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)

Racemization kinetics of amino acids, determined for the commonly occurring fossil gastropod Succinea, facilitates the ability to construct an accurate and precise paleothermometer to estimate paleotemperatures over specific time intervals during the last 150,000 years in parts of Central Europe. Racemization within the carbonate shell of Succcinea is induced at high temperatures over increasing intervals of time in the laboratory and measured for aspartic acid (asp), glutamic acid (glu), valine (val), and phenylalanine (phe), by reverse-phase liquid chromatography. The activation energy (Ea), frequency factor (A), and forward rate constant (k1) of the Arrhenius equation are determined from the racemization of specific amino acids over time. The Arrhenius parameters, combined with racemization data and independent age estimates of fossil Succinea shells, are used to solve for temperature in geologic samples. Succinea recovered from a loess sequence in western Germany, located around the town of Nussloch, has been chosen for amino acid paleothermometry calculations. Samples were collected from the Nussloch loess -- paleosol sequence in the summer of 2001. The sequence spans from greater than 130,000 years to the present, is dated by luminescence and radiocarbon methods, and has abundant published proxy paleoclimate data for comparison. Temperatures calculated for the bracketed time interval representing the last glacial maximum (25 - 20ka) averaged -5.3°C± 6.8°C using aspartic acid racemization data. Arrhenius parameters for aspartic acid racemization were the best constrained and provide temperature estimates consistent with previously published data. Paleotemperatures calculated for other bracketed intervals of time within the Succinea shells from Nussloch dated within the last 150,000 years exhibited values similar to previously published data with acceptable error.

Water filters and sediment trap samples were collected weekly from late May to early September 2009 from four lakes of the Lofoten archipelago, northwestern Norway, and were used to explore the applicability of the alkenone unsaturation index (UK37) for temperature reconstruction in limnic systems in the area. For the first time, we observed the occurrence of long-chain alkenones (LCAs) within the water columns of lakes in this region. Water filters from two of the four studied lakes contained measurable concentrations of alkenones that were restricted to spring turnover and disappeared with the onset of summer stratification. These results indicate that alkenones in the lake sediment of these lakes reflect biological production and temperature during lake mixing, taking place in late spring to early summer. Measurements from sediment trap material collected over the sampling season combined with water temperature measurements from automated data loggers provide an in situ calibration of the alkenone paleothermometer (Temperature = 33.0 x UK37 + 22.8; N=10; R2=0.95). Notably, this calibration reveals a UK37 sensitivity to temperature (i.e., the slope of the relationship) that is very similar to previous calibrations reported from both marine and lacustrine environments. LCAs can therefore serve as the first quantitative proxy for reconstructing past temperature variability from the Lofoten Islands. Based on this temperature calibration, a high-resolution temperature record was reconstructed over the past millennium, which shows unprecedented lake surface temperature warming during the past decades.