The geochemistry and sedimentology of quaternary shelf sediments of the Tugela River, Natal, South Africa
Master Thesis
1984
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University of Cape Town
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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 ยท 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.
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Felhaber, T. 1984. The geochemistry and sedimentology of quaternary shelf sediments of the Tugela River, Natal, South Africa. University of Cape Town.