A Dissertation submitted to the Faculty of Science, University of the Witwatersrand; in fulfilment of the requirements for the degree of Master of Science. Johannesburg August 2016. / Rocks of the Neoarchaean Witwatersrand Supergroup exposed in the collar of the impact-induced 2.02 Ga Vredefort Dome exhibit complex geological structures. These structures are generally considered to have been formed by the Vredefort impact event, through rapid deformations on time scales of seconds to minutes associated with the relatively brief impact processes. However, geological mapping of the structures and petrographic analysis from the northern collar of the dome show that the collar hosts at least three generations of pre-impact structures. In contrast to impact-induced structures, these pre-impact structures indicate slow and progressive deformations that are uncharacteristic of impacts. The pre-impact deformations comprise: (a) an extensional D1 deformation characterised by listric faults up to kilometre-scale; (b) Syn-metamorphic (M2(NC)) D2 ductile deformation characterised by regional S2 foliation, which locally indicates northwest-directed vergence; and (c) D3 deformation that crenulated the pre-existing S2 foliation (S3). Pre-impact structures can be distinguished from impact-induced structures by: (1) difference in the geometry and sense of slip between D1 faults and D4 impact-induced faults; and (2) crosscutting relationships between impact-induced D4 features and D2 and D3 pre-impact features. In their present (rotated) orientation, the D1 faults exhibit an apparent strike-slip separation, which translates to normal-slip fault geometries when impact-induced overturning of strata is undone. Displacement affects the Witwatersrand and Ventersdorp Supergroup rocks but no offset is observed of the base of the Transvaal Supergroup. The faults also exhibit a listric geometry, curving into parallelism with bedding in the lower West Rand Group. In their restored orientation, faults define half-graben and horst blocks, synthetic and antithetic faults, and rollover and drag folds, which are typical for extensional tectonics. These geometries and crosscutting relationships of the D1 faults are similar to that of the Neoarchaean listric faults described in the Witwatersrand goldfields and the wider Kaapvaal craton, that exhibit a general west-side-down sense of slip (2.70-2.64 Ga Hlukana-Platberg extensional event). Metamorphic grade in the study area decreases from amphibolite- to greenschist-facies away from the centre of the dome. These are largely M2(NC) metamorphic assemblages that are attributed to elevated regional heat flow related to 2.06 Ga Bushveld magmatism. There is some evidence that M2(NC) metamorphic mineral assemblages developed along the same stratigraphic units differ across the large D1 faults, indicating the pre-impact nature of the D1 faults and implying that the M2(NC) metamorphism occurred after the Hlukana-Platberg event. Also, M2(NC) assemblages are syn-tectonic to the S2 foliation hosted in metapelite units of the West Rand Group and knotted quartzite horizons of the Central Rand Group. The S2 foliation is attributed to the post-Transvaal Supergroup, compressional, Ukubambana Event. Crosscutting relationships in the study area indicate a deformational period of 2.06 Ga to no less than 2.02 Ga. The northwest-directed vergence exhibited by the S2 foliation is broadly consistent with the regional, general north-directed, vergence exhibited by post-Transvaal Supergroup foliation developed in the northeastern collar and the Johannesburg Dome. The S2 foliation and M2(NC) mineral assemblages are crosscut by D4 pseudotachylitic breccia, micro-faults and kinks, and M4(NC) metamorphic features associated with the impact. / LG2017

The Vredefort Dome is located southwest of Johannesburg, South Africa, and represents the deeply eroded remnant of the central uplift of the world’s largest known impact structure, with an estimated diameter of ~300 km. The Vredefort impact structure is also the oldest known impact structure on Earth (~2.02 Ga). The Vredefort Dome comprises an ~40 km wide core of Archaean basement gneisses and an ~20 km wide collar of subvertical to overturned Late Archaean to Palaeoproterozoic supracrustal strata. This project presents the results of Landsat-TM and aerial photograph analysis, as well as field mapping of Witwatersrand Supergroup metasedimentary strata in the collar of the Vredefort Dome. The aim of this study was to investigate the structures (such as folds, faults, fractures), at all scales, and other deformation features (such as shatter cones and pseudotachylitic breccias) in the field area, and to establish geometric and temporal relationships between these features with regard to the impact cratering process. This study revealed a highly heterogeneous internal structure of the collar involving folds, faults, fractures and melt breccias that are interpreted as the product of shock deformation and central uplift formation during the Vredefort impact event. Broadly radially-oriented symmetric and asymmetric folds, with wavelengths from tens of metres to kilometres, and conjugate radial to oblique faults with strike-slip displacements of, typically, tens to hundreds of metres accommodated tangential shortening of the collar of the dome that decreased from ~17 %, at a radial distance from the dome centre of 21 km, to <5 % at a radial distance of 29 km. Ubiquitous shear fractures containing pseudotachylitic breccia, particularly in the metapelitic units, display variable local slip senses consistent with either tangential shortening or tangential extension; however, it is uncertain whether they formed at the same time as the larger faults during the rise of the central uplift or earlier, during the shock compression phase of cratering. Contrary to the findings about shatter cones of some earlier workers in the Vredefort structure, the Vredefort cone fractures do not show uniform apex orientations at any given outcrop, nor do small cones show a pattern consistent with the previously postulated “master cone” concept. The model of simple back-rotation of the strata to a horizontal pre-impact position also does not lead to a uniform centripetal-upward orientation of the cone apices. Striation patterns on the cone surfaces are variable, ranging from typically diverging, i.e., branching off the cone apex, to subparallel to parallel on almost flat surfaces. Striation angles on shatter cones do not increase with distance from the crater centre, as suggested previously. Instead, individual outcrops present a range of such striation angles, and a more irregular distribution of striation angle values with regard to the distance from the crater centre suggests localised controls involving the nature and shape of various heterogeneities in the target rock on this aspect of cone morphology. On the basis of the observations made during this study on small-scale structures in the collar of the Vredefort Dome, the relationship of shatter cones with curviplanar fractures (multipli-striated joint sets - MSJS) is confirmed. Pervasive, metre-scale tensile fractures crosscut shatter cones and appear to have formed after the closely-spaced MSJ-type fractures. The results of this study indicate that none of the existing models is able to explain all characteristics of shatter cones fully; therefore, a combination of aspects of the different models may currently be the best possible way to explain the formation and origin of shatter cones, and the formation of the related MSJ and their characteristic aspects (e.g., curviplanar shape, melt formation, etc.). The observed variety of shatter cone orientations, surface morphology and striation geometry in the dome concurs broadly with the results of some previous studies. The abundance of striated surfaces along closely-spaced sets of fractures (MSJ) observed in this study can be reconciled with reflection/scattering of a fast propagating wave at heterogeneities in the target rocks, as proposed by recent studies. This would mean that closely-spaced fractures and shatter cones were not formed during shock compression, as widely postulated in the past, but immediately after the passage of the shock wave, by the interference of the scattered elastic wave and the tensional hoop stress that develops behind the shock front. In addition to shatter cones, quartzite units show two other fracture types – a centimetre-spaced rhomboidal to orthogonal type that may be the product of shock-induced deformation and related to the formation of shatter cones, and later joints accomplishing tangential and radial extension. The occurrence of pseudotachylitic breccia within some of these later joints confirms the general impact timing of these features. Pseudotachylitic breccias in the collar rocks occur as up to several centimetre-wide veins with variable orientations to the bedding and as more voluminous pods and networks in zones of structural complexity, such as the hinges of large-scale folds and along large-scale faults, as well as locally, at lithological interfaces. In places, tension gash arrays along thin veins are observed indicating that movement occurred along these planes. Initial cooling calculations for pseudotachylitic breccias of different widths and compositions (metapelite or quartzite) suggest that thick veins (<10 cm) could have stayed molten over the entire duration of crater development (at least 10 minutes), making it possible for shock-induced melts to intrude dilational sites, such as fold hinges and extensional fractures, during the formation and subsequent collapse of the central uplift. Intrusion of such melts may also have lubricated movements along brittle and ductile structures. Thus, the presence of both shock- and friction-generated melts is likely in the collar of the Vredefort Dome. Based on the spatial and geometric relationship between the structures and other deformation features observed in the collar rocks of the Vredefort Dome, it is possible to establish a temporal sequence of deformation events. Shatter cones and related closely-spaced fractures were formed during the contact/compression phase of the cratering process. The formation of at least some shock-induced pseudotachylitic breccia also belongs into this phase. Large-scale folds and faults and friction-generated melts can be related to the initial formation of the central uplift and extensional joints to the subsequent collapse of the central uplift.

Please read the abstract in the thesis. / Thesis (PhD)--University of Pretoria,1969. / gm2015 / Plant Production and Soil Science / PhD / Unrestricted

Since the Vredefort Dome‟s listing as a World Heritage Site in June 2005, the area has seen a steady increase in tourists to both the local towns of Parys and Vredefort and the Vredefort Structure. Tourists venturing into the field in an attempt to explore the area have an insatiable appetite for information. By unfolding the gold and granite mining heritage of the area, a world of interesting facts and fables is exposed. The special geological character of the Vredefort Dome World Heritage Site is enhanced by the mining interventions which started in the 1800s. The mines provide a glimpse into the earth‟s fresh crust which would otherwise have been obscured form the eye of the scientist/researchers, young potential earth scientists and the enquiring tourist. This study is aimed at identifying, for the first time, the localities of the major mining and quarrying sites in the area. This enabled investigation into and characterization of the exposed sites on the basis of their tourism and academic value. These sites were classified in order to identify those sites that should be made safe, rehabilitated and allowed access to tourists and scientists and those where access should be restricted but made safe in such a way that will allow access to animals and birds. The value of this initiative with regard to the stimulation of learners‟ scientific needs should not be under-estimated. The wide spectrum of natural, biological and physical sciences can be inspiring. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

Since the Vredefort Dome‟s listing as a World Heritage Site in June 2005, the area has seen a steady increase in tourists to both the local towns of Parys and Vredefort and the Vredefort Structure. Tourists venturing into the field in an attempt to explore the area have an insatiable appetite for information. By unfolding the gold and granite mining heritage of the area, a world of interesting facts and fables is exposed. The special geological character of the Vredefort Dome World Heritage Site is enhanced by the mining interventions which started in the 1800s. The mines provide a glimpse into the earth‟s fresh crust which would otherwise have been obscured form the eye of the scientist/researchers, young potential earth scientists and the enquiring tourist. This study is aimed at identifying, for the first time, the localities of the major mining and quarrying sites in the area. This enabled investigation into and characterization of the exposed sites on the basis of their tourism and academic value. These sites were classified in order to identify those sites that should be made safe, rehabilitated and allowed access to tourists and scientists and those where access should be restricted but made safe in such a way that will allow access to animals and birds. The value of this initiative with regard to the stimulation of learners‟ scientific needs should not be under-estimated. The wide spectrum of natural, biological and physical sciences can be inspiring. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

New technologies are continuously being developed that can aid us in archaeological research. The purpose of this project is to revisit an area containing Late Iron Age (LIA) Stone Walled Structures (SWS) that have received sporadic archaeological research over time, and employ new techniques and technologies to test/re-evaluate previous findings. This involves developing new mapping techniques, which involve the use of Geographical Positioning Systems (GPS), which allowed for a wide survey/mapping exercise in a time effective and budget conscious manner. From these data, a new typology was created in order to reflect new types as well as further segregate exiting types. The resulting data was analysed in a Geographic Information Systems (GIS) environment, allowing us to tackle issues such as spatial distribution and landscape patterns in a digital environment. This analysis allowed us to re-evaluate the original spatial distribution, looking at possible reasons for the inaccuracies in the original study. We then explore the implications of these new data. We tested the results of these analyses based on proposed scenarios for the location of these sites, in order to try better understand the positioning, as we as identify possible diagnostic sites that can undergo further examination.

The settlement history of the Vredefort Dome can be described as a process of cultural development. The Vaal River hydrosphere, which was for many years a prestigious settlement site, initially attracted large scale game and later livestock farmers. The drifts were a central part of a network of early strategic communication routes and outspans. From 1838, pioneer settlement, farm occupation and agricultural development followed, and the area eventually entered an agriculture-mining era. Gold-mining stimulated the regional economy and also played a significant role in the development of towns in the area. The Vaal River did not play a significant role from a mining perspective, but featured more prominently in the development of villages and, in a sense, served as a political boundary. The location of the water source often determined where people settled permanently. It also decided the position of the house and yard. From the outset, riparian dwellers attempted to manipulate the flow of the river by creating dams and utilising water for irrigation and domestic purposes. Drought conditions also left historical traces; water management projects upstream transformed the Vaal River into a steadily flowing stream, which led to the economic and cultural segregation of north and south. Man's fear associated with drought (too little water), floods (too much water), meteorology (the necessity of water), and the role of the supernatural (divining water) and superstition (the water snake stories) were expressed in the interaction between people and this water environment. A wide variety of people with distinct cultures lived alongside each other in the area. Western and African cultural goods, as well as customs and beliefs, were mutually adopted by these different cultural groups as a result of this contact. The way land has been used in the Dome area has evolved over the years. The culling of game made way for the permanent establishment of the livestocktravelling farmer. Hereafter prolonged drought conditions destroyed pastures and, consequently, large areas of land were ploughed for agricultural use. Agriculture, which is more labour intensive and needs more water for irrigation, was replaced by game farming, which is less labour intensive and requires less water This world heritage site has drawn global interest and ecotourism has attracted visitors to the Vaal River area. The riparian dwellers, however, remain victims of up-stream industrial and sewage pollution; in future, they are likely to fall prey to acid mine water pollution, with disastrous consequences. / PhD (History), North-West University, Vaal Triangle Campus, 2013

The settlement history of the Vredefort Dome can be described as a process of cultural development. The Vaal River hydrosphere, which was for many years a prestigious settlement site, initially attracted large scale game and later livestock farmers. The drifts were a central part of a network of early strategic communication routes and outspans. From 1838, pioneer settlement, farm occupation and agricultural development followed, and the area eventually entered an agriculture-mining era. Gold-mining stimulated the regional economy and also played a significant role in the development of towns in the area. The Vaal River did not play a significant role from a mining perspective, but featured more prominently in the development of villages and, in a sense, served as a political boundary. The location of the water source often determined where people settled permanently. It also decided the position of the house and yard. From the outset, riparian dwellers attempted to manipulate the flow of the river by creating dams and utilising water for irrigation and domestic purposes. Drought conditions also left historical traces; water management projects upstream transformed the Vaal River into a steadily flowing stream, which led to the economic and cultural segregation of north and south. Man's fear associated with drought (too little water), floods (too much water), meteorology (the necessity of water), and the role of the supernatural (divining water) and superstition (the water snake stories) were expressed in the interaction between people and this water environment. A wide variety of people with distinct cultures lived alongside each other in the area. Western and African cultural goods, as well as customs and beliefs, were mutually adopted by these different cultural groups as a result of this contact. The way land has been used in the Dome area has evolved over the years. The culling of game made way for the permanent establishment of the livestocktravelling farmer. Hereafter prolonged drought conditions destroyed pastures and, consequently, large areas of land were ploughed for agricultural use. Agriculture, which is more labour intensive and needs more water for irrigation, was replaced by game farming, which is less labour intensive and requires less water This world heritage site has drawn global interest and ecotourism has attracted visitors to the Vaal River area. The riparian dwellers, however, remain victims of up-stream industrial and sewage pollution; in future, they are likely to fall prey to acid mine water pollution, with disastrous consequences. / PhD (History), North-West University, Vaal Triangle Campus, 2013