- Title
- Application of geophysical methods to investigate the subsurface geology of Kuruman and Kono areas in Griqualand West Basin, South Africa
- Creator
- Mthintweni, Sylvia Lwandisa
- Subject
- Geology
- Subject
- Soil surveys--Geophysical methods
- Date
- 2021-05
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10353/22555
- Identifier
- vital:52456
- Description
- Kono and Kuruman areas belong to the geology of the Campbell Rand and Asbestos Hills Subgroups, Ghaap Group in the Griqualand West Basin. Campbell Rand Subgroup comprises interbedded chert, limestone and dolomite rocks of dominantly the Kogelbeen Formation covered with a thick regolith of red sand and weathered material. The Asbestos Hills Subgroup consists of a banded iron formation (BIF) of the Kuruman Formation overlain by the Kalahari sands. Petrographic and mineralogical analyses and various geophysical methods were utilised to investigate the surface and subsurface conditions of the study areas. This study was done to characterize and understand the geology of Kuruman and Kono and identify the structural lineaments. Rock samples of varying lithology were collected in the field for laboratory analyses that include preparation of thin sections and petrographic analyses and density and porosity determinations. Both the petrographic results and XRF analyses revealed that iron oxide (Fe2O3) and silica (SiO2) are the most abundant minerals in BIF. Iron oxide and silica percentages range between 21.17-39.97 wt % and 59.03-78.01 wt %, respectively. BIF has an average density of 3.0 g/cm3 and porosity of 2.51% and dolomite has an average density of 2.8 g/cm3 and porosity of 0.17%. The Bouguer anomaly values range between - 119.00 mGal and -1 17.29 mGals. High gravity anomalies are attributed to shallow fresh bedrock and this was confirmed by the seismic line that cuts across the map. The gravity high observed in the Kuruman profile coincides with the thick BIF body observed in the field. The gravity analytic signal indicates a width of about 1125 m for the BIF and inferred two normal faults at about 675 m and 1500 m. The high magnetic anomalies in the ground magnetic map correspond to chert rich dolomite ridges in the field and the intermediate to lows correspond to dolomitic terrains. A geological map was superimposed on an aeromagnetic map to correlate the two. The linear magnetic high trending from NW – SE coincide with BIF. Older dykes trending east-west were intruded by younger dykes trending north-south. The total counts channel map for Kono area shows the measured total gamma radiation count in the study area and the concentrations of radioelements range between 51.84 and 94.64 counts/sec. The concentrations of potassium, thorium and uranium range from 0.12 – 0.51%, 0.83 – 5.23 ppm and 0.06 – 2.27 ppm, respectively. A high concentration of radiometric elements cutting through the central part of the map stretching from northwest to southeast was observed in a ternary map and this could be associated with chert rich dolomite outcrops. Seismic refraction tomography (SRT) cross-section for study area 1 in Kono revealed 3 different layers. The topmost layer comprises sand and loose material and has a velocity ranging from 614 – 1194 m/s. It is underlain by highly to slightly weathered dolomite with a velocity that ranges from 1774 – 2354 m/s. Layer 3 is the fresh bedrock dolomite and has a velocity of 2934 m/s. Three layers were observed in study area 2 for Kuruman. Layer 1 had a velocity of 300 – 750 m/s, the second layer had a velocity of 1200 – 2100 m/s and the bottom layer’s velocity was 2500 – 2999 m/s. An inferred fault is indicated on the western side of the seismic section at about 650 m. The dipole-dipole resistivity model for the main survey line in Kono revealed that the area is underlain by fractured bedrock with high resistivity in places. A thick conductive stratum was observed at the beginning of the line. The resistivity models for the sinkhole in Kono were characterized into three resistivity zones. High resistivity values (1000 – 134202 Ωm) are due to slightly weathered to fresh bedrock, intermediate values (24 – 5770 Ωm) are interpreted to be due to highly weathered dolomite and compacted dolomitic soils and very low resistivity zones (4 – 397 Ωm) are inferred to be karstic cavities.
- Description
- Thesis (MSc) -- Faculty of Science and Agriculture, 2021
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (xvii, 143 pages)
- Format
- Publisher
- University of Fort Hare
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- rights holder
- Rights
- All Rights Reserved
- Rights
- Open Access
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UFH Department of Geology
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details | SOURCE1 | Mthintweni MSC Geology dissertation.pdf | 10 MB | Adobe Acrobat PDF | View Details |