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No description available.

No description available.

No description available.

No description available.

Palaeobotanical records of Holocene climate change in the southern Coast Mountains identify a cooler/wetter Neoglacial period subsequent to 6600 BP. Geomorphic evidence of alpine glacier advance suggests that there were three distinct cooler/wetter periods during the Neoglacial, but this pattern has not been identified in palaeobotanical studies. By careful selection of a sensitive alpine site this thesis has recognised this structure in a palynological record of Neoglacial climate. This continuous record of Neoglacial climate which has the same basis as records of early Holocene climate (i.e. palynological) and hence allows more direct comparisons of the two periods. Pollen spectra, conifer needle macrofossils, organic matter content, and magnetic susceptibility were assessed for a 4800 year continuous sequence of sediment from an alpine lake. Calibration of the Picea/Pinus pollen ratio by using an altitudinal transect of surface pollen samples allowed partial quantification of shifts in treeline. Treeline at the site was at least 85 m above the present level from 4800-3800 BP, suggesting that summer temperatures were at least 0.6°C above the present. High treeline until 3800 BP indicates a relatively late date for the Hypsithermal/Neoglacial transition at this site. Alternatively, the apparent complexity of this transition in the Coast Mountains may be due to difficulties of separating temperature and precipitation signals in many climatic records. Treeline declined to near present levels by 2500 BP and was lower than present from 2500-1500 BP and from 1200 BP until close to the present. Estimates of equilibrium line altitude depression for Coast Mountain glaciers during the Little Ice Age suggest that these periods of lower treeline were due to a cooling of up to 0.8°C. During the last 5000 years the Southern Coast Mountains have experienced fluctuations on the order of 1.5°C.

Kimberlite whole rock geochemistry has been under-appreciated in deciphering Group I kimberlite petrogenesis. Although there is considerable debate on the definition of Group I kimberlite, there is agreement on certain characteristics. These include that Group I kimberlites are ultramafic rocks (MgO >15 wt%), have near primitive mantle nickel (∼ 1400 ppm) and chromium (∼1600 ppm) contents, have close to bulk silicate earth radiogenic isotopic signatures, are volatile rich (predominantly CO2) and have stable isotopic signatures typical of mantle sources. The debate, however, centers on petrogenetic models and parental magmatic compositions of Group I kimberlites. Petrogenetic models include both low degree (<1 %) partial melting of metasomatized asthenospheric mantle (Dalton and Presnall, 1998a; 1998b; Becker and Le Roex, 2006) and, conversely, high degree partial melting (10<20 %) of metasomatized veined asthenospheric mantle (Mitchell, 1995, 2004). Inferred kimberlite parental magma compositions have been suggested to be low silica (<5 wt%) and high CO2 (<44 wt%) melts, as suggested by high-pressure melt experiments conducted on synthetic carbonatized mantle (Dalton & Presnall, 1998a, 1998b), or much higher silica (<30 wt%) and lower CO2 (<12 wt%) melts as suggested by geochemical analysis of aphanitic kimberlite (Price et al., 2000; Kopylova et al., 2007). In an effort to contribute to the resolution of this debate on petrogenic models and parental magma compositions of Group I kimberlites, I have completed a systematic investigation of the whole rock geochemistry and petrology of three kimberlite occurrences in the Foxtrot Kimberlite Field of Northern Quebec. A clear correlation exists between whole rock chemistry, mantle source, and diamond grade of the three Group I kimberlites in the Foxtrot Kimberlite Field. Two phases, olivine and carbonate, dominant theserocks and thus control the kimberlites geochemistry. Electron microprobe analysis of over 800 olivines in the Foxtrot kimberlite indicate that it is predominantly xenocrystic (Mg# (Mg/(Mg+Fe)) of 91.5), largely derived from harzburgite mantle, but the absence of harzburgitic orthopyroxene in the Foxtrot kimberlites suggests that it has been assimilated. Whole rock geochemistry (major and trace elements) of the Foxtrot hypabyssal kimberlite dykes indicate they have chemical characteristics similar to Group I kimberlite from the Slave Province. The olivine content of the Foxtrot kimberlites, and thus their Mg#'s, are positively correlated with diamond abundance indicating that diamond grade is a reflection of the incorporation of harzburgite mantle. These results indicate that Group I kimberlite petrogenesis in the Foxtrot example is best modeled as a mixture of harzburgitic mantle xenocrysts and a carbonate rich fluid, and that the parental magma is silica poor "5 wt %) and CO 2 rich (<40 wt%).

Forest clearance can affect the levels of dissolved organic carbon (DOC), nutrient concentrations and algal biomass in streams, but the possible effect of these inputs on downstream lakes is usually surmised rather than demonstrated. To evaluate the effect of forest clearance on DOC and nutrient cycling in lakes, DOC, total phosphorus (TP), total nitrogen (TN) and chlorophyll (chl a) concentrations were measured in 47 Canadian Shield lakes in Quebec. Of these lakes, 25 were located in drainage basins that were partially clear-cut one to four years previously. In the disturbed sites, an uncut 20-m bufferstrip was left around the lakes and permanent water courses. / To account for differences among the watersheds that are not related to forest harvesting, I also collected a series of catchment and morphometric variables (watershed area, lake area, drainage ratio, forest, wetland, and upstream lake area, watershed slope, water residence time and lake depth). Lake characteristics in undisturbed and disturbed watersheds were compared to determine if forest clearance has a detectable effect on the water quality of downstream lakes. Although comparisons of seasonal and monthly means of the water quality variables between disturbed and reference sites were inconclusive, likely because of high natural variability, the size of the clear-cut was significantly related to means of the water quality characteristics. DOC, TP, TN and chl a increased in lake water with the area of the clear-cuts when large portions of the watershed ($>$50%) were cleared. The results of this study suggest that logging has an effect on water quality and even though a bufferstrip of twenty meters reduces this effect largely, it may not be enough to provide complete protection against the effects of logging activities.

In contrast to the wealth of palaeoenvironmental research stemming from the eastern Afromontane archipelago, the southern Afromontane component, which comprises largely of the Drakensberg, remains understudied. The Drakensberg constitute an area of significant biodiversity, cultural and economic importance. Suitable sites for palaeoenvironmental research are rare in South Africa due to general arid climatic conditions over much of the country. The KwaZulu-Natal Drakensberg offers a unique opportunity for palaeoenvironmental research through its increased rainfall and higher altitudes, which enable the development of wetlands that have the potential for polliniferous accumulation to occur. Catchment Six in Cathedral Peak is one such wetland that has provided an opportunity to research palaeoenvironmental conditions of the southern Afromontane archipelago component. A 371 cm sediment core was extracted from a subalpine wetland in Catchment Six and analysed using multiple proxies including; pollen, charcoal and geochemistry (carbon and nitrogen stable isotopes). A chronological framework for the core was established based on accelerated mass spectrometry radiocarbon dating of eight bulk sediment samples. A basal date of 15,100 ± 445 cal yr BP was determined at a depth of 298 cm. Poor pollen preservation of the basal portion of the core limited palaeoenvironmental inference for the late Pleistocene section of the record. The multiproxy record provides high chronological resolution for the early to late Holocene. Multi-proxy data indicate that the Holocene period in the Drakensberg was characterised by variable climatic conditions. Charcoal data indicate periods of increased regional fires in the last ca. 400 cal yr BP. Palaeoenvironmental inferences from the Catchment Six record are broadly in agreement with regional climatic indications based on existing literature. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 1994.