Thesis (Ph. D.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on Mar. 18, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geophysics, Department of Physics, University of Alberta. Includes bibliographical references.

The purpose of this thesis is to establish possible changes in the CI/Br ratio of ancient oceans over the past 2 x 10 9 years. Variations in the Cl/Br ratio of carbonate rocks are used to indicate these changes. A secondary objective of this thesis is to determine the distribution patterns of F in limestones and dolomites. Variations in the F content of dolomites are shown to be related to environment of deposition and can be used to establish tho genesis of dolomite. The contents of the thesis include; 1) a comprehensive review of the pertinent literature, 2) a discussion of the evolution of the Cl/Br ratio of the ocean. 3) application of F in paleoenvironmental reconstruction, and 4) suggestions for further research. / Thesis / Doctor of Philosophy (PhD)

No description available.

Chemical sediments in a variety of geomorphic environments (pedogenic, fluvial, palustrine, lacustrine and pan) were investigated from seven regions (SW Kalahari, Kgalagadi, Kalkweissrand, Etosha, Linyanti, Okavango and Ngami) in the Kalahari of southern Africa. These primary and multi-phase sediments were characterised by a range of pure and intergrade silcrete, calcrete and dolocrete fabrics which contained an array of structures indicative of the crystalline and biogenic processes responsible for their precipitation, epigenesis and paragenesis. Petrography, mineralogy and isotope geochemistry provided significant insight regarding the environmental and geochemical conditions at the time of precipitation. Petrography indicated that the majority of chemical sediments were undergoing epigenetic modification as a consequence of the desiccation induced transition from phreatic to vadose diagenetic and geochemical conditions. The role of rapidly infiltrating meteoric water, associated with unstable wetting fronts, is believed to be instrumental in vadose diagenesis and the precipitation of crystalline/alpha fabric carbonate. Salinisation within the capillary fringe and deeper vadose zone is believed to be responsible for the sequence dolomitisation of crystalline calcite within mature sequences. Highly saline pan conditions instigate the precipitation of authigenic dolomite, calcite and K-feldspar within the surface sediments and authigenic silica at depth. Phreatic water beneath the islands, floodplains and fluvial systems of the Okavango, which undergoes evapotranspirational and transmission salinisation and ultimately terminal desiccation, are similarly precipitating silcrete. Pedogenic processes principally associated with C₄ vegetation are responsible for the gratification of carbonate mud within desiccating lacustrine, palustrine and pan sediments. Within the thin sandy Kalahari soils, pedogenesis is limited, but biogenic/beta fabric precipitation linked to mycorrihizae and tree/shrub savanna vegetation is instrumental in the formation of hardpans and the modification of upper calcrete horizons. The dominance of a distinct assemblage (smectite/kaolinite or sepiolite/palygorskite) of authigenic clay minerals present within all the environments provides evidence of semi-arid precipitation within Mg and Ca enriched saline/rapidly evaporating water or brackish/reduced permeability environments.

The latitudinal motion of the Tibetan Himalayathe northernmost continental unit of the Indian plateis a key component in testing paleogeographic reconstructions of the Indian plate before the India-Asia collision. Paleomagnetic studies of sedimentary rocks (mostly carbonate rocks) from the Tibetan Himalaya are complicated by potentially pervasive yet cryptic remagnetization. Although traditional paleomagnetic field tests reveal some of this remagnetization, secondary remanence acquired prior to folding or tilting easily escapes detection. Here we describe comprehensive rock magnetic and petrographic investigations of Jurassic to Paleocene carbonate and volcaniclastic rocks from Tibetan Himalayan strata (Tingri and Gamba areas). These units have been the focus of several key paleomagnetic studies for Greater Indian paleogeography. Our results reveal that while the dominant magnetic carrier in both carbonate and volcaniclastic rocks is magnetite, their magnetic and petrographic characteristics are distinctly different. Carbonate rocks have wasp-waisted hysteresis loops, suppressed Verwey transitions, extremely fine grain sizes (superparamagnetic), and strong frequency-dependent magnetic susceptibility. Volcaniclastic rocks exhibit pot-bellied hysteresis loops and distinct Verwey transitions. Electron microscopy reveals that magnetite grains in carbonate rocks are pseudomorphs of early diagenetic pyrite, whereas detrital magnetite is abundant and pyrite is rarely oxidized in the volcaniclastic rocks. We suggest that the volcaniclastic rocks retain a primary remanence, but oxidation of early diagenetic iron sulfide to fine-grained magnetite has likely caused widespread chemical remagnetization of the carbonate units. We recommend that thorough rock magnetic and petrographic investigations are prerequisites for paleomagnetic studies throughout southern Tibet and everywhere in general.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

An interbasinal study of Late Cambrian cyclic carbonate successions in the Appalachian and Cordilleran passive margins, the Texas cratonic embayment and the southern Oklahoma aulacogen has provided controls on the simultaneous development of peritidal to subtidal meter-scale cycles and the larger scale depositional sequences on which they are superimposed. Fining-upward peritidal cycles grade seaward into coarsening-upward, shallow to deep subtidal cycles that form a continuum across the carbonate platforms and are genetically linked to one another by shared lithofacies. Eustacy appears to exert the dominant control on the simultaneous development of peritidal and subtidal cycles on different carbonate platforms. Based on the recognition of dominant periodicities on power spectra derived from time series of subtidal cycles, high frequency eustatic oscillations may be controlled by Milankovitch astronomical rhythms. Interbasinal correlation of Late Cambrian depositional sequences was performed by graphic correlation and the time-equivalent intervals were correlated lithostratigraphically using isochronous biomere boundaries as time datums. Fischer plots of meter-scale cycles define changes in relative sea level based on the amount of extra accommodation space produced by eustacy beyond that provided by subsidence. Residual eustatic curves derived from subsidence analysis are useful for correlating the longer-term Late Cambrian sea level events and changes in the rate of sea level rise and fall can be used to define shorter-term events. Combining the sea level curves defined by Fischer plots and subsidence analysis with paleobathymetric curves of Late Cambrian cyclic strata suggests that the curves may approximate the form of the eustatic sea level curve. A composite "eustatic” sea level curve for the Late Cambrian was created by qualitatively combining the sea level curves defined by the different techniques for each of the four localities. “Eustatic" sea level curves defined by Fischer plots and subsidence analysis may be used to apply sequence stratigraphic concepts to onedimensional outcrop sections. Combined with systematic changes in the stacking patterns of meter-scale cycles, they can be used to define the internal composition of systems tracts, sequence boundaries, and flooding surfaces of third-order depositional sequences. One- and two-dimensional models of peritidal and subtidal cycle development indicate that peritidal cycle thickness is primarily controlled by accommodation space and deeper subtidal cycle thickness is primarily controlled by sedimentation rate. Whereas lithofacies within peritidal cycles alternate in response to fluctuations in sea level, subtidal cycle development may be related to fluctuations in fairweather and storm wave base that oscillate in harmony with sea level fluctuations. / Ph. D.

Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.