The first publication on southern African geocryology in 1944 resulted in a recognition of the potential of cryogenic phenomena in establishing long-term climatic records in the region, leading to a substantial increase in publications and research. Cryogenic studies are concerned with the way frost-induced processes have modified, and continue to modify, the mountain regions of the subcontinent. However, problems exist in interpreting relict forms, while supportive evidence for glacial and periglacial hypotheses are lacking. Insufficient data regarding Quaternary cryogenic activity have resulted in contradicting qualitative interpretations of the palaeoclimate and poor spatial and temporal resolution. It is apparent that there is a need for a more rigorous approach in southern African cryogenic studies as well as a better understanding of relict phenomena and the palaeo-environment. For this purpose a database that acts as a supplementary source and a tool for GIS-based analysis, was compiled. In addition, several glossaries and indices were constructed. The main glossary is a first effort at explaining past terminology usage and providing a terminology basis specifically for current research in southern Africa. Through database manipulation, the spatial distribution of past and present cryogenic phenomena as found in southern Africa, was mapped and it was found that cryogenic features and processes cluster along the Main Escarpment and the Western Cape Mountains. It is not clear if this is the actual situation or whether it represents a bias in the areas investigated. Further, likely regions for glacial ice development and survival and regions for periglacial activity were determined. The extent of relict and contemporary cryogenic activity was also verified. Evaluation of available data indicates that the extent of the cryogenic palaeo-environment did not differ considerably from the current one. An improved understanding of the spatial distribution of both relict and current cryogenic phenomena was achieved. The database represents a contribution towards the reconstruction of the southern African Quaternary environment and supplements current knowledge on the subject. While not necessarily providing solutions to current research problems, the database, combined with the glossaries and indices, will be invaluable in future research and modelling of the Quaternary in southern Africa. / Dissertation (MA)--University of Pretoria, 2007. / Geography, Geoinformatics and Meteorology / Unrestricted

Au Nunavik, l’augmentation des températures atmosphériques en lien avec les changements climatiques influence la capacité portante du sol en modifiant le régime thermique de la couche active et du pergélisol. Selon la nature du sol et des cryostructures, les processus de fluage et tassement différentiel du sol peuvent être considérables. La forte croissance démographique au Nunavik nécessite la construction de plusieurs nouvelles unités d’habitation. La présente étude a produit des outils pour permettre un aménagement durable du territoire par l’interprétation géomorphologique du paysage et l’étude des propriétés géotechniques des cryofaciès qui compose la cryostratigraphie des unités géomorphologiques de Puvirnituq afin d’estimer le comportement du pergélisol au dégel. Trois unités géomorphologiques principales ont été distinguées sur le territoire. Le socle rocheux est stable au dégel ainsi que les dépôts minces qui le recouvrent puisqu’ils sont contenus dans la couche active (unité P1). Le till remanié est dominé par du sable pauvre en glace, lui conférant une stabilité, mais les moraines de De Geer pourraient incorporer des dépôts marins riches en glace à l’intérieur d’un till remanié (unité P2). Les dépressions comblées de dépôts marins et littoraux sont probablement situées sur du till remanié mais contiennent une zone de transition riche en glace entre ~0,9 et 1,7 m de profondeur, excluant les possibilités de construction (unité P3). La principale contribution à l’aménagement du territoire découlant de cette étude a été la production de deux cartes. La première présente la distribution des unités géomorphologiques sur l’ensemble du territoire, permettant d’identifier rapidement le potentiel d’aménagement de l’environnement de Puvirnituq; la seconde carte montre l’emplacement des moraines de De Geer au-delà du village. Ces données trouveront des applications dans l’évaluation de substrats pour l’expansion de l’environnement bâti de Purvinituq et de granulats non-gélifs pour la construction des infrastructures construites sur remblais. Cette carte souligne l’importance de l’histoire Quaternaire sur les conditions actuelles de pergélisol. / In Nunavik, a sustained increase of surface temperatures linked to climate change, affects the bearing capacity of the permafrost by modifying its thermal regime. Depending on the nature of the soil as well as its cryostructures, creep and differential thaw-settlement processes can be significant. The rapid demographic growth in Nunavik requires the construction of several new housing units. In order to estimate the behaviour of permafrost to thaw, this study has contributed to a sustainable land-use planning by the geomorphological interpretation of the landscape and the study of geotechnical properties of the different cryofacies that compose the geomorphological units of Puvirnituq. Three main geomorphological units were distinguished within the territory. The bedrock is thaw-stable as well as the veneer of surficial deposits since they are contained within the active layer (P1 unit). The reworked till is dominated by ice-poor sand, providing a certain stability, but the De Geer moraines could incorporate ice-rich till and ice-rich thaw sensitive marine deposits (P2 unit). The depressions, filled with marine and littoral deposits, probably contain stable reworked till at the bottom but the presence of an ice-rich transition zone between ~0,9 and 1,7 m depth, makes this geomorphological unit improper for construction (P3 unit). The principal contribution to landuse planning of this study is the production of two maps. The first presents the distribution of the geomorphological units over the entire territory, allowing for a quick identification of potential areas to support the development of Puvirnituq; the second map shows the location of De Geer moraines beyond the study area to extrapolate the result of this study to the landscape scale.