- Title
- Mineralogy, geochemistry and pebble morphology of the Katberg Formation around Graaff Reinet and East London, Eastern Cape province of South Africa
- Creator
- Ndlazi, Nondumiso Zandile
- Subject
- Mineralogy|
- Date
- 2020
- Type
- Thesis
- Type
- Masters
- Type
- MSc (Geology)
- Identifier
- http://hdl.handle.net/10353/18631
- Identifier
- vital:42615
- Description
- The Katberg Formation forms the upper part of the Tarkastad Subgroup in the Beaufort Group of the main Karoo Supergroup. The Katberg Formation consists of siliciclastic sedimentary rocks mostly dominated by greyish sandstone, red mudstone with minor siltstone occurrences. The Katberg Formation also consists of calcareous and ferruginous concretions that formed during diagenesis. Braided streams deposited the Katberg Formation with a predominantly sand bed load. The Katberg Formation sandstones contain pebbles with no true conglomerates identified in the study area. This study was conducted in the Katberg Formation to understand the mineralogy, geochemistry, and pebble morphology around Graaff Reinet and East London areas. The major and trace elements were analyzed through X-Ray Fluorescence (XRF) to deduce the source rock provenance, tectonic setting, paleo-weathering conditions, climatic conditions, and sediment maturity. The X-Ray Diffraction (XRD) was used to highlight a detailed distribution and variation of mineralogical polymorphs of the minerals present in sandstones and mudstones. The pebble morphology was used to confirm the depositional environment of the Katberg Formation. The use of The bivariate plots of the Maximum Projection Sphericity Index (MPSI) and the Oblate-Prolate Index (OPI) showed that 79 % of pebbles fall in the fluvial environment, whereas 21 % of pebbles fall in the beach environment. A small proportion of beach pebbles within the Katberg Formation suggests that the river reached the marginal marine environment during its flow. The majority of the pebbles yielded a bladed shape with a dominating Sphericity Index symptomatic of fluvial sediments. All the bivariate plots illustrate the fluvial depositional environment for the sediments of the Katberg Formation. Petrographic studies based on the prepared 15 thin sections indicated that the Katberg Formation rocks are dominated by quartz, feldspar, and clay minerals. However, they show more plagioclase feldspar than k-feldspars. The grains are poorly sorted and immature, with irregular grain sizes and shapes. The angularity of clasts indicates that the grains have travelled shorter distances. The abundance of feldspar minerals suggests that the arkose sandstone was derived either from situ or from a short distance. The albitization of plagioclase to illite and the replacement of plagioclase feldspars by calcite and laumontite is very common in the Katberg Formation, which points out deep burial diagenesis. The XRD analysis revealed the occurrence of 14 minerals in the siliciclastic rocks of the Katberg Formation, namely: quartz, albite, clinochlore, muscovite, phlogopite, annite, illite, orthoclase, anorthoclase, laumontite, calcite, and ankerite. Amongst these minerals, albite, clinochlore, muscovite, and phlogopite show variation in crystal forms known as polymorphs. Geochemical analysis of the Katberg Formation sandstones and mudrocks revealed that all samples show a high concentration of SiO2, Al2O3, Fe2O3, K2O, Na2O, CaO, and MgO. The trace elements: TiO2, MnO, P2O5, BaO, SrO, ZrO2, and V2O5 are depleted with values ranging below 1 wt %. The geochemical classification of the Katberg Formation sandstones revealed the origin from wacke and arkose sources. The geochemical diagrams and indices of paleoweathering conditions suggested that the Katberg Formation underwent a moderate degree of chemical weathering. The geochemistry revealed that the sediments were 4 Final Submission of Thesis, Dissertation or Research Report/Project, Conference or Exam Paper deposited during the arid climate conditions. The studied sandstone and mudstone samples pointed an active continental margin and passive margin tectonic setting of the Katberg Formation.
- Format
- 200 leaves
- Format
- Publisher
- University of Fort Hare
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- University of Fort Hare
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UFH Department of Geology
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details | SOURCE1 | Dissertaion-Ndlazi NZ_201206979_Geology.pdf | 10 MB | Adobe Acrobat PDF | View Details |