Kimberlites and lamproites are ultramafic igneous rocks believed to originate from the convective asthenosphere and sub-continental lithospheric mantle, respectively, however, the genetic link between these rock types is still a debate among researchers. Recently, it has been shown (e.g., in the Dharwar Craton, India) that both kimberlites and lamproites may be derived from the same asthenospheric mantle source. During their ascent to the surface, they assimilate differently metasomatized SCLM material. However, it is not clear if this process applies to all cratonic regions. The Man Craton, West Africa, is a host to diamondiferous rocks that share petrographic and geochemical characteristics with both kimberlites and lamproites, thus not easy to classify. The Camp Alpha (possibly Precambrian in age) and Neoproterozoic-aged Weasua clusters are the selected locations for this study. To further assist with the classification of peculiar West African diamondiferous rocks and evaluate their genetic link and origin, I provide detailed petrography, as well as phlogopite and spinel chemistry, bulk-rock geochemistry (for the Camp Alpha samples) and perovskite chemistry (for the Weasua samples). The Camp Alpha rocks contain abundant macrocrysts of olivine (that are completely altered) and ilmenite occurring in a groundmass that comprises spinel, phlogopite (the samples are phlogopite-poor), perovskite, calcite, serpentine, and rare apatite. Most importantly, there is no evidence of diopside in the Camp Alpha samples. The Camp Alpha phlogopite is enriched in Al2O3 but slightly depleted in FeO and TiO2 and the spinel exhibits a kimberlitic compositional evolution (i.e., trend 1). The bulk-rock trace element ratios Ba/Nb (0.91 - 9.55), La/Nb (0.12 - 1.22; mostly < 1.10) and Ce/Pb (6.77 - 99.2; mostly > 22), fall within the ranges defined by kimberlites. Additionally, primitive mantle normalised trace element patterns are similar to kimberlite patterns (e.g., Rb, K, Sr and P 2 show negative anomalies). As a result of these characteristics, the studied Camp Alpha rocks are classified as kimberlites. A close to parent melt composition of the Camp Alpha kimberlite is provided in this study, based on bulk rock geochemistry. The composition of the estimated melt is similar to that of kimberlite magmas and characterised by low K2O (of 0.80 wt.% relative to 3.63 ± 1.40 wt.% of orangeites for example; reflective of mica-poor nature). The Weasua rocks, in this study, are micaceous (phlogopite-rich) and contain primary groundmass diopside and calcite, which suggests that the studied Weasua rocks represent carbonate-rich olivine lamproites. From the inversion of trace element data for the perovskites using known partition coefficients, the composition of the melt in equilibrium with perovskite at the time of crystallisation is determined. The composition of this Weasua parent melt is similar to that of kimberlite magmas (i.e., similar primitive mantle-normalised trace element patterns, Ba/Nb, Ce/Pb and La/Nb ratios). Whereas the Camp Alpha and Weasua rocks are classified as kimberlite and lamproite, respectively, the trace element composition of the parent melt is similar to that of kimberlite magmas for both cases. This suggests a common asthenospheric magma source for the Camp Alpha kimberlite and Weasua lamproite. En route to the surface, these rock types assimilated differently metasomatized SCLM material (i.e., the Weasua lamproite magma assimilated mica-diopside-rich wall rock). The Camp Alpha kimberlite was shown to be approximately 800 Ma old, similar to the Weasua lamproite. Therefore, the Camp Alpha and Weasua magmas were interpreted to be broadly coeval based on the similarity in age and location, In addition to the Indian Dharwar Craton, the hypothesis that kimberlites and lamproites share a common convective asthenospheric magma source but assimilate differently metasomatized SCLM material en route to the surface is confirmed in the Man Craton, West Africa.

It has long been thought that low-δ 18O magmas (<5.7‰) are only found in extensional tectonic settings. Low-δ 18O magmas are rare, worldwide, especially in subduction zone settings. The main objective of this study was to conduct a search for low-δ 18O magmas in the Central Volcanic Zone (CVZ) of the Andes, to verify if their rarity is due to under sampling. If no low-δ18O magmas were found, the question of why low-δ 18O magmas have appeared to be absent from the region would be addressed. This study has determined the variation in oxygen isotope composition of rocks across the CVZ, ranging in age from about 12 Ma to Recent. The δ18O values were measured in selected bulk rock samples and separated quartz phenocrysts in order to identify potential low-δ 18O rocks (from whole rock analyses) and magmas (from the quartz phenocrysts). The average δ18O values for quartz phenocrysts and whole rocks are 8.6‰ and 10.5‰ respectively, and no low-δ 18O magmas were found. Hydrogen isotope values range from -32 to -119‰, with the highest value in the most altered rock. The results from this study show no evidence for low-δ 18O magmas; the lowest value (5.0‰) was found in one sample (for both quartz and whole rock) and this sample appears to have been affected by interaction with meteoric water. The overall high δ18O values in the CVZ rocks are best explained as the result of alteration by fluids having high δ18O values. These were probably meteoric fluid whose δ18O were enriched due to fluid-rock exchange. The high δ18O values of the magmas must reflect the absence of low-δ 18O rocks that could be melted, and a relatively crustal input to magmas. This study agrees with the conclusions of Folkes et al. (2013), which explains the absence of low-δ 18O magmas as a result of tectonic history and climatic conditions of the central Andes; where low precipitation and high evaporation rates, high aridity, limited supply of meteoric waters, and high elevation all played significant roles in the lack of low-δ 18O magmas in the region.

The islands of the Comores Archipelago define a short, NNW-trending, volcanic lineament across the northern entrance to the Mozambique Channel in the western Indian Ocean and are considered to represent the surface expression of the Comores mantle plume. New mineral and bulk-rock analyses, as well as selected rare earth element (REE), 87Sr/86Sr and 143Nd/144Nd compositions for lavas from three of the four main islands of the archipelago are presented. The alkaline lavas of the Comores range in texture from sparsely to strongly porphyritic, containing phenocrysts of olivine, clinopyroxene, amphibole, feldspar, Fe-Ti oxide and in one sample nepheline and garnet, which are typically set in a fine-grained groundmass of clinopyroxene, feldspar or nepheline, Fe-Ti oxide, lesser olivine and accessory apatite and titanite (sphene). With the exception of a few hypersthene- and even quartz-normative samples, all of the rocks analysed are moderately to strongly silica-undersaturated, nepheline-normative lavas. On Grande Comore, the youngest island in the archipelago, a clear distinction exists between the generally alkali basaltic lavas erupted by Karthala volcano and the basanites of La Grille volcano. The samples from the island of Moheli are classified as alkali basalts, basanites and nephelinites. The lavas of Mayotte, the oldest Comorean island, were erupted during three phases of volcanic activity and display greater chemical variation than both Grande Comore and Moheli lavas. Mayotte lavas range in composition from alkali basalt through trachybasalt, basaltic trachyandesite and trachyandesite to trachyte, and from basanite and nephelinite through phonotephrite to phonolite. Comorean lavas have high incompatible element abundances and display strongly light rare earth element-enriched chondrite-normalised REE patterns. On the basis of their primitive mantle-normalised incompatible element patterns (spidergrams), all of the lavas analysed may be assigned to one of two very distinct Comorean lava types: La Grille-type (LGT) lavas display strong relative depletions in K (and sometimes Rb), whereas Karthala-type (KT) lavas do not show such depletions. Both LGT and KT lavas were erupted on Grande Comore, Moheli and Mayotte. With the exception of the lavas erupted by La Grille volcano, which exhibit the petrographic and geochemical characteristics expected of primary mantle magmas, all Comorean lavas analysed have experienced compositional modifications after they segregated from their source regions. Quantitative major and trace element modelling suggests that much of the compositional variation observed amongst Comorean lavas is explicable in terms of fractional crystallisation processes dominated by the early fractionation of olivine and clinopyroxene. Plagioclase appears to have been an additional fractionating phase during the evolution of Moheli basanites. The more advanced stages of the differentiation history of Mayotte lavas were dominated by the fractionation of increasing quantities of feldspar and amphibole, as well as smaller amounts of clinopyroxene, Fe-Ti oxide and accessory apatite and titanite. The presence of high-pressure clinopyroxene, amphibole and possibly garnet crystals in Comorean lavas suggests that the crystal fractionation processes involved in their differentiation may have been initiated at relatively elevated pressures. Partial melting in the presence of residual amphibole is proposed to be the most likely mode of origin for the K-depletions which characterise LGT Comorean lavas. It is suggested that primary LGT magmas were generated by small degrees of partial melting of an amphibole-bearing garnet-lherzolite mantle source at depths corresponding to pressures greater than 25 kb. Primary KT magmas, on the other hand, are considered to be the product of somewhat larger degrees of partial melting of an amphibole-free spinel-lherzolite source at shallower depths. The Nd and Sr isotopic compositions of Comorean lavas bear evidence for a timeaveraged depletion in incompatible elements, whereas the high incompatible element abundances of these lavas are proposed to reflect the effects of a recent mantle enrichment event. It is suggested that the garnet-lherzolite source of LGT Comorean lavas experienced recent modal metasomatism, resulting in the precipitation of amphibole, whereas the shallower spinel-lherzolite source of KT lavas underwent cryptic metasomatism only, without the introduction of new minerals. The ambient subComorean upper mantle is proposed to consist of a mixture between the HIMU mantle component and a depleted component (DMM, PREMA or a component on the mantle array). The Nd and Sr isotope signature of the majority of Comorean lavas (both LGT and KT) may be explained as a mixture dominated by the components comprising the sub-Comorean mantle with limited contributions from the EM I-type Comorean mantle plume itself. The lavas erupted by Karthala volcano (the youngest Comorean lavas), however, have significantly different isotopic compositions than all other Comorean lavas (lower 143N d/144N d and higher 87S r / 86S r ), suggesting significantly increased contributions from the Comores mantle plume. An alternative model, equally consistent with the present data, involves an ambient sub-Comorean mantle consisting of a depleted component that is mixed with a Comores mantle plume which contains both HIMU and EM I components. In this scenario, the character of the plume would have to change from one dominated by the HIMU component during most of the volcanic history of the Comores, to one dominated by the EM I component during the generation of the lavas erupted by Karthala. An internally consistent, broadly chronological petrogenetic model for the evolution of Comorean volcanism is presented.

The estimated total annual production of waste in South Africa is 318 million metric tons. Of this waste, 3.8%, approximately 12 million metric tons, arises from the chemical manufacturing industry. Although increasing attention is being given to methods of land treatment for waste disposal waste is still disposed of by dumping/stockpiling. This study focuses on the effects of such waste disposal on soil and water chemistry at an industrial complex near Somerset West, South Africa. Since 1903 a multitude of industrial activities have occurred on the site including manufacture of explosives, chemicals, fertilizers and vinyl coated products: Decommissioning of the industrial complex is presently in progress. The overall objective of this study was to conduct an investigation of the water and soils in an area termed the Dead Tree Area. The area was considered of particular interest due to the presence of a sulphur stockpile, gypsum waste dumps and fertilizer wastewater evaporation site located immediately adjacent to the area. Four key objectives were addressed in the study, namely: (i) to chemically characterise the water and soils in the Dead Tree Area, (ii) to assess the degree of contamination of the water and soils in the area, (iii) to question whether tree mortality in the area could have resulted from toxicy or deficiency effects, and (iv) to determine the potential of gypsum application as a means of remediating dispersed, sodic soils.

Aeolian systems have a particular sensitivity to climate change, and where these are preserved in the geological record, they can provide insights into palaeo-climatic drivers of erg dynamics through time. This thesis investigates the sedimentary geology of the southern extension of a vast ancient desert system that was active over Pangaea and formed part of one of the largest known sand seas in Earth's history. The Lower Jurassic Clarens Formation in the main Karoo Basin of southern Africa has been interpreted as an aeolian succession that is dominated by massive sandstones in the lower and upper parts of the unit, whereas large-scale cross-bedded sandstones are mostly associated with its middle part. Lenticular mudstones and sandstones with ripple marks, ripple crosslamination, horizontal lamination and desiccation cracks have also been reported from the lower and upper parts of the succession. Based on the stratigraphic distribution of the sedimentary facies, the formation is informally subdivided into 3 zones that seem to reflect a wet-dry-wet climate megacycle. To date, the age of the formation is based on a very small detrital zircon dataset, the bioand chronostratigraphy of the conformably underlying Elliot Formation and the radioisotopic dates of Drakensberg Group basalts that are conformably overlying the Clarens Formation. Thus far, few investigations have targeted the evolution of this Early Jurassic fluvio-lacustrine-aeolian system, and the origin of massive sandstone facies that dominates parts of the formation. Therefore, this study re-evaluates the origin and basinal distribution of the sedimentary facies, and the spatiotemporal controls on erg development during the deposition of the Clarens Formation. Moreover, this study provides the first robust chronostratigraphic framework and provenance history for this iconic Early Jurassic aeolian system of southwestern Gondwana. The wet-dry-wet climate megacycle is not only corroborated herein, but using maximum depositional ages from detrital zircons, these climatic changes are now better dated. The results show a Late Sinemurian wet phase, an larly Pliensbachian dry phase and a late Pliensbachian wet phase during Clarens times. Newly documented field evidence shows that ponds and large lakes coexisted with aeolian dunes, with sand sheets, loess plains and fluvial systems having been established downwind. The size of the late Sinemurian ponds and lakes were controlled by their proximity to the erg margin, such that small ponds developed close to the erg centre, and large lakes were established along the erg margin. By the Early Pliensbachian, an intensification of the arid conditions led to the increased availability of sediments for aeolian entrainment, resulting in expansion of the erg eastward. Wet conditions ensued once again in the Late Pliensbachian, and lead to the contraction of the erg and expansion of loess plains with seasonally wet interdunes. Sediment, mostly supplied from the west, was overwhelmingly recycled from pre-existing, Karoo-age deposits and sedimentary rocks associated with the Pan-African orogeny, although evidence for some non-sedimentary and young, syn-Clarens sources are also present. The youngest zircon population show subtle temporal and spatial trends that can be used as proxies for the erg development. The late Sinemurian signal is identified in the lower zone in the south of the basin and is incorporated in subsequent zones in the central and northern parts of the basin, suggesting that, although the main wind direction was from the west northwest, the basin was filled from south to north. This newly established temporal framework of the wet-dry-wet climate cycle in the Clarens Formation corresponds well with the palaeoclimatic trends interpreted for the Tethyan margin of Gondwana, signifying that this may have been a global trend in the Early Jurassic.

The islands of the Comores Archipelago define a short, NNW-trending, volcanic lineament across the northern entrance to the Mozambique Channel in the western Indian Ocean and are considered to represent the surface expression of the Comores mantle plume. New mineral and bulk-rock analyses, as well as selected rare earth element (REE), 87Sr/86Sr and 143Nd/144Nd compositions for lavas from three of the four main islands of the archipelago are presented. The alkaline lavas of the Comores range in texture from sparsely to strongly porphyritic, containing phenocrysts of olivine, clinopyroxene, amphibole, feldspar, Fe-Ti oxide and in one sample nepheline and garnet, which are typically set in a fine-grained groundmass of clinopyroxene, feldspar or nepheline, Fe-Ti oxide, lesser olivine and accessory apatite and titanite (sphene). With the exception of a few hypersthene- and even quartz-normative samples, all of the rocks analysed are moderately to strongly silica-undersaturated, nepheline-normative lavas. On Grande Comore, the youngest island in the archipelago, a clear distinction exists between the generally alkali basaltic lavas erupted by Karthala volcano and the basanites of La Grille volcano. The samples from the island of Moheli are classified as alkali basalts, basanites and nephelinites. The lavas of Mayotte, the oldest Comorean island, were erupted during three phases of volcanic activity and display greater chemical variation than both Grande Comore and Moheli lavas. Mayotte lavas range in composition from alkali basalt through trachybasalt, basaltic trachyandesite and trachyandesite to trachyte, and from basanite and nephelinite through phonotephrite to phonolite. Comorean lavas have high incompatible element abundances and display strongly light rare earth element-enriched chondrite-normalised REE patterns. On the basis of their primitive mantle-normalised incompatible element patterns (spidergrams), all of the lavas analysed may be assigned to one of two very distinct Comorean lava types: La Grille-type (LGT) lavas display strong relative depletions in K (and sometimes Rb), whereas Karthala-type (KT) lavas do not show such depletions. Both LGT and KT lavas were erupted on Grande Comore, Moheli and Mayotte. With the exception of the lavas erupted by La Grille volcano, which exhibit the petrographic and geochemical characteristics expected of primary mantle magmas, all Comorean lavas analysed have experienced compositional modifications after they segregated from their source regions. Quantitative major and trace element modelling suggests that much of the compositional variation observed amongst Comorean lavas is explicable in terms of fractional crystallisation processes dominated by the early fractionation of olivine and clinopyroxene. Plagioclase appears to have been an additional fractionating phase during the evolution of Moheli basanites. The more advanced stages of the differentiation history of Mayotte lavas were dominated by the fractionation of increasing quantities of feldspar and amphibole, as well as smaller amounts of clinopyroxene, Fe-Ti oxide and accessory apatite and titanite. The presence of high-pressure clinopyroxene, amphibole and possibly garnet crystals in Comorean lavas suggests that the crystal fractionation processes involved in their differentiation may have been initiated at relatively elevated pressures. Partial melting in the presence of residual amphibole is proposed to be the most likely mode of origin for the K-depletions which characterise LGT Comorean lavas. It is suggested that primary LGT magmas were generated by small degrees of partial melting of an amphibole-bearing garnet-lherzolite mantle source at depths corresponding to pressures greater than 25 kb. Primary KT magmas, on the other hand, are considered to be the product of somewhat larger degrees of partial melting of an amphibole-free spinel-lherzolite source at shallower depths. The Nd and Sr isotopic compositions of Comorean lavas bear evidence for a timeaveraged depletion in incompatible elements, whereas the high incompatible element abundances of these lavas are proposed to reflect the effects of a recent mantle enrichment event. It is suggested that the garnet-lherzolite source of LGT Comorean lavas experienced recent modal metasomatism, resulting in the precipitation of amphibole, whereas the shallower spinel-lherzolite source of KT lavas underwent cryptic metasomatism only, without the introduction of new minerals. The ambient subComorean upper mantle is proposed to consist of a mixture between the HIMU mantle component and a depleted component (DMM, PREMA or a component on the mantle array). The Nd and Sr isotope signature of the majority of Comorean lavas (both LGT and KT) may be explained as a mixture dominated by the components comprising the sub-Comorean mantle with limited contributions from the EM I-type Comorean mantle plume itself. The lavas erupted by Karthala volcano (the youngest Comorean lavas), however, have significantly different isotopic compositions than all other Comorean lavas (lower 143N d/144N d and higher 87S r / 86S r), suggesting significantly increased contributions from the Comores mantle plume. An alternative model, equally consistent with the present data, involves an ambient sub-Comorean mantle consisting of a depleted component that is mixed with a Comores mantle plume which contains both HIMU and EM I components. In this scenario, the character of the plume would have to change from one dominated by the HIMU component during most of the volcanic history of the Comores, to one dominated by the EM I component during the generation of the lavas erupted by Karthala. An internally consistent, broadly chronological petrogenetic model for the evolution of Comorean volcanism is presented.

The Namaqualand olivine melilitite pipe cluster is a 40 km by 10 km north/south oriented area with at least 10 closely spaced alkaline ultramafic subvolcanic pipes and diatremes containing olivine melilitite and nephelinite, spanning an age range of 35-56 Ma. A related carbonatite complex containing olivine melilitite is also found within this cluster, with an emplacement age of ≈ 55 Ma. The Namaqualand cluster represents the southernmost component of the Late Cretaceous to Paleogene-age Namaqualand-Bushmanland-Warmbad (NBW) lineament, representing a 400 km long NNE-SSW trending feature made of hundreds of diatremes containing ultramafic lamprophyre and kimberlite in addition to the rock types named above. The NBW lineament appears to be an ageprogressive feature, with ages increasing toward the northeast at a rate and direction roughly consistent with Late Cretaceous to Cenozoic African plate motion. This suggests that it could have formed from a single source, such as a mantle plume, with the earlier products being the Warmbad kimberlites, followed by the later diatremes of the Bushmanland cluster and the youngest being the Namaqualand olivine melilitites. This study focuses on the petrography and geochemistry of fresh igneous rocks sampled from 10 pipes in the Namaqualand cluster. The samples have unusual compositions for diatreme-hosted alkaline igneous rocks in that they are relatively differentiated, with whole rock Mg numbers of between 71 and 45. This suggests that many of these samples represent magmas that evolved though more than 50% fractional crystallization of mineral assemblages dominated by olivine but also containing significant melilite, nepheline, phlogopite, titanomagnetite and perovskite. However, least-squares fractionation modelling appears to only provide an approximate guide to the fractionating mineral assemblages. The concentrations of most incompatible trace elements in the Namaqualand melilitites are relatively uniform, suggesting a common source and petrogenesis. Low Pb concentrations in the Namaqualand melilitites, along with their SiO2- and Al2O3-poor major element compositions make it unlikely that they experienced significant (e.g., more than 5-10%) assimilation of local continental crust. The Namaqualand melilitites are characterized by extraordinarily high and variable Nb/Rb and U/Th ratios, and correlations with other elements indicate that these ratios have been affected by variable fractional crystallization of phlogopite and perovskite, respectively. However, this cannot explain the unusually high U concentrations and low Th/U ratios of the most primitive Namaqualand melilitites, which appear to be a source feature. Oxygen isotope ratios of olivine separates indicate that olivines from a large majority of the melilitite pipes have compositions indistinguishable from those from typical upper mantle peridotite (4.9-5.2‰). However, three melilitite pipes emplaced within the mid-Cretaceous Koegel Fontein igneous complex contain M. D. Kirchner University of Cape Town (2022) MSc Thesis olivines with exceptionally low δ18O values (i.e., down to +4.2 ‰). The crustal country rock surrounding the Koegel Fontein complex, as well as igneous rocks strongly contaminated by this crust, have exceptionally low δ18O values (down to -4 and -5.3‰, respectively). The unusually low -δ 18O values of these olivines could be explained by the assimilation of up to 10% of Koegel Fontein country rock crust having the lowest δ18O values measured. Larger amounts of crustal assimilation are not plausible as they would result in detectable increases in SiO2 and Pb/Ce ratios. It is unclear whether the crustal assimilation detected in the melilitites emplaced within the Koegelfontein complex is typical of most Namaqualand melilitites. The Namaqualand melilitites have radiogenic isotope compositions that overlap with those of melilitites and kimberlites from the Bushmanland and Warmbad clusters, as well as with southern African Group I kimberlites. However, the Namaqualand pipes are unique in that some samples have radiogenic isotope values approaching those of HIMU oceanic island basalts (e.g., from St. Helena, Mangaia, Tubuai), whereas the Bushmanland and Warmbad clusters display isotopic compositions that only extend to weaker HIMU signatures. The geochemical and age-distance patterns displayed by the NBW igneous rocks are most consistent with the action of a mantle plume passing beneath the western margin of southern Africa in the Late Cretaceous to Paleogene, resulting in the generation of the NBW lineament. This is consistent with the fact that the samples with the strongest HIMU signatures in the NBW lineament are those that have been emplaced on the thinnest lithosphere, nearest the continental margin. The HIMU signature dominant in the Namaqualand melilitites is presumably related to the plume source, which could contain ancient recycled oceanic crust. The formation of the African megalineament could theoretically be related to the same plume that caused the NBW lineament by triggering a zone of magmatism along a deep-seated zone of weakness in the lithospheric mantle between Southern Africa into the east African rift zone, however, more evidence would be needed to fully support this possibility.

Although life on Earth evolved in the Archean, complex hard bodied animals only emerged in shallow marine environments during the late Ediacaran (~550 Ma). The trigger for the appearance of these hard-bodied animals is still debated but it was probably related to ecological and/or environmental change. Continental weathering fluxes into the oceans can influence redox conditions and seawater chemistry and can be tracked using the strontium isotope ratio of seawater, which can be faithfully captured by carbonate minerals. However, analysis of strontium isotopes in ancient carbonates can be complicated by diagenetic alteration. To ensure that the 87Sr/86Sr ratios generated in this study were reflective of primary seawater signals, a sequential leaching procedure, first proposed by Bailey et al., (2000), was tested on Ediacaran bulk rock carbonate samples. The successful implementation of the sequential digestion technique was verified through careful examination of samples for diagenetic alteration using petrography, trace element ratios and  18O. The sequential digestion technique was then applied to a high-resolution stratigraphic transect through terminal Ediacaran carbonate rocks from the Nama Group, collected in South Africa and Namibia. The isotopic signature of these rocks is consistent with other terminal Ediacaran age rocks, with typically slightly positive  13C and relatively high 87Sr/86Sr ratios (~0.7085). Correlation with other Ediacaran basins reveals a drop in 87Sr/86Sr from ~0.7090 to ~0.7085 ca. 550 Ma. The drop was likely due to location of palaeocontinents compounded by palaeoclimatic cooling during the terminal Ediacaran. These changes provide important context for a critical period in metazoan evolution and may have influenced the cost-benefit ratio of producing hard body parts.

Global climate change is well documented and recorded by various marine and terrestrial archives, predominantly by benthic ocean sediment and ice cores. These records are characterized by cyclical variation, suggesting changing polar ice volumes from glacial to interglacial conditions, driven by Milankovich cycles and greenhouse gas concentration feedbacks. While these records have informed much of our understanding of past climate variability, they are from either the deep ocean or high latitudes, with a huge bias to the Northern Hemisphere. More terrestrial, mid latitude, Southern Hemisphere (SH) palaeoclimate records are needed to plug this gap in our knowledge. With a rapidly changing and uncertain climate future, these new records should intersect with past records of human activity. South Africa (SA) has a huge geographic advantage, sitting at the confluence of the Southern Atlantic and Indian Ocean systems and hosting an almost unprecedented rich record of human occupancy spanning the last 2.6 Ma, but particularly the Last Glacial Maximum (LGM). An equator-wards shift in the SH Westerlies has long been used to account for increased precipitation in SA during the LGM. While this narrative is challenged by a few records from the Southern Cape, which suggest aridity during the LGM, it remains an overarching idea. In this thesis, I test these two apparently contradictory climate responses by using fossil charcoal and pollen records from two archaeological sites: Boomplaas Cave (BPC) in the Year-round Rainfall Zone (YRZ), and Elands Bay Cave (EBC) in the Winter Rainfall Zone (WRZ). By quantifying changes in Mean Annual Temperature (MAT), Total Annual Precipitation (TAP), and Dry Quarter Precipitation (DQP), I explore the potential of using archaeological charcoal to reconstruct a palaeoclimate throughout the LGM in SA. Specifically, I use a Canonical Correspondence Analysis to interrogate the species response to modern climate and a Weighted Average – Partial Least Squared regression to reconstruct paleoclimate. These results display the promising ability of fossil charcoal records to represent changes in hydroclimate given a few conditions. Both sites record an average decrease in MAT of 5°C at the LGM compared to modern conditions, consistent with existing regional records. Precipitation results from BPC show ~200mm less precipitation around the LGM compared to present day, this is consistent with other proxies from the Southern Cape, as well as global climate model results suggesting decreased precipitation in the region. The EBC charcoal record proved its ability to reconstruct MAT trends and (given a few conditions) the potential to reproduce TAP results. Interestingly, at the LGM, the EBC pollen record suggests a decrease in TAP of ~150mm, which does not agree with existing records (see chapter 2). This decrease in LGM TAP recorded at both sites, together with reconstructions of DQP are used to argue that the WRZ did not expand to reach BPC during the LGM. Overall, the new records present here are more consistent with a pole-wards shift in the SH Westerlies, challenging the long-held notion of a wet LGM in SA.

No description available.