The late Palaeozoic coal-bearing Madzaringwe Formation of the Karoo Supergroup in the Tshipise-Pafuri Basin in the Limpopo Province, South Africa, records part of the infill of a passive continental margin terrain. Lithofacies analysis was performed with a view to deduce the nature of depositional environments of the Formation. Sedimentological and sequence stratigraphic evidence indicates that this unit represents a complex siliciclastic facies that reflects a fluvial paleodepositional environment. Eleven facies, which were grouped into five facies associations, were recognised. The base of the Madzaringwe Formation (Lower Member) represents a sequence deposited by braided channels. The coal deposits represent flood plain and swamp deposits, which is characterised by shale, thick coal seams, siltstone, and sandstone. The Middle Member is characterised by both clast and matrix supported conglomerates, major tubular and lenticular sandstones, and finely calcareous, micaceous siltstone. The deposition represents a sequence being formed from fluvial and particularly braided channels. The crudely stratified, coarse to pebbly sandstone indicates channel lag deposits within a heavy loaded fluvial system. The fine-grained sandstone represents deposition by shift channel and side bar deposits during lower flow conditions. The Upper Member is characterised by facies associations similar to the Lower Member, representing a new depositional cyclothem.
The objective of this study was to investigate the impact of anthropogenic and natural sources of contamination on the groundwater quality of the unconfined aquifer system of the Soutpansberg Basin around Tshikondeni. Fifteen groundwater samples were collected and analysed for physical and chemical parameters. Groundwater samples were analysed for pH, EC, TDS, major cations (Na
+
, Ca
+2
, K
+
, and Mg
+2
), major anions (Cl
−
, SO
4
−2
, NO
3−
, CO
3−
and HCO
3−
). Groundwater in this area was found to be above the desirable Department of Water and Sanitation (DWS) and World Health Organisation (WHO) limits for domestic and irrigation purposes. After the physicochemical analysis of groundwater, samples shows that, the type of water that predominates in the study area is Na
+
-K
+
-Ca
+2
-Mg
+2
type during the summer of the year 2008, based on hydro-chemical facies. Interpretation of hydro-geochemical data suggests that leaching of ions followed by weathering and anthropogenic impact (mainly mining and agricultural activities) control the chemistry of groundwater in the study area. Groundwater suitability for drinking purpose was also evaluated by the synthetic pollution index (SPI), it suggested that most of the samples fall in seriously polluted categories. The calculated values of SAR, Na%, RSC, PI, and MH have shown that except at few locations, most of groundwater samples are not suitable for agricultural and domestic purposes.
The subsidence history of the Soutpansberg Basin was reconstructed by a tectonic subsidence analysis coupled with backstripping calculations based on data of newly interpreted sequence boundaries. Furthermore, burial and time plots were constructed in order to understand the burial and thermal history of the basin. Input data were based on facies, lithostratigraphic models and tectonic interpretations. The studied succession is up to 1000 m and is underlain by the Achaean Limpopo Mobile Belt. The subsidence within the basin supports the primary graben system which must have been centred within the present basins, and later became a region of faulting. The subsidence and burial history curves suggests two phases of rapid subsidence during the Early‐Late Permian (300–230 Ma) and Middle Triassic (215–230 Ma). The areas of greater extension subsided more rapidly during these intervals. Two slow subsidence phases are observed during the Late Triassic (215–198 Ma) and Early Jurassic (198–100 Ma). These intervals represent the post‐rift thermal subsidence and are interpreted as slow flexural subsidence. Based on these observations on the subsidence curves, it is possible to infer that the first stage of positive inflexion (300 Ma) is therefore recognised as the first stage of the Soutpansberg Basin formation.
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