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No description available.

<p> This dissertation explores the internal geochemistry of Sepia officinalis cuttlebones and the rostra of several genera of extinct Belemnoidea with the aim of improving our ability to reconstruct the palaeoclimatic record. Sepia share several unique morphological features with Belemnoidea and may be their most suitable modern analogue. Consequently, a geochemical comparison between the internal skeleton of Sepia and Belemnoidea may help improve the understanding of the geochemistry of Belemnoidea rostra, which are often used to investigate Mesozoic palaeoenvironmental conditions.</p> <p> High resolution sampling of oxygen isotope values from five S. officinalis cuttlebones from the English Channel confirmed that S. officinalis cuttlebones provide an accurate record of water temperature that preserves seasonal temperature variation consistent with sea surface temperature records. Carbon isotope values show increasing values with growth until a sharp decline late in life, documenting a decrease in metabolism with ontogeny, followed by a late life increase. Trace element concentrations measured from two of these cuttlebones document a small but statistically significant correlation between oxygen isotope values and both Sr and Mn concentration, suggesting some degree of temperature control on their rate of incorporation. Mg concentration exhibits a small but statistically significant correlation with carbon isotope values, suggesting metabolism may exert some control on the rate of Mg incorporation.</p> <p> Due to the process of fossilisation, diagenesis may alter the geochemistry of Belemnoidea rostra, which is difficult to detect using stable isotope values alone. It is necessary to detect samples that have diagenetic overprinting of the original environmental signal so that past geochemical relationships may be accurately reconstructed. As Mn and Sr are enriched and depleted (respectively) in diagenetic fluids, they may be used as indicators of alteration. Following the removal of diagenetically altered samples, the carbon isotope values of Belemnoidea rostra sampled from the Green Beds at Carbondale River, Alberta, Canada document a statistically significant increase with ontogeny, suggesting a decrease in metabolic rate similar to S. officinalis. Contrasting with S. officinalis, oxygen isotope values do not show seasonal palaeotemperature cycles, possibly the result of latitudinal migration with favourable water temperatures. Trace element concentrations of Mg exhibit a small but statistically significant correlation with Belemnoidea oxygen isotope values, contrasting with Sr and Mn in S. ofjicinalis, suggesting some temperature control on the incorporation rate of Mg in belemnoidea calcite. The ranges in oxygen isotope and Mg values were used to investigate changes in surface and deeper water palaeotemperatures during the deposition of the Green Beds. Similarly, the range in carbon isotope values within individual Green Bed Belemnoidea rostra documented a positive isotope excursion in the Green Bed section, which may become a useful geochemical marker for the region.</p> <p> In most previous studies, palaeoenvironmental conditions have been reconstructed using a single sample from unspecified locations within Belemnoidea rostra. A high resolution sampling approach is necessary to capture the range of geochemical values preserved in individual rostra and may help to minimise the effects of sample bias in the geochemical record. Sampling radially from the apical line to the outside edge of an individual Belemnoidea rostrum is permits the collection of geochemical information spanning the organism's lifespan, and will improve the interpretation of the biology and environment while minimising sample bias.</p> / Thesis / Doctor of Philosophy (PhD)

Clumped isotope paleothermometry defines carbonate formation temperature based upon the relative abundance of the 13C18O16O isotopologue within CO2 (Δ47) formed through phosphoric acid digestion of carbonates. When precipitated in equilibrium, resultant Δ47 values are inversely-proportional to growth temperature, where 13C18O16O is more abundant at lower temperatures. To precisely define Δ47 values, a rigorous analytical protocol is required to: (1) minimize CO2-H2O isotope exchange during acid digestion; (2) purify CO2 to remove contaminants; (3) quantify the raw Δ47 value using a mass spectrometer configured for m/z 44 – 49; and (4) normalize the raw Δ47 value to account for machine-specific isotopic scrambling and Δ47 vs. δ47 non-linearity. Amongst laboratories with well-established analytical protocols, substantial disagreement still exists between proposed clumped isotope calibrations at low temperatures. To investigate the source of this discrepancy, calcite was precipitated between 15 – 40 °C from a HCO3-(aq)-dominated solution using an upgraded constant addition technique. This technique is the first to provide simultaneous control of δ18OH2O and δ13CDIC values of parent solution. Observed oxygen isotope fractionation between calcite and water is in agreement with Kim and O’Neil (1997), providing robust evidence of calcite precipitation in oxygen isotope equilibrium. Δ47 values were determined using McMaster’s clumped isotope facility, yielding the following calibration: Δ47-RF = 0.0351 (± 0.0021) × 106/T2 + 0.2982 (± 0.0233) This calibration observes a similar temperature dependency to theoretical models as well as ‘shallow’ slope experimental studies. To provide context to experimental calibrations with ‘steep’ slopes, we consider the non-equilibrium isotope effects of CO2 hydration/hydroxylation and HCO3- dehydration/dehydroxylation reactions on precipitating calcite. We propose that low temperature calcites primarily responsible for the ‘steep’ slopes of certain calibrations have partially inherited the disequilibrium isotope composition of DIC due to significant non-equilibrium isotope effects associated with the aforementioned CO2 hydration/hydroxylation and HCO3- dehydration/dehydroxylation reactions. / Thesis / Master of Science (MSc)

<p> Two isotopes of platinum, Pt192 and Pt194, have been investigated using Ge(Li) vs. NaI coincidence techniques. The following corrected angular distributions and mixing ratios in Pt192 were obtained: 468-316 keV A22 = 0.100(8) A44 = 0.011(8) 604-316 keV A22 = -0.410(15) A44 = -0.070(22) 308-612 keV A22 = -0.120(20) A44 = -0.027(20) 417-468 keV A22 = -0.120(26) A44 = -0.110(30) δ308 = -9.4(15) δ604 = + 3(1) |δ417|> 11 g factors for the following five levels of these nuclei were obtained using the method of perturbed angular correlations where the perturbing agent was the hyperfine field on platinum in an iron alloy: Pt192 316 keV g = 0.30(3) Pt192 612 keV g = 0.28(7) Pt192 785 keV g = 0.14(10) Pt194 329 keV g = 0.28(3) Pt194 622 keV g = 0.22(4) A comparison with the predictions of a microscopic collective model, the pairing-plus-quadrupole model, is made. / Thesis / Master of Science (MSc)

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No description available.

Through stable isotope analysis of human tooth dentine, this thesis investigates breastfeeding and weaning patterns in relation to rickets in a sample of sub-adults (n=12) interred in the nineteenth century sub-adult cemetery located at the Church of the Trinitarias in Madrid, Spain. The main objectives of this research are to create early life feeding histories for each individual using dentine serial sectioning techniques and apply these histories to investigate the relationship between breastfeeding, weaning, and vitamin D deficiency. The early life feeding histories allows for the determination of the onset and complete age of weaning at an individual level. These stable isotope data are then used to estimate general trends in breastfeeding and weaning practices in nineteenth century Spain. The results of this study indicate that the onset age of weaning for most of the individuals in this sample was between 10 and 14 months of age. The age at which breastmilk consumption stopped entirely was more difficult to estimate, however, in individuals that did show evidence of completed weaning, it was estimated to occur around the age of three. These ages are slightly higher than those discussed in historical sources for nineteenth century Spain. When these results are compared to contemporaneous, more industrialized, European countries the comparison shows that the initialization of weaning occurred slightly later and was a more gradual process in this Spanish sample. The results also demonstrate that there is no direct relationship between weaning patterns and the occurrence of skeletal vitamin D deficiency. It may be that the high prevalence of vitamin D deficiency is linked with the nuances of breastfeeding and other biocultural variables, such as a lack of sun exposure, an inadequate weaning diet, or childcare practices. / Thesis / Master of Arts (MA)

In this dissertation, I explore elements of the changing Arctic Ocean through the application of Stable Isotope, Noble Gas Isotopes, and sulfur hexafluoride (SF6) to better understand ice dynamics for freshwater balance, air/sea gas exchange and ocean circulation. For the tracer studies of stable isotope fractionation, our approach is to use sea ice core data to determine the stable oxygen isotope effective fractionation coefficient. The result is an average value close to 2.2 ‰, which is compared to literature values. For the tracer studies of air/sea gas exchange, we use Neon (Ne) and Helium (He) isotope data sets collected in the ‘Switchyard’ region of the Arctic Ocean between 2005 and 2013 and in the Greenland and Norwegian seas between 1994 and 1999. The Switchyard data show a distinct excess in Ne concentrations in the upper waters. We hypothesize that rejection of Ne during sea ice formation accounts for the Ne excess in the Switchyard area of the Arctic Ocean. Based on this hypothesis we estimate sea-ice formation rates by integrating the Ne excess from the surface to the Atlantic Water layer. The resulting amount of excess Ne corresponds to formation of a nearly 4 m thick sea ice layer. We compare the sea ice formation obtained from the Ne excess method with an independent estimate based on oxygen isotope ratio anomalies ?18O, which is nearly 6.07 m. The difference in the sea ice formation estimated by these two methods indicates loss of Ne through leads. We estimate that the gas exchange rate through the sea-ice cover is ca. 11.3 percent per year. The gas exchange rate through sea-ice covered water would be 0.015 meters per day. For the tracer studies of mean residence times, we analyzed tritium (3H), helium isotope (3He and 4He) and sulfur hexafluoride (SF6) samples collected in the ‘Switchyard’ region of the Arctic Ocean between 2008 and 2013. We calculated apparent tracer ages using the 3H/3He ratios and the partial pressure of SF6 and compare their values for the depth interval between the surface and the core of the Atlantic Water layer. The apparent tracer ages range from zero to about 30 years. Generally, the linear correlation between the 3H/3He and SF6 apparent ages was strong, with the coefficient of determination R2 of 0.94. We explore deviations from this linear trend and discuss them in the context of mixing, air-sea gas exchange, and the impact of sea ice formation on the helium and SF6 gas balances in the surface mixed layer.