Northern Oman is an arid area almost entirely dependent upon groundwater recharged by highly sporadic rainfall. Precipitation estimates are hampered by a lack of any reliable altitude-rainfall relationship. Below 700 m there is no statistically significant relationship. The isotopic composition of groundwater is strongly influenced by the rainfall amount (related to storm frequency), and not just by altitude/temperature. Storm events with long return periods are of disproportionate importance to recharge. Despite the huge volume of carbonate formations, holokarstic development is generally immature, and groundwater storage is greatest in alluvial piedmont surrounding main limestone massifs. Isotopes, chemistry and hydrologic measurements show that post-storm evaporative losses are very large. The origin of limestone springs and their chemical and physical anomalies are described. Structure rather than petrology controls groundwater flow in the limestones, hence regional differences in structural style produce contrasting hydrologic regimes between the various massifs. The Semail nappe mantle sequence is the only other hard-rock formation of groundwater significance. Though much less productive than the carbonates, these ultramafics display extraordinary chemical activity, yielding bicarbonate waters from the weathered zone, whilst more deeply circulating groundwaters produce hyperalkaline springs by low-temperature serpentinisation. Associated processes include solute reduction, hydrogen evolution, hydroxide and carbonate precipitation, hydroxide-basic rock reaction, salt enrichment and water-rock isotopic exchange. Throughout the interior catchments, groundwater mostly flows into narrow buried alluvial channels which are often constricted at hard-rock nodal points, thus facilitating very efficient interception and recovery by the "falaj" system. Traditional agriculture has evolved to cope with fluctuating groundwater supply but is sensitive to increased abstraction. On the Batinah plain, greatly increased coastal abstraction has locally induced moderate to severe salinisation. Existing process studies are insufficiently quantified to provide the resolution necessary to manage groundwater resources, especially in high-risk coastal areas.

An airborne radar survey was conducted over the ice-filled volcanic caldera at Mt. Wrangell, Alaska. Research reported here involves computer processing and interpretation of radio-reflection data acquired over 21 traverses of the summit. In addition to describing useful data enhancement techniques, a dynamic programming approach is introduced for topographically controlled data positioning and spatial correction. Interpretation focusses upon a well defined radio-stratigraphy attributed to high acidity horizons deposited at the ice surface during periods of elevated volcanic activity. A comparative analysis of layer character indicates that echoes from the caldera floor are not continuously detected because of anomalously high signal absorption. Consequently, results impose a lower limit upon maximum ice thickness. A numerical interpretation scheme, incorporating both glaciological measurements and empirical relations governing the behaviour of firn and ice, is developed to aid interpretation of the glacio-volcanic stratigraphy. Preliminary modelling yields a speculative volcanic record that roughly matches the known eruption sequence at Mt. Wrangell and suggests a significant extension of the volcanic history. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Fifty-three earthflows in south-central British Columbia were identified from an air photograph search and from a review of previous geologic reports. Many have parallel 'en echelon1 lateral deposits indicative of several movement phases during the postglacial period, and some have been active during the present century up to the time of the study. The purpose of this study was to date phases of earthflow activity during the postglacial period and relate them to climatic fluctuations. Earthflows in the study area are concentrated in serpentinised peridotite, basalt, sediments (mainly volcaniclastics), and other volcanics. Earthflows take place preferentially down dip in sediments and many are associated with fault lines. All earthflow materials, except those derived from serpentinised peridotite, weather to montmorillonite-rich material, and each yields a characteristic grain-size distribution. Earthflow gradient in the study area depends upon material type, indicating that earthflow texture and mineralogy govern shearing resistance and hence partially determine characteristic slope angles. Earthflow movement during the past 60 years was investigated using air photograph chronosequences dating back to 1928. Reactivations of six flows were identified in the period 1950 to 1960, and an analysis of precipitation records from four stations around the study area showed that the level of winter precipitation increased around 1950. It was concluded that the observed reactivation was a response to rising groundwater levels during a period of increased winter precipitation. Earthflow movement and climatic fluctuations over the last 200 years were investigated in an analysis of tree-ring width records at four sites. Moist phases were recorded in the periods 1800-1830, 1870-1920 and from 1945 to the present. Compression wood formation at three sites corresponded with moist phases, so it was concluded that, over the last two centuries, earthflow movement was probably coincident with phases of higher precipitation. A postglacial climatic chronology was inferred from published pollen analyses and from Neoglacial ice fluctuations, both within and outside the study area. New palynological data were collected from Red Mountain, a high elevation site in the west of the study area. These showed a two-phase cooling period following the close of the Hypsithermal. The first cooling period took place around 6-7,000 BP, and the second around 3,000 BP. Earthflow movement during the postglacial period was analysed using radiocarbon dates, tephrochronology, stratigraphy, carbonate accumulation, and earthflow morphology. Data from twenty-one sites showed that movement was concentrated mainly after 7,000 BP, and at several sites the stratigraphic position of the Bridge River tephra dated movement around 2,400 BP. It was concluded that, at this longer timescale, movement at many sites could be attributed to post-Hypsithermal climatic deterioration. / Arts, Faculty of / Geography, Department of / Graduate

No description available.

No description available.

No description available.

abstract / Earth Sciences / Master / Master of Philosophy

Chemical input-output analyses were used to evaluate the rate of rock weathering and soil development on a granitic inselberg of the Dragoon Mountains in southeastern Arizona. Soil genesis relationships were investigated through field and laboratory study of the soil profile, parent rock, microclimate and vegetation, on different catena positions and hillside aspects. Precipitation and runoff water qualities were determined, with increased summer acidity. Precipitation volume was estimated by extrapolating data from a nearby recording station. Runoff volume was estimated by the U.S.D.A.-S.C.S. Curve Number Method (1972). These data enabled the quantitative determination of cationic solution loss. The indicated decreasing order of cation mobility is calcium, sodium, potassium and magnesium. Cations of higher mobility are relatively depleted in the hillcrest soils, while transported to the footslope or beyond. Calcium, and to a lesser extent sodium, have experienced more extensive off-site removal. Differences resulting from the transformation of parent material to soil were analyzed by field morphology, X-ray analysis, laser light-scattering particle size analysis, and chemical analyses. The study site was surveyed, mapped and the spatial arrangement of soil taxa and their compositional variation were studied. Nearly all pedons on the crest or transport slope are Lithic Ustic Torriorthents; whereas footslope soils show greater development, as exemplified by the occurrence of various Haplargids, Haplustolls and Argiustolls. Weathering rates were calculated using a methodology similar to that of F. W. Barth (1961). Potassium and magnesium provided the most reasonable data of 350 and 430 Kg ha⁻¹ yr⁻¹, respectively. (equivalent to 13.5 and 16.5 mm of rock weathered per 1000 years). Two serrated projectile points were found inbedded on the clayey soil surface of an adjacent ancient pond site. These artifacts resemble another projectile point found in southeastern Arizona which has been radiocarbon dated ~7,000 yr B.P. A minimum age for the pond and immediate surrounding topography is suggested to correspond with the end of the western subhumid pluvial period. The assessment of the geochemical budget provided a valuable framework for quantification of the various processes which interactively determine the rates of weathering and soil formation.

No description available.

Graduation date: 1994