Stratigraphy and sedimentology of the Msikaba formation in KwaZulu Natal South Coast, South Africa
- Authors: Busakwe, Nolukholo Sinovuyo
- Date: 2015
- Subjects: Geology, Stratigraphic Sedimentology -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2501 , vital:27877
- Description: The Msikaba Formation is a Late Devonian fluvial and marine succession which outcrops from Hibberdene to Port Edward along the south coast of KwaZulu-Natal Province, South Africa. The Formation is composed of brownish conglomerate at the bottom and white-greyish quartz arenite sequence in the middle and mixed quartz-arenite with feldspathic sandstone in the upper sequence. Previous studies put more emphasis on the correlation of Msikaba Formation with the Natal Group and Cape Supergroup, whereas this study revised the stratigraphy, and also put new insight on the petrography, sedimentary facies, depositional environments and diagenesis of the Formation. The total stratigraphic section attains a thickness of 184 m at Margate area and 186 m at Port Edward area. The stratigraphy of Msikaba Formation is well exposed on the outcrops along the KwaZulu-Natal coastline. The stratigraphy is subdivided into 4 new members along Margate to Shelly beach section; namely Manaba Member, Uvongo Member, Mhlangeni Member and Shelly Beach Member from bottom upward. Twelve sedimentary facies were identified and the sedimentary facies were integrated into 4 facies association: Facies association 1 (Gmm+Sm) represents braided fluvial deposits, Facies association 2 (Gcm+St+Sp+Sl+Shb) represents tidal channel and tidal flat deposit, Facies association 3 (St+Sp+Sr+Sl) is result of shallow marine deposit and Facies association 4 (Sp+Sl+St+Sm) is a mixed marine and fluvial deposit. Each facies association represents a specific stratigraphic unit and were deposited in a specific sedimentary environment. Grain size analysis was conducted on seventeen thin sections and 500 grains were counted from each thin section. The sandstone grain size parameters of mean, sorting, skewness and kurtosis fell under the average of 0.75, 0.78, 0.4 and 1.2φ respectively. The results show that most of the grain size are coarse to medium grained throughout the study areas and sorting of the sandstones are moderate to poorly sorted. The cumulative frequency diagrams and bivariate plots show positive skewness and negative kurtosis, which indicate a high hydrodynamic environment. Modal composition analysis and petrography studies show that detrital components of the Msikaba Formation are dominated by monocrystalline quartz, feldspar (mostly K-feldspar) and lithic fragments of igneous and metamorphic rocks. The sandstones could be classified as quartz arenite, sub-arkosic sandstone and feldspathic litharenite; and the provenance analysis indicates that the sandstones were derived from craton interior, recycled or quartzose recycled sources which may derived from weathering and erosion of igneous and metamorphic rocks. Diagenetic processes of the Msikaba Formation have been passed through early, mid- and late diagenetic stages. Cementation, mineral conversion and compaction affect early diagenetic stage; authigenic minerals, quartz and feldspar overgrowth are presented in mid-diagenetic stage, whereas recrystallization, replacement, deformation and dissolution have been strongly affected late diagenetic stage. Microscopy, XRD and SEM-EDX studies have identified five types of cements including smectite clay, kaolinite, hematite, quartz and feldspar cements. Quartz cement, pore-filling and pore-lining clay are the major type of cements in the Msikaba Formation. Based on the lithology, sedimentary structure and facies variations, the Manaba Member was most probably deposited in a braided fluvial environment, the Uvongo Member was deposited in a tidal channel environment, the Mhlangeni Member was formed in shallow marine storm-influenced environment, whereas the Shelly Beach Member was represented mixed marine and fluvial environment. The sequence stratigraphy of Msikaba Formation constitutes a transgressive sequence from Manaba Member to Uvongo Member, whereas it ended as a regressive sequence from Mhlangeni Member to Shelly beach Member. The Msikaba Formation shows major differences with the Natal Group and Table Mountain Group (Cape Supergroup) in the lithology, stratigraphic sequence, sedimentary structures, facies system, palaeocurrent styles, fossil contents and depositional environments, which demonstrate that they are not the equivalent stratigraphic unit. Therefore, the Msikaba Formation is a separate, younger stratigraphic unit, and cannot correlate with the Natal Group and Table Mountain Group as suggested by previous researchers.
- Full Text:
- Authors: Busakwe, Nolukholo Sinovuyo
- Date: 2015
- Subjects: Geology, Stratigraphic Sedimentology -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2501 , vital:27877
- Description: The Msikaba Formation is a Late Devonian fluvial and marine succession which outcrops from Hibberdene to Port Edward along the south coast of KwaZulu-Natal Province, South Africa. The Formation is composed of brownish conglomerate at the bottom and white-greyish quartz arenite sequence in the middle and mixed quartz-arenite with feldspathic sandstone in the upper sequence. Previous studies put more emphasis on the correlation of Msikaba Formation with the Natal Group and Cape Supergroup, whereas this study revised the stratigraphy, and also put new insight on the petrography, sedimentary facies, depositional environments and diagenesis of the Formation. The total stratigraphic section attains a thickness of 184 m at Margate area and 186 m at Port Edward area. The stratigraphy of Msikaba Formation is well exposed on the outcrops along the KwaZulu-Natal coastline. The stratigraphy is subdivided into 4 new members along Margate to Shelly beach section; namely Manaba Member, Uvongo Member, Mhlangeni Member and Shelly Beach Member from bottom upward. Twelve sedimentary facies were identified and the sedimentary facies were integrated into 4 facies association: Facies association 1 (Gmm+Sm) represents braided fluvial deposits, Facies association 2 (Gcm+St+Sp+Sl+Shb) represents tidal channel and tidal flat deposit, Facies association 3 (St+Sp+Sr+Sl) is result of shallow marine deposit and Facies association 4 (Sp+Sl+St+Sm) is a mixed marine and fluvial deposit. Each facies association represents a specific stratigraphic unit and were deposited in a specific sedimentary environment. Grain size analysis was conducted on seventeen thin sections and 500 grains were counted from each thin section. The sandstone grain size parameters of mean, sorting, skewness and kurtosis fell under the average of 0.75, 0.78, 0.4 and 1.2φ respectively. The results show that most of the grain size are coarse to medium grained throughout the study areas and sorting of the sandstones are moderate to poorly sorted. The cumulative frequency diagrams and bivariate plots show positive skewness and negative kurtosis, which indicate a high hydrodynamic environment. Modal composition analysis and petrography studies show that detrital components of the Msikaba Formation are dominated by monocrystalline quartz, feldspar (mostly K-feldspar) and lithic fragments of igneous and metamorphic rocks. The sandstones could be classified as quartz arenite, sub-arkosic sandstone and feldspathic litharenite; and the provenance analysis indicates that the sandstones were derived from craton interior, recycled or quartzose recycled sources which may derived from weathering and erosion of igneous and metamorphic rocks. Diagenetic processes of the Msikaba Formation have been passed through early, mid- and late diagenetic stages. Cementation, mineral conversion and compaction affect early diagenetic stage; authigenic minerals, quartz and feldspar overgrowth are presented in mid-diagenetic stage, whereas recrystallization, replacement, deformation and dissolution have been strongly affected late diagenetic stage. Microscopy, XRD and SEM-EDX studies have identified five types of cements including smectite clay, kaolinite, hematite, quartz and feldspar cements. Quartz cement, pore-filling and pore-lining clay are the major type of cements in the Msikaba Formation. Based on the lithology, sedimentary structure and facies variations, the Manaba Member was most probably deposited in a braided fluvial environment, the Uvongo Member was deposited in a tidal channel environment, the Mhlangeni Member was formed in shallow marine storm-influenced environment, whereas the Shelly Beach Member was represented mixed marine and fluvial environment. The sequence stratigraphy of Msikaba Formation constitutes a transgressive sequence from Manaba Member to Uvongo Member, whereas it ended as a regressive sequence from Mhlangeni Member to Shelly beach Member. The Msikaba Formation shows major differences with the Natal Group and Table Mountain Group (Cape Supergroup) in the lithology, stratigraphic sequence, sedimentary structures, facies system, palaeocurrent styles, fossil contents and depositional environments, which demonstrate that they are not the equivalent stratigraphic unit. Therefore, the Msikaba Formation is a separate, younger stratigraphic unit, and cannot correlate with the Natal Group and Table Mountain Group as suggested by previous researchers.
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Stratigraphy, geochemistry and origin of the manganese ore deposit in Carletonville, North West province of South Africa
- Authors: Pharoe, Benedict Kinshasa
- Date: 2015
- Subjects: Geology, Stratigraphic Geology--South Africa Geochemistry--South Africa
- Language: English
- Type: Thesis , Masters , Geology
- Identifier: http://hdl.handle.net/10353/11641 , vital:39092
- Description: The Carletonville manganese ore-deposit is a Neogene weathered nodule deposit which was developed on the Early Proterozoic Malmani dolomite succession of the Transvaal Supergroup in Carletonville area, North-West Province, South Africa. The deposits were formed from surficial weathering of the underlying Mn-rich dolomites of the Malmani Subgroup and some were formed from weathered Mn-rich Tertiary alluvial-fluvial sediments. These deposits are currently mineralized and hosted in modern Mn-Fe rich soil profiles and occurs at shallow depths, thus the ore is suitable to be mined by open-cast mining. The study dealt with the stratigraphy, petrology, geochemistry, diagenesis and origin of the ore-deposit. The stratigraphic profile of the manganese ore-deposit was subdivided into 8 zones, namely the (A, B, C, D, E, F, G, and H) zones from the surface downwards. On the basis of variation in mineralogical and chemical composition, nodule grain sizes and the zonation colour, the above mentioned zones were further integrated into the Upper (A and B), Middle (C, D and E) and Lower (F, G and H) Zone, with the I zone, the basement zone, representing the underlying Malmani Subgroup stromatolitic dolomite. The Upper Zone represents organic rich, fine grain silty soil which caps the stratigraphic succession in the mine area. Mineralogically, these zones are depleted in manganese and comprises of hematite, kaolinite, micas and quartz grains, with Mn-Fe coated terrigenous clasts concentrated at the lowermost portion of the B-zone along the contact with the underlying zones. The Middle Zone is characteristically medium to fine in grain sizes with reddish colour due to intense weathering of iron minerals to hematite and is depleted in Ca, Na and Mg bearing minerals as a result of dissolution and leaching and is highly concentrated in quartz and caliche fragments. The Lower Zone is coarse grained with dark, reddish-brown colour. The Middle and Lower Zones comprise mainly of Mn and Fe oxides, clays, quartz, limonite, micas and caliche patches. The concentration of manganese is, however, not consistent in these zones from one borehole to the next, it deviates with topography and depth. The overall stratigraphic succession in the mine area can be described as characterizing of basal stromatolitic dolomite of the Malmani Subgroup, overlain by zone of black, powder-like manganiferous wad which is in turn overlain by weathered Mn-rich Tertiary alluvial-fluvial sediments hosting manganiferous nodules. The whole succession is covered by Quaternary sands. The studies undertaken on grain size analysis for the determination of variation in nodule grain sizes with increasing depth along the profile has indicated a perfect variation trend in grain sizes, where the underlying Lower Zone characterizes of coarse grain fraction whilst the overlying Middle Zone is mainly medium to fine grained and the Upper Zone comprise of very fine silt soil. Statistical parameters were used to classify these sediments under Udden-Wentworth grain size classification scheme. Based on these parameters the samples were classified as pebbles and/or gravel on GRADISTAT program and were found to be moderately to poorly sorted, positively skewed with moderate kurtosis and displays a bimodal distribution. Mineralogical analysis with X-Ray Diffraction and petrographic studies indicates that cryptomelane (KMn8 O16) is the major manganese mineral, whereas pyrolusite occurs as a minor manganese mineral in the mine. Other mineral constituents include hematite/goethite, clay minerals, muscovite, quartz, calcite, limonite with minor amount of heavy minerals. The modal composition studies carried out on the terrigenous clasts which are coated on surface by Mn-Fe oxide concentric laminae indicated their nature to be sub-arkoses and quartz arenites. These clasts are found to occur in association with manganiferous nodules in the mine area, with high concentration experienced at the uppermost portion of the profile below the top soil. The provenance studies indicates the source of these terrigenous sediments from cratonic interior to recycle orogen at low plains with a temperate and subhumid climate and on tropical, humid conditions within an area of moderate to low relief. Based on the geochemical studies, different manganese classification schemes were adopted in this study and inferences were made from geochemical data which indicated supergene and hydrogenous source of the Carletonville manganese nodules suggesting precipitation from weathering residues of Malmani dolomite at passive continental margin of tectonic provenance, with temperate and tropical to humid climatic conditions. The diagenetic features were broadly divided into early, mid and uplift diagenetic stage. Early stage includes sediment consolidation which characterized of cementation and neomorphism in carbonate sediments. This period was followed by mid (burial diagenesis) stage which brought about an increase in tightness of grain packing, loss of pore spaces and thinning of beds due to weight of overlying sediments and selective dissolution of framework grains. Mineral dissolution and replacement were common factors during this stage. In the last diagenetic stage, rocks were uplifted, weathered and unroofed by erosion bringing mineral assemblage including newly formed diagenetic minerals into environment of low temperature and pressure, and high oxygen environment.
- Full Text:
- Authors: Pharoe, Benedict Kinshasa
- Date: 2015
- Subjects: Geology, Stratigraphic Geology--South Africa Geochemistry--South Africa
- Language: English
- Type: Thesis , Masters , Geology
- Identifier: http://hdl.handle.net/10353/11641 , vital:39092
- Description: The Carletonville manganese ore-deposit is a Neogene weathered nodule deposit which was developed on the Early Proterozoic Malmani dolomite succession of the Transvaal Supergroup in Carletonville area, North-West Province, South Africa. The deposits were formed from surficial weathering of the underlying Mn-rich dolomites of the Malmani Subgroup and some were formed from weathered Mn-rich Tertiary alluvial-fluvial sediments. These deposits are currently mineralized and hosted in modern Mn-Fe rich soil profiles and occurs at shallow depths, thus the ore is suitable to be mined by open-cast mining. The study dealt with the stratigraphy, petrology, geochemistry, diagenesis and origin of the ore-deposit. The stratigraphic profile of the manganese ore-deposit was subdivided into 8 zones, namely the (A, B, C, D, E, F, G, and H) zones from the surface downwards. On the basis of variation in mineralogical and chemical composition, nodule grain sizes and the zonation colour, the above mentioned zones were further integrated into the Upper (A and B), Middle (C, D and E) and Lower (F, G and H) Zone, with the I zone, the basement zone, representing the underlying Malmani Subgroup stromatolitic dolomite. The Upper Zone represents organic rich, fine grain silty soil which caps the stratigraphic succession in the mine area. Mineralogically, these zones are depleted in manganese and comprises of hematite, kaolinite, micas and quartz grains, with Mn-Fe coated terrigenous clasts concentrated at the lowermost portion of the B-zone along the contact with the underlying zones. The Middle Zone is characteristically medium to fine in grain sizes with reddish colour due to intense weathering of iron minerals to hematite and is depleted in Ca, Na and Mg bearing minerals as a result of dissolution and leaching and is highly concentrated in quartz and caliche fragments. The Lower Zone is coarse grained with dark, reddish-brown colour. The Middle and Lower Zones comprise mainly of Mn and Fe oxides, clays, quartz, limonite, micas and caliche patches. The concentration of manganese is, however, not consistent in these zones from one borehole to the next, it deviates with topography and depth. The overall stratigraphic succession in the mine area can be described as characterizing of basal stromatolitic dolomite of the Malmani Subgroup, overlain by zone of black, powder-like manganiferous wad which is in turn overlain by weathered Mn-rich Tertiary alluvial-fluvial sediments hosting manganiferous nodules. The whole succession is covered by Quaternary sands. The studies undertaken on grain size analysis for the determination of variation in nodule grain sizes with increasing depth along the profile has indicated a perfect variation trend in grain sizes, where the underlying Lower Zone characterizes of coarse grain fraction whilst the overlying Middle Zone is mainly medium to fine grained and the Upper Zone comprise of very fine silt soil. Statistical parameters were used to classify these sediments under Udden-Wentworth grain size classification scheme. Based on these parameters the samples were classified as pebbles and/or gravel on GRADISTAT program and were found to be moderately to poorly sorted, positively skewed with moderate kurtosis and displays a bimodal distribution. Mineralogical analysis with X-Ray Diffraction and petrographic studies indicates that cryptomelane (KMn8 O16) is the major manganese mineral, whereas pyrolusite occurs as a minor manganese mineral in the mine. Other mineral constituents include hematite/goethite, clay minerals, muscovite, quartz, calcite, limonite with minor amount of heavy minerals. The modal composition studies carried out on the terrigenous clasts which are coated on surface by Mn-Fe oxide concentric laminae indicated their nature to be sub-arkoses and quartz arenites. These clasts are found to occur in association with manganiferous nodules in the mine area, with high concentration experienced at the uppermost portion of the profile below the top soil. The provenance studies indicates the source of these terrigenous sediments from cratonic interior to recycle orogen at low plains with a temperate and subhumid climate and on tropical, humid conditions within an area of moderate to low relief. Based on the geochemical studies, different manganese classification schemes were adopted in this study and inferences were made from geochemical data which indicated supergene and hydrogenous source of the Carletonville manganese nodules suggesting precipitation from weathering residues of Malmani dolomite at passive continental margin of tectonic provenance, with temperate and tropical to humid climatic conditions. The diagenetic features were broadly divided into early, mid and uplift diagenetic stage. Early stage includes sediment consolidation which characterized of cementation and neomorphism in carbonate sediments. This period was followed by mid (burial diagenesis) stage which brought about an increase in tightness of grain packing, loss of pore spaces and thinning of beds due to weight of overlying sediments and selective dissolution of framework grains. Mineral dissolution and replacement were common factors during this stage. In the last diagenetic stage, rocks were uplifted, weathered and unroofed by erosion bringing mineral assemblage including newly formed diagenetic minerals into environment of low temperature and pressure, and high oxygen environment.
- Full Text:
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