Lake Wairarapa and the Onoke Bar

Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the pennission of the Author. ii ABSTRACT The lower Wairarapa Valley was an estuary as late as 6 500 years ago. Since then sediments from the Ruamahanga and Tauherenikau Rivers have deposited large loads of sediment into the area, prograding the eastern shore and changing the system from an estuary into lakes and rivers. The aims of this study were to investigate the late Quaternary deposits and soils of the eastern shore of Lake W airarapa, using the information gained to look at the way in which infilling has taken place. The surface geology and soils of the study area were mapped. The mapping units were described and defined. Some chemical tests were carried out on selected soil samples. The order and method of infilling of the deposits are discussed. 111 TABLE OF CONTENTS PAGE Abstract . ii Table of Contents . iii List of Figures . v List of Tables . v List of Plates . vi CHAPTER ONE: INTRODUCTION. 1 1.1.0 Aims and scope of study . 1 1.2.0 Location and setting of the study area . 2 1.2.1 Location and extent of study area . 2 1.2.2 Setting of the study area . 2 1.3.0 Oimate of southern @airarapa . 8 1.4.0 History of the Wairarapa . 14 1.4.1 Introduction . 14 1.4.2 Early Maori occupation . 14 1.4.3 Later Maori occupation . 16 1.4.4 European settlement . .. ·. 17 1.4.5 The struggle for control of lake levels . 18 1.5.0 Past vegetation . 19 1.5.1 Early European descriptions . 19 1.5.2 Effect of the European settlers . 22 CHAPTER TWO: GEOLOGY AND PHYSIOGRAPHY . 23 2.1.0 Literature review. 23 2.1.1 Introduction. 23 2.1.2 The western ranges. 24 2.1.3 The eastern ranges. 26 2.1.4 Wairarapa valley. 29 2.1.5 Formation of Lake W airarapa. 31 2.1.6 Holocene sedimentation. 34 2.2.0 Description of the late Quaternary deposits . 37 2.2.1 Deposits of the dunes and sandflats. 38 2.2.2 Deposits of the alluvial plains. 40 2.3.0 The change from an estuarine to lacustrine environment. 45 2.3.1 Theory and discussion of estuarine sedimentation. 45 2.3.2 The oldest dune-line. 50 2.3.3 Theory and discussion of delta formation. 52 2.3.4 Theory and discussion of dune formation. 63 2.3.5 Formation of the Onoke gravel bar. 71 2.4.0 Physiographic units of the study area . 72 2.4.1 The sand dunes . 73 2.4.2 The alluvial plains . 73 CHAPTER THREE: SOILS . 77 3.1.0 The soil survey . 77 3 .1.1 Introduction. 77 3.1.2 Soil mapping. 79 3.2.0 Literature review . 86 3.3.0 Description and distribution of soils. 97 3.3.1 Soils of the sand dunes. 93 3.3.2 Soils of the slowly accumulating flood plain. ............ 120 3.3.3 Soils of the rapidly accumulating flood plain.............. 131 3.4.0 Summary and discussion of soil properties ................... 147 3.4.1 Yellow-brown sands ............................. 147 3.4.2 Recent soils and gleyed recent soils ................... 152 IV CHAPTER FOUR: LABORATORY WORK ........................... 158 4.1.0 Introduction . 158 4.1.1 Sampling procedure . 158 4.1.2 Chemical analyses . 159 4.2.0 Soil pH ......................................... 163 4.2.2 Measured pH of soil samples ...................... 165 4.3.0 Soil organic matter .................................. 169 4.3.1 Literature review ............................... 169 4.3.2 C%, N% and C/N ratios of soil samples . 172 4.4.0 Phosphorous ....................................... 176 4.4.1 Literature review ............................... 176 4.4.2 Phosphorous levels of soil samples . 178 Bibliography ................................................ 187 Appendix One .............................................. 195 Appendix Two . 196 Appendix Three ............................................. 197 Appendix Four . 200 Appendix Five . Pocket V LIST OF FIGURES PAGE Figure 1 Location of the study area. 3 Figure 2 Extent of the W airarapa Valley . 4 Figure 3 illustration of set up. 7 Figure 4 Extent of the highest shoreline (from Heath 1979) . 9 Figure 5 Windrose . 11 Figure 6 Recent climatic changes in New Zealand (from Leach 1981). 15 Figure 7 Wairarapa vegetation c. 1853 (from Hill) . 21 Figure 8 Faulting and folding of the southern Wairarapa Valley. 25 Figure 9 Movement caused by the 1855 earthquake. 27 Figure 10 Eparaima marine benches. 30 Figure 11 Summary of descriptions of Kumenga and Birchwood . 33 Figure 12 Tributaries of the Ruamahanga River. 35 Figure 13 Circulation in a salt wedge estuary. 47 Figure 14 Two methods of bar development. 49 Figure 15 A method by which dunes climb cliffs. 51 Figure 16 Cross section through a simple delta. 53 Figure 17 The abundance and distrubution of gravels. 56 Figure 18 The 0porua floodway cross section. 61 Figure 19 Mid-ground bar development . 64 Figure 20 Wind strength and the movement of sand. 66 Figure 21 Flown diagram showing stages in preparation of a soil resource survey. 67 Figure 22 Spade dimensions . 90 Figure 23 The relationship of soils to physical position, dune set two . 100 Figure 24 The relationship of soils to physical position, dune set three . 90 Figure 25 The variation of measurement pH in distilled water, 1 M KO and 0.01 M CaO2 with depth. 168 Figure 26 The variatio of C%, N% and the carbon:nitrogen ratio with depth for three profiles ............................................... 175 Figure 27 The variation in organic and non occluded inorganic P% with depth for 3 representative soil profiles. 181 Figure 28 Changing shoreline positions recorded on the eastern side of Lake W airarapa. 186 LIST OF TABLES PAGE Table I Legend for the map of late Quaternary deposits . 40 Table II Physiographic unit legend. 76 Table III Pedologic Legend . 91 Table IV Physiographic legend . 92 Table V Correlation and classification of soils defined in previous surveys. ........................... 146 Table VI Laboratory Analyses .................................... 167 Table VII Phosphoroufa Values Adjusted for Depth ...................... 180 Vl TABLE OF PLATES PAGE Plate 1 Lake Wairarapa and the Onoke bar . 5 Plate 2 Dune bedding . 39 Plate 3 Oporua floodway . 59 Plate 4 Cross bedded sands and grits in the Oporua floodway. 61 Plate 5 Buried soil in the Oporua floodway. 62 Plate 6 Dune set one. 94 Plate 7 Kahutara sand . 95 Plate 8 Dune set two . ..

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