Development of clumped isotope techniques and their application to palaeoclimate studies

The aims of this research were to firstly help development of clumped isotope measurements of carbonate samples at UEA, and to then explore whether the technique could be used to retrieve robust environmental signals from geological material. This specifically looks at the Hirnantian glaciation at the boundary between the Ordovician and Silurian periods. Using the MIRA instrument, it is possible to make high precision measurements to enable the assessment of Earth surface temperatures. Long term precision of standard material is comparable to existing studies. MIRA is also absent of any non-linearity issues. Removal of contaminants and the identification of samples displaying contamination is stringent, as we find contamination has a serious effect on the Δ47 signal. Using modern biogenic carbonates and controlled temperature precipitates, the relationship between the clumped isotope signatures represented by the Δ47 value and temperature is: Δ47(ARF) = 3.5 x 10⁴/ T² + 0.2416. The relationship lies within measurement error of the theoretical estimate of temperature sensitivity. Applying this temperature calibration to fossil material collected from across the Ordovician/Silurian boundary found that the clumped isotope signal had been overprinted during diagenesis, and it has not been possible to extract an original Earth Surface temperature. However, the isotopic signal does show how the basin has developed during diagenesis under closed system conditions. As a result, the bulk δ¹⁸O and δ¹³C values have not been altered and record an original environmental signal.