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EVOLUTION OF PROGRADED COASTAL BARRIERS IN NORTHERN N EW Z EALAND

by

Amy Jennelle Dougherty

A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in Geography,

The University of Auckland, 2011.

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ABSTRACT

Anticipating the likely physical response of coastal barriers to future climate change requires knowledge of their past evolution. Many studies have considered beach and barrier coasts and great advances have been made in understanding short-term beach morphodynamics and longer-term barrier evolution. However, linkage between these scales is limited, primarily due to lack of stratigraphic detail in models of barrier evolution. Previous barrier studies have provided excellent morphochronologic control, but the shallow subsurface stratigraphy is typically highly generalized due to a reliance on point-source data collected form widely spaced cores. Recent developments in geophysical methods make it possible to augment coring and dating techniques using ground- penetrating radar (GPR), which enables rapid acquisition of high-resolution subsurface stratigraphic data. This presents an opportunity to use existing knowledge of beach morphodynamics in the interpretation of paleo-beachfaces imaged in geophysical surveys, potentially allowing new insight into many aspects of barrier evolution.

This thesis describes morphostratigraphic studies of seven strand plains around northern New Zealand in which GPR is a principal tool. The evolution of Holocene beach ridge barriers, dune ridge barriers, transgressive dunefield barriers, a chenier plain and a Pleistocene beach ridge barrier are discussed in detail. Three-dimensional morphostratigraphic models are provided for each of these strand plains by incorporating facies architecture over hundreds of metres with decimeter resolution.

Ultimately, millennial-scale evolution of individual barriers is deciphered in a range of geologic settings encompassing both the straight, high-energy, sediment-rich west coast, and the embayed, lower-energy, sediment-starved east coast. The detailed morphostratigraphic models facilitate a new consideration of the nature of, and interdependence between, five fundamental boundary controls of barrier evolution. 1) Accommodation space dictates not only barrier location, but also barrier type, either spit or embayed, and was the limiting factor for barrier progradation on the west coast. 2) Sediment supply determines barrier size, drives the rate of progradation along the west coast, and is the limiting factor for barrier existence along the east coast. 3) Sea-level fall drives progradation along the east coast by sourcing offshore sediment and maintaining a constant accommodation space during progradation. In this thesis a novel approach is developed using GPR to map a sea-level proxy within the stratigraphy of prograding barriers. 4) Wave energy varies around the coast of the study area resulting in a range of modal beach states that are preserved in the paleo-beachface stratigraphy, similar to the corresponding present-day beach profiles. 5) Storm events are clearly preserved in paleo-beachfaces along intermediate east coast beaches, and represent an important control on the initiation of strand plain morphology, both cheniers and beach/dune/foredune ridges.

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ACKNOWLEDGMENTS

Thanks to the University of Auckland for the award of an International Doctoral Scholarship which allowed me to undertake this study. I would like to acknowledge my first supervisor Dr. Scott Nichol for his initial enthusiasm about this research. His encouragement to pursue this project as a PhD rather than a Fulbright topic was truly a catalyst. Thanks to Dr. Paul Kench for agreeing to be a primary supervisor when Scott Nichol left the University of Auckland in 2007. This gesture was greatly appreciated knowing that in addition to existing graduate students and teaching; he was also acting as Head of Department during the merger of School of Environment and embarking on a six month sabbatical. Finally in the list of tag-team advisors I would especially like to thank Dr. Mark Dickson. Mark’s willingness to step in at the last stage, after the thesis was written, and be the first to read it was greatly appreciated. More than just Mark’s help honing the written document, his incredible enthusiasm and encouragement was essential to the completion of this thesis. I would also like to acknowledge that this final thesis was professionally proofread by Martin Watson of Abacus Proofreaders.

Thanks to all who offered intellectual input with regard to my research at various coastal conferences and international meetings. A special thanks my Masters supervisor Dr. Duncan FitzGerald and unofficial co-supervisor Dr. Ilya Buynevich for their continued collaboration. Your willingness to sound out some of the ideas in this thesis was invaluable. This work is very much inspired by the lively lessons learned about GPR and coastal evolution sparked at Popham Beach, Maine. Thanks to Ms. Selfridge, Ms. Kerr, Ms. Price Ms. Carol, Ms. Bridges, Ms. Jackson, Ms.

Dugan, and all of the teachers I had at Glassboro Intermediate and High School. A special thanks to my 8^th grade science teacher Ms. Porter and my high school physics teacher Mr. Reiner Schmidt, for inspiring my interest science. I would also like to acknowledge my professors at Union College, with special thanks to John Garver, Kurt Hollocher, Don Rodbell, George Shaw, Bill Neubeck of Geology and Charles Scaife of Chemistry.

Many thanks to Dr. Navin Juyal, Dr. Vikrant Jain and Dr. Gary Briely for the opportunity to acquire luminescence dates for East Beach. Thanks to Murray Ford for assistance with GIS and one day of fieldwork at Miranda. Thanks to Hiroki Ogawa for 2 days assistance in the field at Miranda and many coastal conversations. Thanks to Marty Roest for introducing me to South Head as well as helping for a day of fieldwork there. Special thanks to my brothers Malcolm and Brendan Dougherty for taking a day out of their holiday to New Zealand in order to help me finish my fieldwork.

Thank you Dave Jenkinson, Peter Crossley, Brendan Hall, Dave Wacker for not just your technical advice, but always making me smile. Igor Drecki, Graeme Glen, Anna-Marie Simcock, Willie Smith, Colin Young and Charlie Tu’U thank you for your various assistance and lovely interactions. Thanks to Lyndsay Blue, Gretel Boswijk, Ward Friesen, Jao Gao, David Hayward, Nick

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Lewis, Marie McEntee, Susan Owen, Melanie Wall, and Paul Williams for making the department a better place. Another special thanks to everyone at The Institute of Earth Science and Engineering (IESE). The opportunity to work in such collaborative and inspiring environment has not only bettered my science, but broadened it.

Michelle Caldaia, Erika Whittome, Eugene Rees, Jo O’Callaghan, Drew Lorrey, Wes Clapp, the Coatesville Crew, Pippa Mitchell, Murray Ford, Keith Adadms, Joe Fagan, Hiroki Ogawa, Eric Lafary, Steve Imre, Darren Gravley, Dan Hikoroa, Angela Slade, (in order of appearance) and a huge cast of characters I have not named (I hope you know who you are)…Thank you so much for your friendship! A special thanks to Martin Roest for everything! Also to Paul, Ria, and Frans Roest your treatment of me like family is greatly appreciated, especially at a time when I was so far away from my own.

A very special thanks to my dear friends and family in the United States. I could not have done this without your love and support during this endeavor. I appreciate your patients in my being so far away and for twice as long as initially expected. I am sorry for all that I have missed in my absence. Thanks to Beth Fleming-Gorman, Alison Holland-Aria, Tonya Capparello-Basch, Brian Scholl, Elizabeth Pendleton-Bailey, Shelley J. Johnston-Whitmeyer and all of your family’s for being such amazing friends through sporadic times. I would like to thank Mike and Elizabeth Krol for their guidance and friendship in Boston. Special thanks to my Boston family Pam, Jacqueline, Ali, Freddie, Mrs. and Mr. Holland for their incredible hospitality. Lori, Bret, Max and Tess Immel- Eckhardt thanks for all the pictures, smiles and skype chats. Jess, Dave, Nolan, Charlie and Penny Seagreaves-Floyd (and your amazing Woodbury crew) thanks for reunions that felt like I never left and my spot on your porch. Thanks to Nathaniel, Tyler, Caitlyn, Cindi and Eric Clark for being such a special part of my life. My beloved family: Danny, Irene, Case, Ryan, Brittani, Josh, Chloe, Malcolm, Linda, Connor, Karissa, Seth, Nancy, Amber, Nicole, Dane, Seanan, Seliena and Brendan…there are no words to thank you for all you mean to me. Mom and Dad, there is so much to thank you for that I would not even know how start and it would be another thesis. Therefore, I dedicate this dissertation to you both for instilling a curiosity of the earth, inspiring me to travel it, and encouraging my many years of studying it!

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LIST OF TABLES

Table 5.1: Quartz OSL Ages, East Beach, New Zealand. ... 151

Table 7.1: Summerises some of hypotheses and data for the initiation of sand ‘‘beach ridges’’. ... 234

TABLE OF FIGURES

Figure 1.1: Global distribution of barriers ... 2

Figure 1.2: Generalized cross-sectional diagram of barrier systems ... 3

Figure 1.3: Upper left is a generalized stratigraphy of a double a barrier system ... 5

Figure 1.4: Schematic of GPR Unit and data collection. ... 6

Figure 1.5: Sample of raw data collected for this thesis using the GSSI SIR 2000 digital GPR... 8

Figure 1.6: Outcrop exposure versus GPR transect through progrdaing barrier. ... 9

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Figure 1.7: Modified version of Cowell and Thom (1997) Scale Cascade ... 10

Figure 1.8: Location of barriers in New Zealand.. ... 13

Figure 1.9: Generalized morphostratigraphic models of New Zealand prograding barrier types. ... 14

Figure 1.10: Northern New Zealand coast ... 15

Figure 1.11: Location map of study sites. ... 16

Figure 1.12: Air photographs of the seven study sites ... 18

Figure 1.13: A photo of the GSSI SIR-2000 ground-penetrating radar (GPR) system. ... 21

Figure 1.14: Techniques used to ground-truth the geophysical data. ... 21

Figure 1.15: Sokkia Electronic Total Station used to collect surface elevation data ... 22

Figure 2.1: Summary figure of a study on a double barrier system ... 27

Figure 2.2: Location map of Bream Bay, New Zealand ... 28

Figure 2.3: Photo documentation of various beach stages at Marsden Point. ... 31

Figure 2.4: Oblique photograph of mid-late Holocene dune ridges ... 32

Figure 2.5: Photograph taken along a Pleistocene beach ridge. ... 33

Figure 2.6: Small-scale stratigraphy of the Pleistocence barrier facies ... 35

Figure 2.7: Small-scale stratigraphy of the Holocene barrier facies ... 36

Figure 2.8: Small-scale stratigraphy of the barrier facies along the present-day beach. ... 38

Figure 2.9: Medium-scale outcrop and GPR stratigraphy of the Pleistocene barrier. ... 40

Figure 2.10: Medium-scale GPR stratigraphy of the Pleistocene barrier facies ... 42

Figure 2.11: Medium-scale GPR stratigraphy for the mid-Holocene barrier facies ... 43

Figure 2.12: Medium-scale GPR stratigraphy of the late-Holocene barrier facies ... 44

Figure 2.13: Three-dimensional models of medium-scale barrier stratigraphy from GPR ... 45

Figure 2.14: Photograph of Marsden Point beach taken after a large storm ... 46

Figure 2.15: Beach profiles taken after a storm ... 47

Figure 2.16: Graph of beach profile slopes. ... 47

Figure 2.17: Large-scale stratigraphy along One Tree Point scarp ... 49

Figure 2.18: GPR record collected along One Tree Point Road ... 50

Figure 2.19: GPR record collected along a shore perpendicular transect along Pyle Road ... 50

Figure 2.20: Elevation plot of beach and dune facies exposed along One Tree Point scarp ... 51

Figure 2.21: GPR record collected over the Pleistocene barrier to the mid-Holocene barrier ... 52

Figure 2.22: Large-scale composite GPR record of Holocene barrier ... 53

Figure 2.23: Plot of beach-dune interface from GPR collected along the Holocene barrier ... 54

Figure 2.24: Stratigraphic similarities throughout the barrier ... 58

Figure 2.25: Four-stage model of beach ridge formation as a product of punctuated progradation.... 59

Figure 2.26: Detailed 3-D morphostratigraphic model of a Bream Bay composite barrier system. ... 61

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Figure 3.1: Photograph of a dune scarp that resulted from the 1978 storm at Omaha Beach. ... 67

Figure 3.2: Location map and photograph of Omaha, New Zealand... 69

Figure 3.3: Two pictures taken after the 1978 storm ... 70

Figure 3.4: Oblique air photograph taken of Omaha after the 1978 storm ... 71

Figure 3.5: 1973 air photograph showing the location of the GPR transects and cores ... 73

Figure 3.6: Photo core log of a resin peel from Core #1... 75

Figure 3.7: Small-scale GPR of northern dune ridges barrier facies ... 76

Figure 3.8: Small-scale GPR of the foredune complex. ... 77

Figure 3.9: Small-scale GPR of southern beach ridges ... 78

Figure 3.10: Photograph taken in the northern portion of the study area after the July 2007 storm ... 79

Figure 3.11: Photograph taken in the central portion of the study area after the July 2007 storm ... 80

Figure 3.12: Photograph of the southern end of the barrier after a storm event in July 2007. ... 81

Figure 3.13: GPR collected in the southern section of Omaha beach ... 82

Figure 3.14: GPR collected in front of the central beach ridges at Omaha beach ... 83

Figure 3.15: Topographically-corrected GPR record over two beach ridges ... 84

Figure 3.16: Two-dimensional GPR image collected over two southern beach ridge crests. ... 85

Figure 3.17: A fence diagram and 3-D model of beachface stratigraphy ... 86

Figure 3.18: Photo core log of Cores #3 & #4 ... 87

Figure 3.19: A GPR transect collected across the width of the southern beach ridge system ... 89

Figure 3.20: A topographic profile taken along transects 1 and 2 ... 91

Figure 3.21: Central beach ridges and northern dune ridges stratigraphy ... 92

Figure 3.22: Graph of dune-beachface contact points ... 93

Figure 3.23: Four-stage model of beach ridge formation as a product of punctuated progradation.... 97

Figure 3.24: Four-stage model of dune ridge formation ... 99

Figure 3.25: Detailed three-dimensional morphostratigraphic model of Omaha barrier ... 100

Figure 3.26: Relationship of beach and dune ridges to offshore promontories ... 103

Figure 4.1: The Miranda coastal plain as mapped by Woodroffe et al. (1983). ... 109

Figure 4.2: Stratigraphic cross-section of Miranda chenier plain from Woodroffe et al. (1983). ... 110

Figure 4.3: Location of Miranda chenier plain within the Firth of Thames, New Zealand. ... 112

Figure 4.4: Morphologic expression of chenier 13 along Transect B ... 113

Figure 4.5: Photographs of the present-day beach ... 114

Figure 4.6: Vibracore collected in front of chenier 13... 117

Figure 4.7: Photograph of trench through chenier 10 exposed along Transect B... 118

Figure 4.8: Small-scale GPR from the seaward portion of chenier 10 ... 119

Figure 4.9: Photograph and topographic profile of of the present-day beach ... 120

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Figure 4.10: Medium-scale geophysical stratigraphy of the northern ridge of chenier 11 ... 122

Figure 4.11: GPR of the northern chenier ridges ... 124

Figure 4.12: GPR of the southern chenier spits ... 125

Figure 4.13: GPR cross-sections of the entire northern and southern transects ... 127

Figure 4.14: Composite graph of beachface-nearshore contact points ... 128

Figure 4.16: Schematic representation of a regressive chenier’s sedimentary structres ... 130

Figure 4.15: A series of six air photographs, spanning almost 50 years ... 132

Figure 4.17: 3-D model of regressive chenier stratigraphy across the Miranda chenier plain ... 132

Figure 4.18: 3-D morphostratigraphic model of the Miranda chenier plain. ... 138

Figure 5.1: Gibbs (1986) New Zealand regional Holocene eustatic sea-level curve ... 144

Figure 5.2: Time-depth plots of local relative sea levels for six study sites used by Gibb (1986) .... 145

Figure 5.3: Map of northern New Zealand with the locations of the four study sites ... 150

Figure 5.4: East Beach location map, air photo and GPR ... 151

Figure 5.5: Marsden Point location map, air photo and GPR ... 152

Figure 5.6: Omaha location map, air photo and GPR ... 153

Figure 5.7: Miranda location map, air photo and GPR ... 154

Figure 5.8: Digitized data points with linear regression for each site ... 156

Figure 5.9: Displays both fourth and fifth order polynomial regressions of the data ... 157

Figure 5.10: All data plotted together with fourth and fifth order polynomial regressions. ... 158

Figure 5.11: Running means on data for each site ... 159

Figure 5.12: Time–elevation plot of pre-existing radiocarbon ages and the two OSL dates... 162

Figure 5.13: Oscillating sea-level models proposed for Miranda ... 163

Figure 5.14: Topographic profile for five progradational systems in Northland-Auckland area. ... 164

Figure 5.15: Holocene eustatic sea-level curve in Cochran et al. (2006) using Gibb (1986) data .... 165

Figure 5.16: Woodroffe’s (2009) relative sea-level reconstructions ... 166

Figure 5.17: Lewis et al. (2008) Austrailian sea-level curve with past sea-level interpretations ... 167

Figure 5.18: Time–depth sea-level plot from Sloss et al. (2007) ... 167

Figure 5.19: Time–elevation plot from Baker and Haworth (2000a). ... 168

Figure 5.20: New Zealand's estimated yearly temperatures since the last Ice Age ... 172

Figure 6.1: Map of sediment from New Zealand rivers (Hicks and Shankar, 2003). ... 175

Figure 6.2: Suspended sediment yields to New Zealand coast (Hicks, 2004). ... 176

Figure 6.3: A generalized wave height contour map and average significant wave height chart ... 177

Figure 6.4: Eight beach profiles collected from 1991-2000 along Piha Beach (King et al., 2006)... 177

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Figure 6.5: Sediment supply to the coast and inferred longshore sediment transport paths ... 178

Figure 6.6: Frequent wave direction along the east and west coast (Shepherd and Hesp, 2003). ... 178

Figure 6.7: Comparison of barrier size between South Head and Omaha ... 179

Figure 6.8: An oblique satellite image and stratigraphic model of South Head Kaipara ... 180

Figure 6.9: Cross-shore comparison of scale and morphologybetween Ahipara and East Beach ... 181

Figure 6.10: Photos showing the location of data collected at South Head Kaipara. ... 183

Figure 6.11: Stitched panoramic photograph looking east from 30m dune at Kaipara ... 183

Figure 6.12: Photographs looking southwest from 30m dune at Kaipara... 184

Figure 6.13: Small-scale shore perpendicular stratigraphy. ... 185

Figure 6.14: GPR collected perpendicular to shore ... 185

Figure 6.15: GPR collected parallel to shore ... 186

Figure 6.16: Large-scale stratigraphy of transverse dunes ... 187

Figure 6.17: A model of peak ebb tide velocity in the Kaipara Harbor indicating a stable inlet. ... 188

Figure 6.18: Image of transgressive dunes and wind direction at South Head Kaipara barrier ... 190

Figure 6.19: Evolutionary model of South Head Kaipara modified from Hilton (1982). ... 191

Figure 6.20: Photos showing the location of data collected at Ahipara. ... 192

Figure 6.21: Photographs of the first two dune ridges along Ahipara ... 193

Figure 6.22: Small-scale shore perpendicular stratigraphy ... 194

Figure 6.23: GPR collected perpendicular to shore ... 195

Figure 6.24: GPR collected parallel to shore ... 195

Figure 6.25: GPR depicting large-scale stratigraphy of seaward two dune ridges at Ahipara ... 196

Figure 6.26: Image of Ahipara Headland and waves being refracted onto Ahipara beach. ... 197

Figure 6.27: GPR image along a linear dune in Namibia from Bristow et al. 2005... 198

Figure 6.28: Comparison GPR collected at Ahipara with that from a linear dune in Namibia ... 198

Figure 6.29: Bathymetric data of northern Northland. ... 199

Figure 6.30: Image of Ahipara with differing types of dunes accentuated ... 200

Figure 6.31: Four-stage model of Ahipara barrier evolution ... 201

Figure 6.32: Three-dimensional model of beachfaces from GPR at Ahipara. ... 202

Figure 6.33: Three-dimensional model of beachfaces from GPR at South Head Kaipara. ... 202

Figure 6.34: Three-dimensional fence diagram and isolated beachfaces from the west coast ... 203

Figure 6.35: Topographic profiles displaying the envelope of change along a dissipative beach ... 204

Figure 6.36: General stratigraphic model of Transgressive Dunefield Barrier. ... 205

Figure 6.37: 3-D morphostratigraphic model of South Head Kaipara... 205

Figure 6.38: General stratigraphic model of Foredune Barrier... 206

Figure 6.39: Stratigraphic model of Ahipara. ... 206

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Figure 7.1: Models of some of the major barrier types from Dillenburg and Hesp (2009) ... 211

Figure 7.2: Morphostratigraphic models of New Zealand prograding barrier types ... 212

Figure 7.3: 3-D GPR of the four types of prograding barriers in Northland ... 213

Figure 7.4: 3-D morphostratigraphic models of prograding barriers in Northland. ... 214

Figure 7.5: Early-Pliocene map of New Zealand (Fleming, 1949)... 217

Figure 7.6: Geologic Map of northern New Zealand ... 218

Figure 7.7: A sediment supply map and bathometric map of Northland ... 219

Figure 7.8: Schematic showing the influence of sea level on barrier progradation. ... 223

Figure 7.9: Map of the overall average of significant wave height around New Zealand ... 225

Figure 7.10: Schematic of dissipative, intermediate and reflective beachfaces. ... 227

Figure 7.11: GPR transects from each of the east coast barriers ... 228

Figure 7.12: GPR transects from east and west coast barriers ... 229

Figure 7.13: Storm and swell beach profiles from Bream Bay... 231

Figure 7.14: Model of the formation of beach ridges at One Tree Point, Bream Bay. ... 232

Figure 7.15: Model of the formation of beach ridges at Omaha. ... 233

Figure 7.16: Picture of the internal sedimentary structures of a beach ridge (Hesp et al., 2005) ... 235

Figure 7.17: Dune formation and occurrence in relation to beach and foredune sand budgets ... 238

Figure 7.18: Example of 3-D models of a representative west coast barrier stratigraphy ... 240

Figure 7.19: Example of 3-D models of a representative east coast barrier stratigraphy ... 241