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Item The role of geological structures in the hydrogeology of the Upper Crocodile River Basin, South Africa(2020) Nyebelele, SiphoThe Upper Crocodile River Basin (UCRB) is made up of fractured crystalline rocks such as quartzites, granites, gabbro’s and Bushveld Igneous Complex rocks that are intruded by dykes of varying ages and orientations. A study of the geological structures on the role they play on the hydrogeology of the UCRB was undertaken. The use of ArcGIS for lineament analysis and magnetics data for the interpretation of lineaments in the study area revealed three main trends. A NNE-SSW, E-W and a NW-SE trend, where the NW-SE and NNE-SSW trends form conjugates of each other and the E-W lineaments forming extension release joints. The SW lineaments share their orientation with the southern Pilanesberg dyke swarm whereas the E-W have dykes that are doleritic in composition and are said to be post-Karoo intrusions. Rose diagrams revealed dominant orientations for these lineaments to be 135o, 015o and 085o for the SE, NNE-SSW and E-W, respectively. The drainage pattern is dominantly dendritic, which develops in low porosity rocks with the orientation of the streams following that of the lineaments. Additionally, dendritic pattern is caused by homogeneous material, and that is, geology of similar resistance. Trellis drainage patterns occur in two areas, one being subject to lineament control and the other affected by both the lithology and lineaments. A total of four springs were used to estimate recession coefficients. Three of these were on dolomites and one on quartzites. The dolomitic springs share a similar recession coefficient, suggesting that regardless of their respective locations the dolomites share similar physical properties. The quartzite spring has a higher recession coefficient as such the physical properties are better suited for groundwater circulation than in the dolomites. The Maloney’-Eye has a bigger catchment, which resulted in higher discharge. The smallest spring catchment is observed for the Elandsfontein-Eye, however, it has a similar discharge to that of the quartzite spring. The streams in the UCRB are predominantly gaining streams. However, one of the streams loses and gains depending on the seasons. The gain is facilitated by the fractures and the loss is possibly facilitated by the karsts on the dolomites. The isotopic composition of the groundwater in the study area shows a depletion of heavy isotopes of δD and δ18O. The groundwater samples plotted along Meteoric Water Lines (MWL) shows an evolution pattern of water recharged directly from rainfall or rapid recharge through the fractures. Some samples are extremely depleted, which can be attributed to (1) recharge from high altitudes, (2) low humidity during condensation and/or (3) recharge during a colder climate. The average residence time of the groundwater based on tritium data is around 23 years. Lineaments are very important for the hydrogeology of the UCRB on the basis that they affect the drainage patterns, stream orientation and play a fundamental role in the groundwater circulation. Although, the lineaments facilitate the groundwater flow, the residence time is still high on average and the recession coefficients are also high suggesting deep circulation. This dominance of lineaments and similarities in environmental isotopes shows that the possibility of compartmentalisation (on dolomites in particular) is very lowItem The geology, geochemistry and petrology of the metagabbro units of the tati N1-CU sulphide mines and deposits and associated PGEs mineralisation(2019) Thari, Kabelo ThabisoVarious metagabbro bodies host sulphide mineralisation in the Tati Sulphide Mines and Deposits Complex located in the Tati greenstone belt, southwestern margin of the Zimbabwe craton. The Tati Sulphide Mines and Deposits Complex, referred to here as the TSMDC, is a major metallogenic zone in east Botswana. This study focuses on gaining insight into the geology, whole-rock geochemistry and petrology of the Ni-Cu-PGE- mineralised gabbro units and contact lithologies in order to develop effective exploration targets for the TSMDC. The TSMDC mainly comprises three types of gabbroic units-melanogabbro, mesogabbro and leucogabbro-in contact with a wide range of magmatic rocks that include, granodiorite, porphyritic granodiorite, quartz diorite, tonalite, amphibolite, basalt, dolerite and pegmatites. The gabbro units occur near metasedimentary units that include dolomite, Banded Iron Formation (BIF) and quartzite. Some of the gabbro units host sulphide mineralisation comprising mainly pyrrhotite, pentlandite, chalcopyrite and pyrite, whereas some gabbro units are barren. The gabbro units are generally medium grained and composed mainly of variable propositions of the primary minerals pyroxene (20-30%), plagioclase (30-35%) and quartz (2-7%) and minor secondary minerals that include, chlorite (~2%) and epidote (~1%). The major and trace elements data indicate a suite of variably magmatically evolved gabbro units, which show a wide compositional range in MgO (4-17 wt. %), FeOt (5-20 wt. %), SiO₂ (45-52 wt. %), Al₂O₃ (10-17 wt. %) and CaO (5-15 wt. %). Based on the positive correlations between MgO and FeOtotal, CaO and MgO and Y and Zr, the gabbro units are interpreted as having been generated through a fractional crystallisation process, where pyroxene and plagioclase were the dominant rock-forming minerals. Fractional crystallisation is also evidenced by positive correlation between SiO₂ and Na₂O, + K₂O, and resulted in the formation of an enriched quartz mineralogy in granitoid units of the TSMDC. Generally, gabbro units show chondrite-normalised plots with slight enrichment of LREE relative to depletion of HREE. There is a weak positive Eu anomaly, which suggests plagioclase in combination with pyroxene and sphene controlled the fractionation of the partial melts in the upper crust. The gabbro units and contact lithologies were emplaced in a continental margin environment prior to and following several deformation events. Three deformation events, D1, D2 and D3 were identified in TSMDC. D1 is ductile-brittle in nature and is characterised by folding (fo1), foliation S1, and NE-SW and NNE-SSW trending faults (F1). D2 resulted in the formation of the Phoenix, Selkirk and Rooikoppie shear zones associated with a regional foliation (S2), lineation (L₂) and en echelon quartz veins (V₂). The third deformation event, D₃, is associated with formation of fracture cleavage and joints that dominate most of the study area. On a regional scale, the N-S and NE-SW trends of crustal lineaments controlled the geometry of the Phoenix, Selkirk mines, Tekwane and Rooikoppie deposits. On a local scale, the structural factors controlling the current position of the Phoenix, Selkirk mines, Tekwane and Rooikoppie deposits are a network of proximal fractures to the crustal lineaments, which provided transport and settling of differentiated magma during interaction with sulphide minerals in the formation of the Ni-Cu-PGEs mineralisation. The integration of the geology, whole rock geochemistry and petrology suggests that various gabbro units host Ni-Cu-PGEs mineralisation and are affected by structural lineaments, which include shear zones in TSMDC. The shear zones acted as conduits for the propagation of Ni-Cu-PGEs mineralisation and hydrothermal fluids. The geometry of the Phoenix, Selkirk mines, Tekwane and Tekwane deposits is coincident with NE and NW trends of the shear zones.Item The transition from hypogene to supergene mineralisation at the Mashtu South Cu-co deposit, Katanga, Democratic Republic of Congo(2018) Gigler, Gruffudd MorganMashitu South is a Cu-Co deposit situated in the Katanga Province of the Democratic Republic of the Congo (DRC), about 25km to the east of the city of Kolwezi. It lies within the northwestern portion of the Central African Copperbelt (CAC), an arcuate region with a world class abundance of copper deposits that straddles the external-fold-and-thrust-belt and the Domes region of the Lufilian arc, an orogenic belt that formed during the ∼600-500Ma Pan African orogeny. Cu-Co mineralisation at Mashitu South is hosted in the rocks of the Mines Series and Roches Argillo-Talceuses (RAT) subgroups of the Roan Group, deposited during the early stages of the opening of the Katangan basin, which is constrained to a maximum age of ∼880Ma. This study characterises the mineralisation stages and geochemistry of Mashitu South through a combination of core logging, geostatistical and petrographic techniques. The mineralogical and geochemical changes which occurred to the deposit throughout its paragenetic history are also explored. This is done with the purpose of linking the mineralisation at the deposit to regional metallogenic and geodynamic events, as well as developing vectors to Cu-Co mineralisation. Mineralisation at Mashitu South occurred in four stages. The first stage is characterised by the development of stratiform-disseminated, zoned Cu-Co sulphides restricted to the rocks of the Mines Series, in a manner comparable to the sedimentary hosted stratiform copper (SSC) deposit model. A protracted, syn-diagenetic timing is inferred for this stage, which caused the formation of hypogene, stratiform orebodies, primarily in the Kamoto Formation. Metals emplaced during the first stage were remobilised during the second mineralisation stage, which resulted in the development of vein-hosted hypogene Cu Co sulphides, but does not appear to have concentrated metals into significant orebodies at Mashitu South. The second period of mineralisation is inferred to be early/syn-orogenic in age. Hypogene mineralisation at Mashitu South is found to have an element association of Cu + Co + Bi + Ni + V + S ± Mo ± As ± Fe ± Zn. The deposit was subsequently affected by two discrete stages of supergene alteration and mineralisation. Supergene alteration has resulted in the in-situ oxidation of hypogene Cu-Co sulphides, and also the leaching and remobilisation of metals from hypogene mineralisation. The leaching and remobilisation process formed supergene, malachite-dominated orebodies which have an element association of Cu + Be + P ± Zn, the location of which is primarily controlled by metal availability and permeability of the host rocks. The RAT Subgroup is frequently host to such orebodies, underneath leached and eroded away Mines Series strata. These orebodies are usually found at a depth of ∼30 50m. An occurrence of bacillus-shaped features composed of Cu-Co sulphides was discovered in the lower Shales Dolomitique du Base (SDB) unit of the Mines Subgroup, and investigated with respect to the potential biogenicity and antiquity of the features as candidate microfossils. Further study found these features to be pseudofossils formed primarily by the replacement of diagenetic rutile crystals by sulphides, during the primary, stratiform mineralisation stage. The various elements of the hypogene geochemical association are shown to have different mobilities in the supergene leaching environment, with Cu being relatively mobile and Co + Bi + Ni + V ± Mo being relatively refractory. This variation in mobility between elements, which are associated with Cu in the hypogene environment, suggests a zonation of these elements around Cu in the supergene environment, controlled by the hydrological gradient. At Mashitu South, this has resulted in the relative enrichment of Bi, Mo, V and Co in the upper 10m of the rock profile. Nickel is not as depleted in this interval as Cu, which is strongly depleted in the near-surface environment. It is therefore hypothesised that Bi, Mo, V, Co and Ni would make better surface vectors towards buried Cu-Co mineralisation than Cu, in regions where the supergene leaching process is particularly effective. ‘Cobalt caps’ above Cu-Co deposits in Katanga are well known, but this study suggests that Bi, Mo and V may make even better surface vectors to mineralisation than Co.Item Hydrogeological study of geological features in the groundwater system of Tweefontein 360KT farm, Limpopo Province(2018) Dalasile, Piwo-kuhleA hydrogeological study was conducted to investigate the possible influence of geological structures on the groundwater flow (regime) and dynamics at the Tweefontein farm 360KT, near Steelpoort, Limpopo Province. The aim of the investigation was to understand the groundwater system, as well as to devise appropriate measures that promote proper groundwater resource management, which will allow for prediction and mitigation of possible groundwater ingress into underground workings. Field observations, cross sections, borehole data, chemical analyses and environmental stable isotopes were used to understand the influence of geological features on flow dynamics in Tweefontein farm. Geological features, faults and dykes were found to enhance groundwater flow due to the presence of interconnected cross-cutting joints. Furthermore, weathering was also found to enhance groundwater flow within these structures. Calcrete and ferricrete within the weathered zone can act as a barrier or limit vertical flow of groundwater to the fractured zone, and this can enhance the formation of later flows which may contribute to formation of springs. There is no major ingress of groundwater into existing underground workings near a prominent NE-striking faulted shear zone that is partly overlain by a river. It can be postulated, based on the documentary evidence collected in this study that the inability of water to ingress underground workings overlain by rivers is attributed to depth, as well as the infilling within the prominent NE-striking geological features. Groundwater within the study area shows a Ca-Mg-HCO3-dominated water type indicative of fresh, shallow circulating groundwater. However, there also is a chloride-dominated facies showing the strong effect of evaporation within the shallow weathered zone aquifer. The enrichment in Ca and Mg ions may be attributed to weathering of ferromagnesian silicate minerals of the Bushveld Igneous Complex. Highly enriched stable isotope (δ2H and δ18O) signatures on surface-water and shallow groundwater suggest the presence of evaporation prior to infiltration. Water from mine fissures plot on the local meteoric water line suggesting direct and preferential recharge through geological structures during periods of rainfall in the summer and winter months. Groundwater in deep mine fissures shows a highly depleted isotopic signature compared to water in the shallow weathered aquifer, which suggests limited vertical hydraulic connection.Item Understanding magmatic timescales and magma dynamics in Proterozoic anorthosites: a geochronological and remote sensing investigation of the Kunene Complex (Angola)(2017) Brower, Alan MartinThe Kunene Anorthosite Complex (KAC), located in southwest Angola, is one of the largest Proterozoic anorthosite intrusions on Earth, with an areal extent of at least 18 000 km2. The KAC is composed of anorthosite, leucotroctolite, leuconorite, leucogabbro and granitoids. Many aspects of Proterozoic anorthosite petrogenesis are still unknown with debates including the parental magma source, temporal restriction of anorthosite, and anorthositic magma emplacement mechanisms. Very little research has been conducted on the Angolan portion of the KAC, and published maps lack detail and are often inconsistent. Previous studies considered the Kunene Complex to be have formed as a layered intrusion and, more recently, as a series of coalesced plutons. As one of the largest and least studied Proterozoic anorthosites in the world, the KAC provides a unique opportunity to test recent ideas surrounding Proterozoic anorthosite petrogenesis related to the KAC. Its linear geometry, make-up of multiple plutons and large age range also create a great desire for study. This study allows for the development of new models for the emplacement dynamics, timescales, and tectonic setting of the KAC. This study makes use of the interpretation of remote sensing datasets (Landsat 8 and SRTM 3 – Shuttle Radar Topography Mission) as well as U-Pb TIMS (Thermal Ionisation Mass Spectrometer) geochronology to analyse the composition, structure and age variations of the KAC. In order to extract maximum compositional data from this magmatic complex, various image processing techniques have been performed, including false colour composites, a minimum noise fraction, a principle component analysis, and band ratioing for the Landsat 8 data. To best identify structural data, hill-shading and an automatic lineament extraction was used for the SRTM and Principle Component 1 images. The results of the Landsat Image processing enable identification of different spectral signals and allow for the differentiation of the KAC from country rocks, in addition to separating the anorthositic rocks of the KAC itself. From the SRTM imaging, lineament data were extracted and various structural features identified throughout the KAC. In combination with ground truthing, these lineaments are classified into either magmatic foliations, subsolidus planar structures or fault structures. Using these techniques, this study reiterates the batholitic appearance of the KAC and identifies two main magmatic entities of distinct crystallization age, composition and Landsat spectral response, making up the KAC. In combination with ground truthing, a new interpretative lithological map for the KAC and adjacent country rocks has been produced. Understanding the relative timing of the anorthosite emplacement is crucial for understanding how these enigmatic magmas form and how they rise through the crust. The ages and relative emplacement sequence of the individual batches forming the KAC are unknown. New high precision U-Pb ID-TIMS ages on zircon and baddeleyite for many of the newly defined spectral domains across the anorthositic complex are presented. These new geochronological results reveal subtle variations in crystallisation age within the KAC on the order of 10 Ma. There is no gradual age progression between potential distinct magmatic batches but distinct groupings of ages. Mean age clusters of 1379.8 ± 2.0 Ma (n=5) occurring to the north of the NE – SW striking Red Granite intrusions, whereas in the south there is an older age grouping of 1390.4 ± 2.3 (n=3). Two additional ages of 1400.5 ± 1.3 Ma and 1438.4 ± 1.1 Ma have been obtained in the centre and southeast of the complex, respectively. These results indicate that the Kunene anorthosites were emplaced over 60 Ma. The 40 Ma difference between emplacement of the first anorthositic body and the remaining anorthositic emplacement suggests two possibilities for the long-lived magmatic system: 1) Magma differentiation occurred slowly over an extended period of time with anorthositic mushes reaching their final emplacement depth at a faster rate. 2) Differentiation occurred at a faster rate but the mushes ascended slowly to their final emplacement depths. A link has been found between spectral domain composition and age. In general, leuconoritic domains are older than the leucotroctolitic domains. This may imply that the first pulses of magma received a greater degree of crustal contamination, forcing the initial broadly basaltic magma to produce orthopyroxene as the main mafic phase. The later pulses received less contamination as they ascended through the already partially melted and refractory crust, producing olivine as the mafic phase and deforming the older domains. This study reiterates the multiphase petrogenesis of Proterozoic anorthosites and sheds light on the assembly of crystal-rich magmas as they ascend through the crust. Utilizing the remote sensing data and the geochronological results, a new model for the petrogenesis of the KAC been developed and it is suggested that the most valid setting for the KAC is a continental arc.Item Experimental constraints on crustal contamination in Proterozoic anorthosite petrogenesis(2017) Hill, Catherine MaryMassif-type anorthosites formed in the Proterozoic Eon are the most voluminous anorthosite occurrences on Earth, reaching tens of thousands of square kilometers in aerial extent. While they formed throughout the Proterozoic, most formed during a 700 Ma period between 1800 and 1100 Ma. The rocks are dominated by plagioclase (typically 70 – 95 volume %) of intermediate composition (An40-65). Olivine, orthopyroxene, clinopyroxene and Fe-Ti oxides make up the minor mafic proportion. While most researchers agree that the anorthosites formed from a high-alumina basaltic parental magma, there are disparate views on how that parental magma was generated. Whether the parental magma formed by partial melting of the lower crust, or by mantle melting, is a topic of much debate. The anorthosites commonly have crust-like isotopic signatures, but this could be produced by melting of the lower crust, or by crustal contamination of mantle-derived magmas. Many Proterozoic anorthosite complexes consist of both olivine-bearing and orthopyroxene-bearing anorthosites. This has been attributed to variable amounts of crustal contamination of mantle-derived magmas, based on evidence from isotopes and field relations. While geochemical and petrologic evidence for crustal contamination is plentiful, existing experimental work shows that a thermal divide exists for high-alumina basalts fractionating at lower crustal depths, casting doubts on whether fractionation of a mantle melt could produce anorthosite. Here I use high-pressure experiments to test whether the fractionation of high-alumina basalt can form anorthosites, and to what extent crustal contamination affects the fractionation sequence. The results are compared to new geochemical and petrologic data from the Kunene Anorthosite Complex (KAC), in Angola and Namibia. The KAC is one of the largest anorthosite complexes in the world, with an area of ~18 000 km2. The KAC (1438 – 1319 Ma) has an elongate shape and intruded into Palaeoproterozoic to Mesoproterozoic country rocks (~2200 to 1635 Ma) at the southern margin of the Congo craton. It is associated with a suite of granitoid rocks of variable composition, which are akin to the granitoids associated with nearly all Proterozoic anorthosites. The granitoids have been shown to be coeval with the anorthosites, but were from a chemically independent magma series. The most distinctive granitoids in the KAC are the Red Granites, which outcrop around the southern margins of the complex, and also cross-cut the complex in a NE-SW linear belt, dividing the complex roughly into northern and southern domains. The rocks of the KAC are highly variable in terms of mode, mineral chemistry, and texture, but there is a general trend of more olivine-bearing anorthosites north of the granite belt, and orthopyroxene-bearing anorthosites to the south. The olivine-bearing rocks (or leucotroctolites) typically contain plagioclase and cumulus and/or intercumulus olivine, with lesser interstitial orthopyroxene and/or clinopyroxene, Fe-Ti oxides, and biotite. The orthopyroxene-bearing anorthosites (or leuconorites) contain cumulus plagioclase ± cumulus orthopyroxene, and interstitial orthopyroxene, clinopyroxene, oxides and biotite. The leucotroctolites are characterized by more calcic plagioclase (An56-75), while the leuconorites contain more intermediate plagioclase (An48-56). The variability of the rocks across the complex suggests that the KAC consists of several coalesced plutons with different histories. The petrologic data and field observations in this study are consistent with the leuconorites of the complex being derived from a mantle-derived magma that experienced contamination by silica-rich rocks, crystallizing orthopyroxene rather than olivine, and less calcic plagioclase. The leucotroctolites experienced less or no contamination. To test whether the mineral dichotomy and the variations in plagioclase chemistry observed in Proterozoic anorthosites are due to variably contaminated mantle-derived magma, piston cylinder experiments were conducted on a synthetic high-alumina basalt (HAB) composition, as well as a mixture of this HAB with 30% of a Red Granite composition. Experiments were conducted at 10 kbar, to simulate the depth at which anorthosite differentiation most likely begins (based on Al-in-orthopyroxene geobarometry of highly aluminous orthopyroxene megacrysts that occur in many massifs). The uncontaminated experiments produced olivine as the first liquidus phase, followed by plagioclase (An65-68), and then by clinopyroxene, pigeonite and ilmenite at progressively lower temperatures. Residual liquids evolve towards more silica-rich compositions with decreasing temperature. The contamination experiments produced liquidus orthopyroxene, followed by plagioclase (An51-56), and then by pigeonite at lower temperatures. The experiments show that contamination of a primitive HAB magma by granitic material, most likely produced by partial melting of the lower crust during anorthosite formation, can shift the mineral assemblages of the crystallizing anorthosite from olivinebearing to orthopyroxene-bearing, and produce less calcic plagioclase than the uncontaminated HAB magma. This could explain the observation of olivine-bearing and orthopyroxene-bearing anorthosites in the KAC and many other Proterozoic anorthosites. Previous high-pressure experimental studies, using a slightly more evolved HAB composition, indicated the presence of a thermal divide, which causes liquids to evolve to more Si-poor compositions. The experimental results presented in this study however, do not show a thermal divide, indicating that small variations in experimental starting composition can cause large differences in the liquid line of descent. The results of this study indicate that partial melting of the mantle can produce anorthosite parental magmas, and that the range in mineral assemblages of the anorthosites can be accounted for by crustal contamination of a mantle-derived magma. Fractionation of the experimental starting compositions was also modeled using the MELTS algorithm. These calculations produce a close match to the experimental liquid trends. This allows for modeling of a variety of compositional and environmental variables. The MELTS modeling shows that as little as 10% contamination of HAB magma with a granitic composition may position the magma in the orthopyroxene stability field, forming orthopyroxene-bearing anorthosites. The modeling also shows that a variety of silica-rich contaminants, including granites, granodiorites and tonalities, produce similar results and liquid evolution trends, so a range of granitoid compositions may successfully produce the shift in mineral assemblages of the anorthosites. This suggests that crustal contamination of mantle-derived HAB could be a widespread process and the primary mechanism that produces the distinctive crust-like signatures in Proterozoic anorthosites. In summary, the mineralogical and chemical diversity observed in Proterozoic anorthosites can be produced by variable amounts of crustal contamination of mantle-derived, highalumina basaltic magma. The experimental results in this study combined with field observations, and geochemical and isotopic data, provide evidence for a model of massif-type anorthosite petrogenesis. Orthopyroxene-bearing rocks formed from an originally highalumina basaltic magma that experienced contamination by granitic partial melts of the lower crust, during ponding of the magma at the Moho. This process preconditioned the surrounding crust and possibly prevented further anatexis. Following emplacement of orthopyroxene-bearing anorthosites, subsequent magma pulses ponded at the Moho did not assimilate any/as much granitic material, as they were interacting with preconditioned crust, and formed olivine-bearing anorthosites. With better constraints on the parental magma composition, magma source, and crustal contamination processes, addressing aspects such as the tectonic setting and emplacement mechanisms of these massive intrusions should be prioritized. Understanding these enigmatic aspects of anorthosite petrogenesis is leading the anorthosite community towards answering the ultimate questions of why massif-type anorthosites are restricted to the Proterozoic.Item Modelling the Witwatersrand basin: a window into neoarchaean-palaeoproterozoic crustal-scale tectonics(2017) Molezzi, MarcelloThe aim of this study was to investigate and evaluate the 3D structural architecture around the Vredefort dome in the Witwatersrand basin, in particular the unexposed southern portion. This was done in order to establish strato-tectonic relationships, first order deformation structures, and basement architecture. The outcomes provide a more detailed architecture around the central uplift that may be used in future work aimed at examining the nature of giant terrestrial impacts. In summary, the integration of borehole, surface mapping, and 2D reflection seismic data provides a well constrained 3D geological model of the dome, central uplift, and adjacent areas (covering approximately 11600 km2). Seven structural features are discussed from the 3D modelling results. These include, (1) a normal fault in the lower West Rand Group, (2) an undulate, normal faulted truncation plane, constrained as post-West Rand Group and pre or early-Central Rand Group, (3) a truncation plane and local enhanced uplift constrained as pre to syn-VCF, (4) a listric fault system, constrained as post-Klipriviersberg Group and syn-Platberg Group, (5) a truncation plane, constrained as syn-Black Reef Formation, (6) folds, including a large asymmetric, gentle anticline here named the Vaal Dam Anticline, constrained as post-Magaliesberg Formation and pre-Vredefort impact, and (7) a listric fault across the southeastern margin of the Vredefort dome, constrained as late to post-central uplift formation. The findings support previous work by Tinker et al. (2002), Ivanov (2005), Alexandre et al. (2006), Dankert and Hein (2010), Manzi et al. (2013), Jahn and Riller (2015), and Reimold and Hoffmann (2016). However the findings oppose various parts of previous work by Friese et al. (1995), Henkel and Reimold (1998), and Reimold and Koeberl (2014). A new term is also proposed for the periclinal folds located around the central uplift, i.e., impact-type curvature-accommodation folds. This study demonstrates the importance of integrating multiple sources of data into a single 3D spatial environment in order to better refine and distinguish impact-related deformation from the pre-existing basement architecture.Item Tectonic influence on the evolution of the Early Proterozoic Transvaal sea, southern Africa(2015-01-14) Clendinin, C WThe epeiric Transvaal Sea covered the Kaapvaal Craton of southern Africa during the Early Proterozoic and its remnant strata represent one of the oldest known carbonate depositories. A genetic stratigraphic approach has been used in this research on the evolution and syndepositional tectonics of the Transvaal Sea; research also emphasized the development of basement precursors, which influenced the Transvaal Sea. Eight subfacies were initially recognized and their interrelationships through Transvaal Sea time and space were used to identify ten depositional systems. Paleogeographic reconstructions indicate that the depositional systems developed on morphological variations of a distally-steepened carbonate rarp and that the depositional character of each was simply a function of water Backstripping of the depositional systems indicates that the Transvaal Sea was compartmentalized; three compartments are preserved on the Kaapvaal Craton. Backstripping also indicates that the depositional center of the Transvaal Sea lay over the western margin of an underlying rift. Rifting had developed a major, north-south-trending structure, and its geographical interrelationships with the east-west-trending Selati Trough created the compartment architecture of the basement. Interpretation of syndepositional tectonics suggests that six stages of subsidence influenced the Transvaal Sea. Early subsidence consisted of mechanical (rift) subsidence followed by