University of Windsor Scholarship at UWindsor Electronic Theses and Dissertations Theses, Dissertations, and Major Papers 2006 Petrologic and geochemical attributes of dolomite recrystallization: An example from the Mississippian Pekisko Formation, west-central Alberta. JoAnn Adam University of Windsor Follow this and additional works at: https://scholar.uwindsor.ca/etd Recommended Citation Adam, JoAnn, "Petrologic and geochemical attributes of dolomite recrystallization: An example from the Mississippian Pekisko Formation, west-central Alberta." (2006). Electronic Theses and Dissertations. 3075. https://scholar.uwindsor.ca/etd/3075 This online database contains the full-text of PhD dissertations and Masters’ theses of University of Windsor students from 1954 forward. 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Petrologic and geochemical attributes of dolomite recrystallization: an example from the Mississippian Pekisko Formation, west-central Alberta by JoAnn Adam A Thesis Submitted to the Faculty of Graduate Studies and Research through the Department of Earth Sciences in Partial Fulfillment of the Requirements for the Degree of Master of Science at the University of Windsor. Windsor, Ontario, Canada 2005 © 2005 JoAnn Adam Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 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The author retains copyright L'auteur conserve la propriete du droit d'auteur ownership and moral rights in et des droits moraux qui protege cette these. this thesis. Neither the thesis Ni la these ni des extraits substantiels de nor substantial extracts from it celle-ci ne doivent etre imprimes ou autrement may be printed or otherwise reproduits sans son autorisation. reproduced without the author's permission. In compliance with the Canadian Conformement a la loi canadienne Privacy Act some supporting sur la protection de la vie privee, forms may have been removed quelques formulaires secondaires from this thesis. ont ete enleves de cette these. While these forms may be included Bien que ces formulaires in the document page count, aient inclus dans la pagination, their removal does not represent il n'y aura aucun contenu manquant. any loss of content from the thesis. i * i Canada Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Carbonates of the Pekisko Formation are important reservoir rocks in west-central Alberta, especially in fields along the Pekisko subcrop edge. They represent a transgressive- regressive carbonate ramp sequence comprised of upward shallowing facies, which subsequently underwent extreme erosion leading to the development of karst topography. Lithofacies include grainstones, wackestones/packstones, mudstones, intraclast breccia mudstones and dolostones. Several generations of calcite cementation and dolomitization are the result of very complex diagenetic changes. Calcite cements include: isopachous, drusy mosaic, pendant/meniscus, blocky, syntaxial, fibrous and equant/prismatic. Five dolomite types have been identified: pervasive, dissolution seam-associated, planar void-filling, selective and saddle. Consequently, diagenetic alteration mainly by dolomitization has affected most of the carbonate facies. Pervasive dolomite is the most important and abundant type of dolomite in the Pekisko carbonates. It replaced early calcite phases prior to early chemical compaction and forms the dolostone units. These units contain the best reservoir porosities in the formation. Geochemical analyses suggest a formation from mixed meteoric-marine fluids. Dissolution seam-associated dolomite is a relatively minor phase occurring exclusively in grainstones during early chemical compaction in association with dissolution seams. Void-filling dolomite occurs as relatively clear euhedral cement occluding vugs and molds within dolostone intervals in minor amounts. During intermediate burial, selective dolomitization of several grains, matrix and cement occurred in grainstones and dolostones. The covariant depletion trend revealed by stable isotope values marks a departure from the postulated Mississippian dolomite and represents precipitation from a mixed fluid and/or recrystallization. Saddle dolomite was the last phase to precipitate during deeper burial. Petrographically, it is associated with late chemical compaction and secondary anhydrite and it is isotopically much more depleted than other dolomite phases which implies precipitation from more saline fluids at elevated temperatures. Recrystallization and neomorphism has affected all phases in the Pekisko carbonates. Evidence for recrystallization in pervasive dolomite includes: increasing crystal size, anhedrai crystals, zonations with etched interfaces, dedolomitization, depletion in both stable isotopes and radiogenic strontium isotope ratios. iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I’d like to dedicate this thesis to Scott who encouraged and pushed me more than anyone throughout the process. iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS I would first like to thank my supervisor Dr. I. S. Al-Aasm for his guidance throughout the course of my studies. Dr. Jeff Packard is thanked for the time involved in collecting well data and for giving me a refresher on how to proceed with my core sampling and analysis. I thank Melissa Price for all of her help with the stable isotopes and several other miscellaneous things. My gratitude goes out to Daniel Rivas for answering my millions of questions during my first year. I really appreciated the good conversations, companionship and encouragement from Samantha Raymus. I would also like to thank Denis Tetreault for all of his advice and good conversations. Sharon Horne is also thanked for answering my many questions. I’d also like to thank my mom, my dad and my sister for encouraging and listening to me when times were a little tough. Lastly, I thank Scott Bland for making me laugh when I had a bad day, encouraging me when I just wanted to stop, pushing me to do my best and just for being there for me. v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS ABSTRACT............................................................................................................................................ iii DEDICATION......................................................................................................................................... iv ACKNOWLEDGEMENTS......................................................................................................................v LIST OF FIGURES.................................................................................................................................ix LIST OF PLATES....................................................................................................................................x CHAPTER I: INTRODUCTION..............................................................................................................1 1.1 Purpose of Study .......................................................................................................................... 1 1.2 Previous Studies .......................................................................................................................... 3 1.3 Methods of Study ......................................................................................................................... 5 CHAPTER II: REGIONAL FRAMEWORK............................................................................................8 2.1 Regional Geology ........................................................................................................................