i THE ORIGIN OF SLOPE DEPOSITS IN THE SOUTHERN DRAKENSBERG, EASTERN LESOTHO Stephanie Christiane Mills Submitted in fulfilment of the academic requirements for the degree of Doctor of Philosophy School of Geography, Archaeology and Environmental Studies University of the Witwatersrand, Johannesburg Johannesburg July 2006 ii This thesis is dedicated to the memory of my father, Ken Mills (1946-2004). iii Declaration I declare that this thesis is my own, unaided work, except where otherwise acknowledged. It is being submitted for the degree of PhD to the University of the Witwatersrand, Johannesburg. It has not been submitted before for any degree or examination in any other university. ________________ _____________ (Stephanie Mills) 14th day of July 2006 iv Abstract The high Drakensberg of southern Africa has received considerable geomorphological interest during recent decades. In particular, there has been an ongoing debate concerning the accuracy of landform interpretations which propagate past glaciation and permafrost. This research examines the macro and micro-sedimentology of various deposits found in eastern Lesotho and compares them with possible geomorphological process origins such as debris flows, debris avalanches, mudflows, mudslides, landslides, solifluction deposits, rock glaciers, pronival ramparts, glacial moraines and fluvial deposits. The results support the contention that four of the deposits are moraines, formed by small glaciers, and one is a debris flow which was initiated by a small glacier. However, two further deposits indicate that localities in close proximity to the linear deposits experienced mass wasting, associated with past periglacial conditions. With the assistance of applying glacier reconstruction methods, modelling hillshade, the provision of new palaeoclimatic extrapolations, and correlation of deposits with contemporary snow patch distribution, it is demonstrated that the valley slope deposits are determined by a past climate that was within the glacial/periglacial equilibrium zone, and was influenced by specific topographic and associated micro-climatic thresholds. It is shown that macro-topographic factors (e.g. slope gradient, aspect etc) and summit altitude are critical factors determining whether slopes were influenced by periglacial (mass wasting) or glacial processes (small niche/cirque glaciers) in adjacent valleys. v Preface This work stems from the discovery of debris deposits in eastern Lesotho, which display unique morphological characteristics. No work has previously been undertaken on such deposits in the area, which thus offers a great opportunity to add understanding to the Quaternary history of southern Africa. Having lived and been educated all my life in the northern hemisphere, I was unaware of the controversial debate regarding the Quaternary history of southern Africa. This has helped offer a fresh perspective, without any preconceived ideas as to the processes which formed these deposits. The process origins considered for the formation of these deposits were chosen based on the morphology of such process origins and their role in the alpine environment. The initial aim of this research was to ascertain which processes could have formed the deposits located in eastern Lesotho, however through the use of sedimentological analysis and AMS dating, it soon became clear that a serious contender was that of past glacial processes. Given the controversy surrounding such a claim, it was necessary to investigate this further through the use of glacier reconstruction techniques and the influence of solar radiation. These techniques helped further reinforce that small glaciers had been present in the past, however the lack of further deposits on adjacent slopes indicates that glaciers were restricted to only a few areas. Given the recent prolific production of periglacial-related literature for Lesotho, it is hoped that this research will reawaken the interest into past glacial processes, which were first suggested five decades ago. Sections of this work have been presented at the SASQUA conference in Johannesburg, South Africa in 2003, the Sixth International Conference on Geomorphology in Zaragoza, Spain in 2005 and the Geomorphology and Earth System Science (BGRG) conference in Loughborough, England in 2006. Sections of this work have also been published in Quaternary International, 2005. vi Acknowledgements There are many people who have provided assistance with this research project and they are thanked in no particular order. I would first like to thank Colin Bones, without whom I would never have discovered the wonderful country that is South Africa. Colin has supported me both personally and financially and was also indispensable when it came to field work. Although he swore he would never go back to Lesotho and undertake another minute of fieldwork after his first experience, he returned time and time again, and put up with endless hours of horse riding, digging and carrying very heavy soil samples. He has also proved invaluable in terms of proof reading and checking references and has had to put up with my incessant work during the last few months of this research. Several people have helped me with fieldwork and made the time more enjoyable. Thank you very much Christine Deschamps and Joel LeBaron for your tireless help in the field, friendship and advise throughout. They put up with 12 hours on a horse to get to one of my sites, which was not a particularly enjoyable experience and days camping in the freezing cold, so thanks guys. Thank you also to Nicolas Mulder and Emily Craven for their help in the field on separate occasions. Thank you also to Nicolas for providing the contemporary snow patch distribution diagrams which were used in this research. Many people have also provided their time, energy and expertise to help me in the laboratory. Thanks to Thandiswe Nsimbi for his help in enabling me to have access to the soils lab and in helping me whenever the sieving machine broke down. Due to the lack of equipment at Wits I contacted my old university (Royal Holloway University of London) in order to beg them to let me have the use of their soils lab. Huge thanks to Adrian Palmer for helping me with the sedigraph machine and the manufacturing of the thin sections. Adrian dedicated a lot of his time in supervising me during the manufacturing process and also allowed me the use of microscopes during endless hours and days of analysis. Adrian proved indispensable, when on moving back to the UK the thin sections along with my hand luggage were stolen. Thanks to the insurance pay out he was able to re-do all my thin sections when I just didn?t have the time nor the courage. Many thanks to Stefan Woodborne and staff at the QUADRU, vii CSIR for discussions and providing the AMS dates. Thank you also to Devlyn Hardwick for her advice regarding the DEM and to Eric Hallot for creating it. Statistical analysis would have been much more difficult had it not been for Richard Smerin?s help, which was much appreciated. Scientific advice on the various aspects of my thesis has been provided by several people. I would first like to thank Simon Carr for all his help and advice regarding the glacier reconstruction work. Simon gave up his time to take me through the process step by step, along with his postgraduate student, Chris Coleman. Thanks also for checking that I had undertaken the process correctly and also on the advice regarding several aspects of my PhD. Thanks also to Jim Rose for all his advice regarding the Sehonghong deposits. Jaap Van der Meer gave up time for discussion and looked through my thin sections and advised me on references I should look at. Correspondence by email was also invaluable and I would like to thank Colin Thorn for his advice regarding snow patches, Richard Shakesby for his advice regarding pronival ramparts, Wishart Mitchell for his advice regarding snow blow and Pascal Bertran and John Menzies for their advice on the micromorphology of debris flows. Thank you also to Colin Lewis for his advice regarding the Sehonghong deposits and Richard Washington for his advice regarding past climatic processes. Many people have helped towards the end of this research so I would like to apologise to my friends for roping them into this, but at least they have a better understanding of what I have been doing for the last few years. Thank you to Naomi Davies for checking my references and to Deana Rouse and Helen Cameron for proof reading a few chapters. Thank you also to Claire Munson for proof reading some chapters and for all her support and friendship over the years. I would also like to thank my family for their moral support and for coming out to visit so many times in South Africa so that it didn?t seem we were too far away from home. Thanks to my dad as I?m sure it was his passion for geography that first awakened mine. I?m just sorry that he wasn?t able to see me complete this PhD but his support in the beginning was instrumental. Finally, but by no means least I would like to thank my supervisor, Stefan Grab. Thank you for providing the funding for the AMS dates, without which this thesis would have had much less of a standing in stating that glaciers existed during the Last viii Glacial Maximum (LGM). Stefan believed in me and encouraged me throughout and was the inspiration behind this project. Thank you for going through my thesis with a fine tooth comb, for putting me in touch with others, suggesting various references I should read and for developing my writing skills into what they are now. Thank you also for encouraging me to present my work at various conferences and for all your help with the article that we published. ix Contents Declaration iii Abstract iv Preface v Acknowledgements vi Contents ix List of Figures xv List of Tables xxii CHAPTER 1: Introduction 1.1 GEOMORPHOLOGICAL AND PALAEOENVIRONMENTAL BACKGROUND TO THE STUDY 1 1.2 REGIONAL SETTING 4 1.3 STUDY AREA 7 1.4 AIMS AND HYPOTHESES 9 1.5 THESIS STRUCTURE 10 CHAPTER 2: Literature Review 2.1 PROCESS ORIGINS 11 2.1.1 Introduction 11 2.1.2 Mass movement 11 2.1.2.1 Slope form 11 2.1.2.2 Mass movement processes 12 2.1.2.2.1 Debris flows 14 2.1.2.2.2 Debris avalanches 22 2.1.2.2.3 Landslides 23 2.1.2.2.4 Mudflows/mudslides 26 2.1.2.2.5 Rock avalanches 28 2.1.2.2.6 Solifluction deposits 28 2.1.2.2.7 Mass wasting deposits and the periglacial environment in the Drakensberg 32 2.1.3 Rock glaciers 36 2.1.4 Pronival ramparts 40 2.1.5 Glacial moraines and tills 42 2.1.5.1 Glacial moraine types 42 2.1.5.2 Tills 47 2.1.6 Fluvial deposits 53 2.2 PROBLEMS ASSOCIATED WITH THE IDENTIFICATION OF A PROCESS ORIGIN FOR THE DEPOSITS 56 2.2.1 Similarities between deposits 56 2.2.2 Problems associated with clast orientation and fabric eigenvalues 64 2.2.3 Problems associated with particle shape 66 2.3 COMPARISONS OF THE TIMING OF THE LGM IN SOUTHERN HEMISPHERE AND AFRICAN LOCATIONS 67 2.3.1 Introduction 67 2.3.2 Africa 68 x 2.3.2.1 Ethiopia 68 2.3.2.2 East Africa 71 2.3.2.2.1 Mount Kenya 71 2.3.2.2.2 Kilimanjaro 72 2.3.2.2.3 Summary of LGM glacial advances and climate in East Africa 74 2.3.3 New Zealand 75 2.3.4 Australia and Tasmania 76 2.3.5 South America 77 2.3.5.1 Argentina 77 2.3.5.2 Argentine Patagonia 78 2.3.5.3 Chile 79 2.3.6 Summary 81 CHAPTER 3: Environmental and Geomorphic Setting 3.1 GEOLOGY 83 3.1.1 Background 83 3.1.2 Drakensberg Group 83 3.2 GEOMORPHIC EVOLUTION 89 3.3 SOILS 91 3.4 CLIMATE 93 3.4.1 General Atmospheric Circulation 93 3.4.2 Temperature 95 3.4.2.1 Air temperature variations 96 3.4.3 Precipitation 96 3.4.4 Winds 98 3.4.5 Palaeoclimate 99 3.5 VEGETATION 103 3.6 SUMMARY 105 CHAPTER 4: Methodology 4.1 INTRODUCTION 106 4.2 FIELDWORK 106 4.2.1 Sedimentological analysis 106 4.2.1.1 Field procedure 106 4.2.1.2 Texture 108 4.2.1.3 Sorting 108 4.2.1.4 Colour 109 4.2.1.5 Induration 109 4.2.1.6 Clast fabric 109 4.2.1.7 Particle shape 110 4.2.1.8 Radiocarbon dating 111 4.2.2 Mapping 112 4.2.3 Thin section collection 113 4.2.3.1 Rationale 113 4.2.3.2 Sampling strategy 113 4.2.3.3 Sample collection 113 4.3 LABORATORY WORK 114 xi 4.3.1 Particle size analysis 114 4.3.1.1 Rationale 114 4.3.1.2 Laboratory procedure 115 4.3.1.3 Data representation 117 4.3.2 Thin section manufacturing 118 4.3.2.1 Laboratory procedure 118 4.3.2.2 Analytical procedure 118 4.3.3 Particle shape 119 4.3.3.1 Rationale 119 4.3.3.2 Particle form 119 4.3.3.3 Particle sphericity 120 4.3.3.4 Particle roundness 120 4.4 STATISTICAL ANALYSIS 120 4.4.1 Clast orientation test of significance 120 4.4.2 Clast fabric 120 4.4.3 T-test for particle shape 121 4.5 PAST CLIMATE 121 4.5.1 Palaeoclimatic extrapolations 121 4.5.2 Reconstruction of former glaciers 122 4.5.2.1 Palaeoglacier outline 122 4.5.2.2 ELA calculation 123 4.5.2.3 Ablation gradient 126 4.5.2.4 Glacier mass balance calculations 127 4.5.3 Hillshade modelling 129 CHAPTER 5: Tsatsa-La-Mangaung Results 5.1 INTRODUCTION 131 5.2 MORPHOLOGY 131 5.3 FIELD OBSERVATIONS 132 5.3.1 Tsatsa-La-Mangaung slope deposit 132 5.3.2 Tsatsa-La-Mangaung pits 136 5.4 PARTICLE SIZE ANALYSIS 139 5.4.1 Tsatsa-La-Mangaung slope deposit 139 5.4.2 Tsatsa-La-Mangaung pits 144 5.5 CLAST FABRIC AND EIGENVALUES 149 5.6 PARTICLE SHAPE 151 5.7 MICROMORPHOLOGY 158 5.8 RADIOCARBON DATING 163 5.9 SUMMARY 163 CHAPTER 6: Sekhokong Results 6.1 INTRODUCTION 166 6.2 SEKHOKONG SITE 1 166 6.2.1 Morphology 166 6.2.2 Field observations 167 6.2.3 Particle size analysis 170 6.2.4 Clast fabric and eigenvalues 176 6.2.5 Particle shape 179 xii 6.2.6 Micromorphology 185 6.2.7 Radiocarbon dating 188 6.2.8 Summary 188 6.3 SEKHOKONG SITE 2 191 6.3.1 Morphology 191 6.3.2 Field observations 192 6.3.3 Particle size analysis 195 6.3.4 Clast fabric and eigenvalues 196 6.3.5 Particle shape 204 6.3.6 Micromorphology 210 6.3.7 Radiocarbon dating 212 6.3.8 Summary 212 CHAPTER 7: Leqooa Valley Results 7.1 INTRODUCTION 215 7.2 MORPHOLOGY 215 7.3 FIELD OBSERVATIONS 218 7.3.1 Western slope deposit 218 7.3.2 Eastern slope deposit 220 7.4 PARTICLE SIZE ANALYSIS 222 7.4.1 Western slope deposit 222 7.4.2 Eastern slope deposit 227 7.5 CLAST FABRIC AND EIGENVALUES 234 7.5.1 Western slope deposit 234 7.5.2 Eastern slope deposit 237 7.6 PARTICLE SHAPE 239 7.6.1 Western slope deposit 239 7.6.2 Eastern slope deposit 247 7.7 MICROMORPHOLOGY 252 7.7.1 Western slope deposit 252 7.7.2 Eastern slope deposit 255 7.8 RADIOCARBON DATING 259 7.9 SUMMARY 259 CHAPTER 8: Sehonghong Results 8.1 INTRODUCTION 262 8.2 MORPHOLOGY 263 8.3 FIELD OBSERVATIONS 267 8.4 PARTICLE SIZE ANALYSIS 270 8.5 CLAST FABRIC AND EIGENVALUES 276 8.6 PARTICLE SHAPE 279 8.7 MICROMORPHOLOGY 285 8.8 RADIOCARBON DATING 288 8.9 TEMPERATURE DATA FOR NHLANGENI 292 8.10 SUMMARY 293 xiii CHAPTER 9: Discussion 9.1 INTRODUCTION 295 9.2 MORPHOLOGY 295 9.2.1 Debris flows/avalanches 295 9.2.2 Landslides 297 9.2.3 Mudflows/mudslides 298 9.2.4 Solifluction lobes 299 9.2.5 Rock glaciers 300 9.2.6 Pronival ramparts 300 9.2.7 Glacial moraines 301 9.2.8 Fluvial deposits 302 9.2.9 Summary 302 9.3 PARTICLE SIZE ANALYSIS 303 9.3.1 Debris flows/avalanches 303 9.3.2 Landslides and mudflows/mudslides 304 9.3.3 Solifluction lobes 304 9.3.4 Rock glaciers 305 9.3.5 Pronival ramparts 305 9.3.6 Glacial moraines 306 9.3.7 Fluvial deposits 307 9.3.8 Summary 307 9.4 CLAST FABRIC AND EIGENVALUES 308 9.4.1 Debris flows/avalanches 308 9.4.2 Landslides 309 9.4.3 Mudflows/mudslides 309 9.4.4 Solifluction lobes 310 9.4.5 Rock glaciers 311 9.4.6 Pronival ramparts 311 9.4.7 Glacial moraine 312 9.4.8 Fluvial deposits 313 9.4.9 Summary 313 9.5 PARTICLE SHAPE 313 9.5.1 Debris flows/avalanches 313 9.5.2 Landslides and mudflows/mudslides 314 9.5.3 Solifluction lobes 314 9.5.4 Rock glaciers 315 9.5.5 Pronival ramparts 315 9.5.6 Glacial moraines 316 9.5.7 Fluvial deposits 316 9.5.8 Summary 317 9.6 MICROMORPHOLOGY 317 9.6.1 Debris flows, landslides and mudslides 317 9.6.2 Solifluction lobes 318 9.6.3 Glacial moraines 318 9.6.4 Fluvial deposits 318 9.6.5 Summary 319 9.7 EROSION REMNANT 319 9.8 POSSIBLE PROCESS ORIGIN FOR THE TSATSA-LA- MANGAUNG DEPOSIT 320 xiv 9.9 POSSIBLE PROCESS ORIGIN FOR THE SEKHOKONG SITE 1 DEPOSIT 323 9.10 POSSIBLE PROCESS ORIGIN FOR THE SEKHOKONG SITE 2 DEPOSIT 329 9.11 POSSIBLE PROCESS ORIGIN FOR THE LEQOOA VALLEY DEPOSITS 332 9.12 POSSIBLE PROCESS ORIGIN FOR THE SEHONGHONG DEPOSITS 336 9.12.1 Deposits on the south-facing slope 336 9.12.2 Deposits on the north-facing slope 342 9.13 RADIOCARBON DATING 347 9.14 SUMMARY 350 CHAPTER 10: Glacier Reconstruction 10.1 INTRODUCTION 351 10.2 CLIMATE DURING THE LAST GLACIAL MAXIMUM 351 10.3 GLACIER RECONSTRUCTION 361 10.4 SNOWBLOW AND AVALANCHING 367 10.5 SOLAR RADIATION 377 10.6 CONTEMPORARY SNOW PATCH DISTRIBUTION 390 10.7 SUMMARY 393 CHAPTER 11: Conclusion 11.1 INTRODUCTION 396 11.2 EXTENT TO WHICH THE AIMS AND OBJECTIVES ARE REALISED 396 11.3 CONTRIBUTION TO THE QUATERNARY HISTORY OF SOUTHERN AFRICA 397 11.4 INTERNATIONAL CONTEXT 398 11.5 FUTURE RESEARCH IN THE DRAKENSBERG REGION 400 11.6 SUMMARY 400 References 404 xv List of Figures 1.1 Map of South Africa indicating the land-locked position of Lesotho 5 1.2 The road up Sani Pass 5 1.3 The geographic Regions of Lesotho 6 1.4 Location map for the Tsatsa-La-Mangaung, Sekhokong, Leqooa Valley and Sehonghong sites 8 2.1 An example of active periglacial features on British mountains 12 2.2 A theoretical slope profile containing a comprehensive range of slope units related to particular types of slope processes 14 2.3 Idealised representations of a debris flow arm, showing waves and deposits formed by successive waves of debris 16 2.4 The terminology of a landslide 23 2.5 Landslide susceptibility in South Africa 25 2.6 Diagram showing typical features of a small mudflow 27 2.7 Annual moraine ridge formation based upon examples at Sk?lafellsj?kull, Iceland 44 2.8 Idealised model of clast fabric and facies variation within a seasonal push moraine 45 2.9 Lateral moraine formation by dumping of supraglacial debris 46 2.10 The transport pathways of debris through a valley glacier 48 2.11 The concept of an alpine continuum 58 2.12 Effect of snowbed/firn field thickening on the development of a rampart located close to the junction between the talus foot and the valley floor 61 2.13 Pronival rampart as part of a nondevelopmental morphological continuum of talus-derived landforms 63 2.14 Pronival ramparts viewed as part of a linear developmental continuum with rock glacier and glacier formation 63 2.15 The response of individual grains to an applied stress 65 2.16 The location of sites in Africa with records of former glaciation, and generally assumed to date to the Last Glacial Maximum 69 2.17 Lateral moraines on the south-western side of Kibo at 4800 m a.s.l representing a Holocene glaciation period 74 3.1 Geological Time Scale 84 3.2 The configuration of the southern hemisphere continents at the time of the break-up of Gondwanaland 85 3.3 Cross section from the Cape ranges through Lesotho to KwaZulu Natal 85 3.4 Geological sketch map of South Africa 86 3.5 Basalt clasts 88 3.6 The Great Escarpment photographed at Cathedral Peak in the north- eastern Drakensberg 90 3.7 Soils map of Lesotho 92 3.8 Surface air features over southern Africa 94 3.9 Mean January and July sea-level pressure maps, mb, of the Southern Hemisphere for longitude 60?W to 120?E and south of latitude 15?S 95 3.10 Rainfall: altitude relationship along A (Bergville) to B (Mothelsessane), Lesotho 97 3.11 The forcing of climatic change over Africa as a result of the 23 000 year cycle of the precession of the equinoxes 100 xvi 3.12 Palaeoclimatic reconstruction for Africa south of the equator at the Last Glacial Maximum (c. 21-18 kyr) 102 3.13 Vegetation types of Lesotho 104 3.14 An example of the Erica-Helichrysum vegetation in the Drakensberg at 3160 m a.s.l 104 4.1 Data chart for field description of diamicts and associated sediments 107 4.2 Diagram for determining texture 108 4.3 Sorting images 109 4.4 Visual images for the determination of roundness of clasts 110 4.5 Kubiena Tin 114 4.6 Accumulation-area ratio method 124 4.7 Graphical representation of the components of the balance ratio method of calculating glacier ELA?s 126 4.8 Diagram relating accumulation to the ablation gradient of thirteen glaciers 128 4.9 The solar elevation at various times of day in various months at 29? 30? S 129 5.1 The Tsatsa-La-Mangaung slope deposit 132 5.2 Morphological map of the Tsatsa-La-Mangaung deposit 133 5.3 Boulders excavated from a trench at the Tsatsa-La-Mangaung deposit 134 5.4 Sedimentological and stratigraphical data for trench 1 at Tsatsa-La- Mangaung 134 5.5 Sedimentological and stratigraphical data for trench 2 at Tsatsa-La- Mangaung 135 5.6 Sedimentological and stratigraphical data for trench 3 at Tsatsa-La- Mangaung 135 5.7 Sedimentological and stratigraphical data for Pit 1 at Tsatsa-La- Mangaung 137 5.8 Sedimentological and stratigraphical data for Pit 2 at Tsatsa-La- Mangaung 137 5.9 Sedimentological and stratigraphical data for Pit 3 at Tsatsa-La- Mangaung 138 5.10 Sedimentological and stratigraphical data for Pit 4 at Tsatsa-La- Mangaung 138 5.11 Sedimentological and stratigraphical data for Pit 5 at Tsatsa-La- Mangaung 139 5.12 Grain size distributions for the sediment from Trench 1 at the Tsatsa-La- Mangaung Site 140 5.13 Grain size distributions for the sediment from Trench 2 at the Tsatsa-La- Mangaung Site 141 5.14 Grain size distributions for the sediment from Trench 3 at the Tsatsa-La- Mangaung Site 142 5.15 Grain size distributions for the sediment from the pits at the Tsatsa-La- Mangaung Site 146 5.16 Clast orientation, dip and contouring at trenches 1, 2 and 3 at Tsatsa-La- Mangaung 150 5.17 Till fabric using eigenvalue data for the Tsatsa-La-Mangaung deposit 152 5.18 Triangular plot of normalised eigenvalues for the Tsatsa-La-Mangaung deposit 153 5.19 Triangular diagrams for clasts in trenches 1, 2 and 3 respectively at Tsatsa-La-Mangaung 154 xvii 5.20 Isolines of the Oblate-prolate index for trenches 1, 2 and 3 respectively at Tsatsa-La-Mangaung 155 5.21 Isolines of the maximum projection sphericity for trenches 1, 2 and 3 respectively at Tsatsa-La-Mangaung 156 5.22 Graphs representing visual roundness of clasts in trenches 1 (A), 2 (B) and 3 (C) at Tsatsa-La-Mangaung 157 5.23 An example of coarse, weakly oriented, platy, subangular, undulating particles 160 5.24 An example of typical vugh voids 160 5.25 An example of typical channel voids 161 5.26 An example of a basalt grain 161 5.27 An example of an olivine crystal with a brown rim 162 5.28 A basalt clast with a non-laminated silt capping 162 5.29 A basalt clast with a laminated silt capping 163 6.1 The Sekhokong Site 1 slope deposit 167 6.2 Morphological map of the Sekhokong Site 1 deposit 168 6.3 Sedimentological and stratigraphical data for trench 1 at Sekhokong Site 1 169 6.4 Sedimentological and stratigraphical data for trench 2 at Sekhokong Site 1 169 6.5 Sedimentological and stratigraphical data for trench 3 at Sekhokong Site 1 170 6.6 Grain size distributions for the sediment from trench 1, Sekhokong Site 1 171 6.7 Grain size distributions for the sediment from trench 2, Sekhokong Site 1 172 6.8 Grain size distributions for the sediment from trench 3, Sekhokong Site 1 173 6.9 Clast orientation, dip and contouring at trenches 1, 2 and 3 at Sekhokong Site 1 177 6.10 Till fabric using eigenvalue data for the Sekhokong Site 1 deposit 178 6.11 Triangular plot of normalised eigenvalues for the Sekhokong Site 1 deposit 179 6.12 Triangular diagrams for clasts in trenches 1, 2 and 3 respectively at Sekhokong Site 1 180 6.13 Isolines of the Oblate-prolate index for trenches 1, 2 and 3 respectively at Sekhokong Site 1 181 6.14 Isolines of the maximum projection sphericity for trenches 1, 2 and 3 respectively at Sekhokong Site 1 183 6.15 Graphs representing visual roundness of clasts in trenches 1 (A), 2 (B) and 3 (C) at Sekhokong Site 1 184 6.16 An example of plane voids in trench 3 at 125 cm depth taken in XPL 187 6.17 Single crystals within groundmass at Sekhokong Site 1, trench 3, taken in XPL 188 6.18 Rotation structures within trench 3 at 125 cm depth 189 6.19 The Sekhokong Site 2 slope deposit 192 6.20 Morphological map of the Sekhokong Site 2 deposit 193 6.21 Sedimentological and stratigraphical data for trench 1 at Sekhokong Site 2 194 6.22 Sedimentological and stratigraphical data for trench 2 at Sekhokong Site 2 194 6.23 Sedimentological and stratigraphical data for trench 3 at Sekhokong Site 2 195 6.24 Grain size distributions for the sediment from trench 1, Sekhokong Site 2 197 6.25 Grain size distributions for the sediment from trench 2, Sekhokong Site 2 198 6.26 Grain size distributions for the sediment from trench 2, Sekhokong Site 2 199 6.27 Clast orientation, dip and contouring at trenches 1, 2 and 3 at Sekhokong Site 2 202 6.28 Till fabric using eigenvalue data for the Sekhokong Site 2 deposit 203 xviii 6.29 Triangular plot of normalised eigenvalues for the Sekhokong Site 2 deposit 204 6.30 Triangular diagrams for clasts in trenches 1, 2 and 3 respectively at Sekhokong Site 2 205 6.31 Isolines of the Oblate-prolate index for trenches 1, 2 and 3 respectively at Sekhokong Site 2 206 6.32 Isolines of the maximum projection sphericity for trenches 1, 2 and 3 respectively at Sekhokong Site 2 208 6.33 Graphs representing visual roundness of clasts in trenches 1 (A), 2 (B) and 3 (C) at Sekhokong Site 2 209 6.34 Coarse material with very little fine fractions taken in PPL in trench 3 at 150 cm depth 212 7.1 The Leqooa Valley western slope deposit 216 7.2 The Leqooa Valley eastern slope deposit 216 7.3 Morphological map of the Leqooa Valley deposits 217 7.4 Sedimentological and stratigraphical data for trench 1 of the western slope deposit, Leqooa Valley 219 7.5 Sedimentological and stratigraphical data for trench 2 of the western slope deposit, Leqooa Valley 219 7.6 Sedimentological and stratigraphical data for trench 3 of the western slope deposit, Leqooa Valley 220 7.7 Sedimentological and stratigraphical data for trench 1 of the eastern slope deposit, Leqooa Valley 221 7.8 Sedimentological and stratigraphical data for trench 2 of the eastern slope deposit, Leqooa Valley 221 7.9 Sedimentological and stratigraphical data for trench 3 of the eastern slope deposit, Leqooa Valley 222 7.10 Grain size distributions for the sediment from the trench 1 of the western slope deposit 223 7.11 Grain size distributions for the sediment from the trench 2 of the western slope deposit 224 7.12 Grain size distributions for the sediment from the trench 3 of the western slope deposit 225 7.13 Grain size distributions for the sediment from the trench 1 of the eastern slope deposit 229 7.14 Grain size distributions for the sediment from the trench 2 of the eastern slope deposit 230 7.15 Grain size distributions for the sediment from the trench 3 of the eastern slope deposit 231 7.16 Clast orientation, dip and contouring at trenches 1, 2 and 3 at the western slope deposit, Leqooa Valley 235 7.17 Till fabric using eigenvalue data for the western slope deposit 236 7.18 Triangular plot of normalised eigenvalues for the western slope deposit 237 7.19 Clast orientation, dip and contouring at trenches 1, 2 and 3 at the eastern slope deposit, Leqooa valley 238 7.20 Till fabric using eigenvalue data for the eastern slope deposit 240 7.21 Triangular plot of normalised eigenvalues for the eastern slope deposit 241 7.22 Triangular diagrams for clasts in trenches 1, 2 and 3 respectively at the western slope deposit 242 xix 7.23 Isolines of the Oblate-prolate index for trenches 1, 2 and 3 respectively at the western slope deposit 243 7.24 Isolines of the maximum projection sphericity for trenches 1, 2 and 3 respectively at the western slope deposit 244 7.25 Graphs representing visual roundness of clasts in trenches 1 (A), 2 (B) and 3 (C) at the western slope deposit 245 7.26 Triangular diagrams for clasts in trenches 1, 2 and 3 respectively at the eastern slope deposit 248 7.27 Isolines of the Oblate-prolate index for trenches 1, 2 and 3 respectively at the eastern slope deposit 249 7.28 Isolines of the maximum projection sphericity for trenches 1, 2 and 3 respectively at the eastern slope deposit 250 7.29 Graphs representing visual roundness of clasts in trenches 1 (A), 2 (B) and 3 (C) at the eastern slope deposit 251 7.30 Clay capping on clast in trench 2 taken in XPL 255 7.31 Examples of rotational structures about clasts 256 7.32 Silt cappings and coarse material within trench 3 taken in PPL 258 8.1 The colluvial deposits along the south-facing slopes of the Sehonghong River 262 8.2 Morphological map of the Sehonghong River Valley deposits 264 8.3 Site 1 along the Sehonghong River 265 8.4 Site 2 along the Sehonghong River 265 8.5 Site 3 along the Sehonghong River 266 8.6 Sedimentological and stratigraphical data for Site 1 along the Sehonghong River 267 8.7 Sedimentological and stratigraphical data for Site 2 along the Sehonghong River 268 8.8 Sedimentological and stratigraphical data for Site 3 along the Sehonghong River 269 8.9 Grain size distributions for the sediment from Site 1 along the Sehonghong River 271 8.10 Grain size distributions for the sediment from Site 2 along the Sehonghong River 272 8.11 Grain size distributions for the sediment from Site 3 along the Sehonghong River 273 8.12 Clast orientation, dip and contouring at Sites 1, 2 and 3 at Sehonghong 277 8.13 Till fabric using eigenvalue data for the Sehonghong River deposits 278 8.14 Triangular plot of normalised eigenvalues for the Sehonghong River deposits 279 8.15 Triangular diagrams for Trenches 1, 2 and 3 respectively at Sehonghong 280 8.16 Isolines of the Oblate-prolate index for Sites 1, 2 and 3 respectively at Sehonghong 281 8.17 Isolines of the maximum projection sphericity for Sites 1, 2 and 3 respectively at Sehonghong 283 8.18 Graphs representing visual roundness of clasts (after Powers, 1953) at Site 1 (A), 2 (B) and 3 (C) at Sehonghong 284 8.19 Silt capping encircling basal grain taken in PPL at Sehonghong Site 1 289 8.20 Clay coatings at Sehonghong Site 2 taken in XPL 289 8.21 Clay coatings at Sehonghong Site 2 taken in XPL 290 8.22 The site stratigraphy and Radiocarbon dates for the exposure at Site 3 290 xx 8.23 Mean monthly temperatures for Nhlangeni for the period 2000 to 2002 292 9.1 A plan view and a longitudinal cross section of the Sekhokong Site 2 deposit showing waves 296 9.2 Debris deposits in the Drakensberg at Njesuthi 296 9.3 Solifluction lobes on the Drakensberg 299 9.4 An example of where a potential terrace has been separated by tributary entrenchment on the south-facing slope at Sehonghong 303 9.5 Typical grain size distributions for supraglacial debris compared to an example at Tsatsa-La-Mangaung 324 9.6 Co-variance plot of C40 and RA indexes and sediment envelopes in comparison to the three trenches at the Tsatsa-La-Mangaung deposit 324 9.7 The grain-size distribution of subglacially transported debris, composed of three distinct populations compared to an example at Sekhokong Site 1 327 9.8 Co-variance plot of C40 and RA indexes and sediment envelopes in comparison to the three trenches at the Sekhokong Site 1 deposit 328 9.9 Co-variance plot of C40 and RA indexes and sediment envelopes in comparison to the three trenches at the Leqooa Valley deposits 335 9.10 Grain-size curves for Sekhokong Site 1 and 2 compared to Beskow?s (1935) frost susceptibility criteria 338 9.11 Ternary plot of sand-silt-clay for the matrix component of the Sehonghong Site 1 and 2 deposit compared to the textural envelope for active solifluction 342 9.12 Ternary plot of sand-silt-clay for the matrix component of the Sehonghong Site 3 deposit compared to the textural envelope for active solifluction 344 9.13 A view of the Sehonghong Site 3 346 10.1 A 20 year temperature record for Shaleburn 353 10.2 A 25 year precipitation record for Himeville 356 10.3 Plotting of the high Drakensberg LGM palaeoclimates for the Tsatsa-La- Mangaung, Sekhokong and Leqooa Valley sites, with the best-fit climate curve for the ELA of 70 glaciers 357 10.4 Plotting of the high Drakensberg LGM palaeoclimates for the Nhlangeni south-facing slope, with the best-fit climate curve for the ELA of 70 glaciers 359 10.5 Plotting of the high Drakensberg LGM palaeoclimates for the Nhlangeni north-facing slope, with the best-fit climate curve for the ELA of 70 glaciers 360 10.6 The reconstructed three-dimensional form of the possible palaeoglacier at Tsatsa-La-Mangaung 362 10.7 The reconstructed three-dimensional form of the possible palaeoglacier at Sekhokong Site 1 363 10.8 The reconstructed three-dimensional form of the possible palaeoglacier at Sekhokong Site 2 363 10.9 The reconstructed three-dimensional form of the possible palaeoglacier at Leqooa Valley 364 10.10 Surface wind roses for Sani Top 369 10.11 Schematic drawing showing the Drainage area (D) above the temperature- precipitation-wind equilibrium-line altitude (TPW-ELA) and the corresponding Accumulation zone (A) of a cirque Glacier 370 10.12 Potential snowblow areas for each former glacier 371 xxi 10.13 Polar plots of snowblow area and orientation for each Palaeoglacier 372 10.14 Mean monthly solar radiation on a north and south-facing slope at Nhlangeni 377 10.15 Solar radiation for the north and south-facing slope at Nhlangeni for various times of day 379 10.16 An example of afternoon cloud cover, covering Kibo on a south-western facing slope at 3950 m a.s.l 382 10.17 Map indicating areas of shade at different times of the day and year at Tsatsa-La-Mangaung 384 10.18 Map indicating areas of shade at different times of the day and year at Sekhokong Site 1 385 10.19 Map indicating areas of shade at different times of the day and year at Sekhokong Site 2 386 10.20 Map indicating areas of shade at different times of the day and year at Leqooa Valley 387 10.21 Map indicating areas of shade at different times of the day and year at Sehonghong 389 10.22 A comparison of direct sunlight reaching slopes at Leqooa Valley during the winter solstice 390 10.23 A real life colour composite image for the 3rd August 1990 391 10.24 A real life colour composite image for the 19th August 1990 392 10.25 DEM of the position of the palaeoglaciers in relation to each other 395 11.1 Linear deposits identified from areas of late-lying snow cover in the Drakensberg 401 xxii List of Tables 2.1 A review of the literature for southern African high mountain environments, for each process mechanism presented in this research 13 2.2 Classification and characteristics of the major types of mass movement 15 2.3 Summary of clast-fabric data for specific landforms 18 2.4 Summary of the characteristics of particle shape for the various process origins 19 2.5 Typical depth/length (D/L) ratios and limiting (threshold) slope inclinations for landslides in soils 24 2.6 Summary of the main sedimentary characteristics of the main types of till 51 2.7 Criteria for the identification of gravity flow till 52 2.8 Suggested ?diagnostic? criteria indicating a pronival rampart rather than a moraine origin 60 2.9 The different glaciations for Mount Kenya 72 2.10 A summary of the timing of the LGM around the southern Hemisphere 82 3.1 Average composition of Lesotho Formation Basalt 87 3.2 The climatic reconstruction for southern Africa with time 101 4.1 Qualitative scheme for induration (hardness) 109 4.2 List of maximum permissible sieving loadings 115 4.3 Phi-unit to millimetre/micrometer conversion table 116 4.4 Effect of latitude and season on the fortnightly mean day length 130 5.1 Particle size statistical values for the Tsatsa-La-Mangaung slope deposit 143 5.2 Further particle size statistical values for the Tsatsa-La-Mangaung slope deposit 144 5.3 Verbal scale for standard deviation (sorting), Skewness and Kurtosis 145 5.4 Mean and standard deviation for the particle size statistical analysis at the Tsatsa-La-Mangaung slope deposit 145 5.5 Particle size statistical values for the Tsatsa-La-Mangaung pits 148 5.6 Further particle size statistical values for the Tsatsa-La-Mangaung pits 149 5.7 The percentage of clasts falling within the various shape categories at Tsatsa-La-Mangaung 154 5.8 The shape of clasts measured at the Tsatsa-La-Mangaung slope deposit 155 5.9 The percentage of clasts falling in the roundness categories at Tsatsa- La-Mangaung 157 5.10 The statistical significance calculated by the t-test of the shape of clasts sampled in the three trenches in the Tsatsa-La-Mangaung deposit 158 5.11 Micromorphological description of the Tsatsa-La-Mangaung samples 159 5.12 AMS and calibrated ages for the Tsatsa-La-Mangaung deposit 164 5.13 A summary of the sedimentary characteristics at Tsatsa-La-Mangaung 164 6.1 Particle size statistical analysis for the Sekhokong Site 1 deposit 174 6.2 Further particle size statistical values for Sekhokong Site 1 175 6.3 Mean and standard deviation for the particle size statistical analysis at Sekhokong Site 1 176 6.4 The percentage of clasts falling within the various shape categories at Sekhokong Site 1 180 xxiii 6.5 The shape of clasts measured at the Sekhokong Site 1 slope deposit 182 6.6 The percentage of clasts falling in the roundness categories at Sekhokong Site 1 184 6.7 The statistical significance calculated by the t-test of the shape of clasts sampled in the three trenches in the Sekhokong Site 1 deposit 185 6.8 The statistical significance calculated by the t-test of the shape of clasts sampled in the three trenches in the Tsatsa-La-Mangaung and Sekhokong Site 1 deposits 185 6.9 Micromorphological description of the Sekhokong Site 1 samples 186 6.10 AMS and calibrated ages for the Sekhokong Site 1 deposit 190 6.11 A summary of the sedimentary characteristics at Sekhokong Site 1 190 6.12 Particle size statistical analysis for Sekhokong Site 2 200 6.13 Further particle size statistical values for Sekhokong Site 2 201 6.14 Mean and standard deviation for the particle size statistical analysis at Sekhokong Site 2 201 6.15 The percentage of clasts falling within the various shape categories at Sekhokong Site 2 205 6.16 The shape of clasts measured at the Sekhokong Site 2 slope deposit 208 6.17 The percentage of clasts falling in the roundness categories at Sekhokong Site 2 209 6.18 The statistical significance calculated by the t-test of the shape of clasts sampled in the three trenches in the Sekhokong Site 2 deposit 209 6.19 The statistical significance calculated by the t-test of the shape of clasts sampled in the three trenches in the Tsatsa-La-Mangaung and Sekhokong Site 1 deposits 210 6.20 Micromorphological description of the Sekhokong Site 2 samples 211 6.21 AMS and calibrated ages for the Sekhokong Site 2 deposit 213 6.22 A summary of the sedimentary characteristics at Sekhokong Site 2 213 7.1 Particle size statistical analysis for western slope deposit 226 7.2 Further particle size statistical analysis for the western slope deposit 228 7.3 Mean and Standard deviation for the particle size statistical analysis for the western slope deposit 228 7.4 Particle size statistical analysis for the eastern slope deposit 232 7.5 Further particle size statistical analysis for the eastern slope deposit 233 7.6 Mean and Standard deviation for the particle size statistical analysis of the eastern slope deposit 233 7.7 The percentage of clasts falling within the various shape categories for the western slope deposit 242 7.8 The shape of clasts measured at the Leqooa western slope deposit 243 7.9 The percentage of clasts falling in the roundness categories at the western slope deposit 245 7.10 The statistical significance calculated by the t-test of the shape of clasts sampled in the three trenches in the western slope deposit 246 7.11 The statistical significance calculated by the t-test of the shape of clasts sampled in the three trenches for the western slope deposit, Tsatsa-La-Mangaung and Sekhokong Sites 1 and 2 deposits 246 7.12 The percentage of clasts falling within the various shape categories for the eastern slope deposit 248 7.13 The shape of clasts measured at the Leqooa eastern slope deposit 249 xxiv 7.14 The percentage of clasts falling in the roundness categories at the eastern slope deposit 251 7.15 The statistical significance calculated by the t-test of the shape of clasts sampled in the three trenches 252 7.16 The statistical significance calculated by the t-test of the shape of clasts sampled in the three trenches for the eastern slope deposit, western slope deposit, Tsatsa-La-Mangaung and Sekhokong Sites 1 and 2 deposits in the eastern slope deposit 253 7.17 Micromorphological description of the Leqooa western deposit samples 254 7.18 Micromorphological description of the Leqooa eastern deposit samples 257 7.19 AMS and calibrated ages for the Leqooa Valley deposits 260 7.20 A summary of the sedimentary characteristics at the Leqooa western deposit 260 7.21 A summary of the sedimentary characteristics at the Leqooa eastern deposit 261 8.1 Particle size statistical values for the Sehonghong River deposits 274 8.2 Further particle size statistical values for the Sehonghong River deposits 275 8.3 Mean and Standard deviation for the particle size statistical analysis at the Sehonghong River deposits 275 8.4 The percentage of clasts falling within the various shape categories at the Sehonghong Site 282 8.5 The shape of clasts measured at Sehonghong 283 8.6 The percentage of clasts falling in the roundness categories at Sehonghong 284 8.7 The statistical significance calculated by the t-test of the shape of clasts sampled at the three Sehonghong Sites 285 8.8 The statistical significance calculated by the t-test of the shape of clasts sampled at the three sites at Sehonghong, compared to those for the Tsatsa-La-Mangaung, Sekhokong Sites 1 and 2 and Leqooa western and eastern deposits 286 8.9 Micromorphological description of the Sehonghong samples 287 8.10 Radiocarbon dates for Sehonghong Site 3 deposit 291 8.11 Mean annual air temperatures at Nhlangeni during the period 2000 to 2002 293 8.12 A summary of the sedimentary characteristics at Sehonghong 294 9.1 Suitability of geomorphic processes and landform types for the various Tsatsa-La-Mangaung deposit attributes 321 9.2 Suitability of geomorphic processes and landform types for the various Sekhokong Site 1 deposit attributes 326 9.3 Suitability of geomorphic processes and landform types for the various Sekhokong Site 2 deposit attributes 330 9.4 Suitability of geomorphic processes and landform types for the various Leqooa western deposit attributes 333 9.5 Suitability of geomorphic processes and landform types for the various Leqooa eastern deposit attributes 333 9.6 Suitability of geomorphic processes and landform types for the various Sehonghong Sites 1 and 2 south-facing deposit attributes 337 xxv 9.7 Suitability of geomorphic processes and landform types for the Sehonghong Site 3 upper unit north-facing deposit attributes 343 9.8 Suitability of geomorphic processes and landform types for the Sehonghong Site 3 lower unit north-facing deposit attributes 343 9.9 A summary table of the radiocarbon and calibrated ages for the study sites 348 10.1 Summer temperature data for Sani Top 352 10.2 Summer temperature data for Nhlangeni south-facing slope 354 10.3 Summer temperature data for Nhlangeni north-facing slope 354 10.4 Ablation for each contour interval at Tsatsa-La-Mangaung, Sekhokong Sites 1 and 2 and Leqooa Valley 365 10.5 Derived mass-balance characteristics at the four sites investigated 366 10.6 Values of potential snowblow for each 90? sector 374 10.7 D/A ratios for the four sites 374 10.8 Mean monthly solar radiation values for a north and south-facing slope at Nhlangeni 378 10.9 Solar radiation values for a north-facing slope at Nhlangeni at various times of the day 380 10.10 Solar radiation values for south-facing slope at Nhlangeni at various times of the day 380 11.1 A Summary of similar ELAs to those observed for the Drakensberg in East Africa and the southern hemisphere 399