Landscapes and Landforms of Botswana (World Geomorphological Landscapes)

This volume contains 22 chapters introducing a wide range of semi-arid and geologic landscapes. Botswana, a thinly populated nation, the size of France, is a Southern African keystone country at the heart of the Kalahari, sharing some of the major sub-continental drainage basins such as the Limpopo, Zambezi, Orange, and Okavango with its neighbouring countries. The extensive Kalahari Sand surface has been sculptured by numerous past processes which have produced subtle but regional landforms consisting of extensive dunes and shorelines. Incipient rifting has created the dynamic Okavango and Makgadikgadi fan-basin systems which produces iconic wetlands with a world heritage status. Geological outcrops in particular to the east expose highly denuded basement lithologies which produces numerous inselbergs that are home to a rich archaeological heritage. The book also examines the geomorphology of mineral and water resources which sustain the economy and population and also features dedicated chapters that cover diamondiferous kimberlites, caves, pans, dams, duricrusts and wildlife. Chapter 6 is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com. Foreword Dedication to Marty McFarlane Series Editor Preface Preface Contents Editor and Contributors 1 Introduction to the Landscapes and Landforms of Botswana Abstract 1.1 The Regional Landscape of Botswana 1.2 The Geology of Botswana 1.3 The Geomorphology of Botswana 1.4 Geomorphology Taught in Botswana References 2 The Angolan Catchments of Northern Botswana’s Major Rivers: The Cubango, Cuito, Cuando and Zambezi Rivers Abstract 2.1 Introduction 2.2 Gradients 2.3 Soils 2.4 Water Chemistry 2.5 Rivers of Northern Botswana 2.5.1 Cubango River 2.5.2 Cuito River 2.5.3 Cuando River 2.5.4 Zambezi River 2.6 Recharge and Discharge 2.7 Mixing Water 2.8 Conclusion Acknowledgements References 3 The Okavango Delta Peatlands Abstract 3.1 Introduction 3.2 The Inputs and Distribution of Water in the Okavango Delta 3.3 Development of Peat in the Okavango Delta 3.3.1 Backswamp Peatlands and Vegetation Development Along the Maunachira River System 3.3.2 Channel-margin Peat Deposits and Associated Vegetation 3.3.3 Lake Inlet Peat Accumulation and Closure 3.4 Channel Abandonment and the Occurrence of Peat Fires 3.5 A Conceptual Model of Peat Formation at a System-wide Scale 3.6 Conclusion References 4 Landscape Evolution of the Lake Ngami and Mababe Depressions Within the Okavango Rift Zone, North-Central Botswana Abstract 4.1 Introduction 4.2 Geology, Tectonics and Hydrological Change 4.3 Landforms and Geomorphological Evolution 4.3.1 Lake Ngami 4.3.2 The Mababe Depression 4.3.3 Basin Lake Floor Sediments 4.4 Issues and Future Work 4.5 Conclusions Acknowledgements References 5 The Makgadikgadi Basin Abstract 5.1 Introduction 5.2 The Morphology of Makgadikgadi’s Geological History 5.3 Makgadikgadi in the Late Quaternary, the Morphological Record of Climate Change 5.3.1 Beach Ridges 5.3.2 Diatom Deposits 5.3.3 Cuspate Spits 5.3.4 Makgadikgadi ‘Islands’ 5.4 Contemporary Morphodynamics 5.5 Conclusions References 6 Landscapes and Landforms of the Chobe Enclave, Northern Botswana Abstract 6.1 Introduction 6.1.1 Where Is the Chobe Enclave and Why Is It so Interesting? 6.1.2 Topography and Climate of the Chobe Enclave 6.1.3 Hydrological Setting of the Chobe-Linyanti Basin 6.2 Geological Settings 6.2.1 Structural Context 6.2.2 Bedrock Geology 6.2.3 Surficial Sedimentary Geology 6.2.4 Insights into the Quaternary in the Chobe-Lynianti Region 6.2.4.1 Quaternary Palaeo-Lakes and the Chobe-Lynianti Region 6.2.4.2 The Carbonate Islands from the Chobe-Lynianti Region 6.3 Geomorphology and Landforms of the Northern Chobe Enclave District 6.3.1 Importance of Hydrology in Shaping Geomorphological Features 6.3.1.1 The Western Palaeo-Floodplain 6.3.1.2 The Island Area 6.3.1.3 The Eastern Floodplain Area 6.3.1.4 The Complexity of the Chobe’s Geomorphology 6.4 Landscape Components of the Chobe Enclave 6.4.1 Water in the Linyanti-Chobe Region 6.4.2 Vegetation and Soils 6.4.2.1 Floodplains 6.4.2.2 Islands 6.4.2.3 Western Palaeo-Floodplain 6.4.2.4 Baikiaea Forest 6.4.3 The Role of Termites 6.4.3.1 The Potential Impact of Termites in Savanna Ecosystems of the Chobe Enclave 6.4.3.2 Hydric Gradients Influencing FGT Activities 6.4.3.3 Termites Influence the Evolution of the Landscape 6.5 Challenges and Conclusions Acknowledgements References 7 The Chobe-Zambezi Channel-Floodplain System: Anatomy of a Wetland in a Dryland Abstract 7.1 Introduction 7.2 Geographical and Environmental Setting 7.3 Fluvial Landforms 7.4 Development of the Fluvial Landscape 7.5 Possible Future Developmental Trajectories 7.6 Conclusion Acknowledgements References 8 Dunes of the Southern Kalahari Abstract 8.1 Introduction 8.1.1 Early Work 8.2 Dune Sediments 8.3 Technological Developments: The Advent of Systematic Research on Southern Kalahari Dunes 8.4 Southern Kalahari Linear Dune Morphology and Morphometry 8.4.1 Other Dune Forms in the Southern Kalahari and Their Significance 8.5 Late Quaternary Linear Dune Accumulation in the Southern Kalahari 8.6 Dune Surface Processes and Dynamics 8.7 Dune Landscape Response to Environmental Change 8.7.1 Enhanced Sand Dune Mobilisation 8.7.2 Dunes as Emitters of Aeolian Dust 8.8 Conclusion References 9 Dunes of the Northern Kalahari Abstract 9.1 Introduction: When is a Dune Not a Dune? 9.2 Dunefield Patterns and Morphologies 9.3 Controls of Northern Dune Development in the Past 9.3.1 Airflow 9.3.2 Sediment Supply 9.3.3 Aridity 9.4 Dunefield Accumulation 9.5 Dunefield Degradation 9.6 Conclusion References 10 Kalahari Pans: Quaternary Evolution and Processes of Ephemeral Lakes Abstract 10.1 Introduction 10.2 Setting and Location 10.3 Formation of Pans 10.4 Processes in Pans 10.5 Lunette Dunes 10.6 Climatic and Environmental Records 10.7 Conclusions References 11 Dry Valleys (Mekgacha) Abstract 11.1 Introduction 11.2 Major Dry Valley Systems 11.3 Dry Valley Morphology 11.3.1 Older Accounts of Dry Valley Morphology 11.3.2 Advances Since the Advent of Radar Remote Sensing 11.4 Hydrology and Palaeohydrology 11.4.1 Contemporary and Historical Hydrology—Endorheic Valleys 11.4.2 Contemporary and Historical Hydrology – Exoreic Valleys 11.4.3 Pleistocene and Holocene Fluvial Activity 11.5 Ages of Dry Valley Networks 11.6 Theories About the Origins of Dry Valley Systems References 12 Landscape Evolution of the Stampriet Transboundary Basin and Relation to the Groundwater System: The Land of Duricrusts, Pans, Dry Valleys and Dunes, and the Relation to the Groundwater System Abstract 12.1 Introduction 12.2 Setting and Location 12.3 Geology, Hydrogeology and Water Use within the STAS 12.3.1 Geology and Hydrogeology 12.3.2 Groundwater Use and Quality 12.4 Evolution and Development of the STAS Landscape 12.4.1 Development of the Kalahari Basin 12.4.2 Main Geomorphological Components of the STAS 12.4.3 Evolution of Duricrusts, Valleys and Dunes above the STAS 12.4.3.1 Duricrust Formation 12.4.3.2 Dunefield Formation and Valley Incision 12.4.3.3 Syntheses of the Record of Dunefield Accumulation 12.4.3.4 Geomorphic Effects of the Valleys 12.4.3.5 Fluvial Sedimentary Records within the Valleys 12.5 Links between Hydrogeology and Surface Geomorphology 12.5.1 The Geomorphological Roles of Groundwater 12.5.2 Influence of Surface Geomorphology on Groundwater Recharge 12.5.2.1 Focused Recharge (Sinkholes and River Valleys) 12.5.2.2 Diffuse Recharge through Sand Dune and Sand Sheet Cover 12.6 Conclusions References 13 Calcretes, Silcretes and Intergrade Duricrusts Abstract 13.1 Introduction 13.2 Calcrete 13.2.1 Definitions 13.2.2 General Characteristics of Calcretes in the Botswana Kalahari 13.2.3 Processes of Calcrete Formation 13.3 Silcrete 13.3.1 Definitions 13.3.2 Characteristics of Silcretes in the Botswana Kalahari 13.3.3 Processes of Silcrete Formation 13.4 Silcrete-Calcrete Intergrade Duricrusts 13.4.1 Definitions 13.4.2 Processes of Silcrete-Calcrete Intergrade Duricrust Development 13.5 Determining the Age of Kalahari Duricrusts 13.6 Conclusions References 14 Geodiversity of Caves and Rockshelters in Botswana Abstract 14.1 Introduction 14.2 Geological Context 14.3 Caves in Dolomite 14.3.1 Caves in Ngamiland 14.3.2 Lobatse Caves 14.4 Caves in Siliciclastic Rocks 14.4.1 Caves and Rockshelters of the Tsodilo Hills 14.4.2 Siliciclastic Caves and Rockshelters of Southern Botswana 14.4.3 Siliciclastic Caves of Eastern Botswana 14.5 Granitic Caves of Lepokole 14.6 Conclusions Acknowledgements References 15 Kimberlites, Kimberlite Exploration, and the Geomorphic Evolution of Botswana Abstract 15.1 Introduction 15.2 Kimberlite Distribution in Botswana and Surrounding Areas 15.3 Broad Geomorphic Framework of Botswana 15.4 Kimberlites, Kimberlite Exploration, and the Geomorphic Evolution of Botswana 15.4.1 Evidence for Regional Botswana Erosion 15.4.2 Discovery of the Orapa Kimberlite Field 15.4.3 Discovery of the Jwaneng Kimberlite Field 15.4.4 Discovery of the Gope Kimberlites 15.5 Kimberlites Exploration and the Kalahari Formation 15.5.1 Evolution of the Kalahari Basin 15.6 Secondary or False Kimberlitic Indicator Mineral Anomalies 15.7 Kimberlites 15.8 Conclusions Acknowledgements References 16 Geomorphology and Landscapes of the Limpopo River System Abstract 16.1 Introduction 16.2 Physical Background 16.3 Methods 16.4 Limpopo River Analysis 16.4.1 Distribution of Channel Types 16.4.2 Examples from the Botswana Sector of the Limpopo River 16.5 The Tuli Basin 16.6 Discussion 16.6.1 Landscape Development in the Limpopo Catchment 16.6.2 Water and Flood Management in the Limpopo Catchment 16.7 Conclusions Acknowledgements References 17 Dams in Botswana: Drying Times Ahead Abstract 17.1 Introduction 17.2 Basins 17.2.1 Limpopo Basin 17.3 Dams 17.3.1 Large Dams 17.3.2 Medium and Small Dams 17.3.3 Wet and Dry Cycles 17.3.4 Sand Rivers 17.4 Key Concerns 17.4.1 Sedimentation 17.5 Sand Mining 17.5.1 Fly Dumping 17.5.2 Elephants 17.5.3 Pollution 17.5.3.1 Phytoplankton Blooms 17.5.3.2 Aquatic Weeds 17.5.4 Impact on the Morphometric Characteristics of a Catchment 17.5.5 Environmental Flows 17.5.6 Impact of Letsibogo Dam on Motloutse Flow Regime 17.6 Way Forward 17.6.1 Inter-Regional Water Management 17.7 Conclusion Acknowledgements References 18 Gorges of Eastern Botswana Abstract 18.1 Background to Gorge Formation in Botswana 18.2 Geomorphology of Gorges in the Hardveld of Botswana 18.3 Summary Acknowledgements References 19 Soil Development in the Eastern Hardveld Abstract 19.1 Introduction 19.2 Geographical/Environmental Settings 19.3 Development and Distribution of Major Reference Soils Groups 19.3.1 Classification Principles 19.3.2 Regosols 19.3.3 Arenosols 19.3.4 Luvisols 19.3.5 Lixisols 19.3.6 Cambisols 19.3.7 Calcisols (Aridisols containing soluble secondary carbonates (Calcids), Soil Taxonomy) 19.3.8 Vertisols 19.4 Palaeosols on the Eastern Hardveld 19.5 Soil–Landscape Relationships 19.6 Summary Acknowledgements References 20 The Tsodilo Hills: A Multifaceted World Heritage Site Abstract 20.1 Introduction 20.2 Environmental Setting 20.3 Geology of the Tsodilo Hills 20.3.1 Lithology, Stratigraphic Position and Age 20.3.2 Rock Complexes of the Tsodilo Hills 20.4 Geomorphic Relations in the Tsodilo Hills 20.4.1 Wind-Blown Sands 20.4.2 Upper Depressions 20.4.3 Palaeolake 20.4.4 Weathering and erosion of the Tsodilo Hills rocks 20.5 Ancient Human Activity: Mining and Rock Art 20.6 Summary References 21 Geoconservation in Botswana Abstract 21.1 Background to Geoconservation 21.2 Geoconservation in Africa 21.3 Geoconservation Potential in Botswana 21.4 Geoconservation Practice and Approaches in Botswana 21.5 Summary and Recommendations Acknowledgements References 22 Zoogeomorphology of Botswana Abstract 22.1 Introduction 22.2 Landscapes Impacting Animals 22.2.1 Palaeo Pathways 22.2.2 Changing the Nature and Scale of Zoogeomorphology 22.3 Impacts of Animals on the Landscape 22.3.1 Piospheres 22.3.2 Examples of the Impact of Animals on the Landscape 22.3.3 Termites 22.3.4 Biotic Versus Abiotic 22.4 Conclusion Acknowledgements References Index "This volume contains 22 chapters introducing a wide range of semi-arid and geologic landscapes. Botswana, a thinly populated nation, the size of France, is a Southern African keystone country at the heart of the Kalahari, sharing some of the major sub-continental drainage basins such as the Limpopo, Zambezi, Orange, and Okavango with its neighbouring countries. The extensive Kalahari Sand surface has been sculptured by numerous past processes which have produced subtle but regional landforms consisting of extensive dunes and shorelines. Incipient rifting has created the dynamic Okavango and Makgadikgadi fan-basin systems which produces iconic wetlands with a world heritage status. Geological outcrops in particular to the east expose highly denuded basement lithologies which produces numerous inselbergs that are home to a rich archaeological heritage. The book also examines the geomorphology of mineral and water resources which sustain the economy and population and also features dedicated chapters that cover diamondiferous kimberlites, caves, pans, dams, duricrusts and wildlife."--Back cover