W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 2007 Shelf sediment dispersal mechanisms and deposition on the Waiapu River shelf, New Zealand Tara A. Kniskern College of William and Mary - Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Geology Commons, and the Oceanography Commons Recommended Citation Kniskern, Tara A., "Shelf sediment dispersal mechanisms and deposition on the Waiapu River shelf, New Zealand" (2007). Dissertations, Theses, and Masters Projects. Paper 1539616720. https://dx.doi.org/doi:10.25773/v5-05pd-dq04 This Dissertation is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. SHELF SEDIMENT DISPERSAL MECHANISMS AND DEPOSITION ON THE WAIAPU RIVER SHELF, NEW ZEALAND. A Dissertation Presented to The Faculty of the School of Marine Science The College of William and Mary in Virginia In Partial Fulfullment Of the Requirements for the Degree of Doctor of Philosophy by Tara A. Kniskem 2007 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPROVAL SHEET This dissertation is submitted in partial fulfillment of The requirements for the degree of Doctor of Philosophy Tara A. Kniskem Approved May, 2007 Courtney K. Harris, Ph.D Committee Chairman/ Advisor ittee Chairman/ Advisor L i cv\i_£-_ Lionel Carter, Ph.D Victoria University of Wellington Wellington, New Zealand 'v jL Jesse MeNinch, Ph.D A a Linda C.:. Scfiaffner, (Pn.D Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DEDICATION To my husband, Mark Kram. Reproduced with permission of the copyright owner. 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TABLE OF CONTENTS ACKNOWLEDGEMENTS............................................................................................... x LISTOF TABLES.............................................................................................................. xii LIST OF FIGURES.......................................................................................................... xiii ABSTRACT........................................................................................................................xvi INTRODUCTION................................................................................................................2 CHAPTER 1: Sediment accumulation and preservation potential on the Waiapu River shelf, East Cape, New Zealand .................................................................................................................9 ABSTRACT........................................................................................................................... 9 INTRODUCTION..............................................................................................................11 BACKGROUND.................................................................................................................14 OBJECTIVES..................................................................................................................... 16 METHODS...........................................................................................................................17 RESULTS.............................................................................................................................19 A. Sedimentary structure and texture ........................................................19 B. Radiochemical data ................................................................................21 C. Stable Isotope data .................................................................................23 DISCUSSION......................................................................................................................24 A. Calculating 210Pb accumulation rates ................................................... 24 B. Sediment budget ..................................................................................... 30 C. Event preservation ..................................................................................32 D. Identifying low excess 210Pb activity layers .........................................36 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. E. Long- versus short-term accumulation ................................................. 39 CONCLUSIONS....................................................................................................42 REFERENCES.......................................................................................................44 TABLE.....................................................................................................................55 FIGURE CAPTIONS........................................................................................... 56 FIGURES.................................................................................................................60 CHAPTER 2: Flood dispersal and deposition on the Waiapu River shelf, New Zealand ..................... 76 ABSTRACT............................................................................................................ 76 INTRODUCTION.................................................................................................78 OBJECTIVES........................................................................................................ 84 BACKGROUND....................................................................................................84 A. The river and shelf environment ...........................................................84 B. The deployment period ...........................................................................87 METHODS............................................................................................................. 89 APPROACH........................................................................................................... 91 RESULTS................................................................................................................94 A. Simulation estimates compared to observations ................................. 94 1. Bed shear stresses ..................................................................... 94 2. Sediment concentrations ............................................................95 3. Currents ...................................................................................... 95 4. Summary .....................................................................................97 B. Sediment transport and deposition ....................................................... 98 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1. Shelf sediment budget ................................................................98 2. Sediment export ....................................................................... 100 3. Sediment depositional patterns ............................................... 101 C. Floods with large wave energy compared to floods with low wave energy...............................................................................................103 DISCUSSION....................................................................................................... 103 A. Sediment transport mechanisms ..........................................................104 1. Time-averaged flux patterns ....................................................104 2. Flux patterns during high discharge ........................................106 B. Flux convergence and divergence across the shelf. ...........................108 C. Temporal and spatial variability in sediment transport and depositional patterns .................................................................................. I l l D. Sensitivity to settling velocity............................................................. 112 E. Dispersal processes not represented by the model ............................ 113 1. Currents ..................................................................................... 113 2. River-initiated hyperpycnal sediment transport .....................116 CONCLUSIONS..................................................................................................118 REFERENCES..................................................................................................... 120 TABLES.................................................................................................................130 FIGURE CAPTIONS..........................................................................................140 FIGURES...............................................................................................................146 CHAPTER 3: Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Sediment transport pathway sensitivity and strata-formation on the Waiapu River Shelf, New Zealand ........................................................................................................................ 163 ABSTRACT...........................................................................................................163 INTRODUCTION...............................................................................................165