The Livingstone Range anticlinorium (LRA) is a long (>65 km) narrow (<5 km) structural culmination that coincides with a major hanging-wall ramp across which the Livingstone thrust cuts ~1000 m up-section eastward from a regional décollement in the upper part of Devonian Palliser Formation to another regional décollement within Jurassic Fernie Formation. The presence of Precambrian basement fluids prior to thrusting and folding is recorded in the LRA by deformed jasper+/-fluorite+/-sphalerite veins, and adjacent haloes of altered dolomitic host rock with high 87Sr/86Sr ratios (0.7094 to 0.7100) relative to most host rocks. Basement fluids are a possible source for anomalously radiogenic strontium that occurs in the diagenetically altered Paleozoic carbonate rocks in the LRA and throughout the Western Canada Sedimentary Basin, but underlying thick shale strata such as the Exshaw Formation are also a possible source. The earliest stages of thrusting deformation involved the development of distinctive chevron-style, flexural-slip thrust-propagation folds that have conspicuous blind thrust faults along their hinge zones. The hinge-zone thrust system of the Centre Peak anticline consists of a series of stacked detachment thrusts, each of which emerges from a different zone of interbed slip in the backlimb of the anticline and deflects the hinge zone eastward. Each successively higher detachment thrust dies out in the hinge zone at approximately the same stratigraphic level at which an overlying detachment thrust fault emerges from a bedding detachment zone in the backlimb. Fluid flow during thrust-propagation folding is recorded by dolomite+/-calcite veins with isotopic compositions that are similar to those of host rocks. Fluid flow occurred along faults related to thrust-propagation folding, and also along many tear faults and larger thrust faults. Veins in these fault zones have slightly higher 87Sr/86Sr ratios relative to adjacent host rocks and are interpreted to have formed from a mixture of formation fluids and hotter basement fluids in a rock-dominated system. Oxygen isotope thermometry of four syn-folding veins indicates they precipitated at anomalously high temperatures (>250°C). The youngest episode of fluid flow along thrust faults and tear faults is recorded by calcite veins with very low δ18O values (-18 to -9‰ PDB), which are interpreted to have precipitated along faults that were active while the LRA was being transported eastward and elevated by underlying thrust faults, and cooled by infiltrating meteoric water. The conduits along which significant meteoric fluid circulation occurred are marked by visibly altered host rocks that have anomalously low δ18O values and slightly lower δ13C values relative to most host rocks. Rapid cooling due to deep infiltration of meteoric water into the shallow brittle surface of the deforming earth is almost certainly not restricted to thrust and fold belts, nor is its thermal effect necessarily restricted to the upper few kilometers. This model for fluid flow has significant implications for predicting thermal conditions in deep metamorphic rocks that lie beneath the brittle crust, the most obvious effect being to push down the brittle/ductile transition zone, which would enhance even deeper meteoric fluid circulation and cause the deflection of underlying isotherms. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2007-11-01 15:25:23.854

Bythotrephes longimanus, a predatory exotic cladoceran, has spread rapidly to numerous lakes through the Laurentian Great Lakes region of Ontario and North America. Post-invaded lakes are known to have reduced zooplankton species richness, biomass and altered community structure. Bythotrephes may also affect the diet and trophic position of macroinvertebrate predators and prey species for fish (e.g., Mysis relicta). However, the effects of this species in altering higher trophic levels remain largely unexamined. Using a combined approach of stable isotope (d13C and d15N) and THg analysis, the trophic position of Bythotrephes in two invaded lakes was investigated. Based on d15N values, Bythotrephes shared a similar trophic position to native macroinvertebrate predators (9 and 7‰ for Peninsula and Harp lakes, respectively). Using a mixing model and stomach content analysis we show that, despite low and patchy lake abundance, Bythotrephes may be a key prey item to fish and has approximate dietary contributions similar to native prey items, such as zooplankton, Chaoborus and Mysis. In both lakes, Hg conformed to predicted biomagnification trends as indicated by 15N. When Bythotrephes invades lakes with native macroinvertebrate predators, it inserts itself into the same trophic position and does not have major effects on food web length. / Thesis (Master, Biology) -- Queen's University, 2008-01-10 22:00:22.188

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No description available.

This thesis investigates the relationships between mercury (Hg) and stable isotope of carbon (δ13C) in marine pelagic zooplankton (Calanus spp., Themisto spp. and Euchaeta spp.) with water mass characteristics in the North Water Polynya (NOW) and in the Mackenzie shelf – Amundsen Gulf area. Two ship based sampling field expeditions were carried out in late summer of 2005 and 2006 in both regions on board the CCGS Amundsen. In the North Water (NOW) polynya, higher levels of water Hg, depleted δ18O, lower salinity and lower nitrate levels were measured at sampling locations near the Prince of Wales glacier (POW) on the eastern coast of Ellesmere Island in the Smith Sound area. These results suggest that the glacier may be a source of Hg to this region which, in turn, is responsible for the correspondingly high concentrations of THg and MMHg measured in Calanus spp. and Euchaeta spp. at the same locations. The Mackenzie shelf – Amundsen Gulf region was characterized by fresher surface water properties (low salinity and depleted δ18O) in the western part and was strongly linked to the influence of the Mackenzie River. Higher THg concentrations in zooplankton were associated with larger fractions of both meteoric water and sea-ice melt. These findings suggest that in the western Arctic, inorganic Hg uptake in zooplankton via-absorption near surface water was highly driven by freshwater inputs into the system. Based on the analysis of three main genus Calanus spp. (mostly adult females Calanus hyperboreus), Euchaeta spp. and Themisto spp. (mostly adult Themisto libellula), THg and MMHg concentrations were the highest in the carnivorous copepod Euchaeta spp. in the North Water polynya followed by the omnivorous hyperiid amphipod Themisto spp. The herbivorous copepod Calanus spp. had both the lowest THg and MMHg concentrations in the Eastern and the Western Arctic. In addition, the Western Arctic is the area in which each zooplankton genus had the most depleted carbon and the most enriched nitrogen. The highest concentrations of THg in Calanus spp., Euchaeta spp. and Themisto spp. were measured in the Western Arctic as well as the highest MMHg in Calanus spp. and Themisto spp. The highest %MMHg was calculated in the Archipelago for Themisto spp., in the Eastern Arctic for Euchaeta spp. and in the Western Arctic for Calanus spp. The relationships observed between THg, MMHg, %MMHg and δ13C in all three major zooplankton taxa and water mass properties were in agreement with what have been previously described in the literature. Our findings suggested that both Hg and δ13C can be used as tracers to help understand zooplankton vertical distribution, feeding ecology and ultimately to predict climate changes impact at lower trophic level in the pelagic food web. The implications for marine mammals foraging in these regions are also discussed.

In order to rationally optimize a reaction, it is necessary to have a thorough understanding of its mechanism. Consequently, great effort has been made to elucidate a variety of reaction mechanisms. However, the fundamental ideas needed to understand reaction mechanisms are not yet fully developed. Throughout the literature, one encounters numerous examples of experimental observations that are not explainable by conventional mechanistic ideas and methods. The research described in this dissertation employs a unique approach towards the identification and analysis of systems whose observations cannot be explained by conventional transition state theory (TST). The nucleophilic substitution of 4,4-dichloro-but-3-en-2-one by sodium-para-tolyl-thiolate was explored. It was deduced that the reaction was concerted and consequently, the product selectivity observed in the reaction cannot be explained by TST. Dynamic effects play a major role in the observed selectivity and this is further supported by the results of dynamic trajectory simulations. Using computational studies, the ethanolysis of symmetric aryl carbonates was also shown to be concerted, provided that the substrate possesses good leaving groups. Furthermore, extensive precedence has been set by Gutthrie, Santos, Schelgel, and others, detailing concerted substitutions at acyl carbon. The Fujiwara hydroarylation is thought to occur by either a C-H activation mechanism or an electrophilic aromatic substitution (EAS). The KIEs associated with this reaction have been determined and provide strong support for the latter. Computational studies also displayed fair agreement with experimentally determined KIEs, further supporting the EAS mechanism. Isotopic perturbation of equilibria is invaluable in helping to determine whether a structure exists as a single structure or whether it is a time average of two equilibrating structures. The bromonium cation of tetramethylethylene and hydrogen pthalate have been wrongly reported as existing as equilibrating structures. The time averaged geometries have been determined in each case, via a variety of methods and the myth of equilibrating structures in the above cases has been debunked.

This thesis presents research that improves our understanding of the relationship between climate and tree-ring stable isotopes in New Zealand kauri (Agathis australis (D. Don) Lindl.) and cedar (Libocedrus bidwillii Hook. F). As a whole, this research creates a framework from which future investigations of stable isotope dendroclimatology can pursued at high temporal resolution across longer term temporal intervals. Such a framework is required to realize the full potential of New Zealand tree-ring records as archives of palaeoclimatic information. In the Southern Hemisphere, mid-to-high latitude terrestrial climate proxy records are sparse; the long-lived endemic conifers of New Zealand present a rare opportunity to gain valuable insight into Late-Quaternary and Holocene climatic change. A major barrier to long stable isotope dendroclimatic proxy records has been the time-and-resource intensive nature of associated sample preparation and analytical processes. Through experimental assessment of the SBrendel α-cellulose extraction method, this research demonstrates that this simple processing method can, with some caveats, be successfully applied to resinous conifers, facilitating rapid chemical preparation of samples. Further efficiency gains are documented in through use of dual element low temperature pyrolysis of cellulose, providing carbon and oxygen stable isotope determinations on a single sample, rather than the traditionally separate analyses. These preliminary investigations into methodological efficiency enabled the ~3000 stable isotope determinations on kauri and cedar, on which the following investigations into isotopic variability, chronology quality and climate-isotope relationships are based. Both kauri and cedar exhibit substantial intra and inter-tree isotopic variability, resulting in greater than normal sample numbers being required to isolate the common variance in composite time-series. Despite sampling 7 trees (18 cores) at one site and 8 trees (21 cores) at another, only oxygen isotope time-series reach an Expressed Population Signal score of 0.85, a common benchmark of chronology quality. Further investigations using high-resolution sequential sampling of single rings show that this variability extends to a sub-annual scale. Within single rings there are large ranges in δ13C and δ18O, generally corresponding with regular annual cycles of up to 4.6‰ for δ13C and 8.1‰ for δ18O. These data show high frequency (sub weekly) changes in δ18O, demonstrating sufficiently fine resolution for event-to-seasonal scale climate/weather reconstruction. However, that potential is complicated by the lack of strong climatic correlations with isotopic cycles. Due to their stronger common signal, δ18O time series are investigated for inter-annual stable isotope dendroclimatic reconstruction from kauri and cedar. Bootstrapped correlation and multiple regression models show strong relationships between kauri and cedar δ18O and relative humidity, accumulated rainfall and soil moisture deficit. The correlations are strongest for all variables during the period from Autumn prior to growth to the current growth summer. Tree-ring δ18O in kauri and cedar is identified as an effective recorder of regional hydroclimate leading up to and during the Austral growth season. While it is demonstrated that tree-ring δ18O holds significant promise for inter-annual palaeoclimate reconstruction, it is equally apparent from this research that stable isotope dendroclimatology in New Zealand faces significant challenges. Foremost is gaining an improved understanding of seasonal dendrochemical cycles and their relationship with tree-physiology. Increasing the spatial and temporal coverage of tree-ring isotope records is vital to realising New Zealand’s vast potential for stable isotope dendroclimatic reconstruction.

Graduate

Records of stable oxygen isotope variations from a variety of proxies have been used in palaeoclimatic research since the 1950’s. Several studies have applied stable isotope analysis of lake sediments to reconstruct past climate changes in central and northern Sweden, including a study of Lake Blektjärnen in Jämtland, central Sweden, by Andersson (2010). In this study, sediments from that same lake were sampled for stable isotope analysis of bulk carbonates with the aim to improve the resolution of the isotopic record for the last two millennia. The results indicate a shift from relatively drier to wetter conditions between ~2,300–1,300 cal. years BP, generally wet conditions close to the Medieval Warm Period (~1,000–750 cal. years BP) and generally dry conditions during the Little Ice Age (~550–150 cal. years BP). These results are in agreement with previous palaeoclimatic reconstructions in the region. The isotopic record of Lake Blektjärnen was completed for the last ~2,350 years at a resolution of ~15 years per sample, three times higher than that of the previous study, displaying the advantages of bulk carbonate sampling for stable isotope analysis and providing a high-resolution dataset on humidity changes in central Sweden during the late Holocene.

The Nopal I uranium deposit located in northern Chihuahua Mexico has been the focus of study for the past 40 years. Information regarding to its formation and evolution through time demonstrate that it has a very complex history. Uranium mineralization occurs in two different styles: uranium oxide uraninite and a secondary phases of silicates (uranophane, soddyite) and oxyhydroxides (schoepite and ianthinite). Petrographic studies have revealed that uraninite is found encapsulated within the host rock (ignimbrites) as fine grains while secondary uranium minerals are filling fractures and micro-veins. Chemical dates from the uranium minerals give a wide range from 0 to 611 Ma; many of the ages may be overestimated since the host rock is 44 Ma. U/Pb isotopic studies demonstrate the presence of common Pb, and after a correction was applied, a new range of dates from 1< to 7 Ma was obtained.