University of Alberta Geomorphology and sedimentology of hununocky terrain, south-central Alberta, Canada Mandy J. Munro-Stasiuk o h thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Earth and Atrnospherïc Sciences Edmonton, Alberta Fa11 1999 National Library Bibliothèque nationale 1*u of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395, ~a Wellington OttawaON KlAON4 OaawaON KlAW Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive Licence ailowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microfonn, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or othenvise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. ABSTRACT The landscape in south-central Alberta, Canada, is dominated by a suite of landfonns that formed beneath the Laurentide Ice Sheet. This thesis explores the origins of those landforms, specifically humrnocky terrain. Sedirnents in the hummocks, hurnmock fom, and associations with other landforms are exarnined to determine hummock genesis. Sediment was exarnined fiom over one hundred exposures through the "Buffalo Lake Moraine" at Travers Reservoir, McGregor Reservoir, and the Little Bow River. This belt of hurnmocky terrain (like most hummocky tenain regions) is traditionally interpreted as fonning at, or near, the stagnating margins of the Laurentide Ice Sbeet by supraglacial letdown. However, hummocks in south-central Alberta contain a complex variety of sediments and materials atypical of supraglacial letdown: in situ bedrock, thrust bedrock, lodgement till, rnelt-out dl, sorted sand and gravel, rippled sand, rhythrnically-bedded sand, silt, and c lay, and pervasivel y sheared beds. Al1 sediment types and deformation structures were deposited, or formed, subglacially. Also, the deposits make up in situ stratigraphies that record the history of initial Laurentide Ice Sheet advance into the area (lodgment till and thrust bedrock), the extensive accumulation of water at the bed (giaciolacustrine beds), and ice stagnation (melt-out tiI1). Regardless of the genesis of sediments in hummocks, sedimentary nits and structures are abruptly tnincated by the surface that represents the hummock and trough morphology, demonstrating that the humrnocks are erosional forms and that they represent a landscape unconformity. Subglacial sediments predating the erosion and subglacial eskers overlying the erosion surface strongly suggest that hummock erosion was subglacial. Also, hummock morphology, Iithostratigraphy correlated fiom hummock to hummock, abrupt truncation at the land surface, and widespread boulder lags support meltwater erosion for hummocky terrain in the region. Well-developed longitudinal and transverse trends in hummocks suggest that these Iandforms are giant erosional bedfoms. Palaeoflows detennined fiom surface trends are approximately from the northwest to the southeast. These are transverse to the flow directions preserved in the youngest unit in the hurnmocks, a basal melt-out till, further supporting an erosional origin for the hummocks. Hummocks are transitional fkom fluted terrain and surface trends are the same for both landform types. Flyted terrain is also erosional as remnant ndges are composed of in situ bedrock and fluvial gravels deposited by rivers flowing fiom the Rocky Mountains before Laurentide Ice Sheet invasion of southem Alberta. Consistent trends in hurnmociq terrain and fluted terrain suggest that the meltwater flow responsible for eroding flutes and hummocks was about 120 km wide. ACKNOWLEDCEMENTS First, and forcmosf 1 would like to thank my supcrvisor. colleaguc. and good fncnd, John Shaw. Such an exciting thcsis topic would not have been possible without the enthusiasm that he providcd, I'd likc to thank you, John, for al1 your heIp, the great discussions, but rnost of all, for kingjust down thc hallway. or at the end of a phone when 1 was in ndof acadcmic or emotional help. Thanks for the Iife experiencc. as wefl as the knowledge. Equally, I'd like to thank Bruce Rains, also a colleague and fnend. Bruce is "the best". I'd like to offer thanks to the members of my supavisory commitlce: John Shaw, Bruce RaUis, and Ed Lozowski, for theû help during ail the stages of reseatchïng, writhg, and groducing this thesis. I'd also like to express my gratitude to Faye Hicks, David Cruden, and Michacl Roberts (Simon Fraser University) for their comments, questions, and kind words about this thesis. As always, research is rarcly possible without frnaacial iielp- 1 am indebted to Natural Sciences and Engineering Rescarch Council (NSERC) for field and scholarly support (awarded to John Shaw). The Geological Society of Amenca provided ficld support in 1996 and 1997. 1 am also thanai to the Department cf Earth and Atmosphaic Sciences, and the University of Alberta for financia! suppon through teaching assistantships, the Andrm Stewart Rizc, and the disscxtation scholarship. Many people have aided me with the rcscarch îhat dtimatcly manifested itsclf in this document. The assistants that helped me in the field wcre invaluable, These people collccted the nal data such as measurhg many, many mck orientations while 1 ohsat and contempld the dirt. For this help 1 am grateful to Fiona Hcndcrson, Kyla EwasiuL, Lisa Sankaalli, Dama Sjogrrn, Elizabeth Sjogrea, Claire Beaney, Kim JardineTShulemit Gordon, and Dave Stasiuk. I'm also gratefUl to Little Bow Provincial Park for the field accommodations in 1995, 1996, and 1997. Vulcan County Council also kindly allowed me to dig ho1e-s in their spaccship laclding pads. Many student coiicagucs in the Earth and Atmospheric Sciences Department became close fiiends in the past five years. These wcrc the people that became part of my cultural bemg as weU as my academic one. I'd like to thank every one of you for your fiiendships: Robbo Young, Jerome Lesemann, Darren Sjogren, Elizabeth Sjogren, Shularnit Gordon, Claire Beaney, Kim Jardine, and Scott L.amoureux. Unfortunately, my tnends who wefe not in this group also had to listen to my rambles about humps and bumps on the Prairies. Th& for the support, and 1 love every ont of you: Bonnie Gallinger. Lce Wcissling, Jackie Chalifow and Louise Chalifoux, Wendy Proudfoot and Alma Vernon. Finally, C'd like to offer my sincerest gratitude to my sou1 mate, my husband Dave. Without sounding too clichéd, thanks for the support always, but especially thanks for the understanding and the caring durir~gthe las few months when times wcre tough. TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES CHAPTER 1: INTRODUCTION INTRODUCTION AND PROBLEM TO BE ADDRESSED IMPORTANCE OF STUDY PRMCWLES THESIS OUTLINE REFERENCES CHAPTER 2: HUMMOCKY TERRAIN GENESIS: A CRITICAL REVIEW INTRODUCI'ION HUMMOCKY TERRAIN CLASSiFICATION TWEORIES OF lWMMOCKY TERRAIN FORMATION Ice-marginal sedimentation Letdown and melt-out during stagnation Ice-pressing Thrusting at, or near the ice margin SubgIacial moulding Subglacial meltwater erosion andlor deposition Subsurface diapirism Periglacial theories DISCUSSION AND CONCLUSIONS REFERENCES CaAPTER 3: MGREGOR AND TEE-PEE PREGLACIAL VALLEY FILLS, SOUTH- CENTRAL ALBERTA: A RECONSTRUCTION OF LATE WSCONSINAN GLACIAL EVENTS INTRODUCTION FACIES DESCEUMIONS AND LNTERPRETATIONS Facies A - moderately sorted pebblekobble gravels with Shield clasts absent Description Interpretation Facies B - disturbed moderately sorted pebblekobble gravels with Shield clasts absent Description fnterpretation Facies C - blue/grey clayey diamicton Description Interpreta f ion Facies D - disturbed bludgrey clayey diamicton Description Interpretation Facies E - disturbed blue/grey clayey diamicton with sofi sediment clasts Descript ion Interpretation Facies F - massive silty diarnicton Description Interpretation Facies G - massive silty diamicton with bluelgrey diamicton clasts Description Interpretation Facies H - massive silty diamicton with some sorted beds Description Interpretation Facies 1 - massive silty diamicton with mal1 (< 1 cm) soîl sediment clasts Description Interpre ration Facies J - diamictonlsilt couplets with large (2 - 6 cm) rip-up clasts Description Intepretat ion Facies K - silt/clay couplets Description Inreprerarion Facies L - laminated silt Description Interpretation Facies M - rippled silt and sand Descnp f ion Interpretation Facies N - sorted pebblelcobble beds with Shield clasts Description Inlerpre ration Facies O - silty diamicton with laterally continuous sorted beds Description ïnterpretation Facies P - massive silt Description ïnr erpretat ion EXPOSURES IN THE PREGLACIAL VALLEYS Tee Pee preglacial valley at Carmangay Tee Pee preglacial valley at Travers Reservoir McGregor preglacial valley at McGregor Reservoir RECONSTRUCTION OF GLACIAL EVENTS SUMMARY AND CONCLUSIONS REFERENCES CHAPTER 4: RHYTHMIC TILL SEDIMENTATION: EVIDENCE FOR REPEA'IED