Field mapping and geochemistry of lower Jurassic sediments and volcanics of the upper Karoo supergroup near Ha Mosi, Lesotho mountains
- Authors: Valashiya, Khaya
- Date: 2023-12
- Subjects: Sediments (Geology) -- South Africa -- karoo basin , Geochemistry , Geological mapping
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62687 , vital:72925
- Description: Geological mapping in the Lesotho-Drakensberg Mountains spans over 100 years with du Toit and Stockley being the major contributors to the published maps and to the understanding of emplacement of the Karoo Large Igneous Province (KLIP) in the countries of South Africa and Lesotho. Despite the detailed previous work, there remains limited data on paleoenvironmental changes at the contact between the sedimentary and volcanic sequences of the upper Karoo Supergroup. This study aims to map the lithostratigraphic boundaries, volcano-sedimentary facies and faults near Ha Mosi in southern Lesotho. A total 48 rock samples were collected for petrography, XRF and ICP-MS analyses. The new results were used to characterize the local chemostratigraphy and to propose new regional correlations across Lesotho and South Africa. In this thesis, eight lithostratigraphic units were defined with a total thickness of 550 m. The first two units (Units 1 and 2) comprise massive and bedded sandstones, interpreted as possible floodplain and ephemeral lacustrine deposits; these are ascribed to the upper Stormberg Group. These units are unconformably overlain by locally preserved thin basaltic (Unit 3) flows that are characterised by high Zr/Nb and Zr/Y ratios; and low Ti/Zr and P/Zr ratios similar to the Golden Gate Unit of the Drakensberg Group. The lava flows are overlain by bedded sandstone ascribed to Unit 4 and volcaniclastic breccia ascribed to Units 5 and 6. Unit 6 consists of a monolithic breccia that is composed of angular sandstone clasts similar to those of the underlying Stormberg Group. The monolithic breccia transitions upwards into a massive megaclastic clast-supported volcanic breccia, which consists of angular to sub-rounded basaltic and doleritic boulders. Petrified wood fragments are found within the megaclastic breccia, indicating the presence of vegetation during deposition and enhanced preservation. Unit 6 laterally grades into Unit 5, which is characterised by poorly bedded breccia composed of angular sandstone, mudstone clasts with minor basaltic and doleritic clasts and, breccia intraclasts. The breccia units are often associated with reworked sediments interpreted to be deposited by fluvial systems. The breccia is conformably overlain by basaltic lava flows (Unit 8) characterised by high Ti/Zr and P/Zr ratios and moderate to low Zr/Y and Zr/Nb ratios compared to the Unit 3 lavas and is similar to that of the Sani Pass Unit of the Drakensberg Group. The basaltic sequences in the Ha Mosi studied area preserve both pahoehoe textures and pillow lavas, indicating subaerial and subaqueous volcanism. The studied lithologies are intruded by gabbro and dolerites of the Karoo Dolerite Suite at 183 Ma. This stratigraphy records the transition from sedimentation in the Karoo Basin through to a dominantly volcanic succession, which has importance in terms of the Toarcian extinction at ca. 182 Ma. Mapped faults and associated fractures are orientated predominantly NW-SE with the hanging walls moved maximum 80 m to the south. The different dykes and fault structures possibly relate to the Weddel Triple Junction that developed during the Early Jurassic break up of Gondwana, between 200 and 180 Ma. The mapped lavas show that the magma source was a chemically heterogenous mantle that was subjected to different degrees of partial melting, with the introduction of small-scale chemical heterogeneities. The geodynamic setting is comparable to the Afar Triangle of north-east Africa where active tectonics created a large-scale NW-SE orientated fault system in response to crustal thinning and rifting. In both the Afar and Lesotho, vertical movements created lowlands that allow for the preservation of volcanic breccia and basalts with pillow lavas. These findings show that existing geological models in the Drakensberg-Lesotho Mountains can be improved upon detailed field mapping and geochemistry. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
- Authors: Valashiya, Khaya
- Date: 2023-12
- Subjects: Sediments (Geology) -- South Africa -- karoo basin , Geochemistry , Geological mapping
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62687 , vital:72925
- Description: Geological mapping in the Lesotho-Drakensberg Mountains spans over 100 years with du Toit and Stockley being the major contributors to the published maps and to the understanding of emplacement of the Karoo Large Igneous Province (KLIP) in the countries of South Africa and Lesotho. Despite the detailed previous work, there remains limited data on paleoenvironmental changes at the contact between the sedimentary and volcanic sequences of the upper Karoo Supergroup. This study aims to map the lithostratigraphic boundaries, volcano-sedimentary facies and faults near Ha Mosi in southern Lesotho. A total 48 rock samples were collected for petrography, XRF and ICP-MS analyses. The new results were used to characterize the local chemostratigraphy and to propose new regional correlations across Lesotho and South Africa. In this thesis, eight lithostratigraphic units were defined with a total thickness of 550 m. The first two units (Units 1 and 2) comprise massive and bedded sandstones, interpreted as possible floodplain and ephemeral lacustrine deposits; these are ascribed to the upper Stormberg Group. These units are unconformably overlain by locally preserved thin basaltic (Unit 3) flows that are characterised by high Zr/Nb and Zr/Y ratios; and low Ti/Zr and P/Zr ratios similar to the Golden Gate Unit of the Drakensberg Group. The lava flows are overlain by bedded sandstone ascribed to Unit 4 and volcaniclastic breccia ascribed to Units 5 and 6. Unit 6 consists of a monolithic breccia that is composed of angular sandstone clasts similar to those of the underlying Stormberg Group. The monolithic breccia transitions upwards into a massive megaclastic clast-supported volcanic breccia, which consists of angular to sub-rounded basaltic and doleritic boulders. Petrified wood fragments are found within the megaclastic breccia, indicating the presence of vegetation during deposition and enhanced preservation. Unit 6 laterally grades into Unit 5, which is characterised by poorly bedded breccia composed of angular sandstone, mudstone clasts with minor basaltic and doleritic clasts and, breccia intraclasts. The breccia units are often associated with reworked sediments interpreted to be deposited by fluvial systems. The breccia is conformably overlain by basaltic lava flows (Unit 8) characterised by high Ti/Zr and P/Zr ratios and moderate to low Zr/Y and Zr/Nb ratios compared to the Unit 3 lavas and is similar to that of the Sani Pass Unit of the Drakensberg Group. The basaltic sequences in the Ha Mosi studied area preserve both pahoehoe textures and pillow lavas, indicating subaerial and subaqueous volcanism. The studied lithologies are intruded by gabbro and dolerites of the Karoo Dolerite Suite at 183 Ma. This stratigraphy records the transition from sedimentation in the Karoo Basin through to a dominantly volcanic succession, which has importance in terms of the Toarcian extinction at ca. 182 Ma. Mapped faults and associated fractures are orientated predominantly NW-SE with the hanging walls moved maximum 80 m to the south. The different dykes and fault structures possibly relate to the Weddel Triple Junction that developed during the Early Jurassic break up of Gondwana, between 200 and 180 Ma. The mapped lavas show that the magma source was a chemically heterogenous mantle that was subjected to different degrees of partial melting, with the introduction of small-scale chemical heterogeneities. The geodynamic setting is comparable to the Afar Triangle of north-east Africa where active tectonics created a large-scale NW-SE orientated fault system in response to crustal thinning and rifting. In both the Afar and Lesotho, vertical movements created lowlands that allow for the preservation of volcanic breccia and basalts with pillow lavas. These findings show that existing geological models in the Drakensberg-Lesotho Mountains can be improved upon detailed field mapping and geochemistry. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-12
Antiproliferative activity of novel rhenium complexes and medicinal plant extracts
- Oosthuizen, Kenneth Thomas, Venables, Luanne
- Authors: Oosthuizen, Kenneth Thomas , Venables, Luanne
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Medicinal plants -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52028 , vital:43441
- Description: Cancer is a complex, multifactorial disease that affects millions of individuals every year. The adverse side effects and escalating costs of current therapies coupled with the increased incidence of resistance to these therapies make it imperative that we explore novel treatments for the disease. This study investigated two avenues for novel drug design namely, novel synthetic compounds and medicinal plant extracts. The benzimidazole ring system has shown potential as a scaffold for designing novel anticancer agents. Conjugation of the metal rhenium to novel variants of this ring system open up the possibility of designing novel drugs that serve both a diagnostic and a therapeutic function. This study investigated the in vitro anticancer potential of ten such complexes against selected breast and cervical cancer cell lines. The selectivity of the complexes for cancer cells over normal cells was also investigated while the mechanism of action of effective complexes was determined by exploring cell cycle arrest, biochemical markers of apoptosis and mitochondrial membrane disruption. All ten complexes were screened against MCF7 breast and HeLa cervical cancer cell lines with four showing antiproliferative activity against both cancer cell lines and one showing cell line specific toxicity against MCF7 breast cancer cells. When looking at the SAR of the compounds it was noted that activity was higher in compounds which contain two potentially bidentate benzothiazole ligands, while compounds with potentially tridentate ligands show good activity, but only if the benzothiazole moiety is not involved in coordination. The complexes showed greater antiproliferative activity against the MCF7 breast cancer cells with IC50 values ranging from 3.2 to 7.0 µM versus a range of 7.6 to 24.4 µM being obtained on the HeLa cervical cancer cells. Antiproliferative complexes were tested against confluent and log phase Vero cells at their respective IC50 values to determine their effect on “normal” cells. Confluent Vero cells showed less cell death than those in log phase indicating that the complexes show preference for proliferating cells. The mechanism of action of the complexes was studied on both cancer cell lines via cell cycle analysis and apoptosis assays investigating phosphatidylserine translocation, caspase -3 and -8 activation and mitochondrial membrane potential with most complexes inducing cell cycle arrest followed by cell death via both the extrinsic and intrinsic pathways of apoptosis. Since 1940, 49% of all the available anticancer drugs approved for cancer treatment were natural products or directly derived from natural products. Plants are an excellent source of secondary metabolites, many of which are unique chemical compounds that cannot be synthesized in a laboratory. Ethnobotanical surveys conducted in conjunction with Traditional Health Practitioners of the Mkuranga and Same districts in Tanzania identified 25 plants that are used for the treatment of cancer. Four of these plants (A. mossambicensis, C. adenocaule, C. pseudopulchelusis and R. natalensis) with ethnobotanically reported anticancer usage showed cytotoxic activity against brine shrimp and were selected for further in vitro anticancer studies. All four plants were found to have antiproliferative activity against HeLa cervical cancer cells with IC50 values ranging from 3.4 to 50.8 µg/mL. This study was also tasked with investigating the mechanism of action of C. pseudopulchelus on HeLa cervical cancer cells by exploring cell cycle arrest, biochemical markers of apoptosis and mitochondrial membrane x disruption. C. pseudopulchelus caused early M phase arrest followed by slippage and subsequent cell death via the extrinsic pathway of apoptosis. In conclusion, this study showed that both novel complexes as well as medicinal plant extracts represent an interesting avenue for the development of novel anticancer drugs that are cheaper and produce less side effects than current therapies. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Oosthuizen, Kenneth Thomas , Venables, Luanne
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Medicinal plants -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52028 , vital:43441
- Description: Cancer is a complex, multifactorial disease that affects millions of individuals every year. The adverse side effects and escalating costs of current therapies coupled with the increased incidence of resistance to these therapies make it imperative that we explore novel treatments for the disease. This study investigated two avenues for novel drug design namely, novel synthetic compounds and medicinal plant extracts. The benzimidazole ring system has shown potential as a scaffold for designing novel anticancer agents. Conjugation of the metal rhenium to novel variants of this ring system open up the possibility of designing novel drugs that serve both a diagnostic and a therapeutic function. This study investigated the in vitro anticancer potential of ten such complexes against selected breast and cervical cancer cell lines. The selectivity of the complexes for cancer cells over normal cells was also investigated while the mechanism of action of effective complexes was determined by exploring cell cycle arrest, biochemical markers of apoptosis and mitochondrial membrane disruption. All ten complexes were screened against MCF7 breast and HeLa cervical cancer cell lines with four showing antiproliferative activity against both cancer cell lines and one showing cell line specific toxicity against MCF7 breast cancer cells. When looking at the SAR of the compounds it was noted that activity was higher in compounds which contain two potentially bidentate benzothiazole ligands, while compounds with potentially tridentate ligands show good activity, but only if the benzothiazole moiety is not involved in coordination. The complexes showed greater antiproliferative activity against the MCF7 breast cancer cells with IC50 values ranging from 3.2 to 7.0 µM versus a range of 7.6 to 24.4 µM being obtained on the HeLa cervical cancer cells. Antiproliferative complexes were tested against confluent and log phase Vero cells at their respective IC50 values to determine their effect on “normal” cells. Confluent Vero cells showed less cell death than those in log phase indicating that the complexes show preference for proliferating cells. The mechanism of action of the complexes was studied on both cancer cell lines via cell cycle analysis and apoptosis assays investigating phosphatidylserine translocation, caspase -3 and -8 activation and mitochondrial membrane potential with most complexes inducing cell cycle arrest followed by cell death via both the extrinsic and intrinsic pathways of apoptosis. Since 1940, 49% of all the available anticancer drugs approved for cancer treatment were natural products or directly derived from natural products. Plants are an excellent source of secondary metabolites, many of which are unique chemical compounds that cannot be synthesized in a laboratory. Ethnobotanical surveys conducted in conjunction with Traditional Health Practitioners of the Mkuranga and Same districts in Tanzania identified 25 plants that are used for the treatment of cancer. Four of these plants (A. mossambicensis, C. adenocaule, C. pseudopulchelusis and R. natalensis) with ethnobotanically reported anticancer usage showed cytotoxic activity against brine shrimp and were selected for further in vitro anticancer studies. All four plants were found to have antiproliferative activity against HeLa cervical cancer cells with IC50 values ranging from 3.4 to 50.8 µg/mL. This study was also tasked with investigating the mechanism of action of C. pseudopulchelus on HeLa cervical cancer cells by exploring cell cycle arrest, biochemical markers of apoptosis and mitochondrial membrane x disruption. C. pseudopulchelus caused early M phase arrest followed by slippage and subsequent cell death via the extrinsic pathway of apoptosis. In conclusion, this study showed that both novel complexes as well as medicinal plant extracts represent an interesting avenue for the development of novel anticancer drugs that are cheaper and produce less side effects than current therapies. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
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