Ice shelves play an important role in the mass balance of an ice sheet, by providing a link between the ocean and ice. Melting at the base of an ice shelf can play a vital role in its mass balance and stability. Topographic channel features have been found on the base of ice shelves, and have been found to alter melting, however the mechanism behind this alteration is unknown. Petermann Glacier is a major outlet glacier in North West Greenland, draining approximately 6% of Greenland Ice Sheet. It terminates in a long, thin ice shelf, constrained within a high-walled fjord. The ice shelf has pronounced longitudinal channel features on its base, which limited observations suggest direct ocean currents in a mixed layer of ocean and melt waters, focusing melt in these regions. Petermann Glacier underwent two large calving events in 2010 and 2012, and the impact of these events, or possible further calving events, on basal melting is unknown. Using the MITgcm to model the ocean cavity beneath an idealised ice shelf, this thesis discusses the impact of basal channels on interactions at the ice base and circulation within the cavity. This is supplemented with a modelling investigation into the interactions beneath Petermann Glacier, and the impact of recent calving events. The inclusion of channels was found to have a stabilising effect on the ice shelf by decreasing the mean basal melt rate, caused by the refocusing, and decrease in intensity of, the meltwater layer flow beneath the ice shelf. This stabilisation and resulting 'survivor bias' explains why channels are commonly found on the base of warm water ice shelves. The model of Petermann Glacier found similar melt patterns to observational studies, however with a lesser magnitude. The calving events of 2010 and 2012 removed areas of ice shelf with low melt rates, resulting in little impact on the overall volume of ice removed through ocean melting, though further calving would vastly reduce the volume of ice melted. One consequence of calving is the increase in melting-induced undercutting at the ice front, leading to the potential for enhanced secondary calving.

The Neoproterozoic is one of the most enigmatic periods in Earth history. In the juxtaposition of glacial and tropical deposits the sedimentary record provides evidence for extreme climate change. Various models have tried to explain these apparent contradictions. One of the most popular models is the Snowball Earth Hypothesis which envisages periods of global glaciations. All climatic models are dependent on palaeogeography which as yet remains poorly constrained for the Neoproterozoic. This thesis presents a multidisciplinary study of two Neoproterozoic sedimentary basins on the Congo and West Africa cratons including radiometric dating of glacial deposits themselves. In the West Congo Belt, western Congo Craton, a new U-Pb baddeleyite age for the Lower Diamictite provides the first high quality direct age for the older of two glacial intervals. This age is significantly different from previously dated glaciogenic deposits on the Congo Craton. This result strongly suggests that the mid-Cryogenian was a period during which several local glaciations occurred, none of which were global. While the palaeomagnetic results from carbonates around the younger glacial interval are probably remagnetised, detrital zircon and chemostratigraphic results allow correlation with numerous late-Cryogenian glaciogenic deposits worldwide and a Snowball Earth scenario is favoured here. In the Adrar Sub-Basin of the vast Taoudéni Basin, West Africa, the terrigenous Jbeliat glacial horizon has been studied in great detail. Detrital zircon geochronology reveals large changes in provenance through this glacial unit with implications for sedimentological approaches and techniques for provenance characterisations based on one sample alone. Together with recently published U-Pb data these results constrain the age of the Jbeliat Group to a narrow window providing vital geochronological information for this younger glacial event. Combining provenance geochemistry, chemostratigraphy and U-Pb dating has greatly improved our understanding of two of the largest Neoproterozoic sedimentary basins. The dominance of Mesoproterozoic detrital material, for which no source has been reported near either of the field areas, has consequences for the proximity of other cratons at the time of deposition, prior to the final amalgamation of Gondwana.

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In this study four different aspects of primary successions on glacier forelands in South-Central Norway are investigated. First, general vegetation and environment trends, which have been observed by other scientists, were studied on two forelands. It is shown that the two selected forelands (one low- and one high-altitude foreland, Nigardsbreen and Storbreen, respectively) differ in the speed of vegetation cover change and in the overall species richness developed over the last 250 years since deglaciation. This is attributed to differences in the severity of the environment between the two forelands. Some support for an early peak in the number of species was found for the Nigardsbreen foreland, whereas the Storbreen foreland shows no significant trend in the development of species richness. Life-forms and soil-depth change on both forelands in the predicted manner. A novel approach for the use of Ellenberg indicator values for the estimation of pH-values from the existent vegetation shows highly significant correlations between predicted pH values and trends measured for similar terrain ages from a study by Messer (1988). Investigation at two different scales indicated that small-scale disturbances (< 100 m) may influence the mosaic of the environment, which affects the results of the chronosequence approach. By using a strict geometrical sampling design more variable conditions entered the analyses than with the stratified random sampling schemes adopted by others, such as Matthews (1979b). Some loss in the power of analysing the data occurred, but the results are still consistent with hypotheses about primary succession on glacier forelands. Second, new aspects of the temporal development and successional change of plant communities were investigated on the same two forelands. There is some evidence of succession from a pioneer community to the local climax community of the surrounding area for both forelands. There is also support for the correlation of timedependent environmental variables with the successional development of plant communities. A new application of Ellenberg indicator values in ordinations was assessed for its value in estimating average environmental conditions derived from the vegetation. As with the previous analyses, investigation of community development at two different scales supported the importance of sampling scale on the analysis of succession data. Third, spatially explicit analyses of distribution patterns of dominant woody species was developed as a means to investigate processes and formulate hypotheses about primary succession on glacier forelands. The data for this part of the study was collected on five glacier forelands, three low-altitude (Nigardsbreen, Austerdalsbreen and Bødalsbreen) and two high-altitude (Storbreen and Høgvaglbreen). Pattern descriptors including perimeter/area index, autocorrelation measures and fractal dimensions, support the hypothesis of differential colonisation of wind and animaldispersed species. Even more convincing is the result that low- and high-altitude forelands show significant differences in the patterns exhibited by wind and animals dispersed species. This result is thought to be related to the differences in environmental severity affecting the establishment of colonising species. Finally, logit modelling of the distributions of dominant woody species provides insights into the sampling effort needed to gather enough data for meaningful analyses. It also leads to the identification of important factors influencing the distribution of those species.

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