The Makgadikgadi Pans in northern Botswana are the desiccated relicts of a former major inland lake system, with fossil shorelines preserved at five distinct elevations (~995 m, 945 m, 936 m, 920 m and 912 m). These lakes persisted in the Makgadikgadi Basin, which evolved in the Okavango-Makgadikgadi Rift Zone: the south-western extension of the East African Rift System (EARS) into northern Botswana. This paper synthesizes cross-disciplinary evidence, which reveals that the antiquity of this lake complex has been widely underestimated. It presents a Regional Drainage Evolution Model that invokes tectonically initiated drainage reorganizations as the underlying control over lake evolution. Lake formation was initiated by rift-flank uplift along the Chobe Fault, across the course of the Zambezi River, which diverted the regional drainage net into the Makgadikgadi Basin. Filling of the basin initiated a major climatic feedback mechanism that locally increased rainfall and lowered evaporation rates. This progressively enhanced water input to the basin, and most likely led to overtopping of the Chobe Horst barrier during the three highest lake stands, with outflow into the Zambezi River. During this period, the hydrology of the basin would have been closely analogous to modern, shallow Lake Victoria. Fragmentation of the regional drainage network by successive river captures resulted in sequential contractions of the lake to lower elevation shorelines. In turn, resultant decreases in areas of these successive lakes modulated the magnitude of the feedback mechanism. Thus, loss of the Upper Chambeshi catchment caused the lake to drop from the 990 to the 945 m level. Severance of the former link between the Kafue and Zambezi resulted in a further drop to the 936 m shoreline. Inflow declined further after the impoundment of a major lake (Palaeo-Lake Bulozi) on the Upper Zambezi River, causing contraction to the 920 m shoreline. Continued incision of the Zambezi channel into the Chobe horst barrier ultimately terminated input from this river to the Makgadikgadi depression, causing contraction of the lake below 920 m, sustained by the Cuando and Okavango prior to final desiccation. This Regional Drainage Evolution Model contradicts previous proposals that have invoked Late Pleistocene climatic forcing to explain inferred fluctuations in lake levels. The timeframe developed for the drainage reorganizations requires that the lake was initiated by ~1.40 to 0.51 Ma at the most recent (Early – Mid-Pleistocene), while archaeological evidence shows that it had contracted below the 936 m shoreline before 500 ka. This contrasts with 14C and quartz luminescence dates (generally <100 ka), which require that the 945 m lake stage was extant during much of the Upper Pleistocene. The calcareous radiocarbon dates reflect multiple episodes of calcrete formation, while the young luminescence dates are ascribed to the extensive bioturbation of older Kalahari landforms.
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... The rugged relief allows for the isolation of some river sections upstream of the falls (Figure 1) and the, at least partially, resulting habitat diversity provides favourable conditions for the occurrence of a diverse ichthyofauna in the UNP. In addition, earlier contacts between the Upper Lualaba and other neighbouring river basins [68,69] may have enriched its species diversity as illustrated for other parts of the Upper Congo Basin, such as the Luongo River [70] and the Luapula River [71] (see below). ...
... This might well be evidenced by, for instance, the presence of Heterotis niloticus in the Upper Lualaba as a result of recent upstream dispersal, although local introduction cannot be excluded. For a long time, the Gates of Hell were considered a physical barrier between the Upper Lualaba and Upper Congo ecoregions [11,69,76]. ...
... It is observed that families such as Citharinidae, Clupeidae, Eleotridae, Latidae, Malapteruridae, etc., do not cross physical barriers such as the Kyubo Falls delimiting the Lower from the Middle Lufira River and the rapids on the Lualaba upstream of Bukama. This confirms the first observations [16,69,90] [97]. However, details as to the nature of the connectivity are lacking at present as it might be solely due to the land-walking capacity of C. gariepienus [73], and/or seasonal connections during high water or even the capture of headwater streams in either direction. ...
Citation: Katemo Manda, B.; Snoeks, J.; Chocha Manda, A.; Abwe, E.; Mukweze Mulelenu, C.; Ilunga Kayaba, M.K.; Kiwele Mutambala, P.; Ngoy Kalumba, L.; Vreven, E.J.W.M.N. Abstract: An annotated checklist of the ichthyofauna of the Upemba National Park, draining part of the Upper Lualaba basin and situated in the southern part of the Democratic Republic of the Congo, is presented, based on a literature review, a re-examination of museum collections, and a study of recent collections (2012-2020). In total, 247 native and 1 introduced species, Heterotis niloticus, are reported. The native species belong to 78 genera, 26 families, and 15 orders. Of these, 45 species (18%) are endemic to the park, 35 species (14%) await formal description, and 5 taxa (2%) need further study to clarify their status. With 51 species, the Cyprinidae is by far the most species-rich family, followed by the Mormyridae (26), Mochokidae (26), Alestidae (18), Distichodontidae (18), Amphiliidae (17), and Cichlidae (16). The remaining families are represented by less than 15 species. Comments about the species distribution and the fish fauna shared with adjacent ecoregions are provided. Although the park provides some protection for the fish species living within its borders by limiting human access to the core zone, the annex and buffer zones are both subject to strong anthropogenic pressure. These observations underscore the need for the implementation and further elaboration of fish-related preservation guidelines and plans to enable better protection/conservation of the park's ichthyofauna.
... However, the potential influence of hydrothermal springs on the sedimentology of the Chobe-Linyanti sub-basin was never mentioned. Furthermore, the hydrological system of northern Botswana and its history through the Quaternary are complex (Nugent, 1990;Moore et al., 2012). In this context, the settings that governed the precipitation of sepiolite might provide interesting evidence on the paleo-environmental system of the Chobe Enclave during the Quaternary (Fig. 2). ...
... In the present day, the main origin of water flowing to the Chobe Enclave is sourced from the watersheds located in the equatorial Angolan highlands and Zambia. Water is provided to the south by three main rivers: 1) the Kwando-Linyanti, 2) the Cuito spilling in the Okavango from the Angola watershed, and 3) the Zambezi from the Zambia watershed (Moore et al., 2012;Fig. 1). ...
... The Pleistocene refuge theory states that maintaining habitat patches in South Africa enabled large mammal persistence through repeated ice ages and promoted the divergence between populations [69]. Southwest Botswana and northwest South Africa underwent a period of intense aridification from about 2.5 to 1.7 mya, during which sand dunes were repositioned across the Makgadikgadi Palaeo-lake [70]. We expect that this caused the historical isolation of the Kalahari-Namibian-Cape region (Figure 1), which has been well-documented in other African taxa [33,71]. ...
Revealing phylogeographic structure is important for accurate subspecies delineation and understanding a species’ evolutionary history. In leopards (Panthera pardus), there are currently nine subspecies recognized. On the African continent, only one subspecies occurs (P. p. pardus), although mitochondrial DNA from historical samples suggests the presence of three putative continental clades: (1) West Africa (WA), (2) Central Africa (CA), and (3) Southern Africa (SA). So far, whole genome data did not recover this phylogeographic structure, although leopards in the southern periphery of their distribution range in Africa have not yet been investigated in detail. The Mpumalanga province of South Africa is of particular interest, as here, the CA and the SA clade possibly meet. The aim of this study was to characterize the first mitogenomes of African leopards from Mpumalanga, to help clarifying how South African leopards fit into continental patterns of genetic differentiation. Complete mitogenomes from nine leopards, including a strawberry leopard, were assembled de novo and included in phylogenetic analysis, in combination with 32 publicly available mitogenomes. Bayesian inference and maximum likelihood analyses identified two deeply diverged putative clades within South Africa, which were more genetically distinct than two subspecies in Asia. The clades dated back to 0.76-0.86 million years ago, indicating that they originated during the climatically unstable Mid-Pleistocene, as seen in other large mammals. The Pleistocene refuge theory states that the maintenance of savanna refugia in East and Southern Africa promoted the divergence between populations. As such, leopards may reflect the unique climatic history of southern Africa, which has resulted in eminent and endemic genetic diversity.
... It highlights two 39 pronounced stages of landscape development, with the most recent major deformation event in (Harvey, 2002;Blair and McPherson, 2009). Extensive research has been performed to 66 study their morphologies, involved processes and mechanisms, as well as the components within 67 the system (e.g., nature of sediments, vegetation, lithology) and to reconcile the respective roles 68 of climate and tectonics in their formation (Lustig, 1965;Hooke, 1967 as the ORZ is bordered by eolian dunes and was subjected to varying zonal climatic interactions 83 (Partridge, 1993;Shaw and Thomas, 1988;Burrough and Thomas, 2013), chronological 84 constraints of landscape evolution that precede the most recent eolian deposition stages are rare 85 (Moore et al., 2012;McCarthy, 2013;Vainer et al., 2021). Therefore, as favored in other regions 86 and settings where recent and earlier fans were studied and compared (DeCelles and Cavazza, 87 1999; Harvey et al., 2005), an investigation of previous phases of landscape development along 88 the ORZ is required. ...
The Kalahari Basin in southern Africa, shaped by subsidence and epeirogeny, features the Okavango Rift Zone (ORZ) as a significant structural element characterized by diffused extensional deformation forming a prominent depocenter. This study elucidates the Pleistocene landscape evolution of the ORZ by examining the chronology of sediment formation and filling this incipient rift and its surroundings.
Modeling of cosmogenic nuclide concentrations in surficial eolian sand from distinct structural blocks around the ORZ provides insights into sand’s residence time on the surface. Sand formation occurred from ~2.2 to 1.1 Ma, coinciding with regional tectonic events. Notably, provenance analyses of sand within ORZ’s lowermost block where large alluvial fans are found indicate different source rocks and depositional environments than those of the more elevated eolian sand. This suggests that the major phase of rift subsidence and the following incision of alluvial systems into the rift occurred after eolian dune formation. Luminescence dating reveals that deposition in alluvial fan settings in the incised landscape began not later than ~250 ka, and that a lacustrine environment existed since at least ~140 ka.
The established chronological framework constrains the geomorphological effects of the different tectono-climatic forces that shaped this nascent rifting area. It highlights two pronounced stages of landscape development, with the most recent major deformation event in the evolving rift probably occurring during the middle Pleistocene transition (1.2-0.75 Ma). This event is reflected as a striking change in the depositional environments due to the configurational changes accompanying rift progression.
... It is a huge basin of internal drainage, wherein aeolian, fluvial and palustrine sediments have accumulated since the late Cretaceous (Grove, 1969). The present-day Chobe Enclave is under the influence of: (i) the Congo Air Boundary (CAB) and Intertropical Convergence Zone (ITCZ), which are major tropical air mass convergence systems; (ii) three main river systems of the Okavango, Kwando-Linyanti, and the Zambezi-Chobe which bring waters from the equatorial Angolan highlands, and (iii) tectonics, given that the local fault system is an extension of the East African Rift Zone (Moore et al., 2012). Therefore, Chobe Enclave owes it geomorphic properties to the complex Quaternary palaeohydrological dynamics influenced by both climate and/or tectonic changes (Diaz et al., 2016). ...
The importance of pedogenesis in understanding soil distribution patterns in current and past geologic periods is well established, but field identification of pedogenic features is always a big challenge in pedostratigraphic units because of post burial alterations. An ~ 8 m landform presents a complete pedostratigraphic section at Chobe Enclave alluvial plain, northern Botswana. This study investigated pedological indices including morphological, physico-chemical, geochemical and mineralogical properties of the landform, with the aim of reconstructing the palaeoenvironments and palaeoclimate during the evolution of the landform. SiO2 is the dominant elemental oxide (40.6–98.9 wt%) followed by CaO (0.02–29.6 wt%), Fe2O3 (0.48–2.64 wt%), MgO (0.14–1.81 wt%) and Al2O3 (0.29–0.93 wt%). The clay-sized minerals present are quartz, calcite, sepiolite and kaolinite. The carbonates had strong positive correlation with Sr (R² = 0.935), while Fe2O3 had weak positive correlation with TiO2 (R² = 0.0187). Gradual obliteration of the sedimentary layers and the formation of indurated illuvial horizon indicate secondary recrystallisation of the palustrine carbonates. There is evidence of two cyclic intervals that produced specific two pedostratigraphic levels and two soil orders—Entisols and Calcisols, and therein pedofeatures and geochemical variations suggest long-term climate change, i.e. from wet to dry in the Chobe Enclave in the late Quaternary. This study has presented a new calibration of the Chobe Enclave landform to include pedogenic horizons instead of a sedimentary bed of palustrine carbonate deposit lying over fine sediments in a fluvial system, as previously documented.
The temporal coupling of the structural evolution of the Kalahari Basin and the accumulation of the Kalahari Group sediments has been an accepted paradigm leading to the assumption that the Kalahari group sediments have been accumulating gradually since the mid-Cretaceous. Here we review the first actual ages for the Kalahari Group based on cosmogenic ages from six geological localities. These results demonstrate that Kalahari Basin infill was a more dynamic process than previously thought and that the Kalahari Group sediments are mostly Plio-Pleistocene in age (∼4 Ma to 1–2 Ma). The hiatus between the initial structural subsidence of the basin, during the Cretaceous, and the general young age of the investigated sediments, implies a dynamic landscape in which significant phases of erosion occurred during the Mesozoic and Cenozoic. The magnitude of erosion is manifested by the fact that in many locations Kalahari Neogene to Quaternary sediments overlie Precambrian basement.
The age of the present infill of the Kalahari thus falls within the temporal range of the genus Homo. In light of this new understanding, we provide a review of the archaeological evidence from the Kalahari Basin and along its southern fringe. Initial hominin presence is found at Wonderwerk Cave during the Olduvai Event and there is subsequent high-density occupation along the southern fringe of the Kalahari Basin during the Acheulean and the Fauresmith. Middle Stone Age occupation is limited to localities of limited size and small artifact counts and it appears that the focus of human occupation, particularly in the later stages of the Middle Stone Age, shifts southward, including along the coastal regions.
The Southwestern Branch of the East African Rift System propagates through the Central and Southern African plateaus and ends in the Okavango Makgadikgadi Zambezi Basin. This basin hosts the Okavango Graben and the Eiseb Graben, considered as the terminus of the Southwestern Branch of the rift. To the southeast, the Makgadikgadi Basin is affected by a series of normal faults forming the Makgadikgadi Rift Zone (MRZ) which regional geodynamic significance remains unclear. Based on fieldwork and geomorphic analysis, we revisited the geomorphological features associated with paleolakes and the fault pattern within the Makgadikgadi Basin to better constrain the dynamics of the MRZ. Fault scarps and offsets along linear dunes show normal‐dip kinematics of faults, indicating a NW‐SE extension direction in the area. Furthermore, lacustrine shorelines in the basin are undeformed, proving that they post‐date the fault activity. The previously published ages of these shorelines demonstrate that the MRZ currently has a low tectonic activity. Integrated in the geodynamic framework of the region, these results suggest that present‐day deformation shifts toward the Okavango Graben north of the MRZ. We therefore propose a “zip‐opening” model to explain the propagation of the Southwestern Branch of the East African Rift System where the tip of the system progressively progresses southwestward, driven by motions of the continental plates.
Revealing phylogeographic structure is important for accurate subspecies delineation and understanding a species’ evolutionary history. In leopards ( Panthera pardus ), there are currently nine subspecies recognized. On the African continent, only one subspecies occurs ( P. p. pardus ), although historic mitochondrial DNA suggests the presence of three putative continental lineages: (1) West Africa (WA), (2) Central Africa (CA), and (3) Southern Africa (SA). So far, genome-wide data did not recover this phylogeographic structure, although leopards in the southern periphery of their distribution range in Africa have not yet been investigated in detail. The Mpumalanga province of South Africa is of particular interest, as here the CA and the SA clade possibly meet. The aim of this study was to characterize the first mitogenomes of African leopards from Mpumalanga, to help clarifying how South African leopards fit into continental patterns of genetic differentiation. Complete mitogenomes from six leopards were assembled de novo and included in phylogenetic analysis, in combination with other publicly available mitogenomes. Bayesian inference and Maximum Likelihood analyses identified two deeply diverged putative lineages within South Africa, which are more genetically distinct than two subspecies in Asia. The lineages dated back to 0.73–0.87 million years ago, indicating that they originated during the climatically unstable Mid-Pleistocene, as seen in other large mammals. The Pleistocene refuge theory states that the maintenance of savanna refugia in South Africa promoted the divergence between populations. As such, leopards may reflect the unique climatic history of South Africa, which has resulted in eminent and endemic genetic diversity.
The black rhinoceros (Diceros bicornis L.) is a critically endangered species historically distributed across sub-Saharan Africa. Hunting and habitat disturbance have diminished both its numbers and distribution since the 19th century, but a poaching crisis in the late 20th century drove them to the brink of extinction. Genetic and genomic assessments can greatly increase our knowledge of the species and inform management strategies. However, when a species has been severely reduced, with the extirpation and artificial admixture of several populations, it is extremely challenging to obtain an accurate understanding of historic population structure and evolutionary history from extant samples. Therefore, we generated and analysed whole-genomes from 63 black rhinoceros museum specimens collected between 1775 and 1981. Results showed that the black rhinoceros could be genetically structured into six major historic populations (Central Africa, East Africa, Northwestern Africa, Northeastern Africa, Ruvuma and Southern Africa) within which were nested four further subpopulations (Massailand, Southwestern, Eastern Rift and Northern Rift), largely mirroring geography, with a punctuated north-south cline. However, we detected varying degrees of admixture among groups, and found that several geographical barriers, most prominently the Zambezi River, drove population discontinuities. Genomic diversity was high in the middle of the range and decayed toward the periphery. This comprehensive historic portrait also allowed us to ascertain the ancestry of 20 re-sequenced genomes from extant populations. Lastly, using insights gained from this unique temporal dataset, we suggest management strategies, some of which require urgent implementation, for the conservation of the remaining black rhinoceros diversity.
This book provides a theory to overcome the problem of identifying the principles behind the interdependence of different aspects of nature. Climate, vegetation, geology, landforms, soils, hydrology, and other environmental factors are all linked. Many scientists agree that there must be some general principles about the way in which earth surface systems operate, and about the ways in which the interactions of the biosphere, lithosphere, hydrosphere, and atmosphere manifest themselves. Yet there may be inherent limits on our ability to understand and isolate these interactions using traditional reductionist science. The argument of this book is that the simultaneous presence of order and chaos reflects fundamental, common properties of earth surface processes and systems. It shows how and why this is the case, with examples ranging from evolutionary and geological times scales to microscale examinations of process mechanics.
Some 700 000 square kilometres have been mapped by a combination of Landsat imagery, air photography, and field investigations. A contribution to the understanding of the nature of Stormberg volcanicity has been made by the observation that the major development of basalts eastwards from Kasungula in northern Botswana is in a number of basinal structures of which the largest is centred on the Zambesi River, a little downstream of the Victoria Falls. The fracture and lineament pattern of the whole of Botswana is considered briefly. The Kalahari desert covers about 70% of the country. -R.A.H.
Geomorphology is the study of the Earth’s diverse physical land surface features and the dynamic processes that shape these features. Examining natural and anthropogenic processes, The SAGE Handbook of Geomorphology is a comprehensive exposition of the fundamentals of geomorphology that examines form, process, and history in the discipline. Organized into four sections, the Handbook is an overview of foundations and relevance, including the nature and scope of geomorphology, the origins and development of geomorphology, the role and character of theory in geomorphology, the significance of models and abstractions to geomorphology; techniques and approaches, including geomorphological mapping, field observations and experimental design, remote sensing in geomorphology, quantifying rates of erosion, measuring fluid flows and sediment fluxes, dating surfaces and sediment, GIS in geomorphology, and modelling landforms and processes; process and environment, including rock weathering, the evolution of regolith, hill slopes, riverine environments, glacial environments, periglacial environments, coastal environments, desert environments, karst landscapes, environmental change and anthropogenic activity; and environmental change, including geomorphology and environmental management, geomorphology and society, and planetary geomorphology.
The recent lacustrine deposits of the Mpulungu basin were studied on the basis of sediment sampling and high-frequency seismic echograms (3.5 kHz). They are characterized by an original organization under the influence of morpho-structural and climatic factors. The lacustrine deposits are formed by 95% of organic-rich clayey material which define a deep autochthonous facies; around the coastal areas, to a depth of 150 to 200 m, allochthonous deposits are made up of sands and silts. Locally some rich-clastic layers can be interbedded in the deep mud facies resulting from temporary turbiditic events. -from Authors
