Southeastern Botswana Research Articles

Impact of Eucalyptus camaldulensis plantation on an alluvial soil in south eastern Botswana

This paper examines the impact of a 33‐year plantation of Eucalyptus camaldulensis on an alluvial soil in Gaborone, south eastern Botswana, by comparing the soil under the plantation with similar soil under an adjoining native savanna woodland dominated by Acacia karoo. Soil clay content was significantly higher in the plantation soil in both the 0–10 cm and 10–20 cm layers. There were no significant differences between soil under the two ecosystems with respect to the levels of organic matter, exchangeable potassium and available phosphorus. Despite the higher clay contents of the plantation soil, exchangeable calcium and magnesium and pH were higher in soil under the native woodland. This suggests that E. camaldulensis immobilizes soil nutrients faster and that plantation nutrient cycles are less efficient than in the native Acacia woodland. Consequently, soil nutrient deficiency will limit plantation productivity after the first few rotations. It is important to adopt tree harvesting techniques that reduce drain on soil nutrients at the end of a plantation rotation.

Freshwater Rhabdocoela (Platyhelminthes) from Ephemeral Rock Pools from Botswana, with the Description of Four New Species and One New Genus

Four new species of freshwater rhabdocoel flatworms from ephemeral rock pools in southeastern Botswana are described and discussed. Two of them, Syringoplana kolasai n. gen. n. sp. and Mesostoma thamagai n. sp. belong to the Typhloplanidae Graff, 1905. The unique construction of the excretory system is the main characteristic of S. kolasai. M. thamagai can be separated from other Mesostoma Ehrenberg, 1837 species by the presence of a bundle of eosinophilic glands at the transition from oviduct to seminal receptacle. The other two taxa, Gieysztoria isoldeae n. sp. and G. faubeli n. sp. belong to the Dalyelliidae Graff, 1905. G. isoldeae is characterised by the presence of four separate hollow spines in the male atrium, which are connected to two accessory glandular organs. G. faubeli can be separated from other Gieysztoria Ruebush and Hayes, 1939 species by the detailed construction of the stylet. Apart from these two species the occurrence of an unidentified Microdalyellia Gieysztor, 1938 species is mentioned.

Bushveld-age magmatism in southeastern Botswana: evidence from U-Pb zircon and titanite geochronology of the Moshaneng Complex

The Moshaneng Complex (southeastern Botswana) consists of a suite of coarse-to-medium-grained gabbros, medium-grained diorites, alkali feldspar-phyric syenites, fine-grained and porphyritic granites. Field studies indicate commingling and mixing of mafic and felsic magmas leading to the production of diorites. U-Pb isotopic analyses of single zircon and titanite grains from the Moshaneng Complex granites yield a crystallisation age of 2054 ± 2 Ma, indicating the Moshaneng Complex is coeval with the Bushveld Complex of South Africa. The Bushveld-age ultramafic, mafic and felsic igneous rocks of southern Africa define a ~2.06 to ~2.05 Ga large igneous province extending from South Africa into Botswana.

AIDS as chronic illness: epidemiological transition and health care in south-eastern Botswana

This paper suggests that people in south-eastern Botswana experience the AIDS epidemic as part of a recent epidemiological transition in which rates of chronic debilitating illness have risen, even as the degree of acute infectious disease has fallen (HIV/AIDS aside). Whereas international health programmes and practitioners focus on AIDS as an acute, lethal, infectious disease, patients and care-givers experience AIDS as a set of chronic, degenerative (and deadly) conditions. This is true whether or not patients know or acknowledge their HIV status. Neither the national health system nor the Tswana medical sector (bongaka) cope well with the particular issues that chronic illnesses present. Thus, the epidemiological context of the AIDS epidemic in Botswana is critical to understanding uneven patient confidence in a comparatively robust health system.

Regional patterns in the paragenesis and age of inclusions in diamond, diamond composition, and the lithospheric seismic structure of Southern Africa

The Archean lithospheric mantle beneath the Kaapvaal–Zimbabwe craton of Southern Africa shows ±1% variations in seismic P-wave velocity at depths within the diamond stability field (150–250 km) that correlate regionally with differences in the composition of diamonds and their syngenetic inclusions. Seismically slower mantle trends from the mantle below Swaziland to that below southeastern Botswana, roughly following the surface outcrop pattern of the Bushveld-Molopo Farms Complex. Seismically slower mantle also is evident under the southwestern side of the Zimbabwe craton below crust metamorphosed around 2 Ga. Individual eclogitic sulfide inclusions in diamonds from the Kimberley area kimberlites, Koffiefontein, Orapa, and Jwaneng have Re–Os isotopic ages that range from circa 2.9 Ga to the Proterozoic and show little correspondence with these lithospheric variations. However, silicate inclusions in diamonds and their host diamond compositions for the above kimberlites, Finsch, Jagersfontein, Roberts Victor, Premier, Venetia, and Letlhakane do show some regional relationship to the seismic velocity of the lithosphere. Mantle lithosphere with slower P-wave velocity correlates with a greater proportion of eclogitic versus peridotitic silicate inclusions in diamond, a greater incidence of younger Sm–Nd ages of silicate inclusions, a greater proportion of diamonds with lighter C isotopic composition, and a lower percentage of low-N diamonds whereas the converse is true for diamonds from higher velocity mantle. The oldest formation ages of diamonds indicate that the mantle keels which became continental nuclei were created by middle Archean (3.2–3.3 Ga) mantle depletion events with high degrees of melting and early harzburgite formation. The predominance of sulfide inclusions that are eclogitic in the 2.9 Ga age population links late Archean (2.9 Ga) subduction-accretion events involving an oceanic lithosphere component to craton stabilization. These events resulted in a widely distributed younger Archean generation of eclogitic diamonds in the lithospheric mantle. Subsequent Proterozoic tectonic and magmatic events altered the composition of the continental lithosphere and added new lherzolitic and eclogitic diamonds to the already extensive Archean diamond suite.

Reconfiguring old age: Elderly women and concerns over care in southeastern Botswana

This paper explores recent changes in the negotiation of female old age in Southeastern Botswana. Over the past one-quarter century epidemiological and demographic transitions, increasing pressures on lay nursing care, changes in work, and the introduction of pensions have led to a fracturing of old age. The constituent elements of old age--senescence and social elderhood--have shifted at different tempos and in different directions in historically contingent ways. Using Margaret Lock's notion of "local biology," this paper explores transformations in the bio-social dialectic that have reconfigured and redefined the aging process. It argues that the "normal" physiology and social position of seniors have changed so that chronic illness is increasingly seen as part of "normal" old age, as is the lack of socio-economic and cultural power to command care.

A glacigenic interpretation of a neoarchaean (≈2.78 Ga) volcanogenic sedimentary sequence in the Nnywane formation, Sikwane, Southeast Botswana

Neoarchaean volcano-sedimentary rocks of the Nnywane formation exposed at Sikwane, Botswana, exhibit palaeo-depositional features that allow the sequence to be interpreted with a glacigenic and volcanic-influenced depositional model. The sedimentary deposits are divided into two facies, a lower Grey facies of tuffitic sandstones, associated with diamictite and conglomerate units and shales, and an upper Red sandstone facies. A volcanic member is inter-layered with shales in the Grey facies, representing penecontemporaneous volcanism. Basal diamictite in the Grey facies contains striated and faceted clasts that reflect an origin as basal debris and which are typical of subglacial facies. Evidence supporting glaciation includes diamictite masses and isolated stones contained within shales, which are interpreted to indicate ice-rafting processes. The Grey facies is associated with a locally preserved smooth-textured tuffitic mudstone that is interpreted to represent glacial rockflour. Ice was probably formed in elevated areas during extensional tectonics associated with the major magmatic event of c.2.78 Ga in Southeastern Botswana, which is linked to the Limpopo Orogeny. Episodic sedimentation is evident in the Grey facies perhaps indicating the influence of glacial melt-waters and intermittent sedimentation associated with volcanic activities. The depositional environment consisted of a volcanic-determined and glacially influenced lake system.

Seasonal Declines in Rangeland Quality in the Cultivated Hardveld of Botswana Using Landsat Thematic Mapper Imagery

The need to combat both seasonal and long‐term drought are endemic in semi‐arid countries such as Botswana. These problems entail inter alia locating browse and certain bush derived foodstuffs (veld products) year long to enable local people to sustain their livelihoods. Seasonal range condition data are also required to help minimise overstocking and degradation. Results from seasonal reflectance curve analysis from southeastern Botswana indicate that most vegetation types can be identified especially on longer Thematic Mapper (TM) wavebands. Spectral Separability Indexes (SSIs) confirmed that range feature separation varies as a function of waveband and that feature separation is more pronounced in the wet, than the dry‐season. Results show that range feature differentiation is best attained using a combination of the chlorophyll absorpance band (TM3) and two mid‐infrared bands (TM5 and TM7). In terms of total seasonal separability, wet‐season vegetation cover differentiation was found to be 1.7 times more effective than that derived from dry‐season data. Both wet and dry‐season data sets were classified separately using maximum likelihood techniques. Although wet‐season data were more accurately classified, satisfactory class coincidence was achieved across the two data sets. Results indicate dry‐season declines in high quality rangeland and increases in bush encroached areas especially in communal areas comprising scattered villages. An appraisal of the ability of rangeland to sustain the needs of the rural poor in semi‐arid areas needs realistically to be undertaken during the dry season. Even though this time is sub‐optimal in terms of range condition assessment, it corresponds to the winter months when the demand for fuelwood is at its peak and available forage is minimal. Optimal timing, high resolution imagery and knowledge of local conditions are required to develop an information base which can help inform policy and direct poverty alleviation strategies.

Origin and palaeo‐environments of calcareous sediments in the Moshaweng dry valley, southeast Botswana

AbstractQuaternary sedimentation in the Moshaweng dry valley of southeastern Botswana is evaluated on the basis of geomorphological evolution and sedimentological analyses. Stratigraphic evidence reveals an upper surface (1095 m) containing abundant sil‐calcrete, an intermediate surface (1085 m) in which sil‐calcrete underlies nodular calcrete and lower (1075 m) surface in which sil‐calcrete and nodular calcrete are interbedded. This subdivision is reflected in the geochemical composition of the sediments which show an overall trend of decreasing SiO2 content (and increasing CaCO3 content) with depth from the highest to the lowest surface levels. The calcretes and sil‐calcretes represent modifications of pre‐existing detrital Kalahari Group sand and basal Kalahari pebbles which thinned over a Karoo bedrock high. Modification took place during wet periods when abundant Ca++‐rich groundwater flowed along the structurally aligned valley system. With the onset of drier conditions, water table fluctuations led to the precipitation of nodular calcretes in the phreatic layer to a depth of about 20 m. A major geochemical change resulted in the preferential silicification of the nodular calcrete deposits. Conditions for silica mobilization may be related to drying‐induced salinity and in situ geochemical differentiation brought about by pebble dissociation towards the top of the sediment pile. As calcretization and valley formation progressed to lower levels, silica release took place on a diminishing scale. Thermoluminescence dating infers a mid‐Pleistocene age for sil‐calcrete formation suggesting that valley evolution and original calcrete precipitation are much older. Late stage dissolution of CaCO3 from pre‐existing surface calcretes or sil‐calcretes led to the formation of pedogenic case‐hardened deposits during a time of reduced flow through the Moshaweng system possibly during the upper or late Pleistocene. Copyright © 2002 John Wiley & Sons, Ltd.

Radionuclide and mineralogical studies of kimberlite slime and soil samples obtained from the jwaneng diamond mine area, Botswana

The -ray spectroscopic and x-ray powder diffraction (XRPD) techniques were applied to study concentrations of three naturally occurring radionuclides: 40K, 238U and 232Th and mineral contents in various types of soils and kimberlite slime samples obtained from Jwaneng diamond mine area, Southeastern Botswana. The distribution of the radioactive elements was observed to be uneven due to varying mineralogical compositions of samples. Quartz was the predominant mineral phase in all the samples. Whereas phlogopite, kaolinite, illite, calcite and smectite occurred in minor quantities, lizardite, talc and halloysite were in trace amounts. The annual dose level for the Jwaneng mine was calculated and found to be 0.012 mSv/yr. This baseline is still below the limits given as 50 mSv/yr and 1 mSv/yr recommended by boththe US National Council on Radiation Protection and Measurement (NCRP) and the International Commission on Radiological Protection (ICRP) for workers and members of the public respectively. However, inhalation of mineral dust particles by both workers and inhabitants of the area may constitute health hazards leading to silicosis and related illnesses. Preventive occupational health measures in the mine are continually advised to remain implemented. (Botswana Journal of Technology: 2002 11(2): 39-45)

Participation in Labor-Intensive Public Works Program (Lipwp): Effect on Staple Crop Production in Southeastern Botswana

A labor-intensive public works program (LIPWP) aims to improve the income of rural households. One of the common criticisms of the LIPWP is that it is a disincentive for staple crop production. This study, conducted between February and May 2000, examined the association between participation in an LIPWP and staple crop production in southeastern Botswana. Participant households were those with at least one member on a semipermanent LIPWP. A control group was drawn from households that were eligible to participate in the LIPWP. All participants in the LIPWP were included, while nonparticipant households were randomly selected. A structured questionnaire was administered to 160 control and 153 participant households. the odds of having no staple crop in the control group were 1.8 times (95% CI, 0.98 to 3.54) higher than that of the LIPWP participants (p = . 087), while the odds of having no staple crop in a household with a head between 45 and 64 years of age were 2.5 times (95% CI, 1.06 to 5.96) higher than that of a household with a head less than 45 years old (p < .037). Having more than 10 livestock equivalent units reduced the risk of having no harvest by 40% (95% CI, 0.29 to 1.12). the view that participation in the LIPWP results in reduced staple crop production does not seem to be supported by our data.

Relationship between Waist Circumference and Blood Pressure among the Population in Baghdad, Iraq

A labor-intensive public works program (LIPWP) aims to improve the income of rural households. One of the common criticisms of the LIPWP is that it is a disincentive for staple crop production. This study, conducted between February and May 2000, examined the association between participation in an LIPWP and staple crop production in southeastern Botswana. Participant households were those with at least one member on a semipermanent LIPWP. A control group was drawn from households that were eligible to participate in the LIPWP. All participants in the LIPWP were included, while nonparticipant households were randomly selected. A structured questionnaire was administered to 160 control and 153 participant households. The odds of having no staple crop in the control group were 1.8 times (95% CI, 0.98 to 3.54) higher than that of the LIPWP participants (p = .087), while the odds of having no staple crop in a household with a head between 45 and 64 years of age were 2.5 times (95% CI, 1.06 to 5.96) higher than that of a household with a head less than 45 years old (p < .037). Having more than 10 livestock equivalent units reduced the risk of having no harvest by 40% (95% CI, 0.29 to 1.12). The view that participation in the LIPWP results in reduced staple crop production does not seem to be supported by our data.

Temporary pools are not `enemy-free'

Temporary pools are traditionally considered as refuges where the conspicuous anostracans are protected from predation. While this is true for the size-selective predation by fish, there is compelling evidence that invertebrate predation is an important biotic stress regulating temporary pool communities. In rock pools in southeastern Botswana, we studied the impact of some suspected invertebrate predators on populations of the freshwater anostracan Branchipodopsis wolfi by means of observations and manipulative experiments. In a survey of 45 pools, the relationship between B. wolfi natural population sizes and the abundance of suspected predators were never negative for turbellarians and mosquito larvae. When dragonfly larvae, notonectids or tadpoles were present, the anostracan populations were generally non-existent or very small. In enclosure experiments with turbellarians, there was a significant effect of predation within one hour of the start; the average daily predation rate was about 1/4 anostracan per turbellarian. Anostracans from a pool with few turbellarians were slightly less vulnerable than those from a turbellarian-rich pool. Furthermore, there was an indication of males being predated on more than females. With dragonfly larvae and notonectids, the predation effect was marked with all six anostracans in an experiment eaten in less than one day by a single predator (predation rate: about one anostracan every 2 h per predator). In a behavioral study, both sexes of B. wolfi avoided swimming above sediment that held more turbellarians than the open patches; there was no evidence for chemical communication with respect to this behavior.

Faunal Remains in the Transition from Hunting to Herding in Southeastern Botswana

Because foragers became pastoralists so late in southern Africa, their well-preserved remains can help us better understand the original herders of this world. The dominant thinking is that becoming herders is hard. Hunters share meat, herders keep it to themselves. Perhaps only a few hunters ever bridged this gap: the socially important habit of sharing meat may have held the rest back. Following this line of thinking, herding must have reached the southern tip of Africa with migrating herders because, otherwise, too many hunters would have had to bridge the gap for sheep to arrive by diffusion. This paper explores the opposite view: that becoming herders may not have been so hard. Faunal remains from two rockshelters in southeastern Botswana suggest that hunters could have first treated domestic stock as socially unimportant meat, not subject to rules of sharing. Continued hunting and sharing of large and medium game could have fulfilled social obligations, while privately owned domestic stock

Spatial utilization by black-backed jackals in southeastern Botswana

Space use by black-backed jackals was investigated between November 1995 and February 1997 in the Mokolodi Nature Reserve (MNR) in southeastern Botswana. Mean aggregate home-range size for the three radio-collared jackals was 15.9 km2. Mean home-range size varied between seasons with a tendency for range expansion during winter. The first two radio-collared jackals had similar activity patterns and were most active at dawn and dusk. Distances moved between hourly re-locations ranged from 2 m to 3000 m, and average distances moved between hourly relocations differed between individuals. The mean distance travelled per 24-hour period was 14.6 km. Time of day influenced movements considerably, with greater distances being moved during dawn and dusk. Extraterritorial excursions directed towards farmland were frequent and accounted for 21.1 % (n = 66) of all radio relocations. Jackals in MNR utilized wooded cover for denning, predator avoidance and foraging. They did not use habitats according to their proportional availability in any season. In all seasons jackals used open savanna grassland, Croton/Combretum tree savanna, and seasonal floodplains less than expected from their availability, and used tree and bush savanna, semi-sweet mixed bushveld and agricultural areas much more than expected. Implications of space use by jackals on management and conservation are discussed.

Provenance of the Kgwakgwe kaolin deposit in Southeastern Botswana and its possible utilization

Petrographic, mineralogical and geochemical studies were carried out on kaolin samples from the Kgwakgwe kaolin deposit in southeastern Botswana in order to understand sediment provenance and suggest its possible utilization. Kaolinite is dominant, whereas illite occurs in a stratigraphically localized area in the northwestern flank of the deposit. Accessory minerals are quartz, sericitic muscovite, goethite, halloysite and hematite. Cryptomelane, bixbyite, and pyrolusite manganese oxide (Mn oxide) associated with the kaolin. Hinckley crystallinity index and differential thermal analyses (DTA) values for dehydroxylation and mullitization peak temperatures were obtained for Kgwakgwe kaolinite. Kaolinite in the deposit occurs as irregular platelets, well-developed irregular flakes and a few pseudo-hexagonal stacks. Sediment provenance and alteration, and kaolinite purity is explained using kaolin mineralogy, particle morphology, and major and trace element geochemical data. The data suggests that the kaolin is derived from the alteration of terrigenous sediments that may have weathered from either the granite of the Gaborone Granite Complex (GGC) or the rhyolite of the Kanye Volcanic Formation (KVF) and deposited in the Kgwakgwe basin. The source sediments form part of the late Archaean lower Transvaal Supergroup and could have been deposited in a shallow lagoonal/lacustrine environment. On the basis of the results obtained from granulometric and mineralogical analyses as well as chemical and diagnostic evaluative analyses, the deposit could be exploited in the fabrication of tiles, bricks, sanitary wares and ceramic ware. It could also be used in rubber and plastic industries as well as making of pesticides, insecticides, and crayons. The raw clay will have to be beneficiated in order to optimize grade and recovery.

Cynodon dactylon control in sunflower (Helianthus annuus) with postemergence graminicides in a semi-arid environment

Field experiments were conducted during two cropping seasons in southeastern Botswana to investigate the efficacy of postemergence graminicides in controlling Cynodon dactylon in sunflower ( Helianthus annuus L.). Treatments consisted of haloxyfop applied at 1.08 and 2.16, fluazifop-p at 0.250 and 0.500, and sethoxydim at 0.150 and 0.300 kg ha −1 plus handweeded and unweeded controls. In 1998, haloxyfop and fluazifop-p applied at high rates reduced C. dactylon shoot dry weight by 80, and 59%, respectively; however, in 1999 they reduced grass shoot dry weight by 77 and 86%, respectively. Sethoxydim was less effective in controlling the perennial grass than haloxyfop and fluazifop-p. Visual assessment indicated that fluazifop-p and haloxyfop provided satisfactory grass control after a single application. Postemergence herbicides offer good weed control on fragile soils in a semi-arid environment.

Regional structuring of genetic variation in short-lived rock pool populations of Branchipodopsis wolfi (Crustacea: Anostraca).

The genetic structure of three metapopulations of the southern African anostracan Branchipodopsis wolfi was compared by analysing allozyme variation at four loci (PGM, GPI, APK, AAT). In total, 17 local populations from three sites (metapopulations) were analysed from rock pools in south-eastern Botswana ranging from 0.2 to 21 m2 in surface area. In three populations we found significant deviations from Hardy-Weinberg (H-W) equilibrium at one or more loci due to heterozygote deficiencies. Genetic variability at one site was significantly lower than at the other sites, which may be linked to a greater incidence of extinction and recolonisation, as the basins at this site are shallower and have shorter hydrocycles. Across all local populations, a significant level of population differentiation was revealed. More than 90% of this variation was explained by differentiation among sites (metapopulations), although this differentiation did not correlate with geographic distance, or with environmental variables. Genetic differentiation among populations within metapopulations was low, but significant at all sites. At only one of the sites was a significantly positive association measured between genetic and geographic distance among local populations. Our data suggest that persistent stochastic events and limited effective long-range dispersal appear to dominate genetic differentiation among populations of B. wolfi inhabiting desert rock pools. The lack of association between geographic distance and genetic or ecological differences between rock pool sites is indicative of historical stochastic events. Low heterozygosity, the significant deviations from H-W equilibrium, and the large inter- but low intra-site differentiation are suggestive of the importance of short-range dispersal. Gene flow between metapopulations of B. wolfi appears to be seriously constrained by distances of 2 km or even less.

The Makoro kaolin deposit, southeastern Botswana: its genesis and possible industrial applications

Kaolin samples from the Makoro kaolin deposit in southeastern Botswana were investigated petrographically and mineralogically in order to elucidate the genesis of the deposit. Mineral identification and characterization studies were conducted using powder X-ray diffraction (XRD), differential thermal analyses/thermogravimetric analyses (DTA/TGA), and scanning electron microscopy with an energy dispersive X-ray spectrum (SEM-EDX) technique. Diagnostic tests for several possible industrial applications were performed. Kaolinite is the major phyllosilicate present in the deposit, whereas smectite occurs in minor amounts. Accessory minerals are quartz, goethite, K-feldspar and hematite. Hinckley's crystallinity index (HI) values were determined for kaolinite from the kaolin deposit. Differential thermal analysis (DTA) values obtained for dehydroxylation and mullitization temperatures are close to theoretical values. Hexagonal booklets of kaolinite as well as individual platelets are present in the Makoro kaolin. Based on granulometric and descriptive mineralogical analyses, the mineral assemblages and kaolinite morphology, the Makoro kaolin deposit is derived from the alteration of feldspathic arenites (arkose) that were deposited in a locally developed basin of Permian age. A possible freshwater and/or brackish water depositional environment is suggested. The kaolin is found to be suitable for making sanitary wares, although a beneficiation process would be required; it could also be used in the refractory and vitreous ceramic ware industries.

The 1998 edition of the National Geological Map of Botswana

A new National Geological Map of Botswana incorporates data acquired from a variety of sources; the map is produced as a 1:1 million hardcopy as well as in digital format. The new map shows the pre-Kalahari Group geology. The oldest rocks are exposed in eastern Botswana where three Archaean terranes are recognised: the western parts of the Kaapvaal and Zimbabwe Cratons and the western part of the Limpopo Mobile Belt. All three terranes are lithologically similar but differ in their structural styles and in the timing of major thermal events. The oldest (pre-3.0 Gal high-grade metamorphic rocks are found in the Kaapvaal Craton, and the youngest in the Limpopo Mobile Belt, which appears to record Palæoproterozoic ductile shearing. Proterozoic orogenic belts, mostly concealed beneath Karoo rocks, define the western limits of the Archaean terranes and pprogressively young westwards away from the Archaean rocks. The Palwoproterozoic Magondi and Kheis Belts are well-defined by regional magnetic maps, but both are very poorly exposed in Botswana. The Kheis Belt trends due north from South Africa into central Botswana to define the western edge of the Kaapvaal Craton. The western part of the Magondi Belt, as well as all of a Mesoproterozoic (Kibaran) belt and rift are overprinted by the Neoproterozoic Damara Belt; all have pronounced northeasterly trends. During the Palæoproterozoic, there was also significant intraplate magmatism, sedimentation and deformation within the Archæan terranes. Some of the magmatism (in southeastern Botswana) was contemporaneous with, and lithologically similar to, the Bushveld Igneous Complex of South Africa. The main feature of the Mesoproterozoic geology of Botswana is a northeast trending rift that extends right across the northwest of the country and which is partly infilled with ca 1 106 Ma volcanic rocks. Neoproterozoic sedimentary rocks overlie the volcanics within the rift. The various rocks are exposed along the Ghanzi Ridge and to the northeast in the Chobe District. New detailed airborne magnetic surveys in northwest Botswana (Ngamiland) show the detailed geology of the northeast trending inland branch of the Damara Belt and exactly define its northwestern and southeastern boundaries. The southeastern part of the Damara Belt comprises the Mesoproterozoic volcanics of the Kgwebe Formation and the Neoproterozoic Ghanzi Group sedimentary strata. The full extent of the volcanics, and of the three formations recognised in the Ghanzi Group, is shown on the new map. Deformation of these rocks increases to the northwest where they are bounded by the tectono-stratigraphical Roibok Group. To the northwest of the Roibok Group are poorly dated granitoid rocks separated into several units that are locally overlain by carbonate-dominated sequences. A cover sequence of metasedimentary rocks with northnorthwest trending folds lies northwest of the Damara Belt. These sediments may overlie the southernmost part of the Congo Craton in the extreme northwest of Botswana. Neoproterozoic/ Lower Palæozoic sediments of the Nama Group partly infill a foreland basin to the south of the Damara belt in western Botswana. Karoo strata deposited within the Kalahari Basin underlie central Botswana. The distribution of the four major sedimentary groups, as well as of the capping basalts, is shown. The total thickness of the sediments is < 2000 m and the basalts are up to 1000 m in thickness. The sediments comprise a lower sequence (Dwyka and Ecca Groups) related to regional sagging and an upper sequence (Beaufort and Lebung Groups) that succeeded regional uplift that created intra-Karoo unconformities. Karoo sedimentation commenced towards the end of the Carboniferous Period and the basalts were extruded at about 180 Ma before Present. Wherever there have been detailed studies undertaken on the Karoo rocks, they show intense faulting that may or may not mimic structures in the pre-Karoo bedrock. The faulting appears to be post-sedimentation. No evidence was found for growth faults producing abnormal thicknesses of Karoo sediments. It is always possible to correlate the internal stratigraphy, at least at the formational level across the faults. Abnormal thicknesses of the basalts are preserved on the downthrow sides of the major faults. A major dyke swarm coeval with the extrusive basalts trends east-southeast right across north-central Botswana to cut across older structural trends. Over 200 kimberlites are shown on the new map. The kimberlites are distributed throughout Botswana in a number of separate clusters. Most of the kimberlites are of Cretaceous age. Isopachs are shown of the Kalahari Group, which is generally < 180 m in total thickness.