Abstract:
This thesis examines the geology of the Daspoort Formation (Pretoria Group, Transvaal Supergroup) of
South Africa, with the accent on describing and interpreting its sedimentology. The Palaeoproterozoic
Daspoort Formation (c. 2.1‐2.2 Ga) forms part of the Pretoria Group on the Kaapvaal craton. This
sandstone‐ and quartzite‐dominated lithological formation covers an elliptical geographical area
stretching from the Botswana border in the west to the Drakensberg escarpment in the east, with its
northern limit in the Mokopane (Potgietersrus) area and Pretoria in the south; altered outliers are also
found in the overturned units of the Vredefort dome in the Potchefstroom area. Deposition of the
Daspoort Formation was in a postulated intracratonic basin which applies equally to the entire
Transvaal Supergroup succession in the Transvaal depository. Various characteristics from the
formation, such as sedimentary architectural elements (e.g., channel–fills etc.), maturity trends and
distribution of lithofacies assemblages across the preserved basin give insight into the developing
conditions during deposition and genesis of the Daspoort Formation. Subordinate evidence from basic
geochemistry, ripple mark data and optical microscope petrology studies support the sedimentary
setting inferred for this Palaeoproterozoic deposit. Fluvial and epeiric marine conditions prevailed
during the deposition of the Daspoort clastic sediments into the intracratonic basin. This shallow
epeiric sea was fed by fluvial influx, predominantly from the west when a transgressive regional
systems tract led to the filling of the basin, evolving into the deeper marine Silverton Formation
setting, laid down above the Daspoort. Transgression from the east (marine facies predominate) to the
west (fluvial facies) is supported by cyclical trends, palaeoenvironmental and palaeogeographical
interpretations. Accompanying poorly preserved microbial mat features contribute to the postulated
shallow marine environment envisaged for the eastern part of the basin whereas ripple marks and
grain size distribution support a fluvial setting for the west, with lithofacies assemblages accounting for
both areas’ depositional interpretation.
