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M.Sc. / Certain carbonate bearing formations in the Paleoproterozoic Pretoria Group and its Griqualand West equivalent exhibit remarkable geochemical and stable isotopic signatures. The 8'3Ccarb isotopic signatures from the Duitschland and Silverton Formations exhibit large positive excursions, which seemingly coincide with a significant increase in atmospheric oxygen between 2.4 and 2.0 Ga. The Duitschland Formation with its distinctive basal unconformity is composed primarily of limestone and dolomite units, interbedded with two compositionally different shale units and quartzite. Toward the base of the formation there is a distinct conglomeratic quartzite which forms a sequence boundary above which isotopic and geochemical signatures change dramatically. Normal marine isotopic signatures characterize the lower portion of the succession while above the sequence boundari, the carbonates are enriched in "C. This enrichment, however, appears to be the result of local processes occurring within a closed basin. Furthermore it is apparent that the Duitschland Formation (with its three distinct marker beds) is the equivalent of the Rooihoogte Formation and therefore constitutes the base of the Pretoria Group. The Mooidraai Dolomite Formation which outcrops only locally in the Northern Cape Province, is characterized by fenestral and microbially laminated dolomite. The geochemical properties are relatively homogeneous with increases in the FeO and MnO concentrations, resulting from post depositional diagenesis. The stable isotope signatures of these dolomites represent normal marine signatures. There is, however, a depletion in the 813C and 8180 signatures in the ankeritic and sideritic lithofacies, which suggests that this succession was deposited from a stratified water column with respect to the total dissolved CO2. The positive 6 13C excursion present in the carbonates of the Lucknow Formation in Griqualand West, traditionally grouped with the Olifantshoek Group can be correlated with carbonates near the top of the Silverton Formation in the Transvaal area. The latter also displays distinctly positive 6 43C values. One possibility is that if these successions were deposited in closed anoxic basins and that the isotopic anomalies are the result of local processes such as fermentive diagenesis and methanogenesis. However, the close association of the carbonates with shallow marine orthoquartzites suggests that these were deposited in an open marine system and that the positive 8 !3C values reflect a shift in the composition of the ocean water at the time of deposition of the carbonates at 2.2 Ga. Other carbonates present in the Pretoria Group, namely from the Vermont and Houtenbek Formations, display normal open marine 8' 3C values of close to zero. A systematic stratigraphic compilation of all 6 43C values available from the Transvaal Supergroup indicates that two clear-cut positive 5' 3C excursions are present. These excursions were apparently short-lived and well defined and did not occur over an extended period of time as suggested by earlier studies based on global compilations with large uncertainties in radiometric ages of deposits.

M.Tech. (Extraction Metallurgy) / The discovery of gold at Langlaagte in 1886 led to the development of gold mining in the Far West Rand in 1934. When shafts were sunk, water from the dolomites posed a serious threat to mining. Despite cementation that sealed the many fissures, water still found its way into the underground workings. This led to the “uniform” policy of dewatering. The farming communities in the area that were dependent on the ground water had to be considered, as they had lost their livelihood. As the water levels lowered, dolines and sinkholes were formed, posing a serious threat to life and property. When the mines eventually cease to operate, be it due to high working costs, or the declining grade of the ore body, the re-watering of the dolomitic compartments will occur as a natural consequence. When water comes to within six metres of the original water level, ground instability, the formation of dolines and sinkholes, both new and existing, will occur, threatening the important rail link between Pretoria and Cape Town as it passes through Far West Rand, as well as the N12 between Johannesburg and Potchefstroom, as well as the N14 which lies to the east connecting the Gauteng Province and the North West Province. The dewatering of the compartments caused the soil which formed the roof of the cavities to dry. Re-watering will cause this dry, stable material to become wet and unstable. Where mixtures of slime and/or other material, which is not part of the geological composition of that area was used, the same phenomenon will apply. A further complication is caused by the slimes dams which are unlined. In fact, some of the slime dams were deliberately constructed over cavernous dolomite. This large mass of mine tailings over the dolomitic aquifers will “liquefy”. If the re-watering is not carefully managed the rising water table will undoubtedly trigger a rash of new sinkholes, with catastrophic consequences for unsuspecting communities that may have been established in sensitive areas. The results of previous investigations by the Departments Minerals, Energy and Water Affairs who, due to the loss of institutional memory, might not be able to find the relevant information. Other organizations such as the Council for Geoscience could be using the results for consultancy. The information should be digitized and be available to the broader South African public. FWRDWA is currently in charge of monitoring events in the area. Levelling observations have been carried out quarterly and, so far the movement of ground is minimal. The potential hazard of ground instability will recur with the re-watering of the dolomitic compartments of the Far West Rand. To support what could happen, reference is made to events which took place in the late seventies when the Far West Rand had an above average rainfall. The Donaldson Dam overflowed into the Wonderfontein Spruit and into the dewatered Venterspost compartment. As a result, the water level of the Venterspost Compartment rose rapidly which led to the re-activation of sinkholes and the formation of new ones in the Venterspost area. In the present work levelling has been carried out along most of the loops affected and the results of the levelling give an impression that the surface is currently relatively stable. This Dissertation is presented as an attempt to alert the authorities to the potential dangers if the post mining period is not carefully monitored and insufficient provision made to deal with potential contingencies.

Thesis is submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, 2016 / Keywords/key concepts: Dolomite, Dolomitic ground, Disaster Risk Management, Physical Vulnerability, Low-income settlements, Housing Policy, Services delivery, Responsibility, Living with risk, Human Behaviour, Basic Human Rights Ground underlain by dolomite may be hazardous to development due to the potential occurrence of subsidence and sinkholes. These potentially disastrous occurrences are in many instances caused by human interaction with the soil through the ponding of water or leaking of wet infrastructure such as water and sanitation services. Construction materials and techniques, as well as effective maintenance of waterborne services have traditionally been acknowledged as having a significant bearing on the level of risk that communities face when living on such potentially dangerous land. The spatial distribution of settlements on dolomite in the Gauteng City Region (GCR) is already widespread and expected to increase as urbanisation intensifies. Similarly, the challenge of considering the physical vulnerability of low-income settlements is expected to intensify. Welldefined procedures and guidelines govern the development of human settlements on dolomitic ground. However, the classification and characterisation of low-income and informal settlements are not as advanced as that of formal residential developments. In addition, the guidelines regarding management of settlements on dolomite focus significantly on geotechnical interventions, leaving a gap in the influence that human behaviour can play in possible disaster risk reduction on such ground. The thesis considers the significance of different low-income settlement types on dolomite, relative to perceived human behaviour in association with principles of disaster risk reduction. It hypothesizes that an understanding of settlement type in relation to human behaviour and a stronger emphasis on monitoring via official channels could address some of the conflicts in the development-on-dolomite debate and thereby reduces settlement vulnerability. The research methods included quantitative and qualitative components, commencing with a literature review that spanned multiple disciplines and sectors. Fieldwork included spatial investigation and consideration of low-income settlement types with regard to, for example building material use, dwelling size and dwelling layout, and wet services infrastructure provision and location. The thesis subsequently identify and explore low-income settlement types in the study area. The research explores a number of sample settlements to consider the physical vulnerability and potential key areas of intervention and risk reduction, outside of the traditional geotechnical arena. The evaluation then applies the Analytical Hierarchy Process (AHP), a form of Multi Criteria Analysis (MCA), to identify important variables and indicators related to human behaviour and the physical vulnerability of settlements on dolomite that can be harnessed to intervene in the debate, and possible improve the safety of communities living with this risk. Although not affecting the research outcome directly, a specific observation during the course of engagement with specialists across disciplines was that experts in even closely related practice areas view low-income settlement development and upgrading on dolomite differently. The differences in viewpoints result in contradictions in approaches between housing officials, disaster managers, socio-environmental practitioners, engineers and geologists. Even small differences in approach have been shown to have significant effects on the practicalities surrounding decision making related to low-income settlements and especially informal settlement relocation or upgrading. The outcome is a set of prioritised indicators that could enable specialists, officials and the public to consider different elements of low-income settlements based on its physical vulnerability. By focussing on the indicators most likely to result in reduced vulnerability, actions that drive settlement development, upgrade and resettlement could be prioritised. Interestingly, one of the findings of the research is that it is not so much the settlement type based on informality that makes a difference in the exposure to risk – physical vulnerability is deemed to be significantly affected by official (municipal-sphere) actions, monitoring and awareness. Finally, the research enables the integration of technical knowledge with behavioural considerations when living on dolomite, thus highlighting opportunities to bring technical and non-technically skilled stakeholders in the debate closer together. / MT2017