Trace fossils in the form of large (~11 cm diameter and up to 2 m in length) burrows were studied at three localities in the Early Triassic Katberg Formation in the south-eastern and central parts of the main Karoo Basin, Eastern Cape, South Africa. The most interesting site, Hobbs Hill, northwest of Cathcart (Eastern Cape) has numerous burrows, contains an exceptionally well exposed sedimentary succession and bone beds. This site is also the type locality for the holotype of the parareptile Kitchingnathus untabeni (BP/1/1187). The aims of this dissertation are to: 1) reconstruct the local paleoenvironments of the burrow localities; 2) determine the purpose of the burrows; 3) identify the possible burrow makers based on the sedimentology and burrow morphology and 4) attempt to use photogrammetry and low-cost hardware to produce 3D digital burrows for improved descriptions. Insights into the survival strategies and behaviours of organisms during the P/T extinction recovery period are explored. Detailed analysis is mainly done on observations from the Hobbs Hill site; the results and interpretations are important for and compatible with the entire Katberg Formation. The interactions between the physical (sedimentary) and biological (animal behaviour) processes are important in ichnology and paleoenvironmental reconstruction. The analyses have therefore been undertaken through a multidisciplinary approach based on ichnological, sedimentological, petrographical, stratigraphic and paleontological evidence, gathered both in the field and laboratory.

This thesis investigates the potential for using the stable isotopes of hydrogen and oxygen from surface water and shallow aquifer water in solving urban geohydrological problems in the Cape Town metropolitan region. Three different water groups were chosen for detailed analysis, namely groundwater, springwater and reservoir water destined to join the mains water supply system. The stable isotope composition of groundwater and springwater were assumed to be fairly constant throughout the year, and were thus sampled only once. The reservoir waters were subject to evaporation effects, which result in isotope fractionation. The reservoir waters were sampled at the end of summer (9th April 1996), and near the end of winter (14th August 1996), in order to identify any seasonal isotope variations in the reservoir water isotope values. Reservoir water was sampled before and after the mains water treatment process, to identify any effect water treatment had on the isotope composition of the water. The two effects of water treatment and seasonal variation were determined simultaneously. Chemical analyses (pH, electrical conductivity, alkalinity, major anions and cations) of many of the water samples were performed to investigate the potential for correlating isotope values with chemical concentrations, and for using chemical analyses to complement or supplement isotope studies.

Metabasic rocks constitute a significant proportion of the rock types found within orogenic metamorphic terranes, and the high temperature (T), suprasolidus behaviour of these lithologies provide an important contribution to the process of internal differentiation in the continental crust. The recent development of thermodynamic activity-composition (a-x) relations for high T mineral and melt phases allows the processes of melt generation and segregation to be quantified using high-resolution mineral equilibria modelling for the first time. In this work, calculated Pressure-Temperature (P-T) and Temperature-Mol. % SiO₂ (T-MSiO₂) phase diagrams are used to investigate the suprasolidus evolution of representative amphibolite and eclogite compositions under orogenic P-T conditions in the crust.

Includes bibliography. / The linear Kuboos Bremen Igneous Province (KBIP) stretches 270km from the South African Atlantic coast north-eastwards into southern Namibia, and was emplaced at approximately 500Ma. One central complex within the KBIP is the Kanabeam Igneous Complex (KIC) where practically all the rock types found in the province are represented and include nepheline syenites, quartz syenites as well as granites. In addition to these plutonic phases a number of late stage, xenolith rich porphyry pipes were emplaced, exploiting contact zones between earlier plutons. Xenolith types include gabbro possibly derived from unexposed deeper parts of the KIC, syenites (more proximal components of the KIC), trachytes from an inferred overlying volcanic edifice, basement granites, gneisses and metasediments as well as Nama Group sediments. Petrographicl examination in the porphyries has releaved that there are numerous minerals out of textual equilibrium, including olivine, pyroxene and plagioclase. Other minerals such as biotite, amphibole and alkali feldspar appear more stable.

Includes bibliographical references. / The Outoitspan Group 1 kimberlite pipe forms part of the well-known cluster of pipes located in and around the city of Kimberley, South Africa. Eight macroscopically distinct intrusive phases, i.e. D2 Type 2, D2 Type 3, D2/D5, D5, D18, Type 5, D16 and the D16 dyke are present in the Northwest Corner area of the mine. Microscopically they range from macrocrystic to aphanitic hypabyssal (magmatic) kimberlites with varying amounts of opaque minerals, monticellite and phlogopite. Olivine is the dominant macrocryst phase and alteration varies from unaltered to highly serpentinised. These intrusive phases also contain variable amounts of crustal xenoliths.

Summary in English. / Bibliography: leaves 104-108. / Land treatment is the predominant disposal method of effluents generated by distilling, wine making and grape juice production in the Western Cape. Primary settling and treatment in aerobic and anaerobic lagoons typically precede disposal to land. Land treatment can effectively remove COD and also benefit the soil by increasing organic matter, cation exchange capacity and moisture retention capacity. Adverse effects can include salinisation of soils and groundwater, soil structural degradation and odours generated by anaerobic conditions.

Includes bibliographical references. / Melt migration is an important process in the crust that causes significant mass transport, as well as differentiation and stabilisation of continental crust. Melt migration near the source occurs pervasively, through interconnected networks of melt-bearing structures. This style is restricted to the suprasolidus mid- to lower crust, while focused migration and ascent of magma occurs in isolated dykelike structures under subsolidus conditions, generally in the upper crust where brittle fracturing of rocks can occur. The details of how and when melt migration changes from a pervasive to focused style are poorly understood, particularly the temperature, pressure and deformation conditions which allow the transition to occur. The Nupskapa nunatak, in Dronning Maud Land of East Antarctica, exposes large cliffs that record evidence of multiple episodes of melt movement, in the form of pervasive leucogranite vein networks cross-cut by larger leucogranite dykes. Mineral equilibria modelling with THERMOCALC and comparison of results with previous work indicates that the Nupskapa nunatak records both Grenvillian and Pan-African metamorphism. Coarse-grained peak assemblages in samples from the Nupskapa area record conditions of 820-880 C at 9.5-11.6 kbar, while post-tectonic retrograde assemblages record late Pan-African conditions of 555- 595 C at 3.2{4.8 kbar. These later conditions lie between the wet solidus and the brittle-viscous transition and are inferred to represent the conditions of intrusion for post-tectonic composite dykes. Small-scale leucosomes predominantly lie parallel to the gneissic host rock fabric and define a pervasive network across the Nupskapa cliff. These leucosomes exhibit diffuse feathery boundaries and are inferred to represent in situ melting and melt segregation during M1 granulite facies peak metamorphism. Composite leucogranitic dykes cross-cut both the early leucosome phase and Pan-African shear zones in the field area. These north-trending, subvertical dykes are neariii orthogonal to the gneissic fabric. They are 0.5-2 m wide and spaced ~10-20 m apart but not interconnected except where two dykes coalesce. The dykes show almost no shear displacement, indicating that they formed via tensile fracture. This indicates that their intrusion occurred during extensional or strike-slip deformation, under conditions of low differential stress, probably coupled to high melt pressure. The composite dykes resulted from the far-field transport of melt from a source 5 to 15 km below the Nupskapa outcrop. Although individually they are discrete and focused structures, they are numerous across the field area and closely spaced, so together they do not represent a wholly focused melt transfer system. The style of melt migration displayed by the composite dykes is an example of the transition from pervasive to focused migration, occurring in the mid-crust at subsolidus conditions. This transition involved a network of smaller melt-filled fractures gradually coalescing into larger ones with decreasing depth. If pervasive migration becomes focused via this gradual transition, melt accumulation and mixing need not occur solely in the source or final emplacement structure, but rather occurs throughout transport of the magma.

Includes bibliographical references. / The Mgeni River is vital for the continued industrial and social development of Durban and Pietermaritzburg and the river has been impounded in four places to provide a crucial water resource to these areas. The river is highly susceptible to anthropogenic pollution, particularly phosphorus, which may be derived from unsanitised peri-urban areas or run-off from fertilised agricultural lands. Sediments may be sources or sinks of pollution in aquatic systems. Grab samples of the uppermost sediment layer were taken from sites at each of the impoundments and analysed for salient geochemical characteristics, such as major and trace element concentrations, clay mineralogy, organic carbon, P fractionation, and particle size distribution. Batch experiments were also carried out to determine the P sorption desorption characteristics of the sediments under different pH and redox conditions. The sediments are dominated by clay sized material (< 2mm) which is composed of kaolinite, gibbsite, goethite, mica and other undifferentiated· 2: 1 layer silicates and quartz. Kaolinite, gibbsite and goethite are found extensively throughout the catchment area and are the result of intense weathering. These minerals readily sorb cations onto their surfaces. The significant correlations which were found between the clay content and the concentration of trace metals, particularly Mo, Pb, and Zn, most likely result from accumulations of cations on the mineral surfaces. It was suggested, therefore, that the Mgeni sediments are potential sinks for polluting elements.

Bibliography: pages 52-56. / The River Ranch kimberlite is a 5.2 hectare diatreme from which the original surficial crater facies material has been removed by erosion. Proof of the prior existence of such a feature is provided by down rafted blocks of epiclastic and pyroclastic rocks exposed in the diatreme during open pit mining operations. Six intrusive kimberlite phases have been recognised in the diatreme by careful mapping and confirmed by petrographic observations, particularly variations in groundmass mineralogy. Subsequent to emplacement, the diatreme has been cut by intrusive tholeitic dolerites of apparently Karoo age. The River Ranch occurrence is classified as a Group I kimberlite although the definitive isotopic evidence is lacking due to pervasive alteration of the exposed rocks. The absence of megacrystic and groundmass ilmenite and the presence of groundmass diopside are unusual for the group of rocks. However the presence of monticellite and the low abundance of phlogopite argue against a Group II classification. The overwhelmingly peridotitic nature of the mantle mineral macrocrysts in the kimberlite is consistent with the observations of Kopylova et al (1995) that the diamonds at River Ranch are predominantly peridotitic and are likely to have formed in a single process. The approximate equilibration temperature for a small suite of coarse grained lherzolite from the kimberlites is 1200°C, suggesting a geothermal gradient rather higher than seen in the Kaap-Vaal craton. The diamonds at River Ranch are predominantly brown, strongly resorbed and have less than average value. It is predicted that a combination of kimberlite petrography, micro-diamond measurements and mantle macrocryst studies should be a valuable aid to grade control and mine planning.

This thesis is comprised of geochemical, mineralogical and sedimentological studies of 101 sediment samples recovered from the continental shelf off the Tugela River Mouth, Natal, South Africa, and nine samples taken from the Lower Tugela River. The purpose of the research was to examine the geochemical nature of the sediments in relation to their particle size distributions and the hydrological conditions present in the area in order to elucidate the relationship between an inner shelf mud belt and an outer shelf mud belt located in the area. The river samples were analysed to help in understanding the changes undergone by the continental shelf sediments during their residence on the shelf. All samples were analysed for 10 major and 23 trace elements by X-ray fluorescence spectrometry, particle size distribution, carbonate and organic matter content. X-ray diffractograms were run on all samples to obtain qualitative mineralogy. Multivariate statistical tests were used to aid the interpretation of the data, and to statistically distinguish between the two mud belts. A detailed sedimentological model of the hydraulic populations of sediment in the area has been formulated. The information from this model, taken in conjunction with the mineralogy, provided a framework within which the geochemical data could be interpreted. A geochemical model of sedimentation was developed, based upon the information from the results of the statistical tests and the known geochemical associations of elements in sediments. A geochemical distinction was found between the inner and outer shelf mud belts. An age of 40 650 yr BP was previously reported for a sample on the mid-shelf in the study area, supporting the reconstruction of a paleoenvironment · showing the outer shelf mud belt to be the paleodepocentre for the Tugela River with the inner shelf mud belt representing the present-day depocentre of the Tugela River.