The Kirkwood Formation in the Bushman's River area of the Algoa Basin is characterised by a number of fining-upward cycles. These have been interpreted as indicating deposition in a dynamic aggrading meandering river system with the channel deposits (conglomerates grading upwards into sandstones) fining upward into the overbank deposits (mudrocks). Channel, channel-margin and overbank deposits were recognised. The three mudrock sequences logged comprise compound pedofacies sequences of multistorey, simple and cumulative palaeosols. Distinctive palaeopedological features, such as root traces and pedotubules, soil horizons and structures, mottles, and iron-rich and calcareous glaebules and calcareous hardpan lenses and layers were used to identify a number of palaeosols within the mudrock sequences. Each mudrock sequence comprises multistorey entisol, inceptisol, alfisol, ultisol, aridisol and vertisol profiles at different stags of pedogenic maturity. The entisols and inceptisols are relatively immature profiles formed close to the meandering river channel and are classified as channel-margin palaeosols. The ultisols, alfisols, aridisols and vertisols are more mature and formed at some distance from the channel. They are classified as proximal floodbasin or distal floodbasin palaeosols depending on their maturity, distance from the channel and grain-size. Slickensides, desiccation cracks, and iron-rich concretions occur, indicating multiple cycles of wetting and drying. A low water-table beneath the floodplain is indicated by both the prominent maroon-brown colouration of the mudstones, caused by oxidation during deposition, and the general lack of evaporites in the sequence. Calcretes comprising calcic and petrocalcic horizons are very common in the lower mudrock sequence, rare in the middle mudrock sequence and relatively common in the upper mudrock sequence. The calcretes generally consist a nodular zone which may, in some cases, be capped by a thin hardpan layer. The calcic palaeosols commonly show stages of carbonate accumulation which indicate at least 10 000 years of formation. The lack of calcrete formation in some of the profiles may indicate frequent flooding and high sediment accretion rates or a decrease in the influx of Ca²⁺-rich aeolian dust into the depositional basin. Clay alluviation is common in many of the profiles and soil structures are commonly well developed. The palaeosols are interpreted as having formed on an aggrading floodplain in a warm to hot (25-30°C), semi-arid climate with a low but seasonal rainfall (100-500mm per annum).

Branched glycerol dialkyl glycerol tetraether (GDGTs) membrane lipids have been used as a new proxy for the reconstruction of terrestrial palaeoclimates. These biomarkers (or molecular ‗fossils‘) in conjunction with palynology, have been effective in the novel analysis of Miocene organic-rich sediments from three South African west coast sites at Rondeberg, Noordhoek and Langebaanweg. Lastly, a Quaternary south coast site at Rietvlei, South Africa, was also studied to further elucidate the extent of use of this new proxy. The fluvial peat and organic-rich deposits of the Elandsfontyn Formation (Sandveld Group) were investigated at Noordhoek, Langebaanweg and Rondeberg to provide new evidence for the climate and vegetation patterns during Miocene in this region. Drill-core and quarry samples from all four sites were freeze-dried, powered, and prepared for biogeochemical and palynological analyses. The methylation index of branched tetraethers (MBT) and cyclisation ratio of branched tetraethers (CBT) proxies were used to calculate the mean annual air temperature (MAAT) and pH values of the organic-rich horizons at time of deposition. The Branched versus isoprenoid index of tetraethers (BIT) was used to assess the relative contributions of marine archaeal and terrestrial bacterial tetraethers, and thereby assess the validity of the MBT, CBT and calculated palaeoenvironmental factors. The results presented in this thesis suggest that the use of the MBT/CBT proxy has significant potential in southern Africa, and may complement previously attempted palaeoclimatic and palaeoecological studies of Neogene-aged South African sediments. This type of research has the capacity to provide palaeoenvironmental information where other proxies may be absent. Results indicate that all sites yielded branched tetraether membrane lipids with the exception of Rondeberg, where GDGTs were below detection as a result of poor preservation conditions. Palynological investigation confirmed proxy derived temperatures. Furthermore palynomorph analyses supplemented earlier studies of the Noordhoek site and were piloted for the Rondeberg site, reaffirming alternating sequences of tropical and subtropical palynofloras. The MAATs, likewise, show variability and pronounced trends through time at the Langebaanweg and Noordhoek sites, generally corresponding with the variation and diversity of the pollen population. The terrestrial MAAT results appear to compliment Southern Hemisphere sea level changes associated with Antarctic glaciations. Additionally, this data shows a pattern similar to the Southern and Northern Hemisphere marine isotope records of relative fluctuations in the global climate and sea level change from the early to middle Miocene. The application of these past climate change indicators have been proved to be useful in the reconstruction of South Africa Miocene palaeoclimates, and may aid in understanding the consequences of climate change in the Cape region.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Vaalputs radioactive waste disposal facility is situated in an arid region of Bushmanland currently with evapotranspiration potential that far exceeds precipitation. Dominant soil features in Vaalputs are palimpsests of climates under which they formed. Particle sizes vary drastically between horizons which suggest different modes of sediment transport. Petrographic analyses revealed euhedral habits of primary mineral feldspar within the soils of Vaalputs. This suggests a proximal source of sediments and minimal primary mineral weathering under an arid climate where euhedral grains of feldspar are maintained. The surface horizon of the soils is covered by an equigranular coarse sand of residual aeolian origin. The transition from the surface horizon to the subsurface horizons is widely marked by a pebble sized stone-line. The pebble sized material of the stone-line suggests residual accumulation during the weathering of a previously surface exposed horizon. Since deposition of subsurface sediments (15 Ma) pedogenic alteration has been active in Vaalputs. This has resulted to a complex soil system which displays varied forms of thick dorbank horizons including massive polygonal peds and platy horizons. The polygonal peds are defined by desiccation cracks where vertical and horizontal laminations are hosted. Slaking tests as well as bulk chemistry confirmed that the laminations are composed largely of secondary calcite, however elemental mapping revealed numerous illite bands alternating with calcite layers. It is proposed that calcite layers represent solution features rather than cutanic features. Signs of hydromorphy are commonly observed within the dorbank horizons, since an arid climate currently prevails in Vaalputs such hydromorphic features may indicate formation under past climates. The occurrences of palygorskite, sepiolite and dorbank horizons in Vaalputs require high soil pH (generated by high concentrations of Na) for their formation. Vaalputs soils, however, measured circumneutral pH and relatively low Na concentrations which suggests that palygorskite, sepiolite and dorbank horizons are relic features. Salt casts of lenticular texture occur between polygonal peds of massive dorbank horizons and their enveloping vertical and horizontal laminations. Scanning Electron Microscope analyses indicate high concentrations of Mg, Al, Si and O which suggests sepiolite and palygorskite accumulation through a replacement of gypsum. Elemental maps in conjunction with x-ray tomography and bulk chemical analyses revealed that high concentrations of secondary barite occur along the contact surfaces between dorbank horizons and the laminations. The solution chemistry of all horizons show supersaturation with respect to barite suggesting that the Ba accumulation adjacent to the laminations is likely to have taken place at lower sulphate conditions than those present in the soils today. Evidence shows that Vaalputs soils have experienced at least one climate shift. The preserved soil mottles are indicative of soil environments that remain wet for an extended period. A fine textured platy dorbank horizon is an extensive feature in Vaalputs. The presence of this horizon indicates that the sediments were deposited from a low energy fluvial system. The large polygonal ped units in the lower dorbank units as well as the barite enrichments in pore spaces suggests a climate shift from wet to dry began after the sediments were deposited. / AFRIKAANSE OPSOMMING: Vaalputs radioaktiewe afval fasiliteit is geleë in 'n ariede streek van Namakwaland met evapotranspirasie potensiaal wat neerslag tans ver oorskry. Dominante grond funksies in Vaalputs sluit in 'palimpsests‘ klimaat kondisies waaronder dit gevorm het. Deeltjies groottes wissel drasties tussen horisonne wat op verskillende vorme van sediment vervoer dui. Die oppervlak in Vaalputs word gedek deur 'n gelyke korrelagtige growwe sand van residuele eoliese oorsprong. Die oorgang vanaf die oppervlak horison na die ondergrondse horisonne word algemeen gekenmerk deur 'n spoelsteen grootte kliplyn. Die spoelsteen grootte materiaal van die kliplyn dui op residuele opbou gedurende die verwering van 'n voormalige oppervlak blootgestelde horison. Sedert afsetting van die ondergrondse sedimente (15 Mj) is pedogenetiese veranderinge reeds aktief in Vaalputs. Dit het gelei tot 'n komplekse grond stelsel wat verskillende vorme van dik dorbank horisonne insluitend massiewe veelhoekige pedons en plaatagtige horisonne vertoon. Die veelhoekige pedons word gedefinieer deur uitgedroogde krake waar die vertikale en horisontale lamellering aangetref word. Ontbindingstoetse sowel as heelrots chemiese analiese bevestig dat die lamellering grootliks bestaan uit 'n sekondêre kalsiet. Elementele kartering het egter talle illiet bande afgewissel met kalsiet lae openbaar. Daar word voorgestel dat kalsiet lae verteenwoordigend van oplossingskenmerke is eerder as kuntanise kenmerke. Tekens van hidromorfie word algemeen binne die dorbank horisonne waargeneem, aangesien droë klimaat tans in Vaalputs heers kan sulke hidromorfiese kenmerke dui op die vorming onder vorige klimate. Die groot voorkomste van paligorskiet, sepioliet en dorbank horisonne in Vaalputs vereis hoë grond pH (wat gegenereer word deur hoë konsentrasies van Na) vir hul vorming. Vaalputs grond het egter relatief neutrale pH gemeet en relatief lae Na konsentrasies wat daarop dui dat paligorskiet, sepioliet en dorbank horisonne oorblyfsel kenmerke is. Sout gietforme met lentikulare texture kom voor tussen veelhoekige pedons van massieve dorbank horisonne en hul omhullende vertikale en horisontale lamellerings. SEM analiese toon hoe konsentrasies Mg, Al, Si en O aan wat opbou van sepioliet en paligorskiet deur verplasing van gips voorstel. Petrografiese analiese het euhedraal geaardheid van primere veldspaat mineraal getoon binne die grond van Vaalputs. Dit stel 'n bron van sediment voor en minimale pedogenese in dorre klimaat waar euhedraal korrels veldspate bewaar bly. Elementele kartering tesame met x-straal tomografie en heelrots chemiese analiese het getoon dat hoe konsetrasies sekondere bariet langs die kontak oppervlakke tussen dorbank horisonne en lamellerings voorkom. Die oplossingschemie van alle horisonne toon superversadiging met betrekking tot bariet wat voorstel dat die opbou van Ba langs die lamellerings waarskynlik plaasgevind het by laer sulfaat kondisies eerder as die kondisies wat heedendaags in grond voorkom. Bewyse toon dat Vaalputs grond ten minste een klimaatsverandering ondergaan het. Die gepreserveerde grond vlekke is kenmerkend aan grond omgewings wat vogtig gebly het vir 'n geruime tyd. 'n Fyn getekstuurde plaatagtige dorbank horison is 'n uitgebreide verskynsel in Vaalputs. Die teenwoordiheid van hierdie dorbank toon aan dat sedimente vanuit 'n lae energie fluviale sisteem afgeset het. Die groot veelhoekige pedon eenhede in die laer dorbank eenhede sowel as die bariet verryking in porie spasies stel voor dat 'n klimaatsverandering vanaf vogtig na droog begin het nadat die sediment afgeset het.