Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 138-147).

Thesis (Ph. D.)--University of Wisconsin, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Ecological and ecophysiological investigations carried out at the ultramafic outcrop near Meikle Kilrannoch, Angus, Scotland are reported. The outcrop is botanically famous for its rare plant species, particularly the endemic Cerastium fontanum ssp. scoticum and the nationally rare Lychnis alnina. The studies were made on the main outcrop (called MK1) which is dome shaped, and on a much smaller low-lying area (called MK1.5) about 300 m from it. The overall aim of the studies was to investigate the relationship between the soil physico-chemical environment and species distribution on the open areas of the ultramafic site and to experimentally test for causality; and to offer an explanation for the open character of the vegetation on the skeletal soils. Variograms which were constructed for soil properties and vegetation data to investigate soil micro-spatial variation and vegetation pattern showed differing levels of spatial dependence, always indicating high intrinsic variability. The cause of this high variability was probably cryoturbation for the soil and morphological characters for plants. The gradient analyses (Principal Components Analysis and its canonical form, Redundancy Analysis) used to study soil - vegetation correlations suggested that A ostis vinealis, Cerastium fontanum ssp. scoticum and Lychnis alpina were most abundant in areas up-slope with lower concentrations of soil magnesium; Cochlearia pyrenaica ssp. alpina and Festuca rubra were associated with bigger stone sizes, and the latter occurred in wetter areas with higher of ions. A comparative solution culture experiment based on the local soil chemistry was used to study the growth responses to magnesium and nickel of Cerastium fontanum ss. scoticum, Cochlearia pyrenaica ssp. al ina and Festuca rubra. The results for Festuca and Cerastium were in agreement with the findings of the gradient analysis: Festuca was indifferent to both magnesium and nickel and Cerastium was susceptible to high magnesium; the reduction of dry weight by nickel in the Cochlearia conflicted with its suggested association with high soil nickel in the gradient analysis. The impacts on the photosynthetic systems of three Cochlearia species of different concentrations of iron and nickel were identifiable only in the non-ultramafic C. pyrenaica where the addition of nickel decreased photosynthesis but the effect could be ameliorated by the addition of high concentrations of iron. The open character of the skeletal soil at the MK1 site was discussed in terms of 'carrying capacity'. Vegetation development was suggested to be controlled at least partly by large stones covering the soil surface. Further factors such as space fragmentation, possible plant-to-plant interactions, and low density of flowering individuals and restricted seed dispersal were also considered. To test if major nutrients were limiting plant growth, major nutrients (NPK) were applied to the MK1.5 skeletal soil. The significantly higher X's and recruitment and change in life history traits (larger rosette sizes, earlier maturing and higher seed production) in the fertilised populations of C. pyrenaica ssp. alpina resulted in a significantly higher plant cover in the fertilised quadrats. The better growth of plants in the fertilised quadrats was reflected in their lower total non-structural carbohydrate (TNC) concentrations in May and their higher TNC in August. The present series of investigations found that magnesium and nickel toxicity had an effect on the intra-site distribution of the ultramafic species and also confirmed earlier reports on the importance of magnesium and nickel toxicity in ultsamafic exclusion. Large stones and low soil phosphorus concentration are proposed as limiting factors for the development of closed vegetation on the skeletal soil areas of the sites.

No description available.

Thesis (Ph. D.)--University of Chicago, Dept. of the Geophysical Sciences, August 1999. / Includes bibliographical references. Also available on the Internet.

Thesis (M. Sc.)--Carleton University, 1990. / Also available in electronic format on the Internet.

No description available.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2007. / Includes bibliographical references (leaves 328-335). Also available online.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2014. / Intermediate-depth earthquakes occur at depths of 60 – 300 km at these depths high confining pressure inhibits brittle failure from generating earthquakes. Fault-related pseudotachylytes from Corsica are exhumed paleofaults from a high pressure, low temperature subduction zone environment, and are considered analogues of intermediate-depth earthquakes. Hence, it is important to analyse the physico-chemical processes by which these pseudotachylytes form in order to gain primary insight into the controls of their formation and how this seemingly paradoxical process takes place. Up until the recent discovery of high pressure pseudotachylytes there was no known direct method of evaluating the formation mechanisms of intermediate-depth earthquakes. High pressure pseudotachylytes found in subduction complexes are regarded as relict paleo-earthquakes. Previous research aimed at understanding the generation of these phenomena and the role of fluids on their origin has been based on seismic, experimental and numerical modelling. The principal aims of this project were to carry out detailed geochemical, petrographic and microtextural analyses of such pseudotachylytes located in the Eocene Schistes Lustres Complex, Corsica, and to determine whether the data from natural samples corroborate current models. The pseudotachylytes in this study reside in peridotitic and metagabbroic lozenges enclosed within serpentinites. Pseudotachylytes are notoriously complex and messy, with compositions that vary widely over small distances (< 1 mm). For this reason the pseudotachylytes in this study were systematically analysed from the outcropscale to the micron-scale according to their wallrock type. From these data it was observed that greenschist and blueschist facies hydrous minerals present in the peridotite and metagabbro wallrocks were entrained into pseudotachylyte fault veins. Back scatter electron (BSE) imaging shows that these hydrous minerals underwent wholesale fusion in the melt. No evidence for prograde dehydration reactions was observed in the wallrocks or in association with the pseudotachylytes. Electron microprobe analyses (EPMA) of the bulk matrix of the pseudotachylytes revealed variable H2O content, 0 – 14 wt % in peridotite-pseudotachylytes and 0 – 4 wt % in metagabbro-hosted pseudotachylytes. The principal minerals that underwent fusion are: clinopyroxene, plagioclase, glaucophane, Mg-hornblende and actinolite (metagabbro- hosted) pseudotachylyte), and olivine, orthopyroxene clinopryroxene, chlorite, serpentine and tremolite (peridotite-hosted pseudotachylyte). The bulk of H2O entering the melt remained in solution until it reached supersaturation, upon which it exsolved to form fluid-rich, vesicular veins. Cuspate and lobate rims of microlites (omphacite, clinopyroxene, olivine and orthopyroxene) along the boundaries of hydrous veins indicate that the melt was still molten when the fluids exsolved. The presence of hydrous fluids in the melt appears to have enhanced the fracturing process. Fault veins hosted by peridotite that have the greatest H2O content are the thickest, have more chaotic injection networks and exhibit more cataclastic deformation features than the anhydrous fault veins observed. With regard to the mechanism of pseudotachylyte generation, it is clear that water present in hydrous minerals or entrapped in the crystal lattices of anhydrous minerals plays a fundamental role in facilitating intermediate-depth earthquakes through hydrolytic weakening. A melt richer in hydrous fluid also has a lower viscosity, facilitating fault slip. Dissolved H2O is also a flux and may enhance further melting of the wallrock, relative to an anhydrous pseudotachylyte vein. Sheared, kinked and twinned wallrock minerals and survivor clasts associated with the pseudotachylyte fault veins indicate crystal-plastic deformation. No significant grain size reduction was observed in proximity to fault veins. The grain size of wallrock minerals at fault vein boundaries ranges from 5 – 20 mm. From this it was inferred that the mechanism of deformation is controlled by power law creep, temperature and high strain rate. The presence of metastable high temperature crystallisation products in the pseudotachylyte such as hoppers and dendrites of olivine, orthopyroxene and diopside (in peridotite) and Al-rich omphacite and Fe-rich anorthite (in metagabbro), are suggestive of a short-lived high temperature event resulting from thermal instability. These high temperature mineral assemblages are overprinted by ones indicating a return to ambient conditions (lower temperatures, but still high pressures), namely, glaucophane, albite and epidote (in metagabbro) and clinochore, fine-grained granoblastic olivine, enstatite and diopside (in peridotite). The observations from this detailed study of natural samples suggest that intermediate-depth seismicity may be generated by a thermal runaway process.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Science. / Microfiche copy available in Archives and Science. / Bibliography: leaves 264-283. / Ph.D.