Belly River Formations, West-Central Alberta
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THE ICHNOLOGICAL - SEDIMENTOLOGICAL SIGNATURE OF WAVE- AND RIVER-DOMINATED DELTAS: DUNVEGAN AND BASAL BELLY RIVER FORMATIONS, WEST-CENTRAL ALBERTA Lorraine Coates B.*., McMaster University, 1995 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE In the Department Of Earth Sciences O Lorraine Coates 2001 SIMON FRASER UNIVERSITY May 2001 rights reserved. This work may not be reproduced in whoie or in part, by photocopy or other means, without permission of the author. National Library Bibliothèque nationale l*l ofCanada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395, rue Wellington Otîawa ON K1A ON4 OîîawaON KIA ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant a 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 microfom, vendre des copies de cette thèse sous paper or electronic formats. La forme de microfiche/nlm, 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 substantid extracts fiom it Ni Ia thèse ai 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 The Upper Cretaceous (middle Cenomanian) Dunvegan Formation consists of a series of interbedded marine to non-marine sandstones and shales deposited in an actively subsiding foreland basin setting. It crops out in north- western Alberta and extends into the subsurface of west-central Alberta. It overlies the Shaftesbury Formation and is capped by shales of the Kaskapau Formation. Previous workers subdivided the formation into seven allomembers (A-G), based on detailed analysis of the sedirnentologv and genetic stratigraphy. Allomembers D and E were chosen for this study because they correspond to well-developed wave-dominated and river-dominated deltaic successions, respectively. The Upper Cretaceous (early-mid Campanian) Belly River Formation gradationally overlies the Lea Park Formation. The transition is marked by marine mudstones of the Lea Park passing into deltaic and fluvial sandstones of the Belly River. Previous workers subdivided the formation into eight cycles (A- H), based on detailed analysis of the sedimentology and genetic stratigraphy. Cycles D-G were chosen for this study because they tend to correspond to a rnixed wave/ river deltaic succession. The study area comprises Townships 59 to 64, and Ranges 21W5 to 05W6 for the Dunvegan Formation and Townships 43 to 49 and Ranges 28W5 to 08W5 for the Belly River Formation. Seventy cores, 38 from the Dunvegan Formation and 32 from the Belly River Formation were analysed sedimentologically and ichnologically, in order to compare the ichnologicd characteristics of river- us. wave-dominated and mixed wave/river deltaic successions. The principal differences lie in the prodelta and distal delta front deposits. In the prodelta, the river-dominated succession is characterized by areas largely devoid of bioturbation. Current-generated structures and deformational structures dominate the sandstones, and syneresis cracks are abundant. The facies yield a very Iow abundance but moderately diverse "highly stressed" Cnrzinnn ichnofacies. Burrowing is sporadic, ichnogenera are diminutive in size, and stnictures of trophic generalists domulate. In contrast, the wave-dominated and &ed wave/river successions yield a diverse though low abundance "stressed" Cnrzinnn ichnofacies. Hummocky cross-stratification and storm- induced oscillation ripple laminated tempestites dorninate the sandstones, though deformational structures and syneresis cracks are located throughout. In the wave-dominated succession, bioturbation may cause a graded or rnottled appearance, dismpting the discrete bedded character. This is rarely the case in the rnixed wave/river succession, where bedding contacts are very sharp. Structures of trophic generalists and opportunists dominate these successions. There are two principal differences in the delta front. The first is the comparative abundance of convoluted silty sandstone facies in the river- dominated and mixed wave/river successions of the distal delta front. This facies is typically devoid of burrowing. In contrast, the wave-dominated succession consists of minimal amounts of convolute bedding and other deformational features. Stacked HCS and SC3 beds dominate. Secondly, in the delta front the river-dominated succession yields a very low abundance and very low diversity, "highly stressed" Cnlzinnn ichnofacies, where amalgamated HCÇ beds are intercalated with convoluted and massive sandstone beds. In contrast, the wave- dominated and mixed wave/river successions yield a moderately diverse and locally abundant, mixed Skolithos-Crzrzinnn ichnofacies, where convolute bedding is only locally common. Dwelling/suspension-feeding structures are generally rare in the delta front. Ichnogenera of the proximal Cnrzinnn suite dominate this setting instead. The differentiating factor between the delta front and middle to upper shoreface is the uncornmon occurrence of dwelling/suspension-feeding structures and the dominance of deposit-feeding structures in deltaic settings. In contrast, dwelling/suspension-feeding structures dominate the middle to upper shoreface environment. Organisms inhabiting a substrate are sensitive to environmental conditions and to changes in that environment, responding to both physical and chemical changes in that setting. Variations in salinity, fluctuating oxygenation, an abundance of organic matter, increased turbidity and sedimentation, and unstable/soupy/ shifting substrate affect the resulang ichnofossil morphologies and therefore affect the style of the deltaic successions. First and foremost, 1 would like to thank James MacEachem. In the two years at Simon Fraser, he has dways made hùnself available for questions or discussion. He is a great teacher with a lot to give and should be comrnended for his editing skills! Mostly, 1 would like to thank James for being so patient with me for the past 2 years while 1 worked full time and had a family while finishing my thesis. Then waiting till the end of the semester for the final copy because my family was on vacation! Thanks to the NSERC operating grant 184293, awarded to James MacEachem, which provided the rneans for me to undertake this work. My good friends Paul and Christine McNaughton have to be some of the best. They never thought twice about getting me from the airport, giving me lodge, making me dinners, and driving me to and from ÇFU on my numerous trips to Vancouver. 1would like to thank the most supportive person ever, my husband, Jason. He never complained when 1spent our holidays (Thanksgiving, Christmas, Easter, Sumer) writing and going to Vancouver but gave me the space and support that enabled me to finish. And thanks to my beautiful baby, Elise, for being so good while sitting on my lap, printing out the find copy! TABLE OF CONTENTS PAGE .- APPROVAL PAGE .-.Lf ABSTRACT U1 ACKNOWLEDGEMENTS vi TABLE OF CONTENTS vii LIST OF FIGURES X CHAPTER 1 INTRODUCTION, SCIENTIFIC PROBLEM, OBJECTIVES, STUDY MA,DATA BASE, METHODS, AND STRATIGICAPflY 1.1 INTRODUCTION 1.2 SCIENTIFIC PROBLEM 1.3 OBJECTIVES 1.4 STUDY AREA, DATA BASE, METHODS 1.5 REGIONAL STRATIGRAPHY CHAPTER 2 INTRODUCTION, PREVIOUS WORK, AND PALEOGEOGRAJ?HY/ BIOSTRATIGRAPHY 2.2 INTRODUCTION 2.2 PREVIOUS WORK 2.21 Dunvegan Formation 2.22 Belly River Formation 2.3 PALEOGEOGRAPHY CHAPTER 3 INTRODUCTION, FACIES DESCRIPTIONS 3.1 INTRODUCTION 3.2 FACIES DESCRIPTIONS 3.3 DUNVEGAN FORMATION 3.31 Shingle D3 3.32 Shingle D2 3.33 Shingle Dl 3.34 Shingle E3 3.35 Shingle E2 3.36 Shingle El vii 3.4 BELLY RIVER FORMATION 3.41 Cycle D 3.42 Cyde E 3.43 Cycle F 3.44 Cycle G 3.45 Cycle H CHAPTER 4 FACIES ASSOCIATIONS AND INTEICPRETATION OF DEPOSITIONAL ENVIRONMENTS 4.1 INTRODUCTION 4.2 DUNVEGAN FORMATION, ALLOMEMBER D 4.21 Facies Association and Typical Features 4.22 Introduction 4.23 Interpretation 4.3 DUNVEGAN FORMATION, ALLOMEMBER E 4.31 Facies Association and Typical Features 4.32 Introduction 4.33 Interpretation 4.4 BELLY RIVER FORMATION 4.41 Facies Association and Typical Features 4.42 Introduction 4.43 Interpretation CHAPTER 5 FACIEÇ CRITENA FOR EIFFERENTIATION OF DELTAIC END MEMBERS: RIVER- VS. WAVE-DOMINATED DELTAIC SUCCESSIONS 5.1 INTRODUCTION 0.2 PRODELTA 5.3 DELTA FRONT CHAMER 6 CHARACTERIçTICS OF RIVER-DOMINATED, WAVE-DOMINATED, AND MIXED WAVE/RIVER DELTAIC SUCCESSIONS: DIFFERENTIATION FROM SHOREFACE DEPOSITS 6.1 INTRODUCION 6.2 PRODELTA 6.21 Prodelta of the River-Dominated delta complexes 6.22 Prodelta of the Wave-Dominated delta complexes 6.23 Prodelta of the Mixed Wave/River Influenced delta complexes 6.24 Prodelta: Comparison of Environmental Controls 6.3 DELTA FRONT 6.31 Delta Front of the River-Dominated delta complexes 6.32 Delta Front of the Wave-Dominated delta complexes 6.33 Delta Front: Relative Transgression of the Wave-Dominated delta complexes 6.34 Delta Front of the Mixed Wave/River Influenced delta complexes 6.35 Delta Front: Comparison of Environmental Controls 6.4 DIFFERENTIATING DELTA FROM SHOREFACE SUCCESSIONS 6.41 Introduction 6.42 Prodelta us. Offshore