Evolution of an Archaean intracratonic basin: A review of the Transvaal Supergroup lithostratigraphy in Botswana

Franchi, Fulvio; Mapeo, Read Brown Mthanganyika

doi:10.1016/j.earscirev.2019.02.007

Cited by 14 publications

(7 citation statements)

References 62 publications

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“…The upper Notwane River catchment (3935 km 2 at the site of Notwane reservoir) drains an area characterized by the Neoarchean volcanosedimentary sequence (Fig. 2) of the Lobatse Group, the Gaborone Granites, and the Paleoproterozoic sediments of the Transvaal Supergroup (for a review see: Franchi 2018;Franchi and Mapeo 2019). In the study area, the Lobatse Group is comprised of the alkali porphyritic rhyolites of the Kanye and Nnywane Formations overlaid by the argillites, epiclastic sandstones, and conglomerates of the Mogobane Formation (Modie 1999;Franchi and Mapeo 2019).…”

Section: Study Areamentioning

confidence: 99%

“…2) of the Lobatse Group, the Gaborone Granites, and the Paleoproterozoic sediments of the Transvaal Supergroup (for a review see: Franchi 2018;Franchi and Mapeo 2019). In the study area, the Lobatse Group is comprised of the alkali porphyritic rhyolites of the Kanye and Nnywane Formations overlaid by the argillites, epiclastic sandstones, and conglomerates of the Mogobane Formation (Modie 1999;Franchi and Mapeo 2019). The Transvaal Supergroup sequence in the area is characterized by the karstified dolomite of the Taupone Dolomite Group (known in the Lobatse-Ramotswa area as Ramotswa Dolomite Formation) and coarse siliciclastic deposits of the Bevet's Conglomerate Member and by the sediments of the Ditojana and Tlaameng Formations (Key 1983;Mapeo and Wingate 2006).…”

Section: Study Areamentioning

confidence: 99%

“…2): (i) the upper part from the source to the Nnywane Dam ( Fig. 1a) and in the northern area around Thamaga village, where the dominant lithology is porphyritic alkali feldspar granites of the Thamaga Formation (Gaborone Granite) and the porphyritic rhyolites of the Kanye Formation; (ii) from the Nnywane Dam to the outskirt of Gaborone the geology is dominated by the sediments of the Lobatse Group and the Transvaal Supergroup; (iii) the area around Gaborone, again characterized by porphyritic alkali feldspar granites and by the porphyritic rhyolites of the Kanye Formation (for a review see Franchi and Mapeo 2019). Granites and rhyolites form low productivity, weathered/fractured aquifers while the Ramotswa dolomite (Taupone Dolomite Group) forms a productive, regionally important karstic aquifer (McGill et al 2019).…”

Section: Study Areamentioning

confidence: 99%

“…Schematic geological map of south-east Botswana including the Notwane River sub-catchment (modified fromFranchi and Mapeo 2019) …”

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Modern sediment records of hydroclimatic extremes and associated potential contaminant mobilization in semi-arid environments: lessons learnt from recent flood-drought cycles in southern Botswana

et al. 2019

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The aim of this work was to identify and analyze the records of flood-drought cycles as preserved in the sediments of the Notwane reservoir, southern Botswana, in order to better understand how extreme events affect water and sediment quality. This work represents the first attempt to study the reservoir sediments in arid to semi-arid environments and suggests that they could be used as proxies for the characterization of the effects of flood-drought cycles. Materials and methods For the first time in an arid context like Botswana, sediments from artificial reservoirs were explored through correlating sediment records with the presence and quantity of pollutants in the reservoir's wider arid and semi-arid catchment after the latest extreme flood event of 2017. Sediments from the Notwane reservoir were collected with a push corer to a maximum depth of 80 cm. Sediments were then analyzed for grain size distribution, organic matter content, and concentrations of heavy metals (Fe, Zn, Cu, Cr, and Pb). Concentrations of heavy metals from surface water and groundwater were compared with the metal profiles from the sediment cores and with rainfall series from the CHIRPS (Climate Hazards Group InfraRed Precipitation with Stations) database. Results and discussion The sediments from Notwane reservoir clearly showed two flood couplets characterized by fining upward beds. Water quality data from Notwane reservoir and the surrounding aquifer showed peaks of contaminants following rainfall. Although the couplets found in the sediment record were not always clearly coupled with peaks of metals, some correlation was found between the vertical distribution of metals within the sediments and the most recent sequence and the seasonal metal variation in water. Overall, trace metal contents were very low: < 1 mg L −1 for Cu and Zn and < 2 mg L −1 for Cr and Pb, well below the sediment quality assessment guidelines (SQGs), indicating that the above-average precipitations of the last 10 years did not noticeably contribute to the input of heavy metal contaminants in the reservoir sediments. Conclusions The 2016/17 Dineo cyclone flood was triggered by above-average rainfall, preceded by a 4-year period of severe drought. The deterioration of the basin during the drought has enhanced the effects of the flood, worsening the damages on structures and livelihoods. The lessons learnt from the Dineo cyclone in Botswana highlight the importance of integrated studies that combine hydrological data, rainfall series, and sediments. It is recommended to extend the research for longer time periods.

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Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

“…Schematic geological map of south-east Botswana including the Notwane River sub-catchment (modified fromFranchi and Mapeo 2019) …”

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Modern sediment records of hydroclimatic extremes and associated potential contaminant mobilization in semi-arid environments: lessons learnt from recent flood-drought cycles in southern Botswana

et al. 2019

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“…The Kanye region is underlain by Neoarchean to Paleoproterozoic that include the Neoarchean Gaborone Granite Complex, rhyolites and v o lcanosedimentary rocks of the Lobatse Group. The chemical, volcanic and siliciclastic sedimentary rocks of the Transvaal Supergroup and the continental redbeds of the Waterberg Group cover the basement rocks (Carney et al, 1994;Moore et al, 1993;Mapeo et al, 2006;Franchi and Mapeo, 2019). A hard rock terrain underlies much of the Kanye area, with aquifer formations being of a fractured nature; hence groundwater potential and occurrence are related to the presence of fractures a nd f issu res such as joints, faults and bedding planes that developed due to tectonic deformation.…”

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confidence: 99%

Preliminary assessment of groundwater Hydrogeochemistry in Kanye Area, SE Botswana

Tafesse¹,

Mapeo²,

Laletsang³

et al.

Global NEST International Conference on Environmental Science &Amp; Technology

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A hydrogeochemistry study was conducted in Kanye region, located in south east of Botswana, to determine the main composition controlling mechanisms in the groundwater chemistry of the area. Groundwater samples were collected and analyzed. The samples were analyzed for major cations, anions and some trace elements such as As, Ba, Br, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. To determine the mechanism of salinization and water–rock interaction bivariate graph of the parameters Ca2+ + Mg2+ versus HCO3−+ SO42− was used. The groundwater is neutral to alkaline and fresh. The dominant cations in the groundwater are magnesium and calcium, and the dominant anions are bicarbonate and chloride. The prevailing hydrochemical facies is Mg-Ca-HCO3. The major composition controlling mechanisms in the groundwater chemistry of the area was identified as silicate weathering.

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Geodynamic mechanism and classification of basins in the Earth system

Wang

et al. 2022

Gondwana Research

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Evolution of an Archaean intracratonic basin: A review of the Transvaal Supergroup lithostratigraphy in Botswana

Cited by 14 publications

References 62 publications

Modern sediment records of hydroclimatic extremes and associated potential contaminant mobilization in semi-arid environments: lessons learnt from recent flood-drought cycles in southern Botswana

Modern sediment records of hydroclimatic extremes and associated potential contaminant mobilization in semi-arid environments: lessons learnt from recent flood-drought cycles in southern Botswana

Preliminary assessment of groundwater Hydrogeochemistry in Kanye Area, SE Botswana

Geodynamic mechanism and classification of basins in the Earth system

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