Thesis (M.S.)--Oregon State University, 1991. / Typescript (photocopy). Includes maps in pocket. Includes bibliographical references (leaves 442-458). Also available via the World Wide Web.

Thesis (Ph. D.)--Carleton University, 1993. / Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (leaves 233-242). Also available via the World Wide Web.

Thesis (docteur)--Faculté des sciences de Paris, (197-?). / Includes bibliographical references (leaves 1-12 [2nd group]).

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 172-184).

Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 224-238). Also available on the World Wide Web.

No description available.

Mapping of the north-eastern portion of the Bird1s River Complex revealed that two large xenoliths composed of pyroclastic rocks and sandstone of the Cave Sandstone Stage have reacted with the dolerite. All the reaction phenomena normally associated with Karroo Dolerite are encountered. These are: (a) Metasomatism during the stage of iron enrichment of the dolerite with the production of a pyroxene-plagioclase metasomatic granophyre (b) Metasomatism during the stage of alkali enrichment of the dolerite with the production of a potassium feldspar adinole C c) Assimilation 'vi th the production of contaminated doleri tes Cd) Fusion 'vi th the production of glassy rocks including buchi tes (e) The production of rheomorphic veins

The ~ 73 ka ‘super-eruption’ of the Toba caldera in Sumatra is the largest known eruption of the Quaternary. The products of this eruption, the Youngest Toba Tuff (YTT), have been implicated in global and regional climate deterioration with widespread ecological effects. In this thesis I study the YTT co-ignimbrite ashfall, in particular the mechanisms of transport, sedimentation and preservation of ash deposits. I use distal marine and terrestrial ash sediments: a) to estimate the volume of YTT ash fallout; b) to quantify variability in the geochemistry of YTT ash; c) to assess the reliability of YTT ash as a chronostratigraphic marker; and d) to determine local influences on the reworking of YTT ash deposits. Following the introductory chapters, I address topics a) and b) through detailed investigations of published physical and chemical evidence. Chapter three shows that particle size and sediment thickness do not decline exponentially with distance from the eruption vent, highlighting the limitations of current methods of volume estimation for co-ignimbrite super-eruptions. Chapter four analyses geochemical variation in 72 YTT samples, and reveals the signatures of magma chamber zonation and post-depositional alteration. I address topics c) and d) through fieldwork in six locations, and detailed analysis of ash samples from a wide variety of local depositional environments. Chapter five uses high-resolution stratigraphic analysis of the YTT layer in the Son Valley, India, to show that variable deposition and sediment reworking may compromise the reliability of the ash layer as an isochronous marker for interpreting archaeological sequences. Chapter six combines a new understanding of the mechanisms of reworking, using new data on microscopic characteristics of reworked ash at four sites in Malaysia to demonstrate the necessity of accounting for reworking in palaeoenvironmental reconstructions. I conclude that accurate analyses of distal ash deposits can reliably determine the chemical properties of the YTT eruption, and that a detailed understanding of deposition and reworking processes is essential to inference of the environmental impacts of super-eruptions.

Four papers are presented in this thesis each one reporting on studies relating to volcanic ash with special reference to soils. The first paper reviews a) some of the phenomena relating to the ejection and deposition of ash that are important in interpreting the significance of its occurrence, b) the significance of ash layers to workers in the Quaternary, c) the techniques available for the characterization and recognition of tephra, d) the literature on ash deposits in western Canada and compiles the noted occurrences. In addition this paper presents the data from a study to determine the amount of ash retained by soils within and beyond the major areas of deposition indicated in the literature. The presence of ash in soils was found to be widespread though the amounts present may be limited for identification purposes, in some cases. The second paper describes two soils derived from Bridge River volcanic ash and their underlying paleosols and presents selected physical and chemical analyses. The analyses indicate that in the youthful soils studied the physical properties of the ash soils are inherited from the parent material. The colloidal and chemical properties are initially imparted by organic matter with some influence from ash weathering products especially aluminum. Shallow surface additions of volcanic ash to soils influence soil properties to varying degrees depending on pedogenic environment and depth of material. The third paper evaluates a number of methods that have been used to identify podzolic B horizons and the influence of surface additions of volcanic ash on the podzolic characteristics of soils. Pyrophosphate, pyrophosphate dithionite, citrate dithionite bicarbonate extractions, phosphate sorption capacity and pH-dependent cation exchange capacity determinations all highlighted the podzol B horizons while acid ammonium oxalate extractions and pH determined in NaF did not. The presence of surface additions of Bridge River ash may influence acid ammonium Oxalate or NaF criteria but it was not found to reduce the value of the other diagnostic criteria examined in this study. The final paper studies the amorphous material and clay mineral characteristics of the two aforementioned soils and examines some of the methods of extraction and isolation of clay materials in soils. All of the chemical treatments applied to the soils were found to result in some dissolution of secondary and primary soil materials. The treatments used to extract amorphous materials indicated that the Si to Al ratios of extracted materials was greater than 2. As this value approaches 2 the formation of allophane and imogolite will take place. This situation is indicated as having taken place in isolated capillaries as evidenced by the limited occurrence of imogolite-like material. Chlorite is the dominant clay mineral in the ash soils and is believed to be the weathering product of primary biotite, horneblende and pyroxene. / Land and Food Systems, Faculty of / Graduate