.2 Potential for future oil and gas exploration 101 5.3 Future Research 104 vii References 105 Appendices 114 viii List of Tables Chapter 2: Structural and geometrical characterization of evaporite piercement structures on Ellef Ringnes Island Table 2-1. Parameters and functions used for time-depth conversion 28 Chapter 3: Basin subsidence modelling Table 3-1. Parameters used for exponential depth laws in backstripping 49 Chapter 4: Analogue modeling of diapirism Table 4-1. Scaled parameters and ratios for model and nature 76 Table 4-2. Summary of physical experiments 80 List of Plates Plate 1. Regional seismic profiles Plate 2. G(F) series seismic profiles Plate 3. I(F) series seismic profiles (I) Plate 4. I(F) series seismic profiles (II) ix List of Figures Chapter 1: Introduction Fig. 1-1. Regional extent of the Otto Fiord evaporite facies 2 Fig. 1-2. Physical properties of rock salt in comparison to other lithologies 3 Fig. 1-3. 3D schematic diagram of various shapes and sizes of salt structures 5 Fig. 1-4. Diagram illustrating conditions required for active piercement 6 Fig. 1-5. Diagram illustrating conditions of hydraulic head-gradient analysis for salt tectonics 7 Fig. 1-6. Three stages of diapirism and their characteristic structures 9 Fig. 1-7. Cross-sectional profiles of passive diapirism at various aggradation rates 10 Fig. 1-8. Map and cross-section of the wall-and-basin structures on Axel Heiberg 13 Fig. 1-9. Map of Ellef Ringnes Island 15 Fig. 1-10 Stratigraphy of Ellef Ringnes Island 16 Chapter 2: Structural and geometrical characterization of evaporite piercement structures on Ellef Ringnes Island Fig. 2-1. Index map of seismic reflection and borehole data for Ellef Ringnes Island 22 Fig. 2-2. Synthetic well log for Hoodoo Dome H-37 24 Fig. 2-3. Instantaneous velocity with depth signature of the Deer Bay Formation 26 Fig. 2-4. Line drawing of a cross-section through Dumbells Dome 30 Fig. 2-5. Spatial extent of interpreted canopies and a shear zone at Hoodoo Dome 31 Fig. 2-6. Cretaceous unconformities within sediments adjacent to domes 33 Fig. 2-7. Isopach maps of Mesozoic formations 35 Fig. 2-8. Examples of basement initiated diapirism 37 Fig. 2-9. Schematic of a drape monocline 37 Fig. 2-10. Schematic of the development of asymmetric domes 39 Fig. 2-11. Sedimentary thicknesses and crustal signatures derived from Bouguer gravity data 40 Fig. 2-12. Schematic drag profile adjacent to a passive diapir 42 x Chapter 3: Basin subsidence modelling Fig.